Wheat-fallow Rotation Research Articles

Biosolids in the Dryland Pacific Northwest Seven Years After Application

AbstractIn dryland region of the inland Pacific Northwest (iPNW), the two‐year winter wheat–fallow rotation is associated with wind erosion and a decline in soil organic carbon (SOC) and overall soil health. The use of biosolids, produced as by‐products of municipal wastewater treatment, in agriculture is gaining traction as an effective way to improve SOC and nutrient availability. While immediate benefits of biosolids application have been studied to some extent, there is still a lack of research‐based information on the persistence and residual effects of biosolids applications in the low‐precipitation region of the iPNW. Therefore, a study was conducted to address that gap by assessing the legacy effects of biosolids, seven years after their application. Earn 0.5 CEUs in Soil & Water Management by reading this article and taking the quiz at https://web.sciencesocieties.org/Learning‐Center/Courses.

Winter wheat response to plant density in yield contest fields

AbstractSeeding rate recommendations for wheat (Triticum aestivum L.) are often 150–450 seeds m−2. However, we hypothesize that wheat grown with high resource availability (i.e., fertility and moisture) can maximize yield under considerably lower rates. Our objectives were to explore winter wheat response to low populations under high resource availability using yield‐contest fields as a case study. A factorial experiment evaluated four wheat varieties (i.e., Joe, WB‐Grainfield, Langin, and LCS Revere) exposed to five seeding rates (50, 100, 150, 200, and 250 seeds m−2) during five seasons in commercial wheat fields managed by yield‐contest winning producers near Leoti, KS. Fields were silt‐loam soils with high available water‐holding capacity, long‐term history of manure application with non‐limiting fertility, and adopted a sorghum [Sorghum bicolor (L.) Moench]–fallow–wheat rotation. Plant density ranged from 26 to 341 plants m−2 and yield ranged from 3.2 to 6.8 Mg ha−1. Water use efficiency of 19.5 kg ha−1 mm−1 suggested no management limitations to yield. Quadratic models portrayed the grain yield–plant density relation well, with 95% of the maximum yield reached at 68 to 91 plants m−2 for crops sown at the optimum date (4 out of 5 years), and at 312 plants m−2 for a late‐sown crop. Greater fall temperature accumulation reduced the relative yield between the maximum and minimum seeding rates. There was no variety × plant density interaction and Langin was the most consistent yielding variety across environments. Optimum plant density for winter wheat in environments with high resource availability may be considerably lower than current recommendations.

Tillage practices affect soil fertility of a long‐term winter wheat–fallow rotation

AbstractThe contribution of tillage practices to enhancing soil fertility levels is a major subject of research among agricultural scholars. The objective of this study was to assess the effect of several decades of tillage under winter wheat (Triticum aestivum L.)–fallow on soil fertility. The experiment was established in 1970 as a randomized complete block design with three replications. Treatments included moldboard plow (MP), stubble mulch (SM), no‐till (NT), and native sod. Soil samples were collected from 0–10 and 10–20 cm in 2010 and 2011 and analyzed for several variables including soil organic matter (SOM), total nitrogen (TN), and soil pH. Benchmarks for these variables used to evaluate temporal changes for each treatment were obtained from previous documents containing data that were sampled in 1982 and 1984 from the same site. In 2010–2011, SOM, TN, and pH were all influenced by the tillage practices at 0–10 cm (p ≤ 0.05). For SOM, the magnitude of the difference between native sod and NT in 1986 was 28% (10.1 g·kg−1) and this increased to 30.6% (18.5 g·kg−1) in 2010–2011 with native sod storing more SOM. Over time, NT sustained a high level of SOM with 7.7 g·kg−1 more SOM than the initial 38.3 g·kg−1 reported in 1986. TN with NT was greater than SM and MP by 56%, but 53% lower than TN with native sods. In general, soil fertility and nutrient availability at this site supported crop production for over 50 years without fertilizer application.

Improving semi-arid agroecosystem services with cover crop mixes.

