Claypan Soil Research Articles

Subsurface Drainage and Nitrogen Fertilizer Management Affect Fertilizer Fate in Claypan Soils

Sustainable nitrogen (N) fertilizer management practices in the Midwest U.S. strive to optimize crop production while minimizing N gas emission losses and nitrate-N (NO3-N) losses in subsurface drainage water. A replicated site in upstate Missouri from 2018 to 2020 investigated the influence of different N fertilizer management practices on nutrient concentrations in drainage water, nitrous oxide (N2O) emissions, and ammonia (NH3) volatilization losses in a corn (Zea mays, 2018, 2020)–soybean (Glyince max, 2019) rotation. Four N treatments applied to corn included fall anhydrous ammonia with nitrapyrin (fall AA + NI), spring anhydrous ammonia (spring AA), top dressed SuperU and ESN as a 25:75% granular blend (TD urea), and non-treated control (NTC). All treatments were applied to subsurface-drained (SD) and non-drained (ND) replicated plots, except TD urea, which was only applied with SD. Across the years, NO3-N concentration in subsurface drainage water was similar for fall AA + NI and spring AA treatments. The NO3-N concentration in subsurface drainage water was statistically (p < 0.0001) lower with TD urea (9.1 mg L−1) and NTC (8.9 mg L−1) compared to fall AA + NI (14.6 mg L−1) and spring AA (13.8 mg L−1) in corn growing years. During corn years (2018 and 2020), cumulative N2O emissions were significantly (p < 0.05) higher with spring AA compared to other fertilizer treatments with SD and ND. Reduced corn growth and plant N uptake in 2018 caused greater N2O loss with TD urea and spring AA compared to the NTC and fall AA + NI in 2019. Cumulative NH3 volatilization was ranked as TD urea > spring AA > fall AA + NI. Due to seasonal variability in soil moisture and temperature, gas losses were higher in 2018 compared to 2020. There were no environmental benefits to applying AA in the spring compared to AA + NI in the fall on claypan soils. Fall AA with a nitrification inhibitor is a viable alternative to spring AA, which maintains flexible N application timings for farmers.

Spring applied phosphorus loss with cover crops in no-till terraced field

Cover crops (CC) can improve phosphorus (P) cycling by reducing water related P losses and contributing to P nutrition of a rotational crop. This is particularly important in claypan soils with freeze-thaw cycles in early spring in the Midwest U.S. This 4-year study (2019–2022) examined the impact of CC monoculture and mix of CC species on P losses from a fertilizer application, and determined the P balance in soil compared to no cover crop (noCC). The CC mix consisted of wheat (Triticum aestivum L.), radish (Raphanus raphanistrum subsp. Sativus), and turnip (Brassica rapa subsp. Rapa) (3xCCmix) in 2019 and 2021 before corn, and cereal rye (Secale cereale L.) was planted as monoculture before soybean in 2020 and 2022. The 3xCCmix had no effect on total phosphorus (TP) and dissolved reactive phosphorus (PO4–P) concentration or load in 2019 and 2021. Cereal rye reduced TP and PO4–P load 70% and 73%, respectively, compared to noCC. The variation in soil moisture, temperature, and net precipitation from fertilizer application until CC termination affected available soil P pools due to variability in CC species P uptake, residue decomposition, and P loss in surface water runoff. Overall, the P budget calculations showed cereal rye had 2.4 kg ha−1 greater P uptake compared to the 3xCCmix species which also reduced P loss in water and had greater differences in soil P status compared to noCC. This study highlights the benefit of CCs in reducing P loss in surface runoff and immobilizing P through plant uptake. However, these effects were minimal with 3xCCmix species and variability in crop residue decomposition from different CC species could affect overall P-soil balance.

