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Potassium (K) deficiency of cotton (Gossypium hirsutum L.) has become a common malady across many production regions, including Arkansas. Adequate fertilizer-K management is paramount to ensure optimum plant growth. Field studies were initiated in 2023 evaluating how K availability influences cotton leaf- and petiole-K concentration throughout the growing season. Fertilizer-K rate (0, 40, 80, 120, 160, and 200 lb K2O/ac) trials were established at the University of Arkansas System Division of Agriculture's Lon Mann Cotton Research Station (LMCRS), Milo J. Shult Agricultural Research and Extension Center (SAREC), and Rohwer Research Station (RRS) in soils with Very Low, Medium, and Optimum soil-test K (STK), respectively. Leaf and petiole samples were collected at first flower and analyzed for K concentrations. Leaf- and petiole-K concentrations increased with increasing K availability (either soil or K fertilization), indicating predictability in diagnosing K deficiency. Leaf- and petiole-K concentrations at first flower were significantly (P < 0.10) affected by fertilizer-K rate in all trials except for petiole-K concentration at RRS. Overall, tissue-K concentrations continuously increased with increased fertilizer-K rate, with the greatest leaf- and petiole-K concentration increase (0.71% to 1.21% and 3.27% to 7.0%, respectively) being observed at LMCRS on soil with Very Low K (53 ppm K). Fertilizer-K, regardless of application rate, positively influenced yield at the Very Low STK location, with an average increase of 22% when compared to the no-fertilizer-K control. No significant (P > 0.10) yield increase with K fertilization was observed on soils with Medium and Optimum STK. Additional site-year observations will allow more conclusive information regarding cotton tissue-K and yield responses to different K availability. [ABSTRACT FROM AUTHOR]

Cover crops have the potential to affect soil-test P and K concentrations and the following crop's response to fertilization by influencing soil nutrient cycling. This report summarizes year 7 results of a field trial examining the influence of cover crop and fertilizer-P and -K application on corn (Zea mays) yield response and soil-test P and K. Research was conducted at 2 locations with soil samples collected from the 0-6-in. depth at cover crop planting in fall 2022 and termination in spring 2023. The sixth annual fertilizer-P and -K treatment applications were made to fertilizer treatment subplots, and corn was planted following cover crop termination. Cereal rye (Secale cereal) biomass (2795-4361 lb/ac) contained the equivalent of 20-32 lb P2O5 and 72-94 lb K2O/ac, while biomass from winter fallow treatments at one location averaged 934 lb/ac and contained the equivalent of 8 lb P2O5 and 29 lb K2O/ac. Winter fallow biomass was not sampled at the other location. Dry matter and nutrient accumulation were generally greater with cereal rye than in winter fallow treatments, but fertilizer rate did not influence dry matter or nutrient accumulation. Cover crop did not significantly influence spring soil-test values, but fertilizer rates were consistently reflected in soil-test values following 5 annual applications, with values increasing as rates increased. At one location, corn yields following cereal rye were reduced by 26 and 23 bu./ac in the P- and K-rate trials, respectively, relative to corn following winter fallow. At the other location, grain yields following cereal rye averaged 10 bu./ac greater than corn following winter fallow in the P-rate trial, while yields were unaffected by cover crop treatment in the K-rate trial. Fertilizer-K, regardless of rate, increased yields by an average of 17 bu./ac at one location, but fertilizer rate did not greatly influence yields in the other trials. [ABSTRACT FROM AUTHOR]

Soil sampling and fertilization are not commonly performed annually in hay production, but the system removes vegetative material and nutrients from the field each harvest. Sub-optimum P or K availability affects bermudagrass (Cynodon dactylon L.) forage yield due to their importance in plant physiological processes. This study aims to monitor bermudagrass yield responses and nutrient removal in response to fertilizer-P and -K rates and to develop optimal fertilizer recommendations for hay production. Field studies were initiated in 2019 and have been repeated every year since then in Batesville and Fayetteville, Ark. In P-rate trials, triple superphosphate was applied at rates of 0, 30 (x1), 60 (30x2), 90 (30x3), 120 (40x3), and 150 (50x3) lb P2O5/ac with split applications occurring at green-up (x1), green-up and following harvest 1 (x2), or green-up and following harvests 1 and 2 (x3). Muriate of potash was applied at rates of 0, 70 (35x2), 150 (50x3), 225 (75x3), 300 (100x3), and 375 (125x3) lb K2O/ac, with split applications at the same times as the P trials. Soil nutrient availability and bermudagrass yield and nutrient concentrations were assessed in 2023. Changes in soil-K availability due to long-term fertilizer-K rates significantly (P < 0.05) affected forage yield. Overall, 150 lb K2O/ac treatment increased the forage seasonal yield by 35% and 102%, relative to the no-fertilizer-K control, in Fayetteville and Batesville, respectively. Tissue-K concentrations and K removal increased with increasing fertilizer-K rates. Soil-test P increased with P fertilization in both locations, resulting in greater tissue-P concentrations and P removal. Phosphorus rates ≥30 lb P2O5/ac produced an average of 58%, 13%, and 24% greater yield than the no-fertilizer-P control in the first, third, and seasonal total yield, respectively, in Batesville. Sub-optimal P and K fertilization compromises bermudagrass forage yield, while high fertilizer rates build up soil-test levels and increase nutrient removal. [ABSTRACT FROM AUTHOR]

In the southeastern United States (U.S.), the impact of nitrogen (N) fertilizer rates on blackberry (Rubus L. subgenus Rubus Watson) yield, growth, and fruit quality have not been evaluated. In 2022 and 2023, 6 N rates (0, 30, 60, 90, 120, 150 lb N/ ac) were applied via fertigation for 15 weeks to one-year-old Ouachita blackberries in Clarksville, Ark. Plant tissue nutrient samples of primocane and floricane petioles and leaves were collected in alternate weeks throughout the growing season. From late May through early July, fruit harvest was conducted twice a week, and fruit quality parameters were assessed. Floricane yield and fruit quality were not affected by N fertilization rates, except fruit decay after seven days. Nitrogen fertilization rate x sampling date interaction was significant for primocane petiole NO3-N concentration, where higher N fertilization rates generally had higher petiole NO3-N concentration than lower rates at several sampling dates. Floricane petiole NO3-N concentration was not impacted by fertilizer-N rate. However, floricane leaf-N concentration was affected, and the 0 lb N/ac rate had the lowest leaf-N concentration but was not significantly different from other treatments except the 120 and 150 lb N/ac rates. Our first-year observations agree with previous research findings that blackberry primocanes are impacted more immediately by in-season N application compared to floricanes. Our second-year observations concur with existing literature that we would see differences in the N concentration of floricane tissue after a previous year's application of differing rates of N fertilizer. This trial will be continued through 2024 to study the impact of N rate on yield, fruit quality, leaf and petiole nutrient concentration, and cane characteristics in perennial blackberry production to identify a recommended N fertilization rate and the associated leaf- and petiole-N sufficiency ranges for blackberry in Arkansas. [ABSTRACT FROM AUTHOR]

Potassium (K) deficiencies in irrigated soybean [Glycine max (L.) Merr.] are common in irrigated mid-South production systems that can limit soybean yield potential. A study was conducted to correlate the relative soybean grain yield to the leaf-K concentration at 15 days after first flower (DAR1) and calibrate the fertilizer-K rate needed to correct in-season K deficiencies and maximize grain yield at 15 DAR1 based on the trifoliolate leaf-K concentration. Research was conducted in 2021 and 2022 at 8 site-years across Arkansas on silt loam soils planted with maturity group 4 or 5 cultivars. One treatment received 160 lb K2O/ac as granular muriate of potash (MOP) at preplant, and all other treatments received no preplant fertilizer-K followed by multiple rates of granular MOP ranging from 0 to 160 lb K2O/ac at 15 DAR1. The trifoliolate leaf-K concentration was measured in the upper-most fully expanded leaf at 15 DAR1 and was confirmed to be positively correlated with relative grain yield. Soybean leaf-K concentrations ranged from 0.96% to 1.93% K at 15 DAR1. Soybean with leaf-K concentrations at or less than 1.76% K at 15 DAR1 responded significantly to in-season fertilizer-K applications. Quadratic models were used to predict the fertilizer-K rate needed to reach 95% relative grain yield or the highest relative grain yield achieved for the responsive sites, which ranged from 20 to 120 lb K2O/ac depending on the leaf-K concentrations. Calibrated fertilizer-K rates based on tissue-K concentrations in early reproductive growth will enable producers to correct deficiencies in season with the appropriate fertilizer rate to maximize yield. [ABSTRACT FROM AUTHOR]

