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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]

Potassium (K) loss by runoff has become a concern for cotton (Gossypium hirsutum L.) production in Arkansas. We investigated the transport of K by runoff in rainfed and irrigated cotton production systems and evaluated the contribution of conservation tillage practices in mitigating K losses by runoff. Research was conducted in 2023 on a cotton trial established in 2018 at the University of Arkansas System Division of Agriculture's Judd Hill Cooperative Research Station, Trumann, Ark. The experiment is a 2 x 2 factorial (two irrigation methods x two soil tillage systems). Irrigation treatments are furrow irrigated and rainfed. Tillage systems are conservation with cereal rye (Secale cereal L.) winter cover crop and conventional tillage. Soil-test K, cereal rye biomass production, and K uptake were evaluated in Spring 2023, while runoff water K concentration was analyzed from June 2022 to August 2023. Cereal rye biomass was 562 and 1043 lb/ac and contained 14.6 and 29.1 lb K2O/ac in irrigated and rainfed treatments, respectively. Soil tillage impacted soil-test K among sampling depths, with Mehlich-3 K being 37 ppm greater in the conservation system at the 0-2-inch depth and 19 and 22% lower in the 0-4 and 4-6-inch depths, respectively, compared to conventional tillage. Runoff water K concentration was not affected by the irrigation system but was significantly (P < 0.10) affected by soil tillage. The soil conservation system showed 1.5 times greater average K concentration across runoff events (rain and irrigation) than the conventional tillage system, which might be associated with the higher soil-test K near the soil surface in conservation tillage and the dilution of K concentration in runoff water for the conventional system. More conclusive results will be obtained as this trial continues along with the summary of total water loss and cumulative K loss from each production system. [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]

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]

The fate of field-applied nutrients warrants careful consideration regarding agricultural production. Fertilizer-derived nutrients can be subjected to substantial losses through surface runoff events in certain climactic conditions. Although research of nitrogen (N) and phosphorus (P) in surface runoff has been highly documented, the studies of secondary nutrients such as sulfur (as sulfate, SO42-) surface runoff have not been as extensive. In May 2022, the Arkansas Discovery Farms Program (ADF) initiated a study measuring sulfate-sulfur (SO4-S) concentrations and land area losses collected in edge-of-field runoff samples from 8 ADF research sites. The ADF locations are generally categorized as 6 row crop and 2 forage production systems. Mean SO4-S concentrations in runoff ranged from 2.1 milligrams per liter (mg/L) in Stuttgart (rice and soybeans) to 18.9 mg/L in Dumas (cotton), while sulfate losses ranged from 0.1 pounds per acre (lb/ac) at Wedington and Stuttgart to 1.7 lb/ac in Light. Dumas, Light, and Elkins farms had significantly greater SO4-S concentrations in edge-of-field runoff samples than Delaplaine, Newport, Stuttgart, and Wedington. Interpreting SO4-S losses by mass losses per unit area (concentration*runoff volume/land area), Light had significantly greater losses than Newport, Delaplaine, Stuttgart, and Wedington. In addition, variations in significant differences were observed for the other ADF sites in terms of SO4-S concentrations and land area runoff losses. These observations highlight diverse production and nutrient management strategies among the 8 ADF research locations. Statistical analysis of total runoff per acre showed Newport being significantly higher than Cherry Valley, Dumas, Elkins, and Wedington. Complementary soil sampling events and calculations of SO4-S losses will supplement awareness of SO4-S runoff and soil-based dynamics. [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]

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]

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]

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]

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]

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]

As the level of soil-test K (STK) increases, potash (K) fertilizer recommendations for corn (Zea mays) decrease until a point where STK is high enough that no supplemental potash fertilizer is recommended. Current recommendations are primarily based on observed agronomic yield response trials and STK. Corn price and fertilizer cost/cost of application can be considered in addition to these agronomic values to develop a profit-maximizing fertilizer use rate recommendation. This analysis compares current categorical, uniform rate recommendations determined by STK as well as current variable rate technology (VRT) potash fertilizer rate recommendations to rates that maximize producer profit. Using a ten-year analysis of corn price and fertilizer cost, we conclude that both current application recommendations (categorical and VRT) may be revised to lower potash fertilizer application rates. Producers are encouraged to use a decision tool to offer rate recommendations that consider both agronomic and economic field-specific parameters. [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]

