Semiarid Canadian Prairies Research Articles

PSXI-4 Effect of annual forage diversity on soil nitrous oxide emissions in semiarid Canadian Prairies

Abstract Nitrogen transformation, either from organic amendments or synthetic fertilizers, contributes to nitrous oxide (N2O) emission, a potent greenhouse gas from agricultural soils. In grazing systems, N2O emissions can occur in both stages of production, during the forage growth phase mainly related to fertilizer use and residue transformations as well as the animal phase from animal excreta deposition and transformation. Different management practices with potential to reduce N2O emissions, including the adoption of diverse forage mixtures (poly cropping) has gained attention. Poly cropping can promote high resource use efficiency and influence edaphic-climatic conditions, major controllers for soil N2O emissions. However, information on the effect of poly cropping on soil N2O emissions in the Canadian Prairies under semiarid climate and Brown Chernozem soils is limited. The overall objective of this study was to explore the potential of using poly crop mixtures as an alternative feed source for Canadian beef cattle and its impact on soil N2O emissions. Three treatments were considered: i) control, forage oat monoculture, ii) simple mix, containing four different annual forage species (forage oat, forage pea, forage brassica, and hairy vetch), and iii) complex mix containing eight annual forage species (forage oat, forage pea, barley, forage brassica, hairy vetch, red proso millet, teff grass, and, chicory). Treatments were established in a completely randomized block design scheme with three replicates. The study was conducted at the Swift Current Research and Development Centre, the driest climatological condition in the Canadian Prairies. Following pre-seeding field preparation, treatments were established by the end of May and Urea Phosphate (34-17-0) fertilizer was split-applied at 112 kg/ha. Nitrous oxide emission was measured over the crop phase in 2023 growing season, the first year of a 3-yr trial, using the manual chamber method. Furthermore, ancillary measurements were performed. During the 2023 crop growth phase, N2O emissions ranged from 446 to 610 g Nּ ha-1, and were not affected by treatments. Soil inorganic N was greater in parts of the season for the complex mix, but that did not translate into greater cumulative N2O emissions. Overall, the treatments did not affect soil volumetric water content in the topsoil, a key factor dictating N2O emissions. This project will continue until 2026 and capture emissions from different seasons including major spring-thaw. In those years, measurements will also be extended to an on-farm sites involving farmers situated in contrasting edaphic-climatic conditions of the Canadian Prairies.

Climate conditions in the near-term, mid-term and distant future for growing soybeans in Canada

The soybean industry in Canada aimed to extensively expand soybean production to benefit from new early-maturing varieties and the warming climate. However, setbacks in the soybean industry since 2017 demonstrated the impacts of climate risk and global market uncertainty. Therefore, a better understanding of future climate conditions that will impact soybean growth in Canada is needed for decision-making in the sector, such as prioritizing regions for expansion and developing climate change adaptation strategies through either agronomic management practices or breeding new cultivars. Based on climate projections from a set of global climate models, we analyzed climate conditions for growing soybeans, including growing season start, crop heat units, precipitation, precipitation deficits and climate extremes, in the near-term (2030s), the mid-term (2050s) and the distant future (2070s). We found that a future warmer climate with an increase of 1.6, 2.8 and 4.1 °C in the growing season (May–September) mean temperature averaged over Canada’s land area in the near-term, mid-term and distant future under SSP3-7.0 would favour the expansion of soybean production further north and west. However, an increase of approximately 200 mm in precipitation deficits on the semiarid Canadian Prairies in the mid-term would constrain soybean production unless irrigation could be introduced. Heat- and drought-tolerant cultivars should be developed to adapt soybean production to a changing climate, in addition to the adoption of late-maturing cultivars that would benefit from the lengthened growing season and increased crop heat units.

Land‐use comparison of depression‐focussed groundwater recharge in the Canadian prairies