Comparative analysis of three next-generation sequencing techniques to measure nosZ gene abundance in Missouri claypan soils

Quantitative next-generation sequencing techniques have been critical in gaining a better understanding of microbial ecosystems. In soils, denitrifying microorganisms are responsible for dinitrogen (N2) production. The nosZ gene codes for nitrous oxide reductase, the enzyme facilitating the reduction of nitrous oxide (N2O) to N2. The objectives of this research were to: 1) understand how soil depth influences RNA concentration and nosZ gene abundance; 2) assess the spatial dependence of nosZ gene abundance in two claypan soil fields; and 3) compare and evaluate multiple RNA-based sequencing methods for quantifying nosZ gene abundance in soils in relation to dinitrogen (N2) production. Research sites consisted of two intensively studied claypan soil fields in Central Missouri, USA. Soil cores were collected from two landscape transects across both fields and analyzed for extractable soil RNA at two depths (0–15 cm and 15–30 cm). Measurements of nosZ gene abundance were obtained using real-time quantitative polymerase chain reaction (RT-qPCR), droplet digital polymerase chain reaction (ddPCR), and nanostring sequencing (NS). In both fields, soil RNA concentrations were significantly greater at 0–15 cm depth compared to 15–30 cm. These data indicated low overall soil microbial activity below 15 cm. Due to low quantities of extractable soil RNA in the subsoil, nosZ gene abundance was only determined in the 0–15 cm depth. Sequencing method comparisons of average nosZ gene abundance showed that NS results were constrained to a narrow range and were 10-20-fold lower than ddPCR and RT-qPCR at each landscape position within each field. Droplet digital PCR appears to be the most promising method, as it reflected changes in N2 production across landscape position.

Critical shear stress variability in claypan soils with depth

Critical shear stress variability in claypan soils with depth

Subsurface drainage and nitrogen management affects corn and soybean yield in claypan soils in upstate Missouri

AbstractNitrogen (N) and subsurface drainage water management are crucial and challenging components of sustainable crop production on poorly drained claypan soils. During extreme precipitation events, N fertilizer management is difficult in a corn (Zea mays L.)–soybean (Glycine max L.) rotation that balances productivity and environmental quality. This 4‐year (2018–2021) experiment was conducted on a poorly drained soil to examine the interactive effects of drainage (subsurface tile drainage [SD] and no drainage [ND]) and corn N fertilizer treatments (non‐treated control [NTC], fall‐applied anhydrous ammonia [AA] at 190 kg N ha−1 with nitrapyrin [fall AA + NI], pre‐plant AA [spring AA] at 190 kg N ha−1, and top‐dressed urea [TD urea] as 42 kg N ha−1 SuperU and 126 kg N ha−1 ESN as a 25:75% granular blend) on yield and nutrient uptake. Corn grain yield was 1.22–1.53 Mg ha−1 greater with fertilizer treatments in SD compared to ND. Drought conditions in 2018 lowered corn grain yield compared to 2020. Average over 2 years, corn yield in SD soils was ranked as spring AA > fall AA + NI > TD urea > NTC. While soybean yield following corn was 13% greater in the NTC compared to TD urea. The SD treatment increased soybean yield by 0.6–2 Mg ha−1 compared to ND. This study results showed that fall AA + NI produced corn yields similar to spring AA in SD and ND soils in temperate humid climatic conditions.

Impact of N, P, and K rates on stockpiled tall fescue in claypan soils

AbstractStockpiled tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] is an alternative to extend the grazing season and reduce feeding costs during the winter. In addition, adequate fertility management with N, P, and K nutrients can improve forage production. Our objective was to evaluate the impact of N, P, and K fertilization (from 0 to 120 lb/a, 0 and 50 lb/a, and 0 and 30 lb/a, respectively) on forage accumulation (FA) and nutritive value in stockpiled tall fescue in claypan soils. The study was carried out in Columbus, KS, on established ‘Kentucky 31’ tall fescue pastures in the fall of 2019 and 2021 (two years). The treatments were one unfertilized control and fertilization with six combinations of nitrogen (0, 40, 60, 80, and 120 lb/a), phosphorus (0 and 50 lb/a), and potassium (0 and 30 lb/a) rates. Forage accumulation was greater in the treatments with at least 60 lb N/a compared with the unfertilized control (1,235 vs. 570 lb DM/a). However, the greatest crude protein content (CP; 13%) and crude protein accumulation (CPA; 163 lb CP/a) were produced when 120 lb N/a was applied. Nitrogen fertilization also resulted in greater total digestible nutrients, net energy gain, net energy maintenance, and lower acid detergent fiber. Phosphorus and potassium had little effect on the measured responses. Nitrogen fertilization can be an alternative to increase stockpiled tall fescue FA and nutritive value, reducing the need for energy and protein supplementation of livestock during the winter.

