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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]

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]

Yellow nutsedge (Cyperus esculentus) has the capability of competing with cotton throughout the season, causing a yield reduction of 34%. Envoke gives another option in a cotton production system for controlling problematic weeds such as morningglories and yellow nutsedge. Two studies were conducted in 2022 at Tillar, Ark., in a Herbert silt loam soil with the objective of evaluating Envoke rates and tank mixtures when applied postemergence in Enlist and XtendFlex cotton systems. Trials were arranged in a randomized complete block design with four replications. Herbicides used included individual and combinations of Envoke at 0.075 and 0.125 oz/ac, Enlist One at 32 oz/ac, Engenia at 12.8 oz/ac, Roundup PowerMax 3 at 30 oz/ac, Dual Magnum at 16 oz/ac, and Warrant at 64 oz/ac. All data were analyzed using JMP Pro 17 and subjected to analysis of variance using Tukey's honestly significant difference (a = 0.05). The higher rate of Envoke generally resulted in greater injury, especially when combined with Roundup PowerMax and either Enlist One or Engenia at 21 days after treatment (DAT) compared to the lower rate. No control of Palmer amaranth was observed by Envoke due to it being an acetolactate synthase-resistant population. Palmer amaranth control was not decreased due to the tank mixture of Envoke with either Enlist One or Engenia. The use of Envoke in a tank mixture with either Enlist One or Engenia will provide an alternative to yellow nutsedge control in both Enlist and XtendFlex systems. [ABSTRACT FROM AUTHOR]

The rice cultivar by seeding rate study objective is to evaluate the response of new cultivars to selected seeding rates to determine the most effective seeding rate throughout the diversity of the rice-growing environmental conditions in Arkansas. These cultivars were seeded at 3 University of Arkansas System Division of Agriculture locations in Arkansas: the Rice Research and Extension Center (Stuttgart; silt loam soil), the Pine Tree Research Station (Colt; silt loam soil), and the Northeast Research and Extension Center (Keiser, clay soil). The pure-line varieties evaluated in 2022 were Ozark, Taurus, PVL03, DG263L, and RTv7231 MA seeded at 5, 10, 20, 30, and 40 seed/ft2; and the hybrids evaluated were RT 7321 FP, RT 7331 MA, RT 7421 FP, and RT 7302 seeded at 4, 6, 8, 10, and 12 seed/ft2. Results suggest that seeding rates lower than currently recommended are capable of producing optimal yields for the cultivars evaluated. [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]

A study was conducted to determine the allowable depletion in furrow-irrigated rice that results in yield penalty. The study was conducted at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center, near Stuttgart, Ark. on a Dewitt silt loam soil. The field was set up with a variable flow tailwater recovery system (VFTWRS) that recirculates water from the bottom of the field to the crown. Irrigation treatment timings applied to plots as continuously irrigated using the VFTWRS continuously and irrigation every 3, 7, 10, and 14 days. Yield was highest for the continuous irrigation treatment at 180 bu./ac and lowest for the 14-day irrigation treatment at 138 bu./in. Water use efficiency was only significantly lower for the 3-day irrigation treatment compared to the other treatments. There were only 7.2 inches of rain experienced in the field in 2022; as a result, it was not possible to maintain an average allowable depletion of less than 50% in the 7-, 10-, and 14-day treatments. Only 17 ac-in./ac of total water was applied to the continuous irrigation treatment, while 23.8 ac-in./ac was applied to the 3-day treatment. While not significant, the continuous irrigation treatment resulted in a higher yield (11.9 bu./ac), 6.8 ac-in/ac less irrigation, 51 lb N/ac less fertilizer, and a significantly higher water use efficiency of 2 bushels per inch than the 3-day treatment. The data and results from this study strongly suggest the importance of maintaining adequate water in the soil profile for furrow-irrigated rice. Where yields have been maintained by seasonal rainfall in past studies, this was not possible in 2022 and yield penalties and soil water deficits were greater than in previous studies. [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]

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]

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]

A study was conducted to evaluate a novel cover crop crimper and to evaluate the yield difference when cover crops were seeded in the fall and burndown herbicides were not used. The study was conducted at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center, near Stuttgart, Ark. on a Dewitt silt loam soil. The field was set up with a variable flow tailwater recovery system (VFTWRS) that recirculates water from the bottom of the field to the crown. No significant yield penalty was measured for the cover crop treatment although numerically the yield was 11 bu./ac less. The first preemergent herbicide application and burndown were not applied to the cover crop treatment; rather the crimper was used to attempt to reduce weed pressure and terminate the cover crop. [ABSTRACT FROM AUTHOR]