AbstractIn the cold semiarid Canadian prairies, groundwater recharge is focussed under numerous topographic depressions, in which snowmelt runoff converges. Agricultural land uses on the uplands surrounding the depressions affect snow accumulation, snowmelt infiltration, evapotranspiration (ET) and soil moisture dynamics, thereby influencing snowmelt runoff and depression‐focussed recharge. The objective of this study is to compare the differences in hydrological processes under two common land uses in the Canadian prairies, namely grazed grass and annual crop, and examine how they affect groundwater recharge. A short‐term (3 years) paired catchment study was used for detailed observation of hydrological processes in two depressions, supplemented by a longer‐term (17 years) data set covering a larger scale to quantify the differences in snowmelt runoff between the two land uses. Compared to the grazed grassland, the cropland had a shorter and more intense period of ET, and root water uptake restricted to the shallower (top 0–80 cm) soil zone. The amount of snowmelt runoff was greater in the grazed grassland primarily due to a higher amount of snow accumulation, which was dictated by differences in topography. This finding was contrary to previous studies in the Canadian prairies that indicated substantially smaller snowmelt runoff in ungrazed grassland, but was consistent with the larger‐scale remote sensing results, which showed only a marginal difference between grazed grasslands and croplands. Groundwater recharge rates were estimated using the chloride mass balance method for the present condition using “modern” pore water containing tritium. The rates were similar between the grazed grassland and croplands, implying similarity in snowmelt runoff characteristics. These results suggest that groundwater recharge will continue to be focussed under depressions in the future, though the amount and seasonality of recharge may be influenced by warmer winters.

Relation between flow through and volumetric changes in natural expansive soils

Geology and climate govern the evolution and behavior of natural expansive soils in the semi-arid Canadian Prairies. The Regina clay deposit has a flat topography, a homogenous composition, and contains hair-line fissures. This research focuses on understanding the relation between flow through and volumetric changes in the natural expansive soil. Based on analysis of test data, it is concluded that flow occurs through macro-pores or fissures (5 × 10−8 m/s) during structural volume change and through micro-pores or matrix (10−9 m/s) during normal and residual volume changes. The hydraulic conductivity decreases by several orders of magnitude and becomes asymptotic vapor flow (2 × 10−14 m/s) during residual volume change. A complete assessment of soil behavior requires water retention, swell-shrink, and hydraulic conductivity curves. The proposed straight-line representation of the functions' components is useful for predicting field response of expansive soils.

Water stress, sap flow and transpiration for medium and highly drought resistant poplars grown in the semiarid Canadian prairie

Sap flow was measured to determine transpiration rates for CanAm and Walker poplars grown in the semiarid Canadian prairie. CanAm poplars had higher sap flow rates and were better able to supply water to actively growing regions for all water availabilities (well-watered to drought). CanAm poplars were better able to survive drought.

Plant minus air temperature corresponds to different responses to water stress in wheat, canola, and chickpea grown in the semiarid Canadian prairie

The difference between plant and air temperature (PT–AT) is a good indicator of water stress. PT–AT for chickpea was negatively correlated to water deficit and air temperature and positively correlated to wind; for wheat, PT–AT was positively correlated to water deficit, air temperature and solar energy; for canola, PT–AT was not correlated to the environment. Chickpea maintained positive turgor at the expense of water content and therefore more water was available for transpirational cooling. Wheat maintained water content at the expense of turgor and therefore there was little water available for transpirational cooling. For canola, PT–AT was affected by parameters other than environment.

Plant establishment, yield and yield components of Brassicaceae oilseeds as potential biofuel feedstock

Increasing demand for renewable energy, such as biofuel, is spurring great interest to find productive feedstock for biofuel production. In a nine site-year study, major Brassicaceae oilseeds grown on the Canadian prairie - oriental mustard [Brassica juncea (L.) Czern.], canola (Brassica napus L.), camelina [Camelina sativa (L.) Crantz], Ethiopian mustard (Brassica carinata A. Braun), and yellow mustard (Sinapis alba L.) – were evaluated for their potential as feedstock sources. The plant establishment, seed yield, yield components, and water use efficiency of these oilseeds across diverse environments were determined. Preceding crops had a significant impact on the performance of oilseeds in the following year. Plant establishment were higher when the oilseeds were grown in chem-fellow than in wheat stubble. Canola had highest emergence rate (57.2%) and highest seed yield (3092 kg ha−1) among the oilseeds evaluated. Plant density and pods plant−1 had a strong relationship with seed yield for all the oilseeds; the number of seeds pod−1 and weight seed−1 contributed to seed yield significantly for the oilseeds except oriental mustard and carinata. The growing season temperatures affected seed yield and yield components significantly although the magnitude varied with crop species. Under the semiarid Canadian prairie conditions, canola was most efficient in water use (9.04 kg seed yield ha-1 mm−1) and yellow mustard and camelina were least efficient. The multiple site-years of assessment indicates that canola is the most efficient feedstock source for biofuel uses, while juncea mustard and carinata could be considered as potential alternatives.

