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Context Sustainable management of the soil is one of the pillars of conservation agriculture (CA). Aims The objective of this study was to evaluate the long-term effects of soil management systems (SMS) on liming efficiency, soil chemical properties and wheat yield. Methods This study was part of a long-term experiment established in 1986 in Passo Fundo, Rio Grande do Sul, Brazil, but using data from 2008 to 2015 to explore the effects of agricultural lime applied in 2008. The experiment was laid out in a split-plot design where the main plot (SMS) were arranged in randomised blocks and the cropping systems (sub-plot treatments) were randomised within the main plots. This study assessed the effects of the SMS; i.e. two CA systems [no-tillage (NT) and reduced tillage] and two conventional tillage (CT) systems (disk ploughing + disk harrowing annually, and mouldboard ploughing + disk harrowing annually). Key results The NT system was the most sustainable due to improvements in soil organic carbon concentration. After liming, CT systems were more effective than CA systems in decreasing Al3+ toxicity and increasing soil pH and Ca2+ and Mg2+ concentrations at deeper soil layers. The NT system had a considerable advantage over other SMS, due to a greater average wheat yield (18%). Conclusions The SMS evaluated in this study modified chemical properties when compared with the native forest area. The NT system was the least detrimental to soil organic carbon, an important indicator of soil quality. Implications The NT system provided greater average wheat yield (18%), and thus was the most viable SMS for subtropical spring wheat production.

Made available in DSpace on 2022-05-01T07:59:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-09-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Stimulant fertilization isthe supplementary application of low doses of foliar fertilizers to otherwise well-fertilized crops, and literature suggests that it may increase grain yield. However, the physiological mechanisms behind this potential yield increase are not well understood. This study investigated the effect of supplementary foliar nitrogen (N) in soybean [Glycine max (L.) Merr.] and maize (Zea mays) nutrition, photosynthetic parameters, antioxidant metabolism, agronomic parameters, and grain yield. We tested the presence or absence of low rates of late season (R3 and V10 of soybean and maize, respectively) foliar N fertilization in a main season soybean followed by an off-season maize. While there were no effects of N application on leaf nutrient concentration, the net photosynthetic rate, stomatal conductance, water use efficiency, and carboxylation efficiency increased due to foliar N fertilization in both crops. The improvement in photosynthesis occurred due to a concomitant increase in Rubisco activity and in the concentration of sugar in the leaves prior to grain filling. Foliar N fertilization also improved antioxidant metabolism, suggesting that fertilized plants were less affected by environmental stresses during their cycle. The improvement in the metabolic activity due to foliar N did not affect grains per plant but increased a hundred grain mass and grain yield of both soybean and maize. Our results suggest that foliar N applied as stimulant fertilizer is a promising strategy to increase yield of maize and soybean crops. Dep. of Crop Science College of Agricultural Sciences São Paulo State Univ. (UNESP) Dep. of Agronomy Kansas State Univ., 2004 Throckmorton Plant Sciences Center, 1712 Claflin Road Dep. of Crop Science College of Agricultural Sciences São Paulo State Univ. (UNESP) CNPq: 134588/2018-5 CNPq: 303119/2016-0