Degradation kinetics of veterinary antibiotics and estrogenic hormones in a claypan soil

Veterinary antibiotics and estrogens are excreted in livestock waste before being applied to agricultural lands as fertilizer, resulting in contamination of soil and adjacent waterways. The objectives of this study were to 1) investigate the degradation kinetics of the VAs sulfamethazine and lincomycin and the estrogens estrone and 17β-estradiol in soil mesocosms, and 2) assess the effect of the phytochemical DIBOA-Glu, secreted in eastern gamagrass (Tripsacum dactyloides) roots, on antibiotic degradation due to the ability of DIBOA-Glu to facilitate hydrolysis of atrazine in solution assays. Mesocosm soil was a silt loam representing a typical claypan soil in portions of Missouri and the Central United States. Mesocosms (n = 133) were treated with a single target compound (antibiotic concentrations at 125 ng g−1 dw, estrogen concentrations at 1250 ng g−1 dw); a subset of mesocosms treated with antibiotics were also treated with DIBOA-Glu (12,500 ng g−1 dw); all mesocosms were kept at 60% water-filled pore space and incubated at 25 °C in darkness. Randomly chosen mesocosms were destructively sampled in triplicate for up to 96 days. All targeted compounds followed pseudo first-order degradation kinetics in soil. The soil half-life (t0.5) of sulfamethazine ranged between 17.8 and 30.1 d and ranged between 9.37 and 9.90 d for lincomycin. The antibiotics results showed no significant differences in degradation kinetics between treatments with or without DIBOA-Glu. For estrogens, degradation rates of estrone (t0.5 = 4.71–6.08 d) and 17β-estradiol (t0.5 = 5.59–6.03 d) were very similar; however, results showed that estrone was present as a metabolite in the 17β-estradiol treated mesocosms and vice-versa within 24 h. The antibiotics results suggest that sulfamethazine has a greater potential to persist in soil than lincomycin. The interconversion of 17β-estradiol and estrone in soil increased their overall persistence and sustained soil estrogenicity. This study demonstrates the persistence of these compounds in a typical claypan soil representing portions of the Central United States.

Cover crop and biofuel crop effects on hydraulic properties for claypan soils

AbstractPerennial biofuel and cover crops systems are important for enhancing soil health and can provide numerous soil, agricultural, and environmental benefits. The study objective was to investigate the effects of cover crops and biofuel crops on soil hydraulic properties relative to traditional management for claypan soils. The study site included selected management practices: cover crop (CC) and no cover crop (NC) with corn/soybean rotation, switchgrass (SW), and miscanthus (MI). The CC mixture consisted of cereal rye, hairy vetch, and Austrian winter pea. The research site was located at Bradford Research Center in Missouri, USA, and was implemented on a Mexico silt loam. Intact soil cores (76‐mm diam. by 76‐mm long) were taken from the 0–10, 10–20, 20–30, and 30–40 cm depths with three plot replicates and two sub‐samples per plot replicate per depth. Soil hydraulic properties evaluated for each sample included: saturated hydraulic conductivity (Ksat), water retention, bulk density, and pore size distributions. Results showed with the test of Duncan's least significant differences that treatments of MI (1.18 Mg m−3) and SW (1.21 Mg m−3) had lower values of bulk density averaging across soil depth than CC (1.27 Mg m−3) and NC (1.31 Mg m−3). Management systems significantly increased Ksat with the biofuel treatments at 0–10 cm compared to NC system. The MI management showed a significant increase in macroporosity and fine mesoporosity as compared to other management systems. Slight changes have occurred in the measured soil physical properties for CC system compared to NC plots. Overall, increasing soil organic matter from more plant roots from long‐term biofuel cropping systems can improve soil water storage and crop productivity.