Utilizing chloroacetamide herbicides in current rice herbicide programs would offer a new site of action for producers to control problematic weeds. Recent research has shown that a fenclorim seed treatment can facilitate delayed-preemergence applications of acetochlor by mitigating herbicide injury. However, previous research is limited to silt loam soils and has yet to evaluate the performance on a heavy clay soil. Experiments were conducted at the University of Arkansas System Division of Agriculture's Northeast Research and Extension Center, near Keiser, Ark. to determine the safening potential of a fenclorim seed treatment for microencapsulated acetochlor applications on a Sharkey silty clay. The factors evaluated various acetochlor rates at 0, 1.12, 1.68, and 2.24 lb ai/ac and a fenclorim seed treatment at 0 and 2.5 lb ai/1000-lb of seed. Additionally, barnyardgrass and Palmer amaranth control were evaluated before removing all weeds prior to flood establishment. Increasing rates, unsurprisingly, increased barnyardgrass control and rice injury. Acetochlor rates of 1.68 and 2.24 lb ai/ac, averaged over fenclorim, provided similar levels of weed control with 82% to 87% barnyardgrass control and 89% to 94% Palmer amaranth control. However, 2.24 lb ai/ac caused 34% injury compared to 1.68 lb ai/ac causing 19% injury, averaged over the fenclorim seed treatment. The fenclorim seed treatment did not influence weed control; however, the safener did improve rice tolerance to acetochlor in both forms of injury and yield. Averaged over acetochlor herbicide rate, rice injury and yield were improved by 32 and 12 percentage points, respectively. Results from this study demonstrate the ability of fenclorim to enhance rice tolerance to microencapsulated acetochlor in a conventionally flooded rice system. Additionally, fenclorim would allow for delayed-preemergence applications of acetochlor providing an alternative site of action for rice producers. [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]

A study was conducted to evaluate the interaction of irrigation timing and nitrogen fertilizer rate in relation to yield. The study was conducted at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center, near Stuttgart, Ark. on a Dewitt silt loam soil. Rice was planted in a no-till furrow-irrigated field on 30-in. bed spacing. Fifty-two small plots, 3 beds wide by 20 ft long were marked inside of 4 different irrigation treatments with 208 plots total. Fertilizer treatments consisted of 7 different rates of nitrogen as N-(n-butyl) thiophosphoric triamide (NBPT) urea and 8 different rates of nitrogen as Environmentally Smart Nitrogen (ESN). The results showed increased yields as both N rates and irrigation frequency increased. [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]

Winter cover crops may be used to address soil degradation issues. However, impacts of cover crop biomass on the succeeding cash crop growth are not fully understood on soils common to the Arkansas Delta. From 2018 to 2021, a study was conducted on commercial row crop farms to determine the effects of cover crop termination timing (i.e., biomass production) on corn (Zea mays) growth and yield in the Arkansas Delta. The relationships between cover crop termination timing and corn plant population, cover crop carbon to nitrogen (C:N) ratios and corn yield were investigated. No differences in corn yields or corn plant population were observed among cover crop termination timing treatments. Cover crop C:N ratios were different among treatments but did not impact corn yields. These results suggest that for silt loam and loam soils in the Arkansas Delta, delaying cover crop termination in order to allow the cover crop to produce more biomass is not likely to negatively affect corn crop yields. Moreover, biomass from cover crop residues may increase soil health benefits over time. [ABSTRACT FROM AUTHOR]

Cotton (Gossypium hirsutum L.) herbicide systems that contain multiple modes of action and are applied timely are essential in controlling Palmer amaranth (Amaranthus palmeri). Arkansas cotton growers need new and improved methods and chemistry to manage this and other troublesome weeds. Trials were established in 2019 and 2020 to evaluate weed efficacy and crop response following Loyant applications post-directed in cotton. Trials were established at Marianna, Arkansas, in a Loring silt loam soil and at Tillar, Arkansas, in a Herbert silt loam soil. In 2019, PHY 350 W3FE was established at Tillar and DP 1646 B2XF at Marianna; while in 2020, PHY 400 W3FE was established at both locations. The trials were arranged in a randomized complete block design with four replications. All treatments received Brake FX preemergence at 40 oz/ac (fluometuron 33.2 oz/ac + fluridone 6.8 oz/ac) followed by Liberty (glufosinate) at 32 oz/ac plus Dual Magnum (metolachlor) at 21oz/ac at 3-4 leaf cotton. Post-directed herbicides evaluated included Loyant (florpyrauxifen-benzyl) at 5, 8, and 16 oz/ac, Durango (glyphosate) at 32 oz/ac and Roundup PowerMax (glyphosate) at 32 oz/ac. In 2019 and 2020, post-direct applications of Loyant were applied to 8- or 10-node cotton. Palmer amaranth control and epinasty were recorded at 21 days after 10-node post-direct applications at both locations. Loyant provided greater than 89% control of Palmer amaranth, as long as the rate applied was 8 oz/ac or greater. Cotton injury was significant when Loyant was applied at the 8-node growth stage; however, injury was generally reduced when applications were made to 10-node cotton. Yield reductions from all Loyant applications were observed at Marianna in 2019. No significant yield reductions were observed at either location in 2020, with the exception of, Loyant 16 oz/ac applied to 8-node cotton at Marianna. [ABSTRACT FROM AUTHOR]

Winter cover crops are used to address soil degradation issues. However, impacts of cover crop biomass on cash crop growth are not fully understood on soils common to the Arkansas Delta. In 2020, a study was conducted on commercial row crop farms to determine the effects of cover crop termination timing (i.e., biomass production) on corn (Zea mays) growth and yield in the Arkansas Delta. Investigated were 1) cash crop plant population, 2) cover crop carbon to nitrogen (C:N) ratios 3), and cash crop yield. No differences in crop yields were observed among cover crop termination timing treatments for corn. Cover crop C:N ratios were different among treatments but did not impact corn yields. These results suggest that for silt loam and loam soils in the Arkansas Delta, delaying cover crop termination in order to allow the cover crop to produce more biomass is not likely to negatively affect cash crop yields. Moreover, biomass from cover crop residues may increase soil health benefits over time. [ABSTRACT FROM AUTHOR]