Soybean [Glycine max (L.) Merr.] varieties are currently categorized as chloride (Cl) includers, excluders, or a 'mixed' population. A more specific rating system is needed to differentiate between true Cl-excluding varieties and a considerable proportion of varieties that may be mixed includer/excluder plant populations or a plant population with multiple genes that influence Cl uptake. A field-based Cl monitoring program has been developed with the Arkansas Soybean Performance Tests to provide a more detailed categorization of Cl tolerance in soybean varieties. A 1 to 5 rating system was developed and implemented on 158 varieties belonging to relative maturity groups 3.5 to 5.9 based on trifoliolate leaf-Cl concentrations included in the University of Arkansas System Division of Agriculture's Vegetable Research Station location of the 2022 Arkansas Soybean Performance Tests. Trifoliolate-leaf samples were collected when soybean reached the R3 to R4 growth stage. Ratings of 1 (strong excluder), 2, 3 (intermediate), 4, and 5 (strong includer) were assigned to 39, 24, 40, 39, and 20 varieties, respectively. The detailed rating system provides producers with more information regarding the relative Cl tolerance of available soybean varieties. [ABSTRACT FROM AUTHOR]

Nitrogen (N) fertilizer is essential to maximize cotton (Gossypium hirsutum) yield in most fields across Arkansas, and research regarding optimal rates and timings is limited. Small-plot N response trials were implemented on silt loam soils at the University of Arkansas System Division of Agriculture's Lon Mann Cotton Research Station (LMCRS) and Rohwer Research Station (RRS) in 2023. The cotton cultivar DP 2020 B3XF was planted at both locations, and the cultivar DP 2038 B3XF was also planted at the RRS adjacent to the first cultivar. The six N fertilizer treatments included a nontreated control and a split application of 30 lb N/ac applied preplant and incorporated, followed by 90 lb N/ac sidedress to represent a low and high check, respectively. The four additional N applications were made at the first square growth stage and were applied as sidedress applications of 40, 80, 120, and 160 lb N/ac. The Arkansas Extension recommendation for the production region is 110 lb N/ac. Cotton was managed using Cooperative Extension Service recommendations, and yield was determined using a small plot cotton picker and an assumed turnout of 41%. Cotton lint yields at the LMCRS were excellent, reaching >1115 lb/ac for all treatments, and the cotton was responsive to N fertilizer application. At the RRS, cotton yields were suboptimal (<670 lb/ac) but similar to reports from previous years, with only a significant yield response observed in the DP 2020 B3XF cultivar. Yield results for the LMCRS indicate that 80 lb N/ac (yield of 1613 lb /ac) or 30 lb N/ac applied preplant and incorporated, followed by 90 lb N/ ac sidedress (yield of 1603 lb/ac.) can be used effectively. These results suggest that N management in cotton can be refined to provide producers with additional options and that in-season N applications can be sufficient to maximize cotton yield potential with no preplant N. [ABSTRACT FROM AUTHOR]

Seeking to fine-tune nitrogen (N) application, increase economic returns, and decrease environmental N loss, some Arkansas rice (Oryza sativa L.) producers are turning away from blanket N recommendations based on soil texture and cultivar and using the Nitrogen Soil Test for Rice (N-STaR) to determine their field-specific N rates. In 2010, Roberts et al. correlated years of direct steam distillation (DSD) results obtained from both 0 to 12 and 0 to 18-in. soil samples to plot-scale N response trials across the state to develop a field-specific, soil-based N test for Arkansas rice. After extensive small-plot and field-scale validation, N-STaR is available to Arkansas farmers for both silt loam and clay soils. Samples submitted to the N-STaR Soil Testing Lab in 2022 were summarized by county and soil texture, totaled 45 fields across 9 Arkansas counties, and were from 19 clay and 26 silt loam fields. Depressed sample submissions were again observed likely due to another wet spring and subsequent planting rush. The N-STaR N-rate recommendations for samples were compared to the producer's estimated N rate, the 2022 Recommended Nitrogen Rates and Distribution for Rice Cultivars, and the standard Arkansas N-rate recommendation of 150 lb N/ac for silt loam soils and 180 lb N/ac for clay soils. Each comparison was divided into 3 categories based on a decrease in recommendation, no change in recommended N rate, or an increase in the N rate recommendation. Soil texture was a significant factor in the standard (P < 0.0002) and cultivar (P < 0.0008) comparisons; however, county, unlike previous years, was not a significant factor in any of the comparisons for 2022. Further stressing the potential N cost savings opportunities, reductions of 30 lb N/ac or greater were recommended by N-STaR in 76%, 63%, and 77% of fields in the standard, estimated, and cultivar comparisons, respectively. [ABSTRACT FROM AUTHOR]

Potassium (K) is one of the most limiting nutrients for rice (Oryza sativa L.) grown in the direct-seeded, delayed-flood production system common in the U.S. Mid-South and substantial yield reductions can occur when produced on soils low in exchangeable K. The primary objective of our research was to compare yield responses of pure-line and hybrid rice cultivars to K fertilization in a trial where various K rates (0, 40, 80, 120, and 160 lb K2O/ac) have been applied annually for several years. With Very Low (<61 ppm) Mehlich-3 K in the no-fertilizer-K control plots, both cultivars responded to K fertilization. Without K application, the pure-line (Diamond) produced 67% of the maximum yield produced when fertilized with K, while the hybrid (RT 7321 FP) produced 53% of the maximum yield. Averaged between cultivars, grain yields of 107, 145, 155, 167, and 177 bu./ac, which were all significantly different, were produced from annual application rates of 0, 40, 80, 120, and 160 lb K2O/ac, respectively. Grain yields were significantly less from the hybrid (135 bu./ac) than from Diamond (165 bu./ac), averaged among fertilizer-K rates, but the interaction of cultivar and K rate did not influence yields. Grain yields of the hybrid cultivar were lower than expected, likely due to lodging, which decreased as fertilizer-K rate increased. Results of this study suggest that RT 7321 FP may be more responsive to K fertilizer than pure-line cultivars, but recent trials observed another hybrid (RT Gemini 214 CL) to be less responsive. Based on inconsistent responses of hybrid rice to K fertilization and the fact that earlier studies predominantly evaluated pure-line cultivars, it is important to continue studying the response of hybrid rice to K fertilization to build a database for proper interpretation of tissue data and potential adjustments to K fertilizer recommendations. [ABSTRACT FROM AUTHOR]

The purposes of the cultivar x nitrogen (N) studies are the observation, collection, and analysis of the growth and yield response of new rice (Oryza sativa L.) cultivars to N fertilization. The collection of this data is used to determine the optimal N fertilizer rates across the range of soils and environments in which rice is grown in Arkansas. Eight cultivars were studied in 2022: Addi Jo, Avant, CLL18, DG263L, Diamond, Ozark, PVL03, and Taurus at 4 locations: the University of Arkansas System Division of Agriculture's Northeast Research and Extension Center (NEREC), the Northeast Rice Research and Extension Center (NERREC) the Pine Tree Research Station (PTRS), and the Rice Research and Extension Center (RREC). Seed treatment and seeding rates followed current recommendations and production practices. The grain yields were fair to good for all cultivars studied at the 4 locations in 2021 with little to no lodging reported for all cultivars across all locations. The 2022 season was the first year the cultivars Addi Jo, Avant, CLL18, Ozark, and Taurus were included and the second year of inclusion for the cultivar PVL03; therefore, there is insufficient data to make a N rate recommendation at this time, and hence the response to N reported here can serve as a guide while more data is collected in subsequent years. Three years of results for DG263L provide evidence that this cultivar should have excellent yields with minimal to no lodging if 135 pounds (lb) of N/ac is applied in a 2-way split of 90 lb N/ac at the preflood timing followed by 45 lb N/ac at midseason when grown on silt loam soils and 165 lb N/ac in a 2-way split of 120 lb N/ac at the preflood timing followed by 45 lb N/ac applied at midseason when grown on clay soils. [ABSTRACT FROM AUTHOR]

Corn (Zea mays L.) grain yield is tightly linked to potassium (K) fertilization practices, but so is producer profitability. Work sponsored by the Arkansas Corn and Grain Sorghum Board has been ongoing to verify the current K fertilization rates based on soil test K concentrations and develop leaf tissue correlation and concentration data to diagnose in season K deficiencies. Potassium response trials were established at four research stations across Arkansas in 2022 and included the Milo J. Shult Agricultural Research and Extension Center (SAREC), the Lon Mann Cotton Research Station (LMCRS), the Pine Tree Research Station (PTRS), and the Rohwer Research Station (RRS). Six K fertilizer rates ranging from 0-200 lb K2O/ac were applied preplant and incorporated prior to corn establishment. At the VT growth stage earleaf (leaf immediately subtending the ear) samples were collected, dried, ground and analyzed to determine tissue-K concentration. At maturity corn grain yield was determined using a small plot combine. Preplant soil samples suggested that the PTRS location should be highly responsive to K fertilizer applications, that LMCRS would have little to no response to K fertilization and that SAREC and RRS should not respond to K fertilization. Yield results indicated a significant yield increase from K fertilization at the LMCRS and the PTRS with yield increases of 14 and 83 bu./ac, respectively. Corn earleaf tissue-K concentrations ranged from 0.79% to 2.67 % K and were not statistically different than one another at the SAREC or RRS locations but were influenced by K fertilizer rate at LMCRS and PTRS. The results of this trial suggest that corn response to K fertilization in Arkansas can be significant and that earleaf tissue-K concentrations can be a good indicator of K nutritional status. [ABSTRACT FROM AUTHOR]

