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Maintaining crop residue through no‐tillage (NT) has allowed increased water storage and continuous cropping in dryland wheat (Triticum aestivum L.)‐based systems. However, there is little information regarding nitrogen (N) fertilizer rates for a continuous NT wheat cropping system across various yield environments. The main objective of this study was to determine agronomic optimum N rates for a continuous NT wheat in different yield environments. The study was conducted from 1981 through 2003 at the Kansas State University Agricultural Research Center near Hays, with six N fertilizer rate treatments (0, 22, 45, 67, 90, and 112 kg N ha−1). Experimental years were divided into four yield environments: very low yielding (VLY), low yielding (LY), high yielding (HY), and very high yielding (VHY). Results showed that LY environments required a relatively greater N amount (79–98 kg N ha−1) than HY to VHY environments (72–73 kg N ha−1) to attain optimal yields. The optimal yields at low‐yield environments were smaller (1184–1654 kg ha−1) than in high‐yield environments (2181–2733 kg ha−1). Protein yield increased by 120 g for 1 kg increase in grain yield. We concluded that the optimum N fertilizer rates for continuous NT wheat ranged from 70 to 100 kg N ha−1, but these rates should be adjusted based on yield environments. Core Ideas Optimal N rate was greater in low‐yield (79–98 kg N ha−1) than high‐yield (72–73 kg N ha−1) environments. Yields at optimal N rate for low‐yield (1184–1654 kg ha−1) were less than high‐yield (2181–2733 kg ha−1) environments. Protein yield increased by 120 g for 1 kg increase in grain yield. No‐tillage N rates should be adjusted based on yield environments.

The water-limited environment of the semiarid Central Great Plains may not produce enough cover crop biomass to generate benefits associated with cover crop use in more humid regions. There have been reports that cover crops grown in mixtures produce more biomass with greater water use efficiency than single-species plantings. This study was conducted to determine differences in cover crop biomass production, water use efficiency, and residue cover between a mixture and single-species plantings. The study was conducted at Akron, CO, and Sidney, NE, during the 2012 and 2013 growing seasons under both rainfed and irrigated conditions. Water use, biomass, and residue cover were measured and water use efficiency was calculated for four single-species cover crops (flax [Linum usitatissimum L.], oat [Avena sativa L.], pea [Pisum sativum ssp. arvense L.Poir], rapeseed [Brassica napus L.]) and a 10-species mixture. The mixture did not produce greater biomass nor exhibit greater water use efficiency than the single-species plantings. The slope of the water-limited yield relationship was not significantly greater for the mixture than for single-species plantings. Waterlimited yield relationship slopes were in the order of rapeseed < flax < pea < mixture < oat, which was the expected order based on previously published biomass productivity values generated from values of glucose conversion into carbohydrates, protein, or lipids. Residue cover was not generally greater from the mixture than from single-species plantings. The greater expense associated with a mixture is not justified unless a certain cover crop forage quality is required for grazing or haying.

World corn (Zea mays L.) production has tripled since the 1960s. However, without new breakthrough innovations the trend is expected to plateau or decrease in the future. The objective of this study was to quantify Kansas corn production, economic value, productivity, annual production variation, yield gap trends, and in due course, identify future areas for research. Corn variety performance tests and United States Department of Agriculture (USDA) data were used for this study. Results showed that the area planted to corn in Kansas increased from 0.5 million in 1880s to over 2 million ha by 2022, with an increase of 0.05 million ha year−1 between 1984 and 2022. The value of corn produced in Kansas also increased significantly from below$1 billion annually prior to 1990s to the current value of approximately $ 3–$4 billion. The average corn yield gain from 1972 to 2000 was 132 kg ha−1 year−1, which declined to 12 kg ha−1 year−1 during 2000 to the early 2020s. Also, a relatively high yield variability occurred from 1970 to the early 2020s compared with earlier years (1866–1970), and a 42%–68% gap between the potential and actual corn yields was identified. We concluded that there is a decrease in the rate of corn yield increase and developing farmer awareness and their adoption of new corn production technology, increasing longevity of the Ogallala Aquifer, and integrated research should be priorities to avert the decreasing trend of corn productivity and further increase corn economic value. Core Ideas In Kansas, the amount of land seeded for corn increased at rate of 0.05 million ha year−1 between 1984 and 2022. The value of corn produced in Kansas increased from <1 billion in 1990 to >3 billion dollars year−1 in 2020s. Corn yield gain from 1972 to 2000 was 132 kg ha−1 year−1, which declined to 12 kg ha−1 year−1 during 2000–2020. A relatively high yield variability occurred from 1970 to the early 2020s compared with earlier years (1866–1970). A 42%–68% gap between the potential and actual corn yields was identified.