Furrow-irrigated rice (FIR) acreage is rapidly increasing across Arkansas. Acreage has risen from approximately 10,000 acres in 2015 to over 240,000 acres in 2020. The rapid increase in FIR acres has also resulted in a wide range of practices used to implement FIR. Therefore, a study was designed to assess 4 different methods of seeding and/or seedbed preparation for FIR. Treatments include 1) drilling seed into flat soil followed by creating water furrows post-seeding, 2) forming beds/furrows followed by drilling seed into the previously formed beds, 3) drilling seed into flat soil followed by forming beds/furrows post-seeding over the top of seed, and 4) broadcasting seed on the soil surface followed by forming beds post-seeding. Trials were conducted on both a silt loam and clay soil. At the silt loam site, broadcasting seed followed by forming beds produced significantly higher grain yields compared to drilling flat followed by water furrows and forming beds followed by drilling. Drilling flat followed by forming beds performed similarly to the broadcast treatment. At the clay site, drilling flat followed by water furrows resulted in significantly higher grain yields compared to all other treatments. Differences between sites could be related to soil type and/or equipment available to perform operations, but further study is needed to quantify these differences. [ABSTRACT FROM AUTHOR]

In the last several years, there has been increasing interest in furrow-irrigated rice (FIR) (Oryza sativa L.) production. Cultivar selection recommendations have been general and primarily based on anecdotal evidence to date. In 2021, a small-plot rice cultivar performance trial was established at Jackson Co. on a Dundee silt loam soil. A split-plot design was utilized with the whole-plot factor being the location within the field (top and bottom) and the split-plot factor being cultivar, of which there were 12 evaluated. In 2021, the bottom area of the field had significantly higher yields than the top area of the field. In general, the hybrid cultivars RT XP753, RT 7521 FP, and RT 7401 had significantly higher grain yields than the other entries in the trials at both top and bottom areas of the fields. Jupiter, Lynx, and CLL17 had greater head rice yields than all other entries at the top of the field. Jupiter and Lynx also had the highest head rice yields at the bottom of the field. As plot areas were uniformly managed, additional research is necessary to determine whether varieties can be more competitive with the hybrids when cultivar-specific management practices are implemented. [ABSTRACT FROM AUTHOR]

Sulfonylurea herbicides have been found effective in controlling glyphosate-resistant Italian ryegrass [Lolium perenne L. ssp. multiflorum (Lam.) Husnot] in fields planted to corn (Zea mays L.). FullPage™ rice (Oryza sativa L.) was released in 2020 on a limited basis and has been found to provide increased tolerance to imazethapyr and imazamox herbicide. Two experiments were conducted on a silt loam soil in Tillar, Arkansas, in 2020 and 2021 to determine the tolerance of FullPage™ rice to sulfonylurea herbicides applied preemergence (PRE) and postemergence (POST). Treatments consisted of Resolve Q (rimsulfuron + thifensulfuron) at 1.25 and 0.625 oz/ac, Steadfast Q (nicosulfuron + rimsulfuron) at 1.5 and 0.75 oz/ac, and Accent Q (nicosulfuron) at 0.75 and 0.375 oz/ac. When applied PRE, minimal levels of stunting were observed from most treatments within two weeks after application. When applied POST, crop stunting, chlorosis, leaf malformation, and necrosis were observed with most treatments, with crop stunting being more prevalent throughout the season. In 2020, within 14 days after the POST application (DAPOST), all treatments exhibited varying levels of stunting and chlorosis, with both rates of Steadfast Q resulting in the highest levels of injury. Similarly, by 35 DAPOST, the rates of Steadfast Q continued to exhibit observable levels of stunting. Regardless of the levels of phytotoxicity earlier in the growing season, rice yields were comparable across all treatments when compared to the weed-free check. In 2021, both rates of Resolve Q and Steadfast Q exhibited 8% to 23% stunting at 14 DAPOST. By 45 DAPOST, Steadfast Q at 1.5 oz/ac resulted in a significant delay in heading compared to the weed-free check, in addition to a significant yield reduction. These data suggest that when applied before rice planting or at planting, sulfonylurea herbicides may be beneficial in controlling herbicide-resistant Italian ryegrass. Although minimal yield reduction was observed when these herbicides were applied POST, significant levels of phytotoxicity were observed from all treatments. [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]

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]

A study was conducted to evaluate the performance of three different nitrogen (N) fertilizer source treatments in a furrowirrigated rice field study during 2019 at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center near Stuttgart, Arkansas on a DeWitt silt loam. The N sources used were 32% urea-ammonium nitrate (UAN) solution, Environmentally Smart Nitrogen (ESN), and urea. The N sources were used in several different split application timings. Yield differences between the N treatments were not observed for the hybrid RT 7311 CL (P = 0.184). There was no significant difference in yield between no-till and tillage treatments (P = 0.52). Irrigation timings ranging between continuously irrigated, every 3 days, 7 days and 10 days resulted in no significant difference in yield (P = 0.6). [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]