Cover crops have the potential to affect soil-test P and K concentrations and the following crop's response to fertilization by influencing soil nutrient cycling. This report summarizes year 6 results of a field trial examining the influence of cover crop and fertilizer-P and -K application on soybean (Glycine max) yield response and soil-test P and K. Research was conducted at 2 locations with soil samples collected from the 0-6-in. depth at cover crop planting in fall 2021 and termination in spring 2022. The fifth annual fertilizer-P and -K treatment applications were made to fertilizer treatment subplots, and soybean was planted following cover crop termination. Cereal rye (Secale cereal) biomass (921-1573 lb/ac) contained the equivalent of 9-15 lb P2O5 and 30-47 lb K2O/ac, while biomass from winter fallow treatments (613-822 lb/ac) contained the equivalent of 5-7 lb P2O5 and 21-29 lb K2O/ac. Dry matter and nutrient accumulation were generally greater with cereal rye than in winter fallow treatments, but fertilizer rate only affected dry matter and nutrient accumulation in 1 trial, where the control resulted in greater accumulation than where K was applied. Cover crop generally did not influence spring soil-test values, but fertilizer rates were consistently reflected in soil-test values following 4 annual applications, with values increasing as rates increased. Fertilizer rate also significantly affected grain yield in one K-rate trial, where 60 lb K2O/ac produced greater soybean yield than treatments where 180 lb K2O/ac or no fertilizer-K were applied. Soybean yield in the other trials was not affected by either the main-effect treatments or their interaction [ABSTRACT FROM AUTHOR]

Recent advancements in soil testing and plant analysis have expanded potassium (K) management in soybean [Glycine max (L.) Merr.] from traditional preplant applications based simply on soil test results to also include profit-maximizing K rates using the economic potash rate calculator and in-season diagnosis of hidden hunger using tissue tests. The objective of this research was to validate K management strategies available for soybean, including traditional preplant applications, a reduced preplant rate according to the economic potash rate calculator, in-season granular fertilizer-K applications, in-season foliar fertilizer-K applications, and split fertilizer-K applications. The research was conducted as a randomized complete block design in 2022 on a Henry silt loam with Very Low soil-test K (STK). The site experienced dry weather and delayed irrigation, resulting in visual K deficiencies 15 days after R1 stage (DAR1), confirmed by trifoliolate leaf samples collected at 15 DAR1. The deficiencies were remediated by irrigation and in-season applications of granular fertilizer K. Regardless of the granular fertilizer-K rate, the addition of a foliar K source applied 2 gal/ac (4.6 lb K2O/ac) at 30 DAR1 did not significantly increase grain yield. Additionally, there was no significant yield difference when the same rate of granular fertilizer-K was applied all preplant compared to one-half preplant and one-half 15 DAR1. However, treatments that received additional in-season granular fertilizer-K applications did numerically outyield those which did not. Finally, the yield-maximizing K rate based on soil test values and the profit- maximizing K rate based on fertilizer and grain prices at the time of planting resulted in similar yields. Therefore, both the traditional yield-maximizing K rate and the reduced profit-maximizing K rate are successful management approaches when applied all at preplant or as split applications to include in-season granular fertilizer-K applications. [ABSTRACT FROM AUTHOR]

In the southeastern United States (U.S.) the impact of nitrogen (N) fertilizer rates on blackberry (Rubus L. subgenus Rubus Watson) yield, growth, and fruit quality have not been evaluated. In 2022, 6 N rates (0, 30, 60, 90, 120, 150 lb N/ac) were applied via fertigation for 15 weeks to one-year-old 'Ouachita' blackberries in Clarksville, Ark. Plant tissue nutrient samples of primocane and floricane petioles and leaves were collected in alternate weeks throughout the growing season. From late May through early July, fruit harvest was conducted twice a week and fruit quality parameters were assessed. Floricane yield and fruit quality were not affected by N fertilization rates. Nitrogen fertilization rate x sampling date interaction was significant for primocane petiole NO3-N concentration, where higher N fertilization rates generally had higher petiole NO3-N concentration than lower rates at several sampling dates. Floricane petiole NO3-N concentration was not impacted by fertilizer-N rate; however, floricane leaf-N concentration was affected, and the 0 lb N/ac rate had the lowest leaf-N concentration but was not significantly different from other treatments except the 120 lb N/ac rate. Our first-year observations agree with previous research findings that blackberry primocanes are impacted more immediately by in-season N application compared to floricanes. This trial will be continued through 2024 to study the impact of N rate on yield, leaf and petiole nutrient concentration, and cane characteristics in perennial blackberry production to identify a recommended N fertilization rate and the associated leaf- and petiole-N sufficiency ranges for blackberry in Arkansas. [ABSTRACT FROM AUTHOR]

The goals of this research project are to determine the dry matter production and yield of two modern cotton cultivars (Deltapine 2038 and NexGen 4936) grown in a furrow-irrigated system that is typical of eastern Arkansas production. The study was replicated at three different site years: in 2021 at the University of Arkansas System Division of Agriculture's Lon Mann Cotton Research Station (LMCRS), and in 2022 at the Lon Mann Cotton Research Station and at the Rohwer Research Station (RRS). The 2021 site year was planted on a Zachary silt loam, while the 2022 Lon Mann Cotton Research Station site year was planted on a Convent silt loam, with the 2022 Rohwer Research Station site year on a Sharkey and Desha silt loam. Treatments included two different rates of fertilizer designed to apply 100% and 125% of current University of Arkansas Soil Test Laboratory fertilizer rate recommendations for nitrogen (N), phosphorus (P), and potassium (K) based on soil test nutrient levels where applicable. Fertilizer treatments were applied preplant and at early squaring. For the 100% rate, the sum of the fertilizer treatments was applied as follows: 2021 LMCRS 70 lb P2O5, 60 lb K2O, 110 lb N; 2022 LMCRS 50 lb P2O5, 95 lb K2O, 110 lb N; 2022 RRS 50 lb P2O5, 40 lb K2O, 110 lb N. The sum of the fertilizer treatments applied for the 125% rate were as follows: 87.5 lb P2O5, 75 lb K2O, 137.5 lb N; 2022 LMCRS 62.5 lb P2O5, 119 lb K2O, 137.5 lb N; 2022 RRS 62.5 lb P2O5, 50 lb K2O, 137.5 lb N. Preliminary results show no difference between either the cultivars or the fertilizer treatments. Total averaged aboveground biomass for the first sample time of the year (10 days after emergence) ranged from 11 lb/ac to 33 lb/ac, while the final sample time (at the start of the defoliation period) ranged from 1594 lb/ac to 2722 lb/ac. Lint yields averaged across cultivars and fertilizer treatments within each site year ranged from 427 to 2249 lb/ac. [ABSTRACT FROM AUTHOR]

Hay production removes vegetative material and its compositional nutrients from the field. If soil nutrients are not replenished with adequate fertilizer rates, nutrient deficiencies will develop, affecting forage yields and quality. Field studies were initiated in 2019 and repeated in 2020, 2021, and 2022 in Batesville and Fayetteville, Ark., to monitor bermudagrass (Cynodon dactylon L.) yield responses to phosphorus (P) and potassium (K) fertilization. Triple superphosphate was applied at rates of 0, 30 (x 1), 60 (30 x 2), 90 (30 x 3), 120 (40 x 3), and 150 (50 x 3) lb P2O5/ac with split applications occurring at green-up, following harvest 1, and following harvests 1 and 2. In K-rate trials, 0, 70 (35 x 2), 150 (50 x 3), 225 (75 x 3), 300 (100 x 3), and 375 (125 x 3) lb K2O/ac were applied as muriate of potash, using previously defined application timings. Soil nutrient availability and bermudagrass yield were assessed in 2022. Soil-test K results at both sites reflect the expected influence of annual fertilizer rate with rates greater than forage K removal increasing soil-test K and vice versa. Fertilizer-K rates affected forage yields, with rates ≥70 and 150 lb K2O/ ac producing maximum yields, which were 72 and 83% greater than the no-fertilizer-K control for the season total forage production at Batesville and Fayetteville, respectively. Soil-test P and K increased with increasing fertilizer-P and -K rates at both locations. In Batesville, P-fertilized plots produced greater forage yield in one of the three harvests (26% yield increase on average) and for season-total forage biomass production (19% yield increase on average). Sub-optimal P and K fertilization result in yield reduction, while high fertilizer rates build up soil-test levels and likely increase nutrient removal. [ABSTRACT FROM AUTHOR]