Winter wheat (Triticum aestivum, L.) production in the semi-arid US Northern High Plains (NHP) is challenged by frequent droughts and water-limited, low fertility soils. Composted cattle manure (compost) and cover crops (CC) are known to provide agroecosystem services such as improved soil health, and in the CC case, increased plant diversity, and competition with weedy species. The main concern of planting CC in winter wheat fallow rotation in regions that are more productive than the NHP, however, is the soil moisture depletion. It is unknown however, whether addition of CC to compost-amended soils in the NHP will improve soil properties and agroecosystem health without compromising already low soil water content. The main objective of this study was to assess the effects of four CC treatments amended with compost (45 Mg ha-1) or inorganic fertilizer (IF) (.09 Mg ha-1 mono-ammonium phosphate, 11-52-0 and 1.2 Mg ha-1ammonium sulfate, 21-0-0) on the presence of weeds, soil and plant total carbon (C), nitrogen (N), and biological dinitrogen (N2) fixation (BNF). Mycorrhizal Mix (MM), Nitrogen Fixer Mix (NF), Soil Building Mix (SB), a monoculture of phacelia (Phacelia tanacetifolia Benth L.) (PH), and a no CC control (no CC) were grown in native soil kept at 7% soil moisture in a greenhouse for a period of nine weeks. When amended with compost, MM was the most beneficial (48 g m-2 BNF and 1.7% soil C increase). SB had the highest germination, aboveground biomass, and decreased weed biomass by 60%. It also demonstrated the second highest amount of BNF (40 g m-2) and soil C increase by 1.5%. On contrary, IF hindered BNF by almost 70% in all legume-containing CC treatments and reduced soil C by 15%.

The nitrogen fertilizer replacement values of incorporated legumes residue to wheat on vertisols of the Ethiopian highlands

Soil fertility depletion and continuous cereal cropping are reducing crop production in Ethiopia. Integrated Soil Fertility Management (ISFM) is a good approach for resource-poor farmers because ISFM can help reduce the need for inorganic fertilizer by increasing nitrogen (N) availability in the soil. The study aimed to investigate the effect of preceding crops, legume residue management practices, and N levels on wheat planted. The experiment was set up using a split plot in a randomized complete block design with three replications. The N fertilizer replacement value method was used to estimate the N contribution of legumes to a succeeding wheat crop. The results showed that grain yield and N uptake of wheat crops varied in response to N fertilizer, legume residue management treatments, and tillage practices. Legume residue incorporation positively influenced the agronomic parameters of wheat compared to teff and fallow wheat rotations. The average N fertilizer replacement value from legume rotation was 18–46 kg ha−1. This study showed that a one-year legume-in-biannual wheat rotation is preferable to lying bare fallow during the cropping season. Nevertheless, drainage during legume and wheat cropping is a condition for providing full positive impacts.

Effect of Deep Nitrogen Fertilizer Application on Grain Protein Content and Quality of Bread Wheat

ABSTRACT In dry agricultural areas, plant uptake of nitrogen (N) stored in topsoil is limited as soil excessively dries up, especially in the late period of wheat growth. Deep N application is often suggested to ensure effectively use of water stored in the subsoil. This experiment was carried out in two different fields with different soils at Transitional Zone Agricultural Research Institute (TZARI) between 2012–2015 in the fallow-wheat rotation system. Efficiency of six different applications (1- deep Autumn 40 kg N ha−1(A40), 2- deep Autumn 20 kg N ha−1 (A20), 3-deep Spring 40 kg N ha−1(S40), 4- deep Spring 20 kg N ha−1(S20), 5- Traditional (T), 6- Control (C)) was investigated in Mufitbey and Bezostaja1 cultivars. The highest grain yield (4861 kg ha−1) was obtained in deep application of 20 kg N ha−1 in autumn, and the lowest grain yield (3969 kg ha−1) was obtained in control. Also, the highest protein content of 12.65% was obtained with deep N applications of 20 kg N ha−1 in autumn, while the lowest GPC (11.37%) was found in the control. Significant and high correlations occurred between nitrate content at 60 cm soil depth in the grain filling period and spike N uptake (r = 0.85, P < .001), GPC (r = 0.84 P < .001), farinograph number (r = 0.85, P < .05), development time (r = 0.83 P < .05) and yield (r = 0.96, P < .001). Significant occurred between Bezostaja1 and Müfitbey in rheological (dough) properties. The data showed that climate and soil conditions should be taken into account in deep N application in dryland wheat farming.