Identifying the limiting nutrient, fertilizer source, rate, placement, additives, and timing of application are critical components of fertilizer management. The objective of this study was to quantify the impact of nitrogen (N) fertilizer source, rate, placement method, additives, application timing, and environment on yields of grain sorghum, forage sorghum [ Sorghum bicolor (L.) Moench], and corn (for grain, Zea mays L.). Independent field experiments were conducted at 13 different environments in Kansas from 2008 through 2013 on grain sorghum, forage sorghum, and corn. Treatments were an incomplete factorial combination of four fertilizer placement methods, three fertilizer types, five fertilizer additives, three fertilizer application times, and six fertilizer rates that varied by location and across years. Results showed grain and forage sorghum yields responded to N fertilizer in environments that were not extremely dry (<136 mm) or wet (>651 mm). Corn responded to N fertilizer application only in high‐precipitation environments. For grain sorghum, where rate × placement × source × additive interaction was significant, broadcast application of urea (source) at high rates (67–134 kg N ha −1 ), with summer application timing, or with additive in winter (with environmentally smart nitrogen [ESN]) resulted in up to 43% greater yield compared with application of urea‐ammonium nitrate (UAN; source) and surface band (placement) at 67 kg ha −1 without additives. In the one site‐year where forage sorghum responded to fertilizer application, forage yields with preplant application of UAN at 56–140 kg ha −1 were 164% greater than the control. For corn, application of either urea or UAN fertilizer, UAN in coulter or surface band, with ESN blend, applied at planting, and at highest rates (160 kg ha −1 ) resulted in best yields compared with the alternatives and 110% greater yield compared with the unfertilized control. We concluded that fertilizer rate is an important management component as it consistently affected yield regardless of crop considered. Fertilizer placement and timing have crop‐specific importance as they were significant for only corn, but the main effect of additives (N stabilizers) was not significant for any of the crops. Environment and crop type influenced crop response to N fertilizer rate, timing, placement, and additives. Grain and forage sorghum responded positively to N fertilizer in environments that were not extremely dry or wet. Corn responded to N fertilizer only in high‐precipitation environments. For grain sorghum, in three out of nine trials, source × rate × placement × additive interaction was significant. Regardless of crop, N fertilizer rate was an important management decision that affected yields. Fertilizer placement and timing had crop‐specific importance.

There is limited information regarding the grain sorghum production trends from early in the millennium towards the 2020s. The main objective of this study was to quantify the grain sorghum production area, economic value, productivity, annual production variation, relationship with changing weather patterns, and yield gap and to identify future areas of intervention and research. The results indicated that the grain sorghum production area in Kansas has increased in the most recent decade (2010–2022) at an average rate of 8 thousand ha year−1. With the current 1.2 million ha harvest area, Kansas continues to allocate more land area for sorghum than any other state in the USA. The average current annual economic value of sorghum in Kansas is USD 0.5 billion. The average sorghum grain productivity for recent years (2000–2022) was 4.3 Mg ha−1 in Kansas. The year-to-year yield variation in the grain sorghum average for Kansas in the years 1929–1956 was ±0.5 Mg ha−1 but increased to ±2 Mg ha−1 for the years 1957–2022. The results also showed a 66 to 96% yield gap between the actual yield (USDA data) and potential non-irrigated yield (Kansas State Grain Sorghum Hybrid Performance Trial data). There was a significant positive correlation between the July–August precipitation and a significant negative correlation between air temperatures and sorghum yield. We conclude that there was an increasing sorghum harvest area trend in Kansas for the years 2010 to 2022. Further research that identifies more unique and important agronomic and economic advantages of sorghum, increasing productivity per unit area across different environments, communicating existing benefits, and developing crop production management best practices are essential to sustain gains in the production area.