Recent advancements for in-season potassium (K) management in soybean [Glycine max (L.) Merr.] allows the diagnosis of deficiencies at any point during reproductive growth. However, the rate of fertilizer-K necessary to correct the various levels of deficiency defined by trifoliolate leaf tissue-K concentrations to achieve maximum yield remains unknown, especially as the season progresses. Therefore, our primary objectives were to correlate the trifoliolate leaf-K concentrations with soybean relative grain yield and to calibrate K-fertilizer rates with leaf-K concentrations to create rate recommendations to achieve 95% relative grain yield based on the leaf tissue-K concentrations and days after R1 (DAR1). Treatments included multiple rates of granular muriate of potash at 15 DAR1, 30 DAR1, and 45 DAR1. The research was conducted in 2021 at the University of Arkansas System Division of Agriculture's Lon Mann Cotton Research Station near Marianna, Ark., on silt loam soil. The results indicate that maximal yield can be recovered from a deficient crop at 15 DAR1, a positive yield response can be recovered from a deficient crop at 30 DAR1, and little yield response was observed when fertilizer-K was applied at 45 DAR1. Therefore, in-season applications are effective at maintaining yield if applied during early reproductive growth. However, a delay in application timing may jeopardize yield potential to the degree that correcting it is no longer profitable, especially when the K deficiency is severe. Calibrated K rates based on tissue-K concentrations for a given growth stage will enable producers to correct deficiencies in-season with the appropriate fertilizer rate to maximize yield and profit. [ABSTRACT FROM AUTHOR]

The method to collect a representative sample can be used to accurately diagnose in-season soybean [Glycine max (L.) Merr.] potassium (K) deficiencies rely on the spatial variability of trifoliolate tissue-K concentrations within a field. Five commercial soybean fields were sampled at a 1-acre grid resolution throughout reproductive growth to quantify the trifoliolate tissue-K concentration. The objectives of this study were to identify the potential field variability in soybean leaf tissue-K concentrations in typical Arkansas soybean production systems and develop a sampling protocol for in-season tissue monitoring. No spatial dependencies were found in all fields and sample times, indicating that leaf samples should be collected according to the producer's preferred management strategy instead of specific grid size. One composite sample consisting of at least 18 of the upper-most fully expanded trifoliolate leaves from throughout the delineated management zone is needed to capture the average leaf tissue-K concentration. This sampling protocol, coupled with the newly developed dynamic critical tissue-K concentration curve, will allow producers to effectively monitor soybean for potential hidden hunger and verify K deficiency symptoms in season. [ABSTRACT FROM AUTHOR]

Soybean [Glycine max (L.) Merr.] is widely cultivated on arable soils with limited phosphorus (P) availability which can negatively impact plant yield potential. In this trial, the effects of P deficiency on soybean yield components and seed abortion among node sections were evaluated at two locations. Fertilizer-P rate trials were established in Arkansas at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center (RREC) and in Louisiana at the Macon Ridge Research Station (MRRS). Pioneer 52A43L and 48A60X soybean were planted at RREC and MRRS, respectively. At soybean maturity, 6 plants/plot were collected to evaluate the number of pods and seeds, seed weight, and seed abortion among node sections (2 nodes and 2 internodes/node section, numbered from top to bottom). The maturity group (MG) 4 soybean plants had an average of 21 nodes, with the greatest number of pods and seeds occurring at the intermediate node sections (i.e., 4, 5, 6, and 7), representing 53% of the plant's seed weight. The MG 5 soybean had an average of 16 nodes, with a greater number of pods and seeds in the uppermost node sections (i.e., 1, 2, and 3) and at node section 7 (where branches were frequently observed), representing 72% of the plant's seed weight. Regardless of MG, the no-P control consistently had fewer pods and seeds across node sections than fertilized treatments, resulting in lower seed weight. The mean seed weight of the 0, 40, and 80 lb P2O5/ac treatments was 15, 17, and 23 g/plant, respectively, at RREC and 16, 20, and 21 g/plant at MRRS, respectively. Seed abortion followed a similar trend as soybean yield components, with the highest yielding node sections having the greatest (1.3-2.1%) seed abortion indicating potential competition for P among forming seeds. Sub-optimal P availability affected soybean growth and yield components, highlighting the importance of adequate P fertilization to maximize soybean yield. [ABSTRACT FROM AUTHOR]

Soybean [Glycine max (L.) Merr.] varieties are currently categorized as chloride (Cl) includers, excluders, or a 'mixed' population. A more specific rating system is needed to differentiate between true Cl-excluding varieties and a considerable proportion of varieties that may be mixed, includer/excluder plant populations, or a population of plants having multiple genes that influence Cl uptake. A field-based Cl monitoring program has been developed in conjunction with the Arkansas Soybean Performance Tests to provide a more detailed categorization of Cl tolerance in soybean varieties. A 1 to 5 rating system was developed and implemented on 150 varieties belonging to relative maturity groups 3.5 to 5.9 based on trifoliolate leaf-Cl concentrations included in the University of Arkansas System Division of Agriculture's Rohwer Research Station's location of the 2021 Arkansas Soybean Performance Tests. Trifoliolate-leaf samples were collected when soybean reached the R3 to R4 growth stage. Ratings of 1 (strong excluder), 2, 3 (intermediate), 4, and 5 (strong includer) were assigned to 53, 11, 31, 40, and 15 varieties, respectively. The detailed rating system provides producers with more information regarding the relative Cl tolerance of available soybean varieties. [ABSTRACT FROM AUTHOR]

Potassium (K) is one of the most limiting nutrients for rice (Oryza sativa L.) grown in the direct-seeded, delayed-flood production system common in the U.S. mid-South, and substantial yield reductions can occur when produced on soils low in exchangeable K. The primary objective of our research was to compare yield responses of pure-line and hybrid rice cultivars to K fertilization in trials where various K rates (0, 40, 80, 120, and 160 lb K2O/ac) have been applied annually for several years. Whole, aboveground plant samples were collected at 50% heading in 2020 and Y-leaf samples were collected at the booting growth stage in 2021. With Very Low (<61 ppm) Mehlich-3 K in the control plots, both cultivars responded to K fertilization in 2020 and 2021. Without K fertilization, the pure-line (Diamond) produced 75% and 69% of the maximum yield produced when fertilized with K, while the hybrids produced 64% (RT 7521 FP) and 39% (RT 7321 FP) of maximum yields. For Diamond, the relationship between yield and tissue-K concentration was consistent with critical concentrations suggested by previous research. Grain yields of the hybrid cultivars, however, were lower than expected based on tissue-K concentrations and may indicate a difference in the responsiveness of hybrid and pure-line cultivars to K fertilization. Results of this study suggest that the two hybrids (RT 7521 FP and RT 7321 FP) may be more responsive to K fertilizer than pure-line cultivars, but recent trials have shown another hybrid (RT Gemini 214 CL) to be less responsive than pure-line cultivars. Based on inconsistent responses of hybrid rice to K fertilization and the fact that earlier studies predominantly evaluated pure-line cultivars, it is important to continue studying the response of hybrid rice to K fertilization to build a database for proper interpretation of tissue data and potential adjustments to K fertilizer recommendations. [ABSTRACT FROM AUTHOR]

Seeking to fine-tune nitrogen (N) application, increase economic returns, and decrease environmental N loss, some Arkansas rice (Oryza sativa L.) producers are turning away from blanket N recommendations based on soil texture and cultivar and using the Nitrogen Soil Test for Rice (N-STaR) to determine their field-specific N rates. In 2010, Roberts et al. correlated years of direct steam distillation (DSD) results obtained from 0- to 18-in. soil samples to plot-scale N response trials across the state to develop a field-specific, soil-based N test for Arkansas rice. After extensive small-plot and field-scale validation, N-STaR is available to Arkansas farmers for both silt loam and clay soils. Samples submitted to the N-STaR Soil Testing Lab in 2021 were summarized by county and soil texture, totaled 21 fields across 9 Arkansas counties, and were from 6 clay and 15 silt loam fields. Depressed sample submissions were again observed likely due to another wet spring and lingering effects of the COVID-19 pandemic. The N-STaR N-rate recommendations for samples were compared to the producer's estimated N rate, the 2021 Recommended Nitrogen Rates and Distribution for Rice Cultivars in Arkansas, and the standard Arkansas N-rate recommendation of 150 lb N/ac for silt loam soils and 180 lb N/ac for clay soils. Each comparison was divided into 3 categories based on a decrease in recommendation, no change in recommended N rate, or an increase in the N rate recommendation. In all 3 comparisons, county, but not soil texture, was a significant factor (P < 0.04) in observed decreases in N recommendation strategies demonstrating variations in the soil's ability to supply N across the state. Further stressing the potential N cost savings opportunities, reductions greater than 30 lb N/ac were recommended by N-STaR in 71%, 50%, and 74% of fields in the standard, estimated, and cultivar comparisons, respectively. [ABSTRACT FROM AUTHOR]