The United States (US) is the largest alfalfa (Medicago sativa L.) producer in the world. More than 44% of the US alfalfa is produced under rainfed conditions, although it requires a relatively high amount of water compared to major field crops. Considering that yield and production of rainfed alfalfa have been relatively stagnant in the country for decades, there is a need to better understand the magnitude of yield loss due to water limitation and how far from yield potential current yields are. In this context, the main objective of this study was to estimate the current yield gap of rainfed alfalfa in the US. We collected 10 year (2009–2018) county-level government-reported yield and weather data from 393 counties within 12 major US rainfed alfalfa producing states and delineated alfalfa growing season using probabilistic approaches based on temperature thresholds for crop development. We then calculated county-level growing season rainfall (GSR), which was plotted against county-level yield to determine attainable yield (Ya) using frontier function analysis, and water-limited potential yield (Yw) using boundary function analysis. Average and potential water use efficiencies (WUE) were estimated, and associated yield gap referring to attainable (YGa) or water-limited yields (YGw) were calculated. Finally, we used conditional inference trees (CIT) to identify major weather-related yield-limiting factors to alfalfa forage yield. The frontier model predicted a mean Ya of 9.6 ± 1.5 Mg ha−1 and an associated optimum GSR of 670 mm, resulting in a mean YGa of 34%. The boundary function suggested a mean Yw of 15.3 ± 3 Mg ha−1 at the mean GSR of 672 ± 153 mm, resulting in a mean yield gap of 58%. The potential alfalfa WUE was 30 kg ha−1 mm−1 with associated minimum water losses of 24% of mean GSR, which was three times greater than the mean WUE of 10 kg ha−1 mm−1. The CIT suggested that GSR and minimum temperature in the season were the main yield-limiting weather variables in rainfed alfalfa production in the US. Our study also revealed that alfalfa was only limited by water availability in 21% of the environments. Thus, future research on management practices to narrow yield gaps at current levels of water supply is necessary.

Nitrogen management is central to the economic and environmental dimensions of agricultural sustainability. Yield response to nitrogen fertilisation results from multiple interacting factors. Theoretical frameworks are lagging for the interaction between nitrogen and air temperature, the focus of this study. We analyse the relation between yield response to nitrogen fertiliser and air temperature in the critical period of yield formation for spring wheat in Australia, winter wheat in the US, and maize in both the US and Argentina. Our framework assumes (i) yield response to nitrogen fertiliser is primarily related to grain number per m2, (ii) grain number is a function of three traits: the duration of the critical period, growth rate during the critical period, and reproductive allocation, and (iii) all three traits vary non-linearly with temperature. We show that “high” nitrogen supply may be positive, neutral, or negative for yield under “high” temperature, depending on the part of the response curve captured experimentally. The relationship between yield response to nitrogen and mean temperature in the critical period was strong in wheat and weak in maize. Negative associations for both spring wheat in Australia and winter wheat with low initial soil nitrogen (< 20 kg N ha-1) in the US highlight the dominant influence of a shorter critical period with higher temperature; with high initial soil nitrogen (> 120 kg N ha-1) that favoured grain number and compromised grain fill, the relation between yield response to nitrogen and temperature was positive for winter wheat. The framework is particularly insightful where data did not match predictions; a non-linear function integrating development, carbon assimilation and reproductive partitioning bounded the pooled data for maize in the US and Argentina, where water regime, previous crop, and soil nitrogen overrode the effect of temperature on yield response to nitrogen fertilisation.

Climate extremes cause significant winter wheat yield loss and can cause much greater impacts than single extremes in isolation when multiple extremes occur simultaneously. Here we show that compound hot-dry-windy events (HDW) significantly increased in the U.S. Great Plains from 1982 to 2020. These HDW events were the most impactful drivers for wheat yield loss, accounting for a 4% yield reduction per 10 h of HDW during heading to maturity. Current HDW trends are associated with yield reduction rates of up to 0.09 t ha−1 per decade and HDW variations are atmospheric-bridged with the Pacific Decadal Oscillation. We quantify the “yield shock”, which is spatially distributed, with the losses in severely HDW-affected areas, presumably the same areas affected by the Dust Bowl of the 1930s. Our findings indicate that compound HDW, which traditional risk assessments overlooked, have significant implications for the U.S. winter wheat production and beyond.

BACKGROUND Integrated wheat management strategies can affect grain yield and flour end-use properties. However, the effect of integrated management and its interaction with environmental factors on the phenolic acid profiles of wheat has not been reported. The phenolic acid profile has become another parameter for the evaluation of wheat quality due to its potential health benefits. RESULTS Year × location × management and year × management × genotype interactions were significant for the total phenolic content (TPC) of wheat samples. The year × location × management × genotype interaction was significant for the concentration of trans-ferulic acid and several other phenolic acids. Field management practices with no fungicide application (e.g., farmer's practice, enhanced fertility) may lead to increased accumulation of phenolic compounds, especially for WB4458, which is more susceptible to fungi infection. However, this effect was also related to growing year and location. Higher soil nitrogen content at sowing also seems to affect the TPC and phenolic acid concentration positively. CONCLUSION Wheat phenolic acid profiles are affected by genotype, field management, environment, and their interactions. Intensified field management, in particular, may lead to decreased concentration of wheat phytochemicals. The level of naturally occurring nitrogen in the soil may also affect the accumulation of wheat phytochemicals. © 2021 Society of Chemical Industry.