Spatial variability of denitrification enzyme activity and actual denitrification emissions on Missouri claypan soils

AbstractDenitrification in agricultural soils is responsible for the majority of anthropogenic N2O production. The objective of this research was to assess denitrification potential and the spatial dependence of soil N2O flux from claypan soils in the Central Claypan Region of Missouri. Surface soil samples (0–10 cm) were collected on a 90‐m grid from two claypan fields, one conventionally managed in a corn (Zea maysL.)–soybean [Glycine max(L.) Merr.] rotation with tillage and without cover crops (Field 1), and the other managed as a corn–soybean–wheat (Triticum aestivumL.) rotation with no‐till and cover crops (Field 3). The denitrification enzyme activity (DEA) protocol was used to measure denitrification potential and actual soil denitrification rates of N2O and N2were measured with the N‐free atmospheric recirculation method (N‐FARM). In both fields, DEA fluxes were highest in the toeslope, with a rate of 1.4 kg N ha–1d–1in Field 1, and 1.8 kg N ha–1d–1in Field 3. Actual denitrification was dominated by N2(>85%) rather than N2O emissions, and it was considerably lower than DEA. Actual N2, N2O, and total denitrification (N2+ N2O) fluxes were not different between fields; however, only total denitrification flux showed an effect of landscape position similar to that of DEA in both fields. Although the high smectitic clay content of upland soils provides environmental conditions suitable for denitrification, these results indicate that the accumulation of soil C in the toeslope position controlled DEA and actual denitrification rates.

Long‐term tillage management affects claypan soil properties and soybean cyst nematode

AbstractUse of cover crops with conservation tillage systems can affect soil chemical and biological properties. The objectives of this research were to evaluate the effect of long‐term (1994–2016) no‐till (NT) and reduced‐till (RT) cropping systems on soil chemical properties and soybean cyst nematode (SCN, Heterodera glycines Ichinohe) egg population densities on claypan soils in northeast Missouri. Treatments included a corn (Zea mays L.)–soybean [Glycine max (L.) Merr.]–wheat (Triticum aestivum L.) rotation with three tillage–cropping systems: (a) NT corn–soybean–wheat with double‐crop soybean (NTDCS), (b) NT corn–soybean–wheat with frost‐seeded red clover (Trifolium pretense L.) cover crop (NTFSC), and (c) RT corn–soybean–wheat. Each crop (corn, soybean, and wheat) and tillage system (NTDCS, NTFSC, and RT) was represented every year in nine large plots and replicated four times. Soil was sampled to a 15 cm depth to evaluate soil chemical properties (1994, 2002–2016) and SCN egg densities (2002–2015). Soil test pHs, P, and K were ranked RT = NTDCS > NTFSC, RT > NTDCS = NTFSC and RT > NTFSC > NTDCS, respectively. Long‐term NTFSC cover crop had the greatest soil organic matter levels in four of the 16 yr. When combined over years, SCN egg densities were lowest in NTFSC following corn, soybean, or wheat, which indicates the benefit of NT and extended crop rotations to help manage this pest.

Long‐term yield response of corn, wheat, and double‐crop soybean to tillage and N placement

AbstractOn claypan soils of the eastern Great Plains, yield of no‐till crops often lags yield of crops grown with tillage, especially cereals requiring sound N management. The objective of this 14‐yr study was to determine the yield response of corn (Zea mays L.), winter wheat (Triticum aestivum L.), and double‐crop soybean [Glycine max (L.) Merr.] in a 2‐yr rotation to tillage system and N fertilizer placement. Tillage, N placement, or their interaction affected corn yield in all seven‐corn crop‐years. Corn yields averaged about 25% lower with no‐till than with conventional or reduced tillage and were never greater with no‐till in any year. Nitrogen fertilization increased corn yield by increasing kernels per ear; however, corn yield increase to subsurface band (knife) N applications compared with surface (broadcast or dribble) applications was only about 10%. In the lower‐yielding no‐till system, corn yield increase to knifed N fertilization was greater than in tilled systems and may partially ameliorate the no‐till yield decline. Average wheat yield was unaffected by tillage. Adding N more than doubled wheat yield, but differences in wheat yield between preplant N placements methods were small. Average double‐crop soybean yield was unaffected by tillage with few, inconsistent differences by year. Compared with no‐till, tillage tended to increase soil P and K, but soil organic matter was just redistributed with no net increase with no‐till. Thus, tillage and N placement treatments may affect corn but have lesser effects on wheat and double‐crop soybean and soil properties in this rotation.