The purpose of the cultivar by nitrogen (N) studies is the observation and analysis of the response of new rice (Oryza sativa L.) cultivars to N fertilization in order to determine the optimal N fertilizer rates across an array of soils and environments in which rice is grown in Arkansas. Twelve cultivars were studied in 2021 and included: ARoma17, CLL16, CLL17, CLM04, DG263L, DGL274, Diamond, Jewel, Lynx, ProGold1, ProGold2, and PVL03 at 3 University of Arkansas System Division of Agriculture locations: the Northeast Research and Extension Center (NEREC), the Pine Tree Research Station (PTRS), and the Rice Research and Extension Center (RREC). Seed treatment and seeding rates followed current recommendations and production practices. The grain yields were fair to good for most cultivars studied at the 3 locations in 2021, with lodging ranging from mild to none, with a few plots severely damaged at the PTRS location. The 2021 season was the first year the cultivars DGL274 and PVL03 were included, and the second year for DGL263L, ProGold1, and ProGold2; therefore, there is insufficient data to make an N rate recommendation at this time, and hence the response to N reported here can serve as a guide while more data is collected in subsequent years. Multiple years of results for ARoma17, Diamond, CLL16, CLM04, Jewel, and Lynx provide evidence that these cultivars should have good yields with minimal to no lodging if 150 pounds (lb) of N/ac is applied in a two-way split of 105 lb N/ac at the preflood timing followed by 45 lb N/ac at midseason when grown on silt loam soils and 180 lb N/ac in a two-way split of 135 lb N/ac at the preflood timing followed by 45 lb N/ac applied at midseason when grown on clay soils. [ABSTRACT FROM AUTHOR]

Chloroacetamide herbicides are unavailable for U.S. rice production, likely due to the high risk of injury and variability associated with an early application and activation timings. Environmental conditions can induce severe injury and stand loss at early application timings. Previous research from the University of Arkansas System Division of Agriculture has demonstrated the efficacy of Warrant® [acetochlor, Weed Science Society of America (WSSA) Group 15] to control problematic weeds in rice and a fenclorim seed treatment to reduce rice injury under typical drill-seeded rice-growing conditions but not under cool, saturated conditions. Therefore, two growth chamber experiments were initiated to evaluate rice tolerance with a 12-hour photoperiod, a night temperature of 55 °F, and a 75 °F day temperature. The experiment was designed as a three-factor factorial: with or without fenclorim (2.5 lb/1000 lb of seed), with or without Warrant (2.5 pt/ac) applied delayed-preemergence (DPRE), and a 0.25-in. or 1-in. planting depth. Rice shoots, heights, and visual injury estimates were recorded weekly until termination and biomass collection 30 days after emergence (DAE). The fenclorim seed treatment alone at 7 and 14 DAE caused a reduction in height by delaying emergence relative to the nontreated control, but height recovered by 21 DAE. Warrant alone caused injury ranging from 15% to 60%, while the fenclorim seed treatment reduced injury to rice from Warrant ranging from 0% to 20%. The deeper planting depth also improved tolerance to Warrant alone for all evaluations but did not provide commercial tolerance. Relative to the nontreated control, fenclorim alone improved aboveground rice biomass, while fenclorim and Warrant were comparable to the nontreated control and greater than Warrant alone. After 14 DAE, the fenclorim seed treatment enhanced crop tolerance to Warrant for all evaluations. Based on the results of this study, Warrant applied DPRE at 2.5 pt/ac with a fenclorim seed treatment should provide commercial tolerance in drill-seeded rice. [ABSTRACT FROM AUTHOR]

Three-split N application strategies can help maintain corn yields with smaller total nitrogen (N) fertilizer amounts when applied rates match the crop requirements throughout the growing season. The need for a third application depends on the amount of N provided during the first two applications and how efficiently the applied fertilizer was utilized by the crop. However, current recommendations do not account for early-season N losses and mid-season crop N status, making it difficult to execute optimized N management strategies. Recent research demonstrated that red, green, and blue (RGB) drone imagery can be used to assess mid-season corn N status and fine-tune the current extension guidelines, but adoption of drone imagery is limited because of the need for multi-step image processing. Decision-support system development is needed to make existing research results available to Arkansas corn producers. The objective of this study was to automate drone image processing to assess mid-season corn N status and determine if additional N should be applied to prevent yield loss from N deficiencies. The images used to complete the study objective were collected at the University of Arkansas System Division of Agriculture's Pine Tree Research Station during the 2021 growing season. An algorithm was developed to automate image processing and generate a pre-tassel N fertilizer recommendation from RGB drone images collected between V8 and VT stages. The created algorithm outputs canopy greenness measured using Dark Green Color Index (DGCI), relative grain yield, and N fertilizer recommendation (Yes/No) maps from the collected drone raw images. The next steps toward a functional decision support system are the integration of the created software into a user interface, on-farm validation, and deployment. The created tool will help Arkansas corn producers optimize N input management, which will ultimately increase farm profitability. [ABSTRACT FROM AUTHOR]

Corn grain yield is closely linked to N fertilization practices, but so is producer profitability. Research to verify the capabilities of aerial imagery and dark green color index (DGCI) to successfully identify corn tissue N concentration is ongoing. The ability of DGCI via remote imagery to predict corn response to N fertilization has been further validated in the three site years included in this trial. There is a strong relationship between the N rate and corn DGCI value, with the DGCI properly predicting the sufficient tissue N concentration at the V10 and V13 growth stages. Although the data set is limited, a N rate calibration curve based on the tissue N concentration across corn growth stages (V10-VT) to predict in-season N fertilizer rates to maximize corn grain yield is being developed. The successful development of these calibration curves will allow producers to apply site-specific, in-season N fertilizer rates to ensure that their corn grain yields are being maximized. At the V10 growth stage, significant increases in corn grain yield were seen when tissue N concentrations were less than 3.5%N. However, the yield gains from in-season N applications at V10 ranged from 14-100 bu./ac. Similarly, corn grain yield responses to in-season N applications were observed when tissue N concentrations were less than 3.0% N at both the V13 and VT growth stages. Increased N application rates were required to maximize corn grain yield at lower tissue N concentrations at each growth stage and ranged from 45-150 lb N/ac. Additional data will help to refine these in-season N rate predictions based on tissue N concentrations. [ABSTRACT FROM AUTHOR]

Cover crops may affect soil-test phosphorus (P) and potassium (K) concentrations and the following crop's response to fertilization by influencing soil nutrient cycling. This report summarizes year 5 results of a field trial examining the influence of cover crop and fertilizer-P and -K application on cotton (Gossypium hirsutum) yield response and soil-test P and K. Research was conducted at two locations with soil samples collected from the 0- to 6-in. depth at cover crop planting in fall 2020 and termination in spring 2021. The fourth annual fertilizer-P and -K treatment applications were made to subplot fertilizer treatments, and cotton was planted following cover crop termination. Cereal rye (Secale cereale) biomass (1107 to 3449 lb/ac) contained the equivalent of 8 to 24 lb P2O5 and 30 to 83 lb K2O/ac, but fertilizer rate did not affect biomass content of treatment nutrients in any trial. Soil organic matter was greater with the cover crop, relative to fallow, in 1 of the 4 trials, and the cover crop occasionally resulted in greater soil-test sulfur (S), manganese (Mn), iron (Fe), and copper (Cu), but cover crop generally did not impact spring soil-test values. Fertilizer rates were consistently reflected in soil-test values following three annual applications, with values increasing as rates increased. Fertilizer rate, cover crop, or their interaction had no significant effect on yield in three of the trials, but the interaction between cover crop and fertilizer-K rate did influence cotton yield at one site, where cotton in the winter fallow rotation with no fertilizer-K resulted in lower yield than other cover crop and K rate combinations. [ABSTRACT FROM AUTHOR]