Appropriate genotype selection and management can impact wheat (Triticum aestivum L.) yield in dryland environments, but their impact on yield components and their role in yield modulation are not well understood. Our objectives were to evaluate the yield response of commercial winter wheat genotypes to different management practices reflecting a stepwise increase in management intensity (including a reduction in crop density under high input), and to quantify how the different yield components modulate wheat yield. A factorial experiment evaluated six management (M) intensities [“farmer practice” (FP), “enhanced fertility” (EF), “ecological intensification” (EI), “increased foliar protection” (IFP), “water-limited yield” (Yw), and “increased plant productivity” (IPP)] and four winter wheat genotypes (G) in four Kansas environments (E). Average grain yield was 4.9 Mg ha–1 and ranged from 2.0 to 7.4 Mg ha–1, with significant two-way interactions (E × M and E × G). The EF usually maximized yields in dry environments, while EI, which consisted of EF plus one fungicide application, maximized yields in environments with greater water availability. Across all sources of variation, kernels m–2 and aboveground biomass were the strongest modulators of yield as compared to kernel weight and harvest index, while spikes m–2 and kernels spike–1 modulated yields at a similar magnitude. Foliar fungicides improved yield through increased green canopy cover duration and greater radiation intercepted during grain filling. When crop density was reduced from 2.7 to 1.1 million plants per hectare in an otherwise high-input system, plants produced more productive tillers (with genotype-specific response); however, reduced green canopy cover at anthesis and reduced cumulative solar radiation intercepted during grain filling limited wheat yield—although large differences in canopy cover or intercepted radiation were needed to cause modest changes in yield. Treatments more intensive than EI were not warranted as EF or EI maximized yields at all environments, and practices that promote biomass and kernels m–2 are to be targeted for future increases in wheat yield.

Nutrient management can reduce crop yield gaps, but available literature is mostly restricted to studies limited in time, geography, or in the number of nutrients evaluated. Our objective was to synthesize long-term experiments evaluating wheat (Triticum aestivum L.) yield and grain-N concentration (GNC) response to N, P, and K fertilizer rates and their interactions. We used data from three long-term (1966–2016) experiments conducted in Oklahoma (USA) comprising 155 site-years for yield (n = 8035) and 90 site-years for GNC (n = 4580). The last year of the experiments was the baseline to de-trend yield and GNC data. We first explored relationships between grain yield and GNC, grain N removal, apparent recovery of applied N in the grain (N recovery), and N-use efficiency (NUE) as affected by the presence and rate of N, P, and K across the entire dataset. Then, we subdivided the dataset into yield-environments based on the different data quartiles, and analyzed it using descriptive statistics, multi-level modeling, differences from the control, and conditional inference trees. Our main findings were: i) wheat yield was negatively related to GNC, but positively associated with N removal, N recovery, and NUE. ii) The co-application of P and, to a lesser extent, K, increased N removal and NUE but decreased GNC. iii) The proportion of variability in yield and GNC explained by fertilizer management increased with an increase in yield-environment. iv) Wheat yield response to N and to P were typically quadratic, although response to P was restricted to high yielding environments. v) Wheat GNC increased linearly with increases in N rate, but decreased with increases in P and K rate. vi) Conditional inference trees suggested that the co-application of P and K improved yields but decreased GNC. The co-application of P and K can increased wheat yield, N removal, and NUE, but the increases in yield were greater than those in N removal, thus decreasing GNC.