Influence of crop residues and nitrogen fertilizer on soil water repellency and soil hydrophobicity under long-term no-till

Crop residues and N fertilizer under no-till may increase soil water repellency (SWR) and soil hydrophobicity, but few studies have examined these two treatment factors and their interaction. A laboratory study was conducted using a long-term (since 1999) field experiment on a clay loam soil to determine the effect of three crop residues and two N fertilizer levels on SWR and soil hydrophobicity under no-till within the Dark Brown soil zone of the semi-arid Canadian prairies. The three residue treatments were residues removed from soil (Rx0), residues returned to soil (Rx1), and residues supplemented to soil (Rx2). The two fertilizer N treatments were 0 (N0) and 45 kg N ha−1 (N1). Surface (0–10 cm) soil samples were taken in the spring of 2017 after 17 yr. Laboratory measurements were conducted on air-dried and sieved (<2 mm) soil to determine SWR using the repellency index method (RI), soil organic C, hydrophobic CH and hydrophilic CO functional groups, and soil hydrophobicity (CH/CO ratio). Mean RI values ranged from 2.19 to 2.75, indicating subcritical (RI > 1.95) SWR. Similar (P > 0.05) RI values were found for the three residue and two N fertilizer treatments, but the trend was for greater RI with increased residue addition (by 12%–26%) and N fertilizer (by 8%). Soil hydrophobicity was significantly greater by 47%–82% for straw returned or supplemented than straw removed treatments, and by 33% for fertilized than unfertilized treatments. Overall, greater residues and N fertilizer had no effect on SWR, but significantly increased soil hydrophobicity.

Meteorological, soil moisture, surface water, and groundwater data from the St. Denis National Wildlife Area, Saskatchewan, Canada

Abstract. The St. Denis National Wildlife Area is located in the seasonally frozen and semi-arid Canadian Prairies, close to Saskatoon, Saskatchewan. The site has a hummocky terrain and is underlain by clay-rich glacial tills. Though the site is only 4 km2 it contains hundreds of wetlands containing ponds which range in size, in permanence (from ephemeral to permanent), and in their interactions with groundwater (recharge and discharge ponds are present). The site was established as a research area in 1968 and has long-term records of hydrological observations, including meteorological, snow, soil moisture, surface water (ponds) and groundwater data. Some records, notably the pond level and chemistry data, span the period 1968 to present. Other datasets, notably water level observations from networks of piezometers, have been collected sporadically at different locations and times. Some datasets are collected manually on an annual basis, including pond surveys and snow surveys. Meteorological data have been collected by automatic weather stations since 1989 and have been maintained and upgraded over time, with a flux tower added to the site in 2011. Automatically logged soil moisture profiles and collocated piezometers have been running since 2013. A lidar survey from 2005 provides a 1 m resolution digital elevation map (DEM) of the site and surrounding landscape. The compiled data are available at https://doi.org/10.20383/101.0115 (Bam et al., 2018).

Lentil enhances the productivity and stability of oilseed-cereal cropping systems across different environments

Abstract Enhancing the stability of crop production is vital for agriculture under climate uncertainty. Conventional fallow and shallow-rooting pulse crops such as lentil (Lens culinaris Medic.) have been incorporated in oilseed-cereal cropping systems to cope with dry conditions on the semiarid Canadian prairies. However, the static and dynamic stability of these adaptation practices at a cropping system level is unclear due to the complexity of interactions. This study assessed the effects of diversified rotation systems as drought adaptation practices on the productivity and stability of oilseed-cereal cropping systems. Nine 3-year crop rotations were tested for two cycles at three sites from 2013 to 2016. The 3-year crop sequences included fallow, lentil, and spring wheat (Triticum aestivum L.) in rotation phase 1, followed by canola (Brassica napus L.), oriental mustard (Brassica juncea L.), and camelina (Camelina sativa L. Crantz) in phase 2, and the rotation phase 3 was durum wheat (Triticum turgidum L. subsp. durum (Desf.) Husn.) in all nine rotation systems. On average, the lentil system increased system productivity, expressed by annualized durum wheat equivalent yield, by 24% and 78% compared with the spring wheat and fallow systems, respectively. Stability analysis revealed that the lentil – B. juncea – durum wheat and lentil – B. napus – durum wheat systems had the least variation across the environments and were well adapted to high-yielding sites. The fully-phased rotations across various environments showed that the drought-induced reductions in system productivity ranged from 3 to 47% compared with yields under normal weather, with the lentil – oilseed – durum systems having least reduction. Quantitative assessments revealed that about 36% of the variation in system productivity was associated with rotation systems and additional 30% was due to weather-related factors. In conclusion, the inclusion of lentil in rotation increases systems productivity and reduces yield variation in oilseed-cereal cropping systems in changing environments.