Inadequate soil sampling strategies can lead to errors in sample collection and may affect soil-test results and fertilizer recommendations. Our goal was to examine how soil sampling position on raised beds and prior fertilization influence soil-test results. Two fertilizer-phosphorus (P) treatments (0 and 80 lb P2O5/ac) and fertilizer-potassium (K) treatments (0 and 120 lb K2O/ac) were selected from trials established in 2017 at the University of Arkansas System Division of Agriculture's Lon Mann Cotton Research Station (LMCRS) and Rohwer Research Station (RRS), respectively. Samples were collected from four different positions (base of the bed or furrow, bottom shoulder, upper shoulder, and top of the bed) at the 0- to 4-in. and 0- to 6-in. depths after corn harvest. Mehlich-3 extractable nutrients, pH, and soil organic matter (SOM) were assessed. Soil-test P and K were significantly (P < 0.05) affected by the nutrient-of-interest rate indicating that soil samples are consistently showing the nutrient management practices. Sampling position affected soil pH at the 0- to 6-in. depth, with values fluctuating up to 0.3 pH units. Mehlich-3 magnesium (Mg) and iron (Fe) were affected by sampling position only at one depth or location, while calcium (Ca), copper (Cu), and boron (B) did not change. Soil-test zinc (Zn) and manganese (Mn) were greater at the upper sampling positions, while sulfur (S) and sodium (Na), mobile nutrients, had the opposite behavior. At LMCRS, Mehlich-3 P and K were lower at the base of the beds relative to the top of beds (18% and 20% and 27% and 22% difference for soil-test P and K at the 0- to 4-in. and 0- to 6-in. depths, respectively). The SOM was about 0.2% higher on the top and base of the beds at RRS compared to the bed shoulders. Mehlich-3 K varied about 38 ppm between the bottom shoulder and the top of the bed at RRS, indicating that soil sampling position significantly affects soil-test results and can impact fertilizer-K recommendations. [ABSTRACT FROM AUTHOR]

Soybean [Glycine max (L.)Merr.] varieties are currently categorized as being chloride (Cl) includers, excluders, or a 'mixed' population. A more specific rating system is needed to differentiate between true Cl excluding varieties and a considerable proportion of varieties that may be mixed includer/excluder plant populations or a population of plants having multiple genes that influence Cl uptake. A field-based Cl monitoring program has been developed in conjunction with the Arkansas Soybean Performance Tests to provide a more detailed categorization of Cl tolerance in soybean varieties. A 1 to 5 rating system was developed and implemented on 181 varieties belonging to relative maturity groups 3.5 to 5.9 based on trifoliolate leaf-Cl concentrations included in the University of Arkansas System Division of Agriculture’s Rohwer Research Station location of the 2020 Arkansas Soybean Performance Tests. Trifoliolate-leaf samples were collected when soybean reached the R3 to R4 growth stage. Ratings of 1 (strong excluder), 2, 3 (intermediate), 4, and 5 (strong includer) were assigned to 55, 14, 46, 23, and 43 varieties, respectively. The detailed rating system provides producers with more information regarding the relative Cl tolerance of available soybean varieties [ABSTRACT FROM AUTHOR]

Volatility reducing agents (VRAs) are now required for all in-crop dicamba applications. The University of Arkansas System Division of Agriculture has continued to evaluate potassium tetraborate tetrahydrate (potassium borate) as a VRA and boron (B) nutritional. A greenhouse and field experiment were conducted in Fayetteville, Ark., in 2021, to ensure the crop safety of postemergence mixtures containing dicamba and potassium borate. For each experiment, potassium borate was applied at six rates (0, 0.1, 0.2, 0.3, 0.4, and 0.5 lb B/ac) alone or in combination with the XtendiMax formulation of dicamba at 0.5 lb ae/ac. Additionally, a mixture of XtendiMax, Roundup PowerMax, and Dual II Magnum, as well as Liberty, Roundup PowerMax, and Dual II Magnum at labeled field use rates, were used as a comparison for cotton injury. Treatments were applied in the greenhouse on 1-to 2-leaf cotton and at the pinhead square growth stage in the field. At 3 days after treatment (DAT) for the greenhouse experiment, only three-way mixtures caused injury, showing that potassium borate is not injurious to cotton when applied alone or with dicamba. Biomass collected 28 DAT also reflected that treatments containing potassium borate were comparable to those that were not mixed with the additive. In the field, injury to cotton was not observed for any treatment, possibly due to a later growth stage at application. Based on these findings, it is unlikely that potassium borate would cause unacceptable levels of injury to cotton if utilized in the Xtend system. [ABSTRACT FROM AUTHOR]

Labeled applications of the N, N-bis (3-aminopropyl) methylamine (BAPMA) salt of dicamba (Engenia™) and diglycolamine salt of dicamba with VaporGrip™ (XtendiMax™) have resulted in a record number of off-target complaints following their introduction in 2017 for use as preemergence and postemergence control of broadleaf weeds in Xtend cotton (Gossypium hirsutum L.) and soybean [Glycine max (L.) Merr] systems. In efforts to reduce dicamba volatility, the University of Arkansas System Division of Agriculture has pursued potassium tetraborate tetrahydrate (potassium borate) as a volatility-reducing agent. Two low-tunnel volatility trials were conducted at the University of Arkansas System Division of Agriculture's Milo J. Shult Agricultural Research and Extension Center in Fayetteville, Arkansas, in 2020 to determine the optimal rate of potassium borate to function as a volatility-reducing agent and a nutritional additive. The diglycolamine (DGA) salt of dicamba plus the potassium salt of glyphosate was applied in a mixture with 0, 0.03, 0.07, 0.13, 0.27, and 0.53 lb/ac of boron (B) in the form of potassium borate. Each treatment was applied four times to two moist flats that were placed under each tunnel and removed 48 hours after application. Regarding the three evaluated qualitative parameters (maximum soybean injury, average injury, and distance traveled), dicamba volatility was significantly reduced as potassium borate rate increased. At B rates of 0.13 to 0.53 lb B/ac, dicamba movement was reduced by 9 to 11 ft, respectively, compared to DGA dicamba plus glyphosate. High-volume air sampler data followed similar trends to qualitative assessments, with the least amount of total dicamba detected at 0.27 and 0.53 lb B/ac. As the potassium borate rate increased, the variability in detectable dicamba was likewise reduced. Overall, the addition of potassium borate to dicamba can effectively reduce dicamba volatility at rates sufficient to alleviate potential B deficiencies. [ABSTRACT FROM AUTHOR]

Soil organic matter (SOM) and clay contents are key properties influencing soil nutrient availability but are time-consuming laboratory procedures. A cost-effective alternative is the estimation of SOM and clay contents using information from routine soil-test data. We evaluated the prediction of SOM and clay content using Mehlich-3 extractable nutrients in Arkansas soils. Soil clay content was determined by the hydrometer method and SOM by loss on ignition. Two data sets were used to predict clay (n = 409) and SOM (n = 600) using linear correlation and linear and multiple regression. The estimated cation exchange capacity (ECEC), sum of bases, and Mehlich-3 Mg, Ca, K and Na were highly correlated (r > 0.72) with clay content and resulted in significant (P < 0.0001) clay prediction models (r² = 0.84, 0.79, 0.82, 0.73, 0.55, and 0.52, respectively). Mehlich-3 Na and K had the lowest r² values while prediction accuracy increased when using Ca, the sum of bases, Mg, and ECEC. The clay prediction with ECEC showed the highest r² (0.84) and lowest root mean square error (RMSE) (5.61) values but slightly underestimated the clay content of clayey-textured soils. The strength of the correlation between Mehlich-3 extractable nutrients and SOM was poor, with Mehlich-3 P being the single variable with the highest correlation (r = 0.51, P < 0.0001). The SOM prediction with Mehlich-3 P was low (r² = 0.26, RMSE = 1.11), but the prediction accuracy increased when Mehlich-3 P was combined with ECEC (r² = 0.37, RMSE = 1.02). This behavior highlights the complexity of the soil organic phase and suggests that the consideration of more variables may improve the prediction. Mehlich-3 extractable nutrients can be used to estimate clay content of Arkansas soils, but further research is needed to validate clay prediction models and improve SOM prediction. [ABSTRACT FROM AUTHOR]

Cover crops may affect soil-test P and K concentrations and the following crop's response to fertilization by influencing soil nutrient cycling. This report summarizes year 4 results of a field trial examining the influence of cover crop and fertilizer-P and -K rates on corn (Zea mays) yield and soil-test P and K. Research was conducted at two locations with soil samples collected from the 0-6 inch depth at cover crop planting in fall 2019 and termination in spring 2020. In 2020, the third year of applications of annual fertilizer-P and -K were made to subplot fertilizer treatments, and corn was planted following cover crop termination. Cereal rye (Secale cereal) biomass (1885 to 7359 lb/acre) contained the equivalent of 14 to 39 lb P2O5 and 48 to 151 lb K2O/acre, but fertilizer rate did not affect biomass content of treatment nutrients in any trial. Cover crop increased soil organic matter, relative to fallow, in 2 of the 4 trials but generally did not impact spring soil-test values. Fertilizer rates were consistently reflected in soil-test values following two annual applications, with values increasing as rates increased. The main effect of fertilizer rate had no significant effect on grain yield in any of the 4 trials, but the interaction between cover crop and fertilizer-K rate did influence corn yield at one site. The cereal rye cover crop reduced corn yield in the P and K trials by up to 19% at one location but did not affect corn yield at the other location. [ABSTRACT FROM AUTHOR]