Crop production of a significant portion of the Great Plains has greatly simplified the landscape, which can affect insect pest outbreaks. The Hessian fly is an important economic pest of wheat, a major crop grown in the region. However, outbreaks are often limited to localized events, which may be difficult to predict. Better understanding of where Hessian fly outbreaks are more likely to occur would help producers make informed management decisions. Therefore, the objective of our study was to describe the spatial distribution of Hessian fly infestation within commercial wheat fields, while examining how a simplified landscape may contribute to the distribution of Hessian fly infestations. Spatial distribution modeling was conducted in select fields (n = 6) infested with Hessian fly puparia. A geographic information system was used to create sampling grids for each field (n = 34–50 sample points/field), with one meter row of plants sampled at each sample point. The number of puparia and plants infested at each sample point were used to construct Hessian fly distribution maps for each field. Correlations between environmental factors and fly distribution were then examined. Results show that host plants (wheat and grasses) adjacent to the borders of study fields did not affect the distribution of puparia or plants infested within the field. Rather, the proportion of wheat within a 1 km radius of sampled fields affected the level of Hessian fly infestation, with a smaller proportion of wheat within the 1 km radius increasing the probability of Hessian fly infestation in sampled fields. The results of this study show previously unknown distribution of Hessian fly infestation within commercial wheat fields, resulting in new hypotheses about Hessian fly management in agroecosystems.

We combined field studies to regional soil databases with the objective of presenting a protocol to forecast regional gains in winter wheat (Triticum aestivum L.) forage and grain yield and revenue, from liming or selecting a variety tolerant to acidic soils. First, we developed forage and grain yield response curves to soil pH using a variety by soil pH study conducted during 3 yr (2013–2015) at two Oklahoma locations. Second, we used a database of soil pH samples representing 93% of the wheat growing region of the state (n = 11,905) coupled with 15-yr average county yield and harvested area to estimate potential gains for grain-only and dual-purpose scenarios. Relative grain yield maximized at soil pH of 5.8 for sensitive varieties and 4.8 for tolerant varieties. Forage yield maximized at soil pH of 6.0 for sensitive varieties and 5.5 for tolerant varieties. About 35% of the region had pH limiting to dual-purpose and 28% to grain-only production. Liming could improve grain-only statewide yield in 0.14 Mg ha–¹ and revenue in US$19 ha–¹, and adoption of tolerant varieties could increase yield in 0.11 Mg ha–¹ and revenue in $10 ha–¹. Liming could improve dual-purpose revenue in $37 ha–¹ and variety selection in $28 ha–¹ due to improved yield and forage. Potential additional statewide wheat production resulting from variety selection is 53,800 Mg and from liming 82,500 Mg. Our protocol can be used to aid development of agricultural policies and research prioritization at regional levels where acidic soils are prevalent.

Made available in DSpace on 2021-06-25T11:14:48Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-04-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (1) Background: The aim of this study was to explore whether supplementary magnesium (Mg) foliar fertilization to soybean and maize crops established in a soil without Mg limitation can improve the gas exchange and Rubisco activity, as well as improve antioxidant metabolism, converting higher plant metabolism into grain yield. (2) Methods: Here, we tested foliar Mg supplementation in soybean followed by maize. Nutritional status of plants, photosynthesis, PEPcase and Rubisco activity, sugar concentration on leaves, oxidative stress, antioxidant metabolism, and finally the crops grain yields were determined. (3) Results: Our results demonstrated that foliar Mg supplementation increased the net photosynthetic rate and stomatal conductance, and reduced the sub-stomatal CO2 concentration and leaf transpiration by measuring in light-saturated conditions. The improvement in photosynthesis (gas exchange and Rubisco activity) lead to an increase in the concentration of sugar in the leaves before grain filling. In addition, we also confirmed that foliar Mg fertilization can improve anti-oxidant metabolism, thereby reducing the environmental stress that plants face during their crop cycle in tropical field conditions. (4) Conclusions: Our research brings the new glimpse of foliar Mg fertilization as a strategy to increase the metabolism of crops, resulting in increased grain yields. This type of biological strategy could be encouraged for wide utilization in cropping systems. Department of Crop Science College of Agricultural Sciences São Paulo State University (UNESP) Throckmorton Plant Science Center Department of Agronomy Kansas State University (KSU), 1712 Claflin Road Department of Crop Science College of Agricultural Sciences São Paulo State University (UNESP) CNPq: 134588/2018-5 CNPq: 303119/2016-0