Annual forages can be grown more intensively than grain crops, which may have negative impacts on soil health because of biomass removal. The objective of this study was to determine the effects of annual forage crop rotations of varying intensity, diversity, forage removal, and associated tillage practices on soil physical and chemical properties. A long‐term forage study was conducted near Garden City, KS. The six rotation and tillage combination treatments of the study were (1) forage sorghum (Sorghum bicolor (L.) Moench)–forage sorghum (FS–FS) no‐tillage (NT), (2) triticale (×Triticosecale Wittm. ex A. Camus [Secale × Triticum])/FS–FS–oat (Avena sativa L.; T/FS–FS–O) reduced till (RT), (3) T/FS‐FS‐O NT, (4) T/FS–FS–FS‐O NT, (5) T/FS–FS–FS–O RT, and (6) T–FS–O NT. Soil samples were taken in 2021 and 2022 at depths of 0–5 cm and 5–15 cm from the experimental plots and adjacent land used for grain production in a wheat‐sorghum‐fallow rotation. Results of the study indicated that the less intense rotation, T‐FS‐O, had more water stable microaggregates, the grain control had smaller macroaggregates, and T/FS‐FS‐O RT had larger macroaggregates and tended to have fewer small aggregates. Similarly, diverse forage rotations like T‐FS‐FS‐FS‐O had larger sized (2.0–6.3 mm) dry aggregates and tended to have fewer smaller aggregates. The grain control had more medium sized (0.42–0.84 mm) dry aggregate than T/FS‐FS‐O RT. Soil total nitrogen concentrations were less for less diverse or less intense forage rotations compared with the grain control, and soil organic carbon (SOC) and P were less for all forages compared with the grain control, perhaps because forage harvesting reduced crop residue cover and organic matter cycling. We conclude that forage systems that remove biomass from the field should be integrated with management that leaves more residue on the soil surface, such as allowing forage regrowth after hay harvest, alternating between hay removal and grazing, or rotating between forage and grain crops to keep more residue on the soil surface to maintain SOC and protect the soil from erosion. Core Ideas Soil properties, such as aggregate size, N, P, and SOC concentrations, were affected more by rotation than by tillage. Forage rotations with greater diversity and intensity had 20% larger dry soil macroaggregates than the grain control. Forage rotations resulted in 4%–7% greater bulk density, 23%–36% less K, and 8%–17% less SOC than the grain control. Forage systems that remove biomass from the field should be integrated with management that leaves more residue on the soil surface.

Multiple herbicide classes–resistant (MHCR) kochia poses a serious concern for producers in the Central Great Plains, including western Kansas. Greenhouse and field experiments were conducted at Kansas State University Research and Extension Centers near Hays and Garden City, KS, to evaluate pyridate-based postemergence herbicide mixtures for controlling MHCR kochia. One previously confirmed MHCR population (resistant to atrazine, glyphosate, dicamba, and fluroxypyr) and a susceptible (SUS) kochia population were tested in a greenhouse study. The kochia population at Hays field site was resistant to atrazine, dicamba, and glyphosate, whereas the kochia population at the Garden City site was resistant to atrazine and glyphosate. Colby’s analysis revealed synergistic interactions when pyridate was mixed with atrazine, dicamba, dichlorprop-p, fluroxypyr, glyphosate, or halauxifen/fluroxypyr and resulted in ≥94% control and shoot dry-biomass reduction of MHCR kochia in a greenhouse study. Similarly, synergistic interactions were observed for MHCR kochia control in fallow field studies at both sites when pyridate was mixed with glyphosate or atrazine. Kochia control was increased from 26% to 90% with the application of glyphosate + pyridate and from 28% to 95% with atrazine + pyridate at both sites as compared to separate applications of glyphosate or atrazine. This is the first report for such a strong synergistic effect for both glyphosate and atrazine mixtures with pyridate on a weed resistant to both. All other pyridate-based herbicide mixtures showed an additive interaction and resulted in better control of MHCR kochia (87% to 100%) as compared to their individual applications (23% to 92%) across both sites except 2,4-D. These results suggest that pyridate can play a crucial role in various postemergence herbicide mixtures for effective control of MHCR kochia.

A field study was conducted from 2020 to 2023 at Kansas State University Agricultural Research Center near Hays, KS, to understand the emergence dynamics and periodicity of glyphosate-resistant (GR) Palmer amaranth (Amaranthus palmeri S. Watson) as influenced by cover crop (CC) residue and residual herbicide in grain sorghum [Sorghum bicolor (L.) Moench]. The study site was under a wheat (Triticum aestivum L.)–sorghum–fallow rotation with a natural seedbank of GR A. palmeri. Treatments included (1) fall-planted CC mixture [winter triticale (×Triticosecale Wittm. ex A. Camus [Secale × Triticum])/winter peas (Pisum sativum L.)/ rapeseed (Brassica napus L.)/radish (Raphanus sativus L.)] after wheat harvest and terminated at triticale heading stage (next spring before sorghum planting) with glyphosate alone or (2) glyphosate plus acetochlor/atrazine, (3) chemical fallow (no CC but treated with acetochlor/ atrazine and dicamba before sorghum planting), and (4) nontreated control (no CC and no herbicide). Results indicated that CC terminated with glyphosate plus acetochlor/atrazine had a delayed and reduced cumulative emergence of GR A. palmeri as compared with chemical fallow and CC terminated with glyphosate alone across all 3 yr. Compared with chemical fallow, the CC terminated with glyphosate alone and glyphosate plus acetochlor/atrazine required 66 to 643 and 105 to 1,257 more cumulative growing degree days, respectively, to achieve 90% cumulative emergence of GR A. palmeri across all 3 yr. The combined effect of CC residue with glyphosate plus acetochlor/atrazine reduced the total emergence counts of GR A. palmeri by 42% to 56% and 82% to 94% as compared with chemical fallow and nontreated control, respectively. These results suggest that fall-planted CC combined with a residual herbicide at termination can be utilized for GR A. palmeri suppression in grain sorghum.