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]

In 2020, a weed control study was conducted at the University of Arkansas System Division of Agriculture’s Lonn Man Cotton Research Station near Marianna, Ark., on a Calloway silt loam soil to determine adequate weed control from a full season approach in Enlist® E3 soybeans [Glycine max (L.) Merr.]. The objective of this trial was to evaluate herbicide combinations for burndown control of large Canadian horseweed (Conyza canadensis) commonly called Marestail as well as other winter annuals. Enlist soybean were planted 15 days after burndown herbicide applications and additional herbicide programs were evaluated to determine efficacy on Marestail, Palmer amaranth, and other problematic weeds. Results indicated that herbicide programs containing Elevore® at 1 oz/ac provided the best control of Marestail, with the combination of Enlist One® 32 oz/ac and Durango® 32 oz/ac providing 90% control of Marestail and other winter annual weeds. Gramoxone® 40 oz/ac plus Verdict® 5 oz/ac provided only 73% control of Marestail but controlled Palmer amaranth 98% at the time of planting. Herbicide combinations at planting (PRE) consisted of either Trivence® 8 oz/ac plus 40 oz/ac Gramoxone or Boundary® 32 oz/ac plus 40 oz/ac Gramoxone. There was no difference in residual control of Palmer amaranth with any PRE 14 days after application (DAA). However, Marestail control was higher (>92%) where combinations of Gramoxone plus Trivence were applied compared to <75% with combinations of Gramoxone plus Boundary. This was likely due to the increased control with Elevore treatments before PRE applications. All other winter or summer annual weeds were controlled effectively following early postemergence (POST) applications, regardless of treatment. [ABSTRACT FROM AUTHOR]

The ROXY® Rice Production System (RRPS) was recently commercialized in California, allowing producers to apply oxyfluorfen (HRAC/WSSA Group 14) both preemergence and postemergence. The use of oxyfluorfen in the RRPS provides producers with an additional herbicide option for barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] control in rice (Oryza sativa L.). A field experiment was conducted at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center near Stuttgart, Ark., in 2022, to evaluate residual barnyardgrass control with clomazone and oxyfluorfen alone and in mixture. Herbicide treatments included clomazone at 0.25 or 0.3 lb ai/ac, and oxyfluorfen at 0.6 or 0.75 lb ai/ac applied preemergence followed by a sequential postemergence application. A 1:2 and 1:3 ratio of clomazone and oxyfluorfen (0.3 + 0.6 lb ai/ac and 0.25 + 0.75 lb ai/ac) were also evaluated. At 3 weeks after the preemergence application, but prior to the postemergence application, all rates of oxyfluorfen and clomazone alone provided =94% visual control of barnyardgrass. All combinations of clomazone and oxyfluorfen, provided 100% barnyardgrass visual control at 3 weeks after the preemergence application. At 5 weeks after the postemergence application, all treatments provided = 94% barnyardgrass control. At 6 weeks after the postemergence application, mixtures of clomazone and oxyfluorfen provided 95% or greater barnyardgrass control. Conversely, when sequential applications of oxyfluorfen alone were made, regardless of rate, barnyardgrass control was only 77% and 79% at 6 weeks after the postemergence application. When clomazone and oxyfluorfen were applied at a 1:3 ratio and 1:2 ratio or clomazone alone applied at 0.3 lb ai/ac, rice yields were comparable among treatments, ranging from 106 to 130 bu./ac. Treatments of oxyfluorfen at 0.6 and 0.75 lb ai/ac, and clomazone at 0.25 lb ai/ac, resulted in rice yields of 74 to 93 bu./ac. These results indicate that clomazone will likely be needed with oxyfluorfen to obtain extended residual barnyardgrass control in the RRPS. [ABSTRACT FROM AUTHOR]

Seeking to fine-tune nitrogen (N) fertilizer application, increase economic returns, and decrease environmental N loss, some Arkansas farmers are turning away from blanket N recommendations based on soil texture and cultivar by using the Nitrogen Soil Test for Rice (N-STaR) to determine their field-specific N rates. In 2010, Roberts et al. (2011) correlated several years of direct steam distillation (DSD) results obtained from 18-in. soil samples of silt loam soils to plot-scale N response trials across the state and developed a site-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 (using a 12-in. soil sample). To summarize the samples submitted to the N-STaR Soil Testing Lab in 2018, samples were categorized by county and soil texture. Samples were received from 62 fields across 19 Arkansas counties, with Jackson and Lonoke county submitting the largest number of fields. Total samples received were from 48 silt loam and 14 clay fields. The N-STaR N-rate recommendations for these samples were compared to the producer's estimated N rate, the 2018 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 three categories based on a decrease in recommendation, no change in recommended N rate, or an increase in the N-rate recommendation. While not significant when N-STaR suggested an increase in N rate, county (P < 0.01) and soil texture (P < 0.001) were significant factors when N-STaR called for a decreased N rate in all three comparisons suggesting that some areas of the state and soil series may have higher residual-N not accounted for by other current N-rate recommendation strategies. [ABSTRACT FROM AUTHOR]