Tillage practices influence winter wheat grain yield prediction using seasonal precipitation

Making the best use of limited precipitation in semi-arid dryland cropping systems is important for crop production. Tillage practices may influence how this precipitation is utilized to predict winter wheat grain yield (Triticum aestivum L.). This study examined how tillage practices influence winter wheat grain yield prediction accuracy using precipitation received at three different periods of the season. Data were obtained from the period of 1972 to 2010 from a long-term tillage experiment. The study was designed as a winter wheat-fallow experiment. Each phase of the winter wheat-fallow rotation was present each year. The trial was set up as a randomized complete block design with three replications. Tillage treatments included no-till (NT), stubble mulch (SM), and moldboard plow (MP). Feed-forward neural network and multiple linear regression (ordinary least squares) were used to fit models under each tillage practice. No-till had the highest yield prediction accuracy with a root mean square error (RMSE) of 0.53 Mg ha-1 and accounted for 81% of the variability in grain yield. Stubble mulch had an RMSE of 0.55 Mg ha-1 and explained 73% of the variability in yield. Stubble mulch and NT were more accurate in yield prediction than MP which had an RMSE of 0.77 Mg ha-1 and accounted for 53% of the variability in yield. The multiple linear regression model was less accurate than the feed-forward neural network model since it had at least 0.30 Mg ha-1 more RMSE and accounted for only 5-8% of the variability in yield. Relative RMSE classified all neural network models as fair (21.6-27.3%) while linear regression models for the different tillage practices was classified as poor (33.3-43.6%), an illustration that the neural network models improve yield prediction accuracy. This study demonstrated that a large proportion of the variability in grain yield may be accounted for under NT and SM systems when using precipitation as predictors with neural networks.

Replacing fallow with field pea in wheat production systems across western Nebraska

AbstractIntegration of field pea (Pisum sativum L.) (FP) into dryland cropping systems has increased due to ecological and economic benefits, paired with a growing market for pea‐derived products. Challenges exist in the High Plains that limit the integration of crop rotations to replace fallow periods with FP in wheat (Triticum aestivum L.)‐based systems. This experiment compares chemical summer fallow to FP in a fallow–wheat rotation at two locations in western Nebraska. Soil water content, soil fertility, N mineralization, FP yield, and subsequent hard red winter wheat (HWW) yields were recorded. Subsequent HWW yields were not different between crop sequences (P = .42). The interaction of site‐year with crop sequence explained the HWW yield differences (P = .0005), mostly due to precipitation variability among site‐years. Most soil parameters tested only showed a main effect of date due to temporal changes in soil nutrient cycling. Replacing summer fallow with FP resulted in reduced soil water content, however, that did not result in long‐term moisture deficiency due to crop sequence type. System annualized gross revenue was equal to or greater for 2 site‐years for FP compared with fallow, with an average increase of US$113.15 ha–1. Pea–wheat reduced annualized net losses in 1 site‐year by $70 ha–1 compared with fallow–wheat in the "average" pricing model. Among 3 site‐years and three pricing models, pea–wheat resulted in greater net profit or reduced net losses compared with fallow–wheat in 5 site‐year comparisons.

Changes in Soil Phosphorus Pools in Long-Term Wheat-Based Rotations in Saskatchewan, Canada With and Without Phosphorus Fertilization