Soil-Plant Indices Help Explain Legume Response to Crop Rotation in a Semiarid Environment.

Crop productivity is typically affected by various soil–plant factors systematically as they influence plant photosynthesis, soil fertility, and root systems. However, little is known about how the productivity of legumes is related to crop rotation systems. The objectives of this study were to determine the effect of rotation systems on legume productivity and the relationships among legume productivity and soil–plant factors. Three annual legumes – chickpea (Cicer arietinum L.), pea (Pisum sativum L.), and lentil (Lens culinaris Medikus), were included in various diversified rotation systems and compared with legume monoculture in the 8-year rotation study. Soil N and water conditions, and canopy and root systems were evaluated at the end of 8-year rotation in the semiarid Canadian prairies. Results showed that diversified rotation systems improved leaf greenness by 4%, shoot biomass by 25%, nodule biomass by 44%, and seed yield by 95% for chickpea and pea, but such effects were not found for lentil. Pea monocultures increased root rot severity by threefold compared with diversified rotations, and chickpea monoculture increased shoot rot severity by 23%, root rot severity by 96% and nodule damage by 219%. However, all the legume monocultures improved soil N accumulation by an average 38% compared to diversified systems. Pea and chickpea displayed considerable sensitivity to plant biotic stresses, whereas lentil productivity had a larger dependence on initial soil N content. The 8-year study concludes that the rotational effect on legume productivity varies with legume species, the frequency of a legume appearing in the rotation, and the integration of relevant soil and plant indices.

Effect of crop and residue type on nitrous oxide emissions from rotations in the semi-arid Canadian prairies

Crop rotations on the Canadian prairies commonly include sequences of pulses, oilseeds, and cereals; however, limited information is available regarding the influence that different crop types and sequences may have on direct nitrous oxide (N2O) emissions. A 3 yr field study was conducted on a site near Scott, SK, to compare N2O emissions from selected crop phases of rotations containing pea (Pisum sativum L.), wheat (Triticum aestivum L.), and canola (Brassica napus L.) and to examine the potential influence of these residues on N2O emissions during the subsequent crop phase. Nitrous oxide losses from N-fertilized canola or wheat crops were generally higher than losses from pea or the control treatments. Nitrous oxide losses from N-fertilized wheat or canola crops grown on pea residue were comparable or lower than losses from N-fertilized wheat or canola crops grown on wheat residues. Cumulative N2O loss over the 3 yr was significantly higher from N-fertilized wheat grown on canola compared with pea or wheat residues. Losses from wheat grown on canola residue were 67% and 56% higher than from wheat grown on pea or wheat residue, respectively. This indicates that the emission factors used to estimate direct N2O loss may need to be adjusted upwards for N-fertilized crops grown on canola compared with wheat or pea residues.

Current inventory approach overestimates the effect of irrigated crop management on soil-derived greenhouse gas emissions in the semi-arid Canadian Prairies

Greenhouse gas (GHG) emissions from agricultural soils in the Canadian Prairie region are generally low and, due to dry, well aerated soil conditions, can be quite variable. Compared to dryland (rainfed) crop production, irrigated cropping has potential to contribute greater quantities of soil derived nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) to the atmosphere as producers target higher yields by minimizing soil moisture limitations and applying greater amounts of nitrogen fertilizers. However, the actual GHG dynamics from irrigated soils in this region are not well understood as there have been few field-based studies in the semi-arid prairies of western Canada. The goal of this study was to identify how emissions of soil derived N2O, CO2, and CH4 are influenced by changes in soil temperature, water status, and nitrogen rates brought about by irrigated crop management. This was achieved through continuous, in-situ monitoring of soil conditions and chamber-based measurements of soil GHG flux. The most notable change in soil conditions brought about by irrigation was elevated moisture levels, which appeared to influence the flux dynamics of all three agricultural greenhouse gases—specifically, a reduction in CH4 uptake and periodic increases in CO2 and N2O emissions. Despite the reduced soil moisture limitation, annual N2O emissions from the irrigated cropping system were much lower than those calculated using the current Canadian National GHG Inventory Reporting. This suggests that annual emissions are limited more by N availability rather than moisture deficits, as the current method for emissions accounting assumes. Consequently, our results indicate that emissions from irrigated cropping systems in the semi-arid Canadian Prairies are overestimated by the current inventory approach. Moreover, because irrigated crop production involves more than just the application of water, our results demonstrate that a more systems-oriented approach to GHG accounting is required to capture the combined effects of water-soil-crop management on GHG emissions from irrigated cropping systems.