Integrating cover crops (CCs) in dryland crop rotations could help in controlling herbicide-resistant weeds. Field experiments were conducted at Kansas State University Agricultural Research Center near Hays, KS, from 2020 to 2023 to determine the effect of fall-planted CCs on weed suppression in grain sorghum [Sorghum bicolor (L.) Moench], crop yield, and net returns in no-till dryland winter wheat (Triticum aestivum L.)–grain sorghum–fallow (W-S-F) rotation. The field site had a natural seedbank of glyphosate-resistant (GR) kochia [Bassia scoparia (L.) A. J. Scott] and Palmer amaranth (Amaranthus palmeri S. Watson). A CC mixture [winter triticale (×Triticosecale Wittm. ex A. Camus [Secale × Triticum])–winter peas (Pisum sativum L.)–canola (Brassica napus L.)–radish (Raphanus sativus L.)] was planted after wheat harvest and terminated at triticale heading stage before sorghum planting. Treatments included nontreated control, chemical fallow, CC terminated with glyphosate (GLY), and CC terminated with GLY+ acetochlor/atrazine (ACR/ATZ). Across 3 yr, CC terminated with GLY+ACR/ATZ reduced total weed density by 34% to 81% and total weed biomass by 45% to 73% compared with chemical fallow during the sorghum growing season. Average grain sorghum yield was 786 to 1,432 kg ha−1 and did not differ between chemical fallow and CC terminated with GLY+ACR/ATZ. However, net returns were lower with both CC treatments (−US$275 to US$66) in all 3 yr compared with chemical fallow (−US$111 to US$120). These results suggest that fallow replacement with fall-planted CCs in the W-S-F rotation can help suppress GR B. scoparia and A. palmeri in the subsequent grain sorghum. However, the cost of integrating CCs exceeded the benefits of improved weed control, and lower net returns were recorded in all 3 yr compared with chemical fallow.

Multiple herbicide–resistant (MHR) kochia [Bassia scoparia (L.) A.J. Scott] is a concern for farmers in the Great Plains. A total of 82 B. scoparia populations were collected from western Kansas (KS), western Oklahoma (OK), and the High Plains of Texas (TX) during fall of 2018 and 2019 (from the various locations), and their herbicide resistance status was evaluated. The main objectives were to (1) determine the distribution and frequency of resistance to atrazine, chlorsulfuron, dicamba, fluroxypyr, and glyphosate; and (2) characterize the resistance levels to glyphosate, dicamba, and/or fluroxypyr in selected B. scoparia populations. Results indicated that 33%, 100%, 48%, 30%, and 70% of the tested B. scoparia populations were potentially resistant (≥20% survival frequency) to atrazine, chlorsulfuron, dicamba, fluroxypyr, and glyphosate, respectively. A three-way premixture of dichlorprop/dicamba/2,4-D provided 100% control of all the tested populations. Dose–response studies further revealed that KS-9 and KS-14 B. scoparia populations were 5- to 10-fold resistant to dicamba, 3- to 6-fold resistant to fluroxypyr, and 4- to 5-fold resistant to glyphosate as compared with the susceptible (KS-SUS) population. Similarly, OK-10 and OK-11 populations were 10- to 13-fold resistant to dicamba and 3- to 4-fold resistant to fluroxypyr and glyphosate compared with the OK-SUS population. TX-1 and TX-13 B. scoparia populations were 2- to 4-fold resistant to dicamba, and TX-1 was 5-fold resistant to glyphosate compared with the TX-SUS population. These results confirm the first report of dicamba- and fluroxypyr-resistant B. scoparia from Oklahoma and glyphosate- and dicamba-resistant B. scoparia from Texas. These results imply that adopting effective integrated weed management strategies (chemical and nonchemical) is required to mitigate the further spread of MHR B. scoparia in the region.