Made available in DSpace on 2020-12-10T20:07:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-09-15 Kansas Wheat Alliance Kansas Agricultural Experiment Station (KAES) The complex and interactive effects of genotype (G), environment (E), and management (M) can be a barrier to the development of sound agronomic recommendations. We hypothesize that long-term variety performance trials (VPT) can be used to understand these effects and improve regional recommendations. Our objective was to explore long-term VPT data to improve management and variety-selection recommendations using winter wheat (Triticum aestivum L.) in the U.S. central Great Plains as a case-study. Data of grain yield, variety, and trial management were collected from 748 wheat VPT conducted in the states of Colorado, Kansas, and Oklahoma over nineteen harvest years (2000-2018) and 92 locations, resulting in 97,996 yield observations. Using 30-yr cumulative annual precipitation and growing degrees days, we partitioned the study region into 11 contiguous sub-regions, which we refer to as growing adaptation regions (GAR). We used variance component analysis, gradient boosted trees, and conditional inference trees to explore the management and variety trait effects within each GAR. For the variety trait analysis, the VPT dataset was reduced to account for varieties for which 17 agronomic traits and 11 disease/insect reaction ratings were available (65,264 yield observations). GAR accounted for 46 % of the total variation in grain yield, M for 32 %, residuals (including interactions) for 13 %, year for 7 %, and G for 2 %. Conditional inference trees identified interactions among management practices and their effects on yield within each GAR. For instance, water regime was the most important practice influencing wheat yield in the semi-arid western portion of the study region, followed by sowing date and fungicide. In dryland trials, there was typically an interaction between fungicide, sowing date, and tillage system, depending on GAR. Other management practices (e.g. dual-purpose management, crop rotation, and tillage practice) also significantly affected yield, depending on GAR. The main variety trait associated with increased yields depended on region and management combination. For instance, drought tolerance was the most important trait in dryland trials while stripe rust tolerance was more relevant in irrigated trials in the semi-arid region. In this research, we demonstrated an approach that uses widely available long-term VPT data to improve management and variety selection recommendations and can be used in other regions and crops for which long-term VPT data are available. Kansas State Univ, Dept Agron, Manhattan, KS 66506 USA Kansas State Univ, Dept Stat, Manhattan, KS 66506 USA Kansas State Univ, Dept Plant Pathol, Throckmorton Hall, Manhattan, KS 66506 USA Colorado State Univ, Dept Soil & Crop Sci, Ft Collins, CO 80523 USA Oklahoma State Univ, Dept Plant & Soil Sci, Stillwater, OK 74078 USA Sao Paulo State Univ, Dept Crop Prod, Jaboticabal, SP, Brazil Sao Paulo State Univ, Dept Crop Prod, Jaboticabal, SP, Brazil Kansas Wheat Alliance: GAGR004805BG5828

Wheat (Triticum aestivum L.) grain yield response to plant density is inconsistent, and the mechanisms driving this response are unclear. A better understanding of the factors governing this relationship could improve plant density recommendations according to specific environmental and genetics characteristics. Therefore, the aims of this paper were to: i) execute a synthesis-analysis of existing literature related to yield-plant density relationship to provide an indication of the need for different agronomic optimum plant density (AOPD) in different yield environments (YEs), and ii) explore a data set of field research studies conducted in Kansas (USA) on yield response to plant density to determine the AOPD at different YEs, evaluate the effect of tillering potential (TP) on the AOPD, and explain changes in AOPD via variations in wheat yield components. Major findings of this study are: i) the synthesis-analysis portrayed new insights of differences in AOPD at varying YEs, reducing the AOPD as the attainable yield increases (with AOPD moving from 397 pl m-2 for the low YE to 191 pl m-2 for the high YE); ii) the field dataset confirmed the trend observed in the synthesis-analysis but expanded on the physiological mechanisms underpinning the yield response to plant density for wheat, mainly highlighting the following points: a) high TP reduces the AOPD mainly in high and low YEs, b) at canopy-scale, both final number of heads and kernels per square meter were the main factors improving yield response to plant density under high TP, c) under varying YEs, at per-plant-scale, a compensation between heads per plant and kernels per head was the main factor contributing to yield with different TP.