Long-term drainage, subirrigation, and tile spacing effects on maize production

• Not a single year in 17-yr of research received normal precipitation (Apr to Sep). • Long-term data indicated narrow tile spacing reduce yearly yield variability. • Averaged by weather classifications, yield increase upto 32 % was observed with DSI. • Yields above the DSI tiles were >60 % compared to DP & ND in dry years. • Grain yield variability generally decreased from a dry to a normal year. Flooding and drought are the most damaging abiotic stresses affecting maize production in the United States. To combat these stresses, subsurface tile drainage systems were used in conjunction with water-level control structures for subirrigation of claypan soils. The objective of this research was to develop an understanding of climate and drain tile spacing on maize plant population, grain moisture, grain yield, and grain quality measured from drainage only (DO, tile spacing 6.1 and 12.2 m), drainage and subirrigation (DSI, tile spacing 6.1 and 12.2 m), non-drained delayed planting (DP), and non-drained (ND) treatments in a 17 year (2002–2018) experiment. Production data were classified into normal, wet, and dry years based on precipitation received during the 2nd quarter (Q2, Apr. to Jun.) and 3rd quarter (Q3, Jul. to Sep.). There was not a single year in 17-yr of research that received normal precipitation in Q2 and Q3 (314 ± 43 and 288 ± 34 mm) compared to 29-yr historical precipitation data. Data were collected at 3.1 m intervals above and between the 6.1 and 12.2 m tile lines and compared among drainage treatments and weather classifications (WC). A yield increase of 20–32% (2.6 to 3.9 Mg ha −1 ) with DSI above the tile compared to DP and ND treatments when data were averaged over WC. In years classified as dry-dry, yields above the DSI tiles were >60 % compared to DP and ND. Grain yield was highest for years that had less than average precipitation during Q2 classified (dry) followed by a normal or wet Q3 period. Grain yield variability among WC was between 10.8 to 16.2 Mg ha −1 for DSI-6.1 and -12.2 above the tile whereas it was between 2.9 to 15.1 Mg ha −1 for ND. Grain yield variability generally decreased from a dry to a normal year. Long-term yield data indicated that narrower drain tile spacings with subirrigation reduce grain yield variability in dry and wet environments; however, the cost-effectiveness of these systems needs to be determined.

Corn response to tillage and side‐dress nitrogen management on claypan soil

AbstractSince information islimited regarding N management and tillage options for corn (Zea mays L.) grown on claypan soil in the eastern Great Plains, the objective of this study was to determine the effect of preplant and side‐dress N applications on corn grown in conventional‐ and no‐till systems. The yield penalty for no‐till grown corn was nearly 20% due partially to an 8% stand reduction, but also to lower kernel weight and kernels ear–1 than with conventional till. These yield and yield component reductions with no‐till may be because of lower dry matter production and N uptake throughout the growing season. The general lack of interactions suggest that N management system effects on corn were not influenced by tillage system selection. Fertilizing with N more than doubled corn yields primarily by nearly doubling the number of kernels ear–1, but with additional increases in kernel weight and average number of ears plant–1. Averaged over years, split‐N resulted in up to 15% greater yield, and additional side‐dress N resulted in up to 28% greater yield than when 168 kg N ha–1 was applied only at preplant, with no yield reduction for delaying side‐dress application from V6 to V10. The relationship of relative N uptake to relative corn yield approached a direct 1:1 relationship by R1 (silking). The decision of whether to split‐apply fertilizer N or to add additional N, regardless of tillage system, will likely be influenced by economic factors, but side‐dress N applications may extended to the V10 stage with no yield penalty.

Cover crop influence on soil water dynamics for a corn–soybean rotation

AbstractCrop production is reduced by insufficient and/or excess soil water, which can significantly decrease plant growth and development. Therefore, conservation management practices such as cover crops (CCs) are used to optimize soil water dynamics, since CCs can conserve soil water. The objective of this study was to determine the effects of CCs on soil water dynamics on a corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation at three soil depths over 3 yr. The study was conducted at the Chariton County Cover Crop Soil Health Research and Demonstration Farm (CCSH) in Missouri. Initial CC establishment occurred in 2012. Volumetric soil water content (VWC) was monitored at 15‐min intervals with calibrated Waterscout SM100 soil moisture sensors (Spectrum Technologies) at three depths (10, 20, and 30 cm) in 2016, 2017, and 2018. Cover crop soils maintained numerically higher VWC values compared with no CC (NCC) at both 10‐ and 20‐cm depths throughout the study period where the differences were significant in some weeks. The subsurface soil water recharge was greater in CC soils at both 10‐ and 20‐cm depths compared with NCC in March 2017. The results imply that CC soils have maintained higher VWC levels during vegetative period of the CC growth where the differences were significant in some weeks compared with NCC at all three soil depths. These findings can be used to promote CC adoption for better soil water storage and develop CC management plans for corn–soybean rotations on claypan soils.