Effects of Crop Inputs, Diversity, Environment and Terrain on Yield in an 18-year Study in the Semi-Arid Canadian Prairie

A field experiment was conducted from 1994 to 2013 at Scott, SK, to assess the effects of cropping diversity and inputs on spring wheat, canola, and barley yield in the context of growing season pr...

Technoeconomic analysis of camelina oil extraction as feedstock for biojet fuel in the Canadian Prairies

This study presents a technoeconomic analysis of commercial extraction of camelina oil as an aviation fuel feedstock. An engineering economic model was designed in Superpro Designer® to quantify capital investment, scale, production cost, and profitability for a 120,000–1,500,000 tonnes annum−1 solvent extraction plant. The corresponding estimated capital investment was $24.7 - $155 million. Feedstock cost ($0.29–0.40 kg−1), seed yield (1400–2100 kg ha−1), oil content (38–47%), scale, and camelina meal revenue are key factors in the break-even selling price (BESP) and competitiveness of camelina oil as a feedstock. Feedstock represented 81–90% of operating cost. The BESP ranges from $0.43 -$1.22 L-1. Larger plants have lower BESP compared to smaller plants which require higher breakeven prices. This suggests better economies of scale associated with higher plant scale. Camelina can be introduced into underutilized summerfallow land of semiarid Canadian Prairies of Saskatchewan. Swift Current is an ideal extraction plant location. These results can guide R&D and investment decisions for advancing camelina as an industrial feedstock within the innovation value chain.

Biological nitrogen fixation by pulse crops on the semiarid Canadian Prairie

Pulses play a significant role in nitrogen cycling as they fix atmospheric N2 through symbiosis. However, it is unknown whether there are differences in the ability of biological nitrogen fixation ...

Measuring and Modeling the Long‐Term Impact of Crop Management on Soil Carbon Sequestration in the Semiarid Canadian Prairies

Agricultural management practices which promote soil organic carbon (SOC) sequestration can contribute to the long‐term productivity of soils, thus research must quantify and predict SOC dynamics in response to crop management. Using long‐term (1967–2009) data from 10 cropping systems on a Brown Chernozem (Aridic Haploboroll) in the Canadian semiarid prairies at Swift Current, Saskatchewan, we assessed the effect of fertilizer, cropping frequency, and crop type on SOC dynamics in the 0‐ to 15‐cm depth. Three models: Campbell, introductory carbon balance model (ICBM), and DayCent were evaluated, all of which produced fairly accurate predictions of SOC content and sequestration rates (R2 of 0.64–0.82); however, DayCent had the highest correlation and lowest errors of prediction and was deemed superior. Residue inputs of 0.87 to 1.13 Mg C ha−1 yr−1 maintained the SOC level, and SOC content was directly related to factors which increased C inputs. The SOC content and sequestration rates were lowest for wheat (Triticum aestivum L.)‐based rotations which were frequently fallowed and included flax (Linum usitatissimum L.), but highest for systems which were frequently cropped, well‐fertilized, and included rye (Secale cereale L.) or pulse crops in rotation. For systems with high C input, DayCent projected SOC gains of 12 Mg C ha−1 from 2009 to 2100, indicating that the soil at Swift Current had not reached maximum C capacity. This study was the first to rigorously test and demonstrate the strength of the DayCent for simulating SOC under different cropping systems on the Canadian prairies.