Correct soil sampling is critical for accurate lime and fertilizer recommendations. Soil samples are frequently submitted to the laboratory in very wet or dry conditions reflecting that field conditions sometimes influence sampling procedures and may compromise the integrity of the sample. This study evaluated the effects of soil moisture at sampling time, soil sample depth, and soil sampling probe on soil core uniformity. Soil samples were collected from the 0- to 4-in. and 0- to 6-in. depths of three silt loam soils, including the Captina, Calhoun, and Dewitt series. The effect of soil probe (AMS and Cone) was evaluated in the Captina and Calhoun soils. Six or seven moisture treatments were imposed that encompassed the range from the original dry soil (15.0% to 18.5% moisture) to field capacity and saturation. Core hole depth and oven-dry weight were measured at all three locations. Soil moisture and soil probe alone or their interaction influenced soil core uniformity. The effect of soil moisture on core hole depth and weight was most pronounced for the 0- to 6-in. sampling depth. Sampling soils that were very dry or saturated with water compromised the collection of uniform soil cores. We anticipate that the differences in core depth and weight will also influence soil-test results, especially in fields of cropping systems with nutrient stratification. The results highlight the need to avoid collecting samples when field conditions are too wet or too dry. [ABSTRACT FROM AUTHOR]

Cotton (Gossypium hirsutum L.) cultivars grown in the Arkansas Delta have undergone tremendous genetic and cultural management changes in recent years, which has led to the need to re-evaluate the biomass, nutrient accumulation, and nutrient requirements in these modern cultivars. Our research aims to determine the dry matter production and biomass accumulation of two modern cotton cultivars (Deltapine 2038 and NexGen 4936) produced in a furrow-irrigated system. Treatments included two rates of fertilizer designed to apply 100% and 125% of the current University of Arkansas System Division of Agriculture's Soil Test Laboratory fertilizer rate recommendations for nitrogen (N), phosphorus (P), and potassium (K). Fertilizer treatments were applied preplant ([100% = 36 lb N/ac, 70 lb P2O5/ac, 60 lb K2O/ac] and [125% = 45 lb N/ac, 88 P2O5/ac, 75 lb K2O/ac]) and at early squaring (74 lb N/ac and 93 lb N/ac for the 100% and 125%, respectively). The research was conducted in 2021 at the Lon Mann Cotton Research Station on a Memphis silt loam. Preliminary results show no difference in biomass accumulation between either the cultivars or fertilizer treatments. The research will be repeated in 2022 on silt loam and clay soils to determine if this trend is consistent across environments. [ABSTRACT FROM AUTHOR]

The N,N-bis(3-aminopropyl)methylamine (BAPMA) salt of dicamba (Engenia®) and diglycolamine (DGA) salt of dicamba with VaporGrip™ (XtendiMax™) are labeled for preemergence and postemergence control of broadleaf weeds in Xtend™ cotton (Gossypium hirsutum L.) and soybean [Glycine max (L.) Merr] systems. Dicamba applications to cotton and soybean have resulted in a record number of complaints regarding the off-target movement of the herbicide since the initial introduction in 2017. To counteract dicamba volatility, the University of Arkansas System Division of Agriculture has pursued potassium tetraborate tetrahydrate (potassium borate) as a volatilityreducing tank additive following the success of preliminary volatility experiments conducted in 2019. To investigate the impact of this additive on weed control in an Xtend-based system, an experiment was conducted in 2020 to evaluate the efficacy of dicamba when mixed with the additive on Palmer amaranth (Amaranthus palmeri S. Watson) and johnsongrass (Sorghum halepense L. Pers). Two low-volatile dicamba formulations (XtendiMax and Engenia) plus the potassium salt of glyphosate (Roundup PowerMax®) were combined with potassium borate at 0, 0.015, 0.3, and 0.1 M concentrations. No concentration of potassium borate compromised broadleaf or grass weed control when added to either formulation of dicamba, although some numerical decreases were observed. Overall, the addition of potassium borate to dicamba has great potential in reducing the off-target movement of dicamba without sacrificing efficacy on key weed species. [ABSTRACT FROM AUTHOR]

Seeking to fine-tune nitrogen (N) application, increase economic returns, and decrease environmental N loss, some Arkansas rice (Oryza sativa L.) producers are turning away from blanket N recommendations based on soil texture and cultivar and using Nitrogen Soil Test for Rice (N-STaR) to determine their field-specific N rates. In 2009, Roberts et al. correlated several years of direct steam distillation (DSD) results obtained from 18-in. soil samples to plot-scale N response trials across the state and developed a field-specific, soil-based N test for Arkansas rice. After extensive small-plot and fieldscale validation, N-STaR is available to Arkansas farmers for both silt loam and clay soils (using a 12-in. soil sample). To summarize the samples submitted to the N-STaR Soil Testing Lab in 2019, samples were categorized by county and soil texture. Samples were received from 61 fields across 16 Arkansas counties. Total samples received were from 8 clay and 53 silt loam fields. The N-STaR N-rate recommendations for these samples were compared to the producer's estimated N rate, the 2019 Recommended Nitrogen Rates and Distribution for Rice Cultivars in Arkansas, and the standard Arkansas N-rate recommendation of 150 lb N/ac for silt loam soils and 180 lb N/ac for clay soils. Each comparison was divided into 3 categories based on a decrease in recommendation, no change in recommended N rate, or an increase in the N rate recommendation. No significant differences were found when N-STaR recommended an increased N rate. Soil texture was a significant factor (P < 0.0001) when N-STaR proposed a decrease in the season total N rate when compared to the standard N rate. County was significant (P < 0.05) for decreased N rates when compared to the standard and producer's estimated comparisons suggesting that some areas of the state and specific soil series may have higher residual-N not accounted for by other current N-rate recommendation strategies. [ABSTRACT FROM AUTHOR]

Farmers often apply 'starter' fertilizer-nitrogen (N) shortly after rice (Oryza sativa L.) emergence to stimulate seedling growth. The objective of this research was to examine the effects of starter-N source and preflood-N rate on the grain yield of rice grown on clayey-textured soils. Research was conducted at the University of Arkansas System Division of Agriculture's Rohwer Research Station (RRS), Rohwer, Arkansas and the Delta Research and Extension Center (DREC) in Mississippi. Four starter-N sources including no-N (NONE), ammonium sulfate (AMS), diammonium phosphate (DAP), and urea treated with N-(n-butyl) thiophosphoric triamide (UREA) were applied at 21 lb N/ac at the 2-leaf stage in combination with 5 preflood-N rates (0 to 200 lb N/ac) applied to 5-leaf rice. Rice cultivars CL153 and RiceTec Gemini 214 CL (Gemini) were grown at the RRS, and CL153 and RiceTec CLXL745 (CLXL745) were grown at the DREC. Regardless of N source, starter-N increased canopy cover of CL153 and Gemini up to 5 weeks after starter-N was applied by 2% to 87% compared to rice that received no starter-N. The fertilizer-N recovery efficiency of rice receiving no starter-N ranged from 69% to 79% at RRS and 51% to 60% at DREC. At RRS, grain yields of CL153 increased significantly with each increase in preflood-N rate, averaged across starter-N sources, with maximum yields of 174 bu./ac for rice fertilized with 200 lb preflood-N/ac. Gemini grain yields showed an interaction among starter-N source and preflood-N rates where starter-N applications of AMS and UREA tended to increase grain yields compared to no starter-N at suboptimal preflood-N rates. At DREC, CL153 and RT CLXL745 grain yields increased significantly with each increase in preflood-N rate with a maximum yield of 178 bu./ac (CL153) and 237 bu./ac (RT CLXL745) for rice fertilized with 200 lb preflood-N/ac. Based on the 4 trials, starter-N applied as AMS or UREA tended to increase early season canopy closure and grain yield of rice grown on clayey soils, especially for suboptimal preflood-N rates. [ABSTRACT FROM AUTHOR]