Planting depth and within‐field soil variability impacts on corn stand establishment and yield

AbstractSeedbed conditions during corn (Zea mays L.) planting can have substantial impact on corn stand establishment and final yield. Planting management decisions are complex due to spatial variability caused by changing soil characteristics such as soil texture or landscape position. Field experiments conducted in central Missouri from 2017 to 2019 assessed the effects of varying corn planting depths on stand establishment and yield. Sites included fine‐ and coarse‐textured alluvial soils, and summit, back, and foot slope positions of Alfisol claypan soil landscapes. On alluvial soil, deep planting (7.6 cm) often had the most uniform and timely emergence. Shallow planting (3.8 cm) had the least uniform emergence and was particularly troublesome on fine‐textured soil under warm conditions. Under these conditions, grain yield for one site‐year was 2.8 Mg ha–1 less when planting shallow compared with planting deep. On the claypan landscape position study, stand establishment was affected by both warm and cool growing conditions during the emergence period. During warm conditions, deep planting enhanced emergence uniformity and rate (1.1 d less to reach 90% emergence than shallow planting); the opposite was true for cool conditions (3.7 d more). Yield was not affected by planting depth at any of the site‐years of the landscape position study. These results indicate that certain soil textures and landscape positions require greater attention to planting depth to achieve optimum stand establishment. Differences could be used in on‐the‐go planter prescriptions. These findings also demonstrate that despite early establishment differences, stands can often compensate and maintain similar yield.

Utilizing soil phosphorus and potassium reserves for soybean production on a claypan soil

AbstractUnder temporary economic stress, producers may elect to grow crops without fertilization. However, information is lacking regarding crop and soil response to growing multiple crops without phosphorus (P) and potassium (K) fertilization on claypan soils in the eastern Great Plains. The objective of this study was to determine the effect of utilizing soil‐test P (STP) and soil‐test K (STK) reserves on yield of 5‐yr continuous soybean [Glycine max (L.) Merr.] grown on a claypan soil and on soil‐test values. In the first two low‐yielding years, soybean yield and yield components were unaffected by STP and STK concentrations. In the subsequent three average‐yielding years, soybean yields were up to 0.35 Mg ha−1 less when STP was initially 5 mg kg−1 or STK was initially 57 mg kg−1 than at greater STP or STK. Greater STP increased pods plant−1, whereas greater STK increased pods plant−1, seed pod−1, and seed weight. Even though P and K uptake at R2 (full bloom) did not correlate directly with yields, greater P uptake at R2 in average‐yielding years increased pods plant−1 and greater K uptake at R2 increased seed pod−1. Both STP and STK declined at more than 3 mg kg−1 yr−1 for larger initial STP and 15 mg kg−1 yr−1 for larger initial STK. While using residual soil P and K of varying concentrations in this claypan soil to grow soybeans marginally affected yields, the 5‐yr decline in STP and STK values may greatly affect subsequent sensitive crops and require high rates of fertilization.

Adaptation to Early-Season Soil Waterlogging Using Different Nitrogen Fertilizer Practices and Corn Hybrids