Simulation of long-term spring wheat yields, soil organic C, N and water dynamics using DSSAT-CSM in a semi-arid region of the Canadian prairies

The overall performance of the Decision Support System for Agrotechnology Transfer-Cropping System Model (DSSAT-CSM) was evaluated for simulating wheat (Triticum aestivum L.) yield, grain N uptake, soil organic C (SOC) and N (SON), soil water and nitrate–N (NO3–N) dynamics. The data used was from a long-term (1967–2005) spring wheat experiment conducted at Swift Current, Saskatchewan in the semi-arid Canadian prairies. Four treatments were selected: (1) continuous wheat receiving N and P fertilizer, Cont-W(NP); (2) continuous wheat receiving P only, Cont-W(P); and each phase of a fallow wheat rotation receiving N and P fertilizer, (3) W–F(NP) and (4) F–W(NP). The simulated grain yields matched the measurements well, with high d (0.74–0.83) and EF (0.16–0.33). The grain N uptake was also simulated satisfactorily with RMSE of 14–17 kg N ha−1 and d of 0.66–0.81. DSSAT simulated topsoil (0–0.15 m) SOC and SON well in the drier period (1967–1991), whereas it underestimated SOC in the more humid period (1991–2003). The DSSAT successfully simulated soil water and NO3–N dynamics in 0–0.15 m depth, whereas it overestimated soil water and NO3–N in the deep layers and consequently underestimated NO3–N leaching, suggesting that further improvements in soil water module should be made for the semi-arid climatic conditions in Canadian prairies. Sensitivity results showed that soil water content was sensitive to both lower soil water and upper drainage limits in this study. The performances of DSSAT model to yield and soil dynamics were comparable with other models.

Water use efficiency of spring wheat in the semi-arid Canadian prairies: Effect of legume green manure, type of spring wheat, and cropping frequency

Kröbel, R., Lemke, R., Campbell, C. A., Zentner, R., McConkey, B., Steppuhn, H., De Jong, R. and Wang, H. 2014. Water use efficiency of spring wheat in the semi-arid Canadian prairies: Effect of legume green manure, type of spring wheat, and cropping frequency. Can. J. Soil Sci. 94: 223–235. In the semi-arid Canadian prairie, water is the main determinant of crop production; thus its efficient use is of major agronomic interest. Previous research in this region has demonstrated that the most meaningful way to measure water use efficiency (WUE) is to use either precipitation use efficiency (PUE) or a modified WUE that accounts for the inefficient use of water in cropping systems that include summer fallow. In this paper, we use these efficiency measures to determine how cropping frequency, inclusion of a legume green manure, and the type of spring wheat [high-yielding Canada Prairie Spring (CPS) vs. Canada Western Red Spring (CWRS)] influence WUE using 25 yr of data (1987–2011) from the “New Rotation” experiment conducted at Swift Current, Saskatchewan. This is a well-fertilized study that uses minimum and no-tillage techniques and snow management to enhance soil water capture. We compare these results to those from a 39-yr “Old Rotation” experiment, also at Swift Current, which uses conventional tillage management. Our results confirmed the positive effect on WUE of cropping intensity, and of CPS wheat compared with CWRS wheat, while demonstrating the negative effect on WUE of a green manure crop in wheat-based rotations in semiarid conditions. Furthermore, we identified a likely advantage of using reduced tillage coupled with water conserving snow management techniques for enhancing the efficiency of water use.

Spring wheat yield in the semiarid Canadian prairies: Effects of precipitation timing and soil texture over recent 30 years

The large year-to-year and site-to-site variation in wheat production on rain-fed semiarid areas of the Canadian prairies is mainly due to the timing and amount of precipitation and soil water holding capacity. Here, we identify the critical periods of growing season precipitation on wheat yield and then utilize this information to analyze which type of soil texture had higher drought resistance and higher grain yield when precipitation was more than sufficient. Thirty years (1982–2011) of grain yield data on two sites located in the same rain-fed area with different soil texture types were used in our analysis. To seek the critical periods of precipitation on yield, correlation over the whole growing season between precipitation and yield was first analyzed. By doing this, we calculated not only when the precipitation occurs that was most related to yield but also the duration of this period. To further understand these cause-and-effect interrelationships, a modern version of path analysis – Structural Equation Modeling (SEM) was used. The result of SEM was satisfactory since 67% of yield variation can be explained by only 3 exogenous variables (early and late precipitation and fertilizer N) and 2 intermediate variables (thousand kernel weight and kernel nitrogen concentration). Results showed that early precipitation (from seeding to anthesis) was most critical for high grain yield in our study area. Clay soil has a higher drought tolerance efficiency and lower drought susceptibility index. Grain yield was higher on the clay soil than on the silt loam soil in most dry and wet years. We conclude that early precipitation had a deterministic effect on grain yield. The clay soil has a more stable yield under current fertilizer rates and the climate conditions in our study area. These results may lead to a better understanding of the crop–environmental interactions enabling breeders to analyze their experimental trials with regard to the broad environments that they target.