Water management regimes influence greenhouse gas emissions in rice (Oryza sativa L.) production. The objective of this study was to quantify methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) under direct-seeded conditions in the greenhouse to evaluate the effects of water regime on fluxes and growing-season-long emissions. Research was conducted during 2019 using a hybrid rice cultivar (RT 7311 CL) grown in a DeWitt silt loam (Albaqualf). Six plastic tubs, filled with soil and manually seeded, were arranged in a completely random design in the greenhouse with two replications of three water regime treatments: i) flooded, ii) saturated, but not flooded, and iii) moist soil (i.e., slightly below saturation). On 13 different dates, gas sampling occurred. Methane, N2O, and CO2 fluxes differed among water regimes over time (P < 0.05). End-of-season aboveground rice dry matter differed among water regimes (P < 0.05). Aboveground dry matter was more than two times greater from the flooded-soil than from the non-flooded treatments. Root dry matter was unaffected by water regime due to large measured variability. Season-long CH4 and CO2 emissions differed among water regimes (P < 0.05) and were larger from the flooded-soil condition than from the moist-soil and nearly saturated conditions, while season-long N2O emissions were unaffected by water regime. Characterizing the effects of soil moisture content could improve the understanding of the dynamics that regulate production of greenhouse gases in rice production systems. [ABSTRACT FROM AUTHOR]

The objective of the cultivar × nitrogen (N) studies is to determine the optimal N fertilizer rates for new rice (Oryza sativa L.) cultivars across the array of soils and environments encountered in the Arkansas rice-growing region. The eleven cultivars studied in 2019 were: ARoma 17, CLJ01, CLL15, CLL16, CLM04, Jewel, Lynx, PVL01, PVL02, the experimental line ARX7-1084, and Diamond. Seed treatment and seeding rates were determined following current recommendations and production practices. The grain yields were good to excellent for all the cultivars studied at the three locations in 2019: University of Arkansas System Division of Agriculture's Northeast Research and Extension Center (NEREC), Keiser, Arkansas, on a Sharkey Clay (Vertic Haplaquepts) soil; the Pine Tree Research Station (PTRS) near Colt, Arkansas, on a Calloway silt loam (Glossaquic Fragiudalfs) soil series; and the Rice Research and Extension Center (RREC), near Stuttgart, Arkansas, on a Dewitt silt loam (Typic Albaqualfs) soil. This is the first year the cultivars ARoma 17, CLJ01, CLL15, CLL16, CLM04, Jewel, Lynx, and PVL02 are included in the cultivar × N rate study; therefore there is insufficient data to make a recommendation at this time. Multiple years of results for PVL01 indicate this cultivar should have good yields with minimal to no lodging if 150 pounds (lb) of N/ac is applied in a two-way split of 105 lb N/ac at the preflood timing followed by 45 lb N/ac at midseason when grown on silt loam soils and 180 lb N/ac in a two way split of 135 lb N/ac at the preflood timing followed by 45 lb N/ac applied at midseason when grown on clay soils. [ABSTRACT FROM AUTHOR]

Furrow-irrigated rice (FIR) (Oryza sativa L.) acreage has steadily increased over the past several growing seasons, and it appears this trend will continue. One issue that is likely to be common in FIR is the possible loss of nitrogen (N) via nitrification-denitrification sequences in the alternating aerobic-anaerobic soil conditions. Trials were established in 2019 at 1 commercial site, Almyra, on a Dewitt silt loam and at 2 University of Arkansas System Division of Agriculture research stations, the Pine Tree Research Station (PTRS) on a Calloway silt loam and the Rice Research and Extension Center (RREC) on a Dewitt silt loam. Factors included location within the field (top and bottom), N source [urea + n-butyl thiophosphoric triamide (NBPT) and SuperU®], and N management regime, of which there were six variations of rate and time combinations. The use of SuperU® increased yield at the PTRS by 17.7 bu./ac at the bottom of the field compared to urea + NBPT, but did not affect yield at the top of the field nor did it have an effect at the other two sites. The major yield discrepancy was at Almyra, where the bottom of the field yielded 57.6 bu./ac greater than the top of the field, most likely due to drought stress at the top of the field. Nitrogen source did not affect head rice yield or total white rice yield at any of the locations. Considering current pricing and trial results, urea + NBPT appears to be the optimum N source for furrowirrigated rice production in Arkansas. [ABSTRACT FROM AUTHOR]

Rice (Oryza sativa L.) acres utilizing alternative irrigation practices have increased tremendously over the past several growing seasons, mainly in the form of furrow-irrigated rice (FIR) due in part to its water saving capability and reduced labor requirement. Because this is a new concept for many producers, there is little guidance on producing rice under the FIR and alternate wetting and drying (AWD) systems. A study was initiated in 2018 and continued in 2019 to define the optimum soil moisture threshold for rice produced using furrow-irrigation and AWD production strategies. Large, production-scale trials in both FIR and AWD were conducted at the University of Arkansas System Division of Agriculture's Pine Tree Research Station (PTRS) near Colt, Arkansas on a Calloway silt loam and the Northeast Research and Extension Center (NEREC) near Keiser, Arkansas on a Sharkey silty clay. The timing of irrigation within the FIR treatments was determined based on a soil moisture threshold of either -15, -30, or -45 centibars (cb), while AWD trials utilized the same thresholds but only between 3 weeks after the initial flood establishment and 50% heading. Data from the 2019 growing season suggested that the irrigation threshold did not have a significant influence on rice grain yield under FIR production. However, the control performed better than all FIR at the PTRS, while all FIR performed better than the control at the NEREC. Alternate wetting and drying rice performed equally to the control at the PTRS, but AWD rice with a -15 or -30 cb threshold actually performed better than the -45 cb threshold and the control at the NEREC. The -45 cb threshold also resulted in significant irrigation water savings--17.2% and 34.1% savings in FIR and 17.7% and 73.0% savings in AWD when compared to the control at the PTRS and the NEREC, respectively. These studies suggest that utilizing a -45 cb threshold under alternative irrigation strategies allows for significant water savings while maintaining rice yield and quality. [ABSTRACT FROM AUTHOR]

Hybrid rice (Oryza sativa L.) has accounted for nearly 50% of Arkansas' total rice acres harvested during the last decade. Previous research conducted on the current recommendation of applying 30 lb nitrogen (N)/ac to hybrid rice cultivars at the late-boot growth stage indicated an increase in both grain and milling yields. The conclusions from previous research suggested that significant increases in grain and milling yields were due to the addition of a late-season N application; however, more research is needed to determine if the late-season N application is necessary due to inconsistent results. A study was initiated to examine grain and milling yields on hybrid rice when implementing a late-season N application across varying preflood N application rates. The RiceTec (RT) hybrids, RT Gemini 214 CL and RT XP753, were used in this study and are the most common hybrid rice cultivars grown in Arkansas. These two cultivars were planted at the University of Arkansas System Division of Agriculture's Pine Tree Research Station (PTRS) near Colt, Arkansas, on a silt loam soil, and the Rohwer Research Station (RRS) near Rohwer, Arkansas on a clay soil. Results indicate that there is a positive impact from the late-season N application on both grain and milling yields from both cultivars at each of the locations. When lateseason N was applied, there was an increase of 11 to 16 bu./ac across the two locations. Also, the late-season N application resulted in a significant increase in head rice milling yield from 1% to 5% across both locations but showed no significant difference in total rice. When observing head rice yields from various plant components (main stem vs. tillers) within the same plots, there is a significant increase in head rice yield when applying the late-season N that is equal across both main steams and tillers. It is apparent that the late-season N application results in significant increases in both grain and milling yields. Further research is needed to better understand the relationship contributing to increased grain yield and milling yields when late-season N is applied to hybrid rice and define the physiological mechanism for this response and help predict when and where it will occur. [ABSTRACT FROM AUTHOR]

In Arkansas, nitrogen (N) recommendations for corn (Zea mays L.) are based on soil texture and yield goal. Producers apply the N in a two- or three-way split to decrease N losses from mechanisms such as volatilization, leaching, and denitrification. These split application strategies allow for an in-season assessment of corn N status before applying fertilizer, ultimately narrowing the gap between fertilizer-N supply and crop demand. Several remote sensing techniques have been employed as tools for N status assessment in corn. One assessment tool is the Dark Green Color Index (DGCI) that measures the intensity of greenness, which has been correlated with leaf-N concentration (LN) and relative grain yield (RGY). The present research evaluated aerial DGCI measurements as a tool for crop N assessment and as a guideline for pre-tassel N fertilization. Data from eight site-years utilized 14 N fertilization regimes with the season-total N rates ranging from 0 to 225 lb N/acre and with split-applications at preplant, V10, V12, and VT timings. At the growth stages V10, V12, and VT, leaf samples were collected for TN analysis and red, green and blue (RGB) digital images were captured from the field at 100 ft above ground level with an unmanned aerial system (UAS). Images were processed to create an orthomosaic and data were extracted from orthomosaics to measure DGCI. A multiple regression using DGCI of individual plots and the DGCI value of the high reference N treatment predicted RGY (R2 = 0.71). Likewise, LN and reference DGCI predicted DGCI values well (R2 = 0.89). These results indicate that DGCI is a simple and effective tool for assessing the need for additional N fertilizer applied to corn in-season. [ABSTRACT FROM AUTHOR]