A study was conducted to evaluate the performance of three different nitrogen (N) fertilizer source treatments in a furrow-irrigated rice field study during the season of 2018 at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center near Stuttgart, Arkansas on a DeWitt silt loam. The N sources used were 32% urea-ammonium nitrate (UAN) solution, Environmentally Smart Nitrogen (ESN), and urea. The N sources were used in several different split application timings. Yield differences between the N treatments were observed for the hybrid RT 7311 CL. [ABSTRACT FROM AUTHOR]

Little is known about the effects of soybean (Glycine max L.) management practices on the subsequent rice (Oryza sativa L.) crop's success. This study was continued to determine rice response to different soybean maturity groups (MGs) and planting dates when grown in rotation with rice on a silt loam soil in Arkansas. Various soybean planting dates (optimum and late) and MGs (3.5, 4.7, 5.4, and 5.6) were considered followed with a single cultivar of rice. The rice was measured for the total N uptake (TNU) at 50% heading, grain yield and N fertilizer rate needed to achieve 95% relative grain yield (RGY). Total N uptake was effected by the previous soybean planting date, with significantly higher rice N uptake following a late-planted soybean crop. The interaction of planting date by MG of the previous soybean crop influenced the maximal grain yield achieved by the rice crop (P < 0.0001) and the N rate needed to achieve 95% RGY (P = 0.0007). Management techniques should be considered when implementing a soybean-rice rotation on a silt loam soil in Arkansas to maximize rice grain yield and overall farm profitability through minimizing fertilizer-N needed to achieve high grain yields. [ABSTRACT FROM AUTHOR]

The cultivar × nitrogen (N) fertilizer rate studies determine the proper N fertilizer rates for the new rice cultivars across the array of soil and climatic conditions which exist in the Arkansas rice-growing region. The seven rice cultivars studied in 2018 were: CL153, CL272, PVL01, Thad, and the experimental lines CLX6-1111, CLX6-1133, and CLX5-4083. In general, grain yields were good to excellent for all the cultivars studied at the three locations in 2018. This was the first year the experimental lines CLX6-1111, CLX6-1133, and CLX5-4083 were in the cultivar × N rate studies and, thus, there is not enough data to make a recommendation at this time. The multiple years of results for CL153, CL272, PVL01, and Thad indicate these cultivars should yield well with minimal to no lodging if 150 lb N/ac is applied in a two-way split of 105 lb N/ac at preflood and 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 preflood and 45 lb N/ac at midseason when grown on clay soils. [ABSTRACT FROM AUTHOR]

In Mid-South rice (Oryza sativa, L.) production, nitrogen (N) fertilizer is most often recommended as a single preflood application (SPF) or a two-way split (2WS) application in a dry-seeded, delayed-flood system. The majority of N fertilizer is typically applied at the 4-6 leaf stage onto dry soil, and the second application, if necessary, into the floodwater as a midseason application. Environmental factors do not always allow growers to apply early N fertilizer onto optimal dry soil conditions using these recommendations. This two-year study was conducted to determine N-fertilization best management practices in rice when faced with dry, wet, and flooded soil conditions; this is the second year of that study. Two locations with differing soil textures, a silt loam and a clay, were used to evaluate N-fertilizer treatments to the cultivar Diamond. Treatments included a control receiving no N, SPF and 2WS treatments applied to dry soils, wet soils, and wet soils at elevated N-fertilizer rates, and several treatments using single and multiple N applications into flooded conditions. All standard recommended N treatments applied to dry soil, some to wet soil, and some spoon-fed treatments at elevated N rates were among the highest yielding treatments at both locations. Some of the lowest yielding treatments were SPF N applications into the floodwater at both locations and SPF N applications applied to wet soil at the University of Arkansas System Division of Agriculture's Rohwer Research Station (RRS). [ABSTRACT FROM AUTHOR]

The majority of rice in Arkansas is grown using a direct-seeded, delayed-flooded system. In recent years, growers have increased their interest in alternative irrigation management strategies. Small-plot trials were conducted in 2018 on a DeWitt silt loam soil at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center to evaluate irrigation management practices of rice grown in an alternate wetting and drying system. Water moisture tensions (deficits) of 15, 30, and 45 centibar (cb) were used to trigger irrigation events. A conventional permanent flood was also included for comparison. Alternate wetting and drying systems appeared to remain competitive with a permanent flood for all factors evaluated including grain yield. [ABSTRACT FROM AUTHOR]

The cultivar × seeding rate studies determine the proper seeding rates for new rice (Oryza sativa, L.) cultivars over a range of production/growing conditions in Arkansas. The four rice cultivars evaluated in 2018 were CL153, CL172, Diamond, and Titan. Each cultivar was seeded at 10, 20, 30, 40, and 50 seeds/ft2. In accordance with current recommendations and predominant grower practice, all seed received insecticide and fungicide seed treatments. Trials were seeded at two on-farm locations in eastern Arkansas. Stand density and grain yield results were consistent with current seeding rate recommendations of 30 seeds/ft2 (65 to 80 lb/ac) under optimum conditions and seeding dates on silt loam soils. Adverse conditions such as late seeding date or clay soil types currently recommend a 20% seeding rate increase (36 seed/ft2) compared to a loamy soil and optimum seeding date. It should be noted that without the use of an insecticide seed treatment, stand density and grain yield may be reduced compared to results in this study. Grain yield response to seeding rate was clear at both locations in 2018. Reduced grain yield was observed at times at the two lowest (10-20 seeds/ft2) seeding rates. While grain yields at the currently recommended seed rate of 30 seeds/ft2 were not significantly different than those at the 40 or 50 seeds/ft2. [ABSTRACT FROM AUTHOR]