Excessive rainfall occurring in the early spring season in the Midwestern United States result in waterlogged soils contributing to corn production losses. The objective of our study is to evaluate the impact of soil waterlogging [non-waterlogged or waterlogged for 7 days when corn was at V3 growth stage (corn plant having three fully developed leaves with collar visible)], different pre-plant nitrogen (N) fertilizer sources and post-waterlogging rescue N fertilizer on grain and silage yield of two commercially available corn hybrids with different flood tolerance. Pre-plant N fertilizer was applied at 168 kg N ha−1. Nitrogen sources were a non-treated control (CO), polymer coated urea (PCU), urea (NCU), and urea plus Instinct (NCU + NI). A post-waterlogging rescue N fertilizer was applied at V7 as 0 or 83 kg N ha−1 of urea plus N-(n-butyl) thiophosphoric triamide (NBPT) (NCU + UI). Waterlogging decreased grain and silage yields in different years; however, significant interactions were observed among treatments. Rescue N applications increased grain yields by 6–46% in non-waterlogged treatments, but not in waterlogged treatments. The PCU and NCU + NI increased grain yields compared to the CO. Pre-plant N sources showed no significant differences in grain yield, probably due to existing environmental conditions or incorporation of fertilizer. The N source, application method, and timing for post-waterlogging rescue N application and flood-tolerant corn hybrids needs further investigation in poorly-drained claypan soils prone to waterlogging under a changing climate.

Long‐term perennial management and cropping effects on soil microbial biomass for claypan watersheds

AbstractSustainable vegetative management plays a significant role in improving soil quality in degraded agricultural landscapes by enhancing soil microbial biomass. This study investigated the effects of grass buffers (GBs), biomass crops (BCs), grass waterways (GWWs), and agroforestry buffers (ABs) on soil microbial biomass and soil organic C (SOC) compared with continuous corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation (row crop [RC]) on claypan soils. The RC, AB, GB, GWW, and BC treatments were established in 1991, 1997, 1997, 1997, and 2012, respectively, and are located at Greenley Memorial Research Center in Missouri. Soil samples were collected in May 2018 from the 0‐ to 10‐cm depth at summit, backslope, and footslope landscape positions. Within AB treatment, soils were collected from the 50‐cm and 150‐cm tree distance. Total microbial biomass and biomass of gram‐positive bacteria, gram‐negative bacteria, actinomycetes, rhizobia, fungi, arbuscular mycorrhizae, saprophytes, and protozoa were determined by phospholipid fatty acid (PLFA) analysis. Results showed that soil microbial biomass and SOC across all microbial groups were significantly higher (P < .01) under perennial vegetation treatments compared with RC. The footslope position exhibited the highest total microbial biomass compared with the summit and backslope positions. The sampling distance of 50 cm from the tree base demonstrated 16% greater total microbial biomass and 15% higher SOC compared with 150 cm. These findings highlight the influence of landscape on soil biological properties and show that perennial vegetation systems have the potential to increase soil microbial biomass and enhance agricultural sustainability in degraded RC systems.

Long‐term in‐season grain sorghum and soybean response to tillage and nitrogen management

AbstractInformation on tillage and N management is limited regarding in‐season N uptake by grain sorghum [Sorghum bicolor (L.) Moench] and growth of soybean [Glycine max (L.) Merr.] on claypan soils in the eastern Great Plains. The objective of this study was to determine the 20‐yr effects of tillage (conventional, reduced, and no‐till) and N fertilization (no‐N control; knifed anhydrous NH3; broadcast urea–ammonium nitrate solution, UAN; and broadcast dry urea) on grain sorghum N uptake and soybean biomass and their relationship to long‐term yields of those crops grown on a claypan soil. Nitrogen uptake at the boot stage during the first 10‐yr period was more than 20% greater with either conventional or reduced tillage compared with no‐till, and often greater with anhydrous NH3 and urea N sources than with UAN solution or the no‐N control. During the second 10‐yr period, N uptake was generally greater with conventional and reduced tillage than with no‐till at the 9‐leaf stage, but this response did not persist to the boot stage. Anhydrous NH3 often resulted in greater N uptake at both the 9‐leaf and boot stages compared with the other N sources. The relative yield increases with N uptake at the boot stage appeared due to increasing kernels head−1 but diminished as uptake exceeded 70−80 kg N ha−1. Although dry matter measured at the R2 growth stage of soybean rotationally grown in even‐numbered years was about 10% greater with tilled options than with no‐till, biomass was not related to yield increases.

Pre-Plant Nitrogen Rate and Application Method and Side-Dress Nitrogen Rate Effects on No-Till Corn Grown on a Claypan Soil

Pre-Plant Nitrogen Rate and Application Method and Side-Dress Nitrogen Rate Effects on No-Till Corn Grown on a Claypan Soil