Phosphorus (P) is an essential nutrient for all organisms, and many crops require P fertilization for optimum yield. However, there are concerns about the P in agriculture, including the sustainability of phosphate sources for fertilizers and water quality problems from P loss in runoff from agricultural lands. Most crops do not use all of the P added each year as fertilizer, leaving residual soil P that could potentially be used by subsequent crops, minimizing the need for additional fertilization. However, more information is needed to understand soil residual P pools, and their availability to crops. In Swift Current, SK, Canada, a long-term study was initiated in 1967, with four wheat-based rotations [including continuous wheat (CW), fallow-wheat-wheat (FWW), fallow-wheat (FW) and lentil-wheat (WL), with P fertilization and with or without nitrogen (N) fertilization. In 1995, P fertilization ceased on subplots in the CW and FWW rotations, and in 2008 for the FW and WL rotations. This study examined changes in soil P pools (total P, organic P, and Olsen P) from 1995 to 2015 for CW and FWW rotations and from 2008 to 2016 for FW and WL rotations, plus crop yield and grain and straw N and P concentrations. Long-term P addition increased concentrations of soil total and Olsen P in FWW, CW and FW rotations, particularly in plots without N fertilization. However, calculated P depletions based on fertilizer addition and crop P removal were negative only for plots without N fertilization. Cessation of P fertilization reduced concentrations of soil total and Olsen P, especially in plots with N fertilization. Annual yields were affected more by N fertilization and precipitation than P fertilization. Grain and straw P concentrations were not significantly reduced with short-term P cessation in FW and WL rotations, but were reduced with longer-term P fertilizer cessation in FWW and CW rotations.

Soil water extractable organic matter under long‐term dryland cropping systems on the Texas High Plains

AbstractWater extractable organic matter (WEOM) is critical for soil fertility because of its role as a readily available C substrate for microbial metabolism. In the semi‐arid Texas High Plains, dryland cropping systems are common because of limited precipitation and irrigation water. Little is known about the long‐term effects of dryland cropping on soil WEOM content and composition, and how these differ from native grassland. The objective of this study was to use soils collected near Amarillo, TX, in 1977 and 2013 to examine the long‐term (72 yr total cropping length) effects of dryland cropping systems [continuous wheat and wheat–fallow rotations] and tillage methods (disk plow, stubble‐mulch tillage, and delayed stubble‐mulch tillage) on WEOM characteristics, compared with native grassland. In cropped plots, water‐extractable organic carbon (WEOC) concentrations, a measure of WEOM content, were depleted regardless of tillage or crop, with reductions up to 13% in 1977 and 60% in 2013, compared with native grassland in 2013. Other parameters of WEOM changed over time, where cropped soils from 2013 had proportionally more WEOM in aromatic, phenolic, and lignin‐like forms, attributed to recently incorporated crop residues. In contrast, WEOM in cropped soils from 1977 and native grassland (2013) contained more functional groups (e.g., aliphatic, aromatic, polysaccharide, phenol, etc.) and humic‐like substances than cropped soils in 2013. This suggests that long‐term dryland cropping led to depletion of stable, humic‐like WEOM. Enhancement of WEOM stocks and long‐term sustainability in the Texas High Plains may require more vigorous conservation systems than currently used.

Winter Wheat Performance Following One-time High Rates of Compost and Annual Cover Crop Planting in Wheat-fallow Rotations

Aims: One-time high rates of compost were applied at 15, 30, and 45 Mg ha-1 to improve soil organic matter (SOM) and fertility in dryland organic winter wheat-fallow rotations. Cover crop mixtures (oats and Austrian winter peas) were planted in fallow phases annually to suppress weeds and reduce repetitive tillage used for weed control because the latter breaks down SOM.&#x0D; Study Design: The experiment was laid-out in a split-plot design with four replications. Fertilizer (compost rates, inorganic fertilizer and no amendment control) and cover crops served as main and sub-plot factors respectively.&#x0D; Place and Duration of Study: The experiment was conducted at the Sustainable Agriculture Research and Extension Center, University of Wyoming, from September 2015 to August 2018.&#x0D; Methodology: Soil samples, weed biomass, wheat yield and protein quality data were collected and analyzed over three years.&#x0D; Results: Results indicated that 45 Mg ha-1 compost increased (P=.05) soil total carbon (TC) and nitrogen (TN) concentrations up to 25 and 19% respectively, in the last two years. Wheat yield was not affected (p&gt;0.05) by compost or cover crops in any growing season but 45 Mg ha-1 compost increased (P=.05) protein quality by 2-9% in the first growing season. Cover crops suppressed weeds while growing in the first growing season but had varying effects on weeds in wheat phases that followed them in rotation. It was noted that soil electrical conductivity levels affected by 45 Mg ha-1 compost was 5 times lower than wheat thresholds; and soil moisture loss by cover crops did not affect wheat yield.&#x0D; Conclusion: 45 Mg ha-1 compost improves soil fertility and SOM in the short term. However, significant reflection of soil changes in wheat yield may take longer time. Further research is needed to effectively integrate cover crops as a weed control measure in dryland organic wheat-fallow rotations.