Considering recent advances in technology and cultural management practices as well as concerns about water availability and farm labor, alternative irrigation strategies have gained increasing interest in rice (Oryza sativa L.) production. Success can be realized with these alternative systems, but irrigation guidelines have not been defined. Trials were initiated in 2018 to address the strategies of alternatively irrigated rice compared to conventional flooded systems. Large-block trials were conducted at the University of Arkansas System Division of Agriculture's Pine Tree Research Station (PTRS) on a silt loam soil texture as well as at the Northeast Research and Extension Center (NEREC) on a clay soil texture. Both furrow-irrigated rice (FIR) and alternate wetting and drying (AWD) trials were conducted with soil moisture deficit thresholds of 15, 30, and 45 centibar (cb) and compared to a conventional flood control. The 2018 results of the parameters measured showed little difference among irrigation treatments, including no differences between AWD and conventional flood management. Although no yield differences existed between FIR treatments, FIR did yield significantly less than conventionally flooded rice at NEREC. Results suggest that irrigation quantity and frequency can be reduced in some situations without significant yield penalty. [ABSTRACT FROM AUTHOR]

Conventional (non-GMO) corn production has significantly increased in portions of Arkansas. These conventional hybrids do not contain the Roundup Ready trait, and thus, they are at risk from off-target movement of Roundup (glyphosate) from surrounding crops. Arkansas corn growers can benefit from growing conventional corn hybrids if the impact from off-target movement of Roundup can be understood and minimalized. Trials were conducted in 2019 and 2020 to evaluate the crop response following low rates of Roundup PowerMax applied to a conventional corn hybrid. In 2019, one trial was established with Gateway 7157 conventional hybrid at Tillar, Arkansas in a Hebert silt loam soil. In 2020, trials were established with the same hybrid at Tillar, Arkansas, in a Hebert silt loam soil, Marianna, Arkansas in a Loring Silt loam soil, and Fayetteville, Arkansas in a Captina silt loam soil. Trials were arranged in a randomized complete block design with four replications. Due to uniformity of data across location and years, data were pooled, and means were separated using Tukey-Kramer grouping for treatment least squares means at a = 0.05. All treatments received Aatrex at 64 oz/ac plus Dual II Magnum at 16 oz/ac applied preemergence followed by a Roundup PowerMax treatment at either stage V2 or V6 corn (Barber et al., 2020). Roundup PowerMax rates ranged from 0.32 oz/ac (1/100X) to 6.4 (1/5X) at each stage. Visual corn injury 14 days after V2 applications was highest, with Roundup at 6.4 oz/ac causing 91% and lowest with Roundup at 0.32 oz/ac causing 4%. Stage V2 corn injury increased as the herbicide rate increased, which was expected. Visual corn injury from V2 applications continued 14 days after V6 applications in a similar trend with Roundup applied at 6.4 and 3.2 oz/ac to V2 corn causing the highest injury at 72% and 53%, respectively. These two rates also caused the highest injury when sprayed at V6. Overall injury was higher when Roundup was applied at V2 vs. V6 growth stage. Roundup applied at 6.4 and 3.2 oz/ac rates to V2 corn caused the highest yield reduction, with corn yielding 21 and 68 bu./ac, respectively. Corn yields were not reduced from Roundup rates 1.6 oz/ac or lower for any growth stage. [ABSTRACT FROM AUTHOR]

The cultivar × seeding rate studies determine the proper seeding rates for new rice (Oryza sativa, L.) cultivars over a range of production/growing conditions in Arkansas. The four rice cultivars evaluated in 2019 were CLL15, CLM04, PVL01, and PVL02. Each cultivar was seeded at 10, 20, 30, 40, and 50 seed/ft2. In accordance with current recommendations and predominant grower practice, all seed received insecticide and fungicide seed treatments. Trials were seeded at two on-farm locations in eastern Arkansas. Stand density and grain yield results were consistent with current seeding rate recommendations of 30 seed/ft2 (65 to 80 lb/ac) under optimum conditions and seeding dates on silt loam soils. It should be noted that without the use of insecticide and fungicide seed treatments, stand density and grain yield may be reduced compared to results in this study. At Greene County during 2019, grain yield of each cultivar increased as seeding rate increased. However, reduced grain yield was observed at the lowest (10 seed/ft2) seeding rate and suboptimal stand density (<10-20 plants/ft2) was noted at seeding rates of 10-30 seed/ft2 for CLL15, PVL01, and PVL02 and 10-20 seed/ft2 for CLM04. Optimal grain yield of 95% or greater and optimal stand density of 10-20 plants/ft2 was achieved in 3 of the 4 cultivars using seeding rates of 40-50 seed/ft2 at this location. At Poinsett County, grain yield increased as seeding rate increased for PVL01 but was not significant for CLL15, CLM04, or PVL02. The seeding rates that resulted in greater than 95% optimal grain yield varied between the cultivars, but optimal stand density was noted for CLL15, PVL01, and PVL02 at 20-30 seed/ft2 and 20-40 seed/ft2 for CLM04. Seeding rates below or above these resulted in stand density less than or greater than 10-20 plants/ft2, respectively. [ABSTRACT FROM AUTHOR]