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 and 2021 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 (×1), 60 (30×2), 90 (30×3), 120 (40×3), and 150 (50×3) lb P2O5/ac with split applications occurring at green-up (×1), following harvest 1 (×2), and following harvests 1 and 2 (×3). In K-rate trials, 0, 70 (35×2), 150 (50×3), 225 (75×3), 300 (100×3), and 375 (125×3) lb K2O/ac were applied as muriate of potash, using previously defined application timings. Soil nutrient availability and bermudagrass yield and nutrient concentrations were assessed in 2021. 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 rate affected forage yields with rates ≥150 lb K2O/ac producing maximum yields, which were 80% and 96% greater than the no-fertilizer-K control at Fayetteville and Batesville, respectively. Tissue-K concentrations and K removal increased with each fertilizer-K rate increase. Soil-test P increased with P fertilization in Fayetteville, resulting in greater tissue-P concentrations and P removal, but without a significant effect on bermudagrass yield (average yield of 6674 lb/ac/year). In Batesville, P-fertilized plots produced greater forage yield and tissue-P concentrations in one of the three harvests and for season-total P removal. Sub-optimal P and K fertilization results in yield reduction, while high fertilizer rates build up soil-test levels and increase nutrient removal. [ABSTRACT FROM AUTHOR]

Nutrient management is an essential function of successful agricultural production. Field-applied nutrient loss via surface runoff poses challenges to Arkansas farmers and producers. While the majority of research regarding nutrient runoff loss has mainly dealt with nitrogen (N) and phosphorus (P), runoff loss of nutrients such as sulfur (as sulfate, SO42-) are studied to a lesser extent. In May 2022, the Arkansas Discovery Farms Program (ADF) began research quantifying the concentrations and land area losses of sulfate-sulfur (SO4-S) collected in edge-of-field runoff samples from 8 ADF locations. These ADF sites are composed of 6 row crop and 2 forage operations. Statistical analysis of preliminary data comparing collected edge-of-field runoff samples by ADF location showed that the row crop systems in Light and Dumas, Arkansas had significantly higher SO4-S concentrations in edge-of-field runoff samples than all other ADF sites. In terms of SO4-S losses by land area, Newport, Dumas, Light, and Elkins had significantly higher losses than the other ADF sites. The remaining ADF locations varied in their respective significant differences as well, underscoring the effect of each individual farm's approaches to crop and nutrient management. Statistical analysis of total runoff per acre showed Newport being significantly higher than all other ADF locations. The addition of non-growing season edge-of-field runoff data generated from annual soil sampling events and evaluations of field-applied SO4-S fertilizer efficiency will provide a clearer view of SO4-S runoff aspects and its activity in the soil under a variety of cropping systems. [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]

Hay production removes vegetative material and the compositional nutrients of that material from a site. If soil nutrients are not replenished with soil amendments or fertilizers, nutrient deficiencies will develop, affecting forage yield and quality. Field studies were conducted to monitor the effects of varying rates of phosphorus (P) and potassium (K) fertilizers on bermudagrass (Cynodon dactylon L.) productivity. Two pairs of P-rate and K-rate trials were initiated in separate fields in Batesville, Ark., and in Fayetteville, Ark. Each experiment had a randomized complete block design with five replicates. In P-rate trials, triple superphosphate was applied at rates of 0, 30 (× 1), 60 (30 × 2), 90 (30 × 3), 120 (40 × 3), and 150 (50 × 3) lb P2O5/acre with split applications applied at green-up (× 1), following harvest 1 (× 2), and following harvests 1 and 2 (× 3). In the K-rate trial, muriate of potash was applied at rates of 0, 70 (35 × 2), 150 (50 × 3), 225 (75 × 3), 300 (100 × 3), and 375 (125 × 3) lb K2O/acre, using previously defined timings of applications. All trials were initiated in 2019 and repeated in 2020, except for the P-rate trial in Batesville. Hay yield and forage nutrients concentration were evaluated at each harvest. There was no significant effect of fertilizer-P and -K rates on forage yield at either location, suggesting sufficient soil-P and -K availability to maintain yields in all treatments. Soiltest K was affected by fertilizer-K rate and reflected the total K removal in plant biomass while soil-test P changed at Fayetteville, but no differences in P removal occurred. Suboptimal P and K fertilization may result in yield reductions in subsequent growing seasons as soil-P and -K levels are depleted. It is critical to continue evaluating P and K fertilization rate's effect on yields, nutrient removal, and soil nutrient levels to fine-tune P and K recommendations for bermudagrass hay production. [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]