Plant breeding has increased the yield of winter wheat (Triticum aestivum L.) over decades, and the rate of genetic gain has been faster under high fertility in some countries. However, this response is not universal, and limited information exists on the physiological traits underlying the interaction between varieties and fertilization. Thus, our objectives were to identify the key shifts in crop phenotype in response to selection for yield and quality, and to determine whether historical and modern winter wheat varieties respond differently to in-furrow fertilizer. Factorial field experiments combined eight winter wheat varieties released between 1920 and 2016, and two fertilizer practices [control versus 112 kg ha-1 in-furrow 12 -40-0-10-1 (N-P2O5-K2O-S-Zn)] in four Kansas environments. Grain yield and grain N-removal increased non-linearly with year of release, with greater increases between 1966 and 2000. In-furrow fertilizer increased yield by ~300 kg ha-1 with no variety × fertility interaction. Grain protein concentration related negatively to yield, and the residuals of this relationship were unrelated to year of release. Yield increase was associated with changes in thermal time to critical growth stages, as modern varieties had shorter vegetative period and longer grain filling period. Yield gains also derived from more kernels m-2 resultant from more kernels head-1. Historical varieties were taller, had thinner stems, and allocated more biomass to the stem than semi-dwarf varieties. Yield gains resulted from increases in harvest index and not in biomass accumulation at grain filling and maturity, as shoot biomass was similar among varieties. The allometric exponent (i.e., the slope between log of organ biomass and log of shoot biomass) for grain increased with, and for leaves was unrelated to, year of release. The ability of modern varieties to allocate more biomass to the kernels coupled to an early maturity increased grain yield and grain N-removal over time. However, increases in grain yield were greater than increases in grain N-removal, reducing grain protein concentration in modern varieties.

A great majority of dryland wheat producers are reluctant to intensify management due to the assumption that lack of water availability is the most critical factor limiting yield and thus, the response to management intensification would be limited. We conducted on-farm field experiments across three locations and two growing seasons in Kansas using 21 modern winter wheat genotypes grown under either standard (SM) or intensified management (IM) systems. The goals of this study were to (i) determine whether the SM adopted is adequate to reach achievable yields by farmers in the region and (ii) identify differences in responsiveness to IM among a range of modern genotypes. Across all sites-years and genotypes, the IM increased yield by 0.9 Mg ha-1, outyielding the SM system even in the lowest yielding conditions. As expected, the yield response to IM increased with the achievable yield of the environment and genotype. Across all sources of variation, the yield responsiveness to IM was related to increased biomass rather than harvest index, strongly driven by improvements in grain number (and independent of changes in grain weight), and by improvements in N uptake which resulted from greater biomass and shoot N concentration. The IM system generally also increased grain N concentration and decreased the grain N dilution effect from increased yield. Genotypes varied in their response to IM, with major response patterns resulting from the combination of response magnitude (large vs. small) and consistency (variable vs. consistent). Genotypes with high mean response and high variability in the response to IM across years could offer greater opportunities for producers to maximize yield as those genotypes showed greater yield gain from IM when conditions favored their response. For the background conditions evaluated, intensifying management could improve wheat yield in between c. 0.2 and 1.5 Mg ha-1 depending on genotype. Partial funding for this research was provided by the Kansas Wheat Commission and the Kansas Agricultural Experiment Station. This research is contribution no. 20-027-J of the Kansas Agricultural Experiment Station.