Generally, Arkansas rice producers utilize multiple herbicides throughout the growing season to combat problematic weeds. An experiment was conducted on a silt loam soil in Tillar, Arkansas to evaluate the effectiveness of applying multiple rates of Loyant alone or in combination with commonly applied graminicides. At 20 days after treatment (DAT), Loyant 16 oz/ac + Clincher 31 oz/ac provided the most effective control of hemp sesbania, barnyardgrass, and rice flatsedge, with 99%, 98%, and 99% control, respectively. A positive trend was observed throughout the growing season as the rate of Loyant increased when applied alone or in tank-mixture with the graminicides. By 42 DAT, reduction in barnyardgrass control was observed from all treatments. It can be determined by these data that the most effective combination to control the present weeds is Loyant at 16 oz/ac + Clincher at 31 oz/ac. Regardless of the graminicide, these data suggest that applying Loyant at 16 oz/ac aided in controlling the weeds commonly found in Arkansas rice. [ABSTRACT FROM AUTHOR]

Seeking to fine-tune nitrogen (N) application, increase economic returns, and decrease environmental N loss, some Arkansas farmers are slowly turning away from blanket N recommendations based on soil texture and cultivar by using Nitrogen Soil Test for Rice (N-STaR) to determine their field-specific N fertilizer rates. In 2010, scientists at the University of Arkansas correlated several years of direct steam distillation results (DSD) obtained from soil samples taken to an 18-inch depth to plot-scale N response trials across the state and developed a site-specific soil-based N test for Arkansas rice. After extensive field testing, N-STaR became available to the public for silt loam soils in 2012. The N-STaR has since been correlated for use on clay soils, using a 12-inch depth soil sample, both at small-plot and field scale validation, and has been offered to the public since 2013. To summarize the samples submitted to the University of Arkansas System Division of Agriculture's N-STaR Soil Testing Lab for the 2017 growing year, samples were categorized by county and soil texture. Samples were received from 152 fields across 18 Arkansas counties, with Mississippi County and Arkansas County submitting the largest number of fields, 81 and 13 fields, respectively. The total samples received were from 54 silt loam fields and 98 clay fields. The N-STaR N rate recommendations for these samples were then compared to the producer's estimated N rate, the 2017 Recommended Nitrogen Rates and Distribution for Rice Cultivars in Arkansas, and the standard Arkansas N rate recommendation of 150 lb N/acre for silt loam soils and 180 lb N/acre for clay soils. Each comparison was divided into three categories based on a decrease in the N rate recommendation, no change in recommended N rate, or an increase in the N rate recommendation. County was a significant factor when N-STaR called for a decreased N rate in the standard comparison (P < 0.05) and the cultivar recommendation comparison (P < 0.01) suggesting that some areas of the state may have higher residual-N not accounted for by these current N rate recommendation strategies. Soil texture was a significant factor when N-STaR called for a decreased N rate in the standard comparison (P < 0.05) and the cultivar recommendation comparison (P < 0.001), yet was also significant (P < 0.001) when N-STaR recommended an increase in N rate in the producer's estimated comparison. This further emphasizes the importance of correct soil texture classification and corresponding sampling methods. [ABSTRACT FROM AUTHOR]

Long-term fertilization trials provide insight about crop yield and soil test responses that are important components of developing profitable fertilization practices. This report summarizes the 11-year history of phosphorus (P) and potassium (K) fertilizer rate trials established in 2007 at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center. Four research areas were established on a Dewitt silt loam and generally cropped to a 1:1 rice (Oryza sativa L.)-soybean [Glycine max (L.)] rotation with annual fertilizer rates of 0, 40, 80, 120 and 160 lb K2O or P2O5/acre/year. Soil-test P declined from 19 to 15 ppm when no P fertilizer was applied and increased from 19 ppm to 29 to 95 ppm after 10 annual applications of 40 to 160 lb P2O5/acre. After 10 years, soil-test K declined by approximately 7 ppm/year when no K was applied and declined at slower rates with annual-K rates of 40 to 120 lb K2O/acre/year. The initial soil-test K was increased or maintained annually only by applying 160 lb K2O/acre/year. Rice yields (153-155 bu/acre average) were not affected by annual-K rate. Neither rice (151-152 bu/acre) nor soybean yields (58-60 bu/acre) were significantly affected by annual fertilizer-P rate. Soybean yields were affected by annual-K rate with the 11-year average yields of 40 to 160 lb K2O/acre being 2.6 to 4.5 bu/acre/year greater than soybean receiving no fertilizer K (52.5 bu/acre/year). After 11 crop years, both rice and soybean are starting to show growth differences due to the annual fertilization rates and the trials will be continued. [ABSTRACT FROM AUTHOR]