Cropping systems alter plant volatile emissions in the field through soil legacy effects

AbstractCrops emit a variety of volatile organic compounds (VOCs) that serve as attractants or repellents for pests and their natural enemies. Crop rotations, off-farm chemical inputs, and mechanical and cultural tactics – collectively called cropping systems – alter soil nutrients, moisture content, and microbial communities, all of which have the potential to alter crop VOC emissions. Soil legacy effects of diversified cropping systems have been shown to enhance crop VOC emissions in greenhouse studies, but how they influence emissions under field conditions remains virtually unknown. To determine the effect of cropping systems on plant VOC emissions in the field, air samples were collected from the headspace of wheat (Triticum aestivum L. Judee) grown in simplified wheat-fallow rotations or diversified wheat-cover crop rotations where cover crops were terminated by grazing cattle. Across two growing seasons, wheat grown in rotation with fallow emitted greater amounts of Z-3-hexenyl acetate and β-ocimene, key attractants for wheat stem sawfly (Cephus cinctus Norton), a major pest of wheat. While overall VOC blends were relatively similar among cropping system during the first growing season, emissions varied substantially in the second year of this study where wheat grown in rotation with cover crops emitted substantially greater quantities of volatile compounds characteristic of abiotic stress. Below-average precipitation in the second growing season, in addition to reduced soil water content in cover crop rotations, suggests that cropping system effects on wheat VOCs may have been driven primarily by water availability, a major factor limiting crop growth in dryland agriculture. While the specific mechanisms driving changes in VOC emissions were not explicitly tested, this work shows that agricultural practices applied in one growing season can differentially influence crop VOC emissions in the next through soil legacy effects, illustrating additional avenues through which cropping systems may be leveraged to enhance pest management.

Evaluation of a crop rotation with biological inhibition potential to avoid N2O emissions in comparison with synthetic nitrification inhibition

Agriculture has increased the release of reactive nitrogen to the environment due to crops' low nitrogen-use efficiency (NUE) after the application of nitrogen-fertilisers. Practices like the use of stabilized-fertilisers with nitrification inhibitors such as DMPP (3,4-dimethylpyrazole phosphate) have been adopted to reduce nitrogen losses. Otherwise, cover crops can be used in crop-rotation-strategies to reduce soil nitrogen pollution and benefit the following culture. Sorghum (Sorghum bicolor) could be a good candidate as it is drought tolerant and its culture can reduce nitrogen losses derived from nitrification because it exudates biological nitrification inhibitors (BNIs). This work aimed to evaluate the effect of fallow-wheat and sorghum cover crop-wheat rotations on N2O emissions and the grain yield of winter wheat crop. In addition, the suitability of DMPP addition was also analyzed. The use of sorghum as a cover crop might not be a suitable option to mitigate nitrogen losses in the subsequent crop. Although sorghum–wheat rotation was able to reduce 22% the abundance of amoA, it presented an increment of 77% in cumulative N2O emissions compared to fallow–wheat rotation, which was probably related to a greater abundance of heterotrophic-denitrification genes. On the other hand, the application of DMPP avoided the growth of ammonia-oxidizing bacteria and maintained the N2O emissions at the levels of unfertilized-soils in both rotations. As a conclusion, the use of DMPP would be recommendable regardless of the rotation since it maintains NH4+ in the soil for longer and mitigates the impact of the crop residues on nitrogen soil dynamics.

The Effects of Different Tillage Techniques on the Production Costs in Fallow-Wheat Rotation System

The adoption and applicability of the technologies developed in agriculture by farmers are very important for agronomic studies. There are a limited number of economic studies comparing different tillage methods with each other. This study was conducted in the land of Polatlı Agricultural Enterprise between 2011 and 2017 to determine the amounts of physical production inputs and unit production costs of three different tillage operations in the fallow-wheat rotation system. The data consist of the production inputs in the Conventional Tillage, Minimum Tillage, and Direct Seeding practices. For the economic analysis, Single Product Budget Analysis was used. All the farmers’