Foliar fungicides can account for a large portion of the yield gap in winter wheat (Triticum aestivum L.); however, their impacts on yield have been inconsistent in rainfed environments. We compiled a database of replicated field experiments and producer-reported fungicide and yield data from commercial fields to quantify the effects of fungicide application on winter wheat yield and yield stability. The database of field experiments (i.e., canopy level) included 56 non-inoculated environments spanning 12 growing seasons in eight Kansas locations, and was restricted to field experiments with direct comparisons between a foliar fungicide between Zadoks 40–55 and a side-by-side untreated control, resulting in 393 mean yield comparisons resulting from 3226 yield observations. The producer survey included genotype and fungicide management data from 654 commercial Kansas wheat fields cultivated across three growing seasons. Grain yield and weather conditions in the experimental and producer-reported database were similar, with seasonal precipitation ranging from ˜150 to 1035 mm and average grain yield of ˜3900 kg ha−1 with a ˜7000 kg ha−1 range. Foliar fungicide application resulted in 7.8 % average yield gain in the canopy-level data, ranging from −27 % to +97 %. Yield differences due to fungicide were strongly related to precipitation and to the ratio of precipitation and reference evapotranspiration (WS:WD) during the spring in the experimental data. Grain yield responsiveness to fungicide associated with the responsiveness of green canopy cover, kernel weight, biomass, and harvest index. Analysis of covariance suggested that grain yield usually decreased with increases in disease susceptibility in the absence of foliar fungicides; however, yield-disease relationships were either neutral or positive in the presence of fungicides. Average yield gain for resistant varieties was ˜166 kg ha−1 (5.6 %), which was lower than for intermediate (˜199 kg ha−1; 6.9 %) or susceptible genotypes (˜598 kg ha−1; 16.9 %). Foliar fungicides increased yield stability across genotypes at the canopy level and at the commercial field level. In the commercial-field level data, 53 % of the fields received foliar fungicide, with higher frequency in growing seasons with greater WS:WD (which were also higher yielding). The use of foliar fungicides was associated with improved yields and interacted with genotype’s resistance level to stripe rust and with growing seasons’ WS:WD. This work quantified and explained the yield benefits of foliar fungicide, and characterized its dependency on genotype-specific disease resistance and environmental conditions both at the canopy- and commercial field-levels.

With an annual production of ∼60 Mt, the U.S. accounts for about 8% of the global wheat (Triticum aestivum L.) production. Still, quantification of the yield gaps (YG) and major management factors to reduce it are scarce. We used Kansas, the largest wheat producing state in the U.S. located in the central Great Plains, for an initial assessment of on-farm yield and YG. We collected field-level management (37 variables), weather (8 variables), soil (two variables) and yield data from 656 commercial wheat fields over three harvest years (2016–2018) to (i) quantify management adoption levels, Ya, and YG, and (ii) identify interactions among management practices and weather variables using a data-rich approach. We also used our data as a case-study to detect whether differences in crop management among regions justified data clustering by crop zones. Water-limited yield potential (Yw) was simulated for each field-year using actual soil and weather data and the SSM-Wheat model. Fields were grouped in three climate zones based on their long-term climatology and important differences in cropping systems between zones. Grain yield averaged 3.8 Mg ha−1 and ranged from 0.3–7.1 Mg ha−1 across all regions and years. The YG averaged 44 %, with seasons with high Yw resulting in greater YG. Management practices most often associated with grain yield were management of nitrogen (N), phosphorus (P), and sulphur (S) fertilizer, as well as foliar fungicide and its interaction with variety reaction to major diseases, although these depended on in-season weather. Our analyses highlighted many other genotype × management × environment interactions explaining winter wheat Ya, such as regional-specific cultivar maturity and the dependency of sowing date (and its relation to seeding rate) on cropping system.