In mid-South rice (Oryza sativa, L.) production, nitrogen (N) fertilizer is most often recommended as a single preflood application (SPF) or a two-way split (2WS) application in a dry-seeded, delayed-flood system. The majority of N fertilizer is typically applied at the 4-6 leaf stage onto dry soil, and the second application, if necessary, into the floodwater as a midseason application. Environmental factors do not always allow growers to apply early N fertilizer onto optimal dry soil conditions using these recommendations. This study was conducted to determine N fertilization best management practices in rice when faced with dry, wet, and flooded soil conditions. The study was conducted at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center (RREC) and at the Southeast Rice Research and Extension Center (SEREC) on two differing soil types, a silt loam and a clay, respectively, to evaluate N fertilizer treatments to the cultivar Diamond. Treatments included a control receiving no N, SPF and 2WS treatments applied to dry soils, wet soils, and wet soils at elevated fertilizer rates, and several treatments using single and multiple N applications into flooded conditions. Standard recommended N treatments applied to dry soil and wet soil at elevated N rates were among the highest yielding treatments at both locations, while spoon-fed treatments at RREC and single applications at flood initiation into flooded conditions at SEREC were not significantly different than standard recommendations. [ABSTRACT FROM AUTHOR]

The cultivar x nitrogen (N) fertilizer rate studies determine the proper N fertilizer rates for the new rice cultivars across the array of soil and climatic conditions which exist in the Arkansas rice-growing region. The six rice cultivars studied in 2017 were: Diamond, Titan, Horizon AG's Clearfield CL153 and CL272, BASF and Horizon AG's PVL01, and Thad. Grain yields were excellent for most of the cultivars studied in 2017 at the chosen locations, except at the University of Arkansas System Division of Agriculture's Pine Tree Research Station (PTRS) location where a phosphorus deficiency played a role in reducing yields for all of the cultivars, except possibly Diamond. This was the first year PVL01 and Thad were in the cultivar x N-rate studies and thus there is not enough data to make a recommendation at this time. The multiple years of results for Diamond, Titan, CL153 and CL272 indicate these cultivars should yield well with minimal to no lodging if 150 lb N/acre is applied in a two-way split of 105 lb N/acre at preflood and 45 lb N/acre at midseason when grown on silt loam soils and 180 lb N/acre in a two-way split of 135 lb N/acre at preflood and 45 lb N/acre at midseason when grown on clay soils. [ABSTRACT FROM AUTHOR]

A study was conducted to evaluate the performance of pure-line (conventional) and hybrid rice cultivars in a furrow-irrigated rice field during the growing season of 2017 at University of Arkansas System Division of Agriculture's Rice Research and Extension Center, Stuttgart, Ark. on a De-Witt silt loam. A total of 9 rice cultivars were studies of which 5 were hybrid and 4 were conventional rice cultivars. Results indicated that the yields of all hybrid rice cultivars were significantly better than the conventional rice cultivars. The highest yield was obtained from XP753 of 189 bu/acre. The average yield from all hybrid rice cultivars was calculated as 174 bu/acre while 130 bu/acre was calculated for conventional rice cultivars. Height of plants at the bottom of the field was significantly higher than those at the top and middle position along the furrow length and no difference in plant heights were seen for plants in the furrow and on the bed. The total water consumed by the crop was 11 acre-inches and total rainfall received was 9 acre-inches. [ABSTRACT FROM AUTHOR]

The majority of rice in Arkansas is grown using a direct-seeded, delayed flood system. In recent years, growers have increased their interest in alternative irrigation management strategies. To begin addressing this, large block trials were initiated in 2017 to evaluate irrigation management practices of rice grown in a furrow-irrigated system and an alternate wetting and drying system. Large-block trials were conducted on a silt loam soil at the University of Arkansas System Division of Agriculture's Pine Tree Research Station (PTRS) and on a clay soil at the Northeast Research and Extension Center (NEREC). Additional small-plot trials were conducted on a silt loam soil at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center (RREC). Water moisture tensions (deficits) of 15, 30, and 45 centibars (cb) were used to trigger irrigation events in both furrow-irrigated and alternate wetting and drying trials. A conventional permanent flood was also included for comparison of water use. First year results will be discussed. [ABSTRACT FROM AUTHOR]

With the pending approval of Rogue herbicide, information regarding herbicide-soil interactions is needed to optimize its efficacy for Arkansas rice farmers. Batch equilibration experiments were carried out with a silt loam and a clay soil with benzobicyclon hydrolysate (BH; active metabolite in Rogue herbicide), to determine optimal equilibration time and ratio of soil to solution for soil sorption experiments. Results indicate a soil:solution of 1:1 and equilibration time of 16 hours are optimal for determining the soil sorption of BH in silt loam, and a soil:solution of 1:1 or 1:5 and 16 hours equilibration time is appropriate for clay soil. Using the parameters established in this study, batch equilibration studies will be carried out on a broader range of soils from across Arkansas rice producing regions. Understanding the dynamics between soil and Rogue will inform scientifically sound recommendations to Arkansas farmers for effective weed control and environmental stewardship. [ABSTRACT FROM AUTHOR]