The impact of agricultural technologies on crop yield is influenced by the environment type (ENVT) as determined by weather and soil. Understanding the correlation between the ENVT of the testing site in relation to the ENVT of the target production region is important for the evaluation and scaling out of agricultural technologies. Here we propose and apply the first explicit method to characterize ENVTs for major rainfed maize, soybean, and wheat producing regions in the United States. We combined a tested spatial framework, Technology Extrapolation Domain (TED), with crop modeling, long-term (30-y) daily weather records, and soil and management databases to calculate the frequency of ENVTs per crop for major harvested areas. Each ENVT was determined based on the intensity of drought and heat stress during key crop stages for yield determination. The ENVT repeatability was calculated based on the frequency of the most dominant ENVT in each TED. We found that inter-annual variation in drought and heat stress was larger than spatial variation. Our ENVTs explained 2x to 7x larger portion of the variance in actual yield compared to the existing TED framework that is based on long-term annual climate means and soil water storage. For maize and soybean, ca. 30% of their harvested area was located in TEDs with highly repeatable ENVTs (>66% of years). In contrast, only 15% of the wheat harvested area was located in TEDs with high ENVT repeatability. In comparison to the TED framework, the ENVTs defined here can help better capture G×E×M interactions and determine the environmental correlation between testing sites and target production environments.

Although the U.S. southern Great Plains accounts for approximately 30% of total U.S. wheat ( Triticum aestivum L.) production, yields in the region have rarely surpassed 3.0 Mg ha −1 and quantification of the wheat yield gap (Y G ) and meteorological factors associated with potential wheat productivity are scarce. Our objectives were to identify spatial gradients in key weather variables and to assess the meteorological drivers of wheat productivity and resource-use efficiency, and to quantify the wheat Y G across Texas, Oklahoma, Colorado, and Kansas. Water-limited wheat grain yield (Y w ) was simulated for 30 consecutive years at 68 locations across the southern Great Plains using Simple Simulation Modeling-Wheat (SSM-Wheat), and actual soil and weather data, sowing date, and population density. Regional gradients in meteorological variables were determined for (i) the entire crop cycle, (ii) pre- and post-anthesis, or (iii) jointing-anthesis interval, and Y w were related back to these variables using linear and stepwise multiple-regression. Boundary function analysis determined water productivity (WP) and transpiration-use efficiency (TE). Strong latitudinal gradients occurred for temperatures and longitudinal gradients for precipitation (P), evapotranspirative demand (ET o ), and solar radiation (Rs). Wheat Y w averaged 5.2 Mg ha −1 and followed the longitudinal P gradient increasing from west (3.6 Mg ha −1 ) to east (6.9 Mg ha −1 ). Interannual Y w variability was large with coefficient of variation (CV) increasing from 13 to 51% east to west. Meteorological variables accounting for major portions of the Y w variability were water supply (P + PAW s ) in the west [82% of regression sums of squares (SS)] and cumulative solar radiation (R s ) during the anthesis − physiological maturity in the east (73% of SS). Temperatures during the anthesis-physiological maturity phase negatively affected grain yields across all locations and years (7% of SS). Wheat WP (17.2 kg ha −1 mm −1 ) and TE (20.8 kg ha −1 mm −1 ) benchmarks derived in this study align well with values reported for wheat grown in other regions of the world.

Increasing irrigated wheat yields is important to the overall profitability of limited-irrigation cropping systems in western Kansas. A simulation study was conducted to (1) validate APSIM‘s (Agricultural Production Systems sIMulator) ability to simulate wheat growth and yield in Kansas, and (2) apply the model to assess the response of wheat yield, biomass, and water productivity to irrigation allocation based on growth stage. The methodology involved combining short-term experimental data, long-term historical weather data (1950-2013), and mechanistic crop growth simulation to determine optimum irrigation management strategies. The model adequately simulated measured soil water in the profile. The goodness-of-fit test between the observed and simulated values for phenology, yield, biomass, and ET of the experimental cultivar in 2008-2009 in our study site agreed well with the ‘Batten winter‘ wheat cultivar in APSIM. Results indicated that, on average, an irrigation allocation of 100 mm increased wheat yield by 14% to 46% compared to rainfed (dryland) production. Application of an additional 100 mm of irrigation did not improve wheat yield substantially (on average -1 ). Higher water productivity for grain yield was obtained when irrigation was applied at booting and heading. Overall, irrigation water use efficiency for grain decreased with an increase in irrigation allocation. The highest irrigation water use efficiency was simulated for wheat grown with a limited irrigation allocation of 100 mm applied at booting and heading. This study demonstrates that limited irrigation targeted at sensitive growth stages could enhance wheat yields and improve water productivity of water-limited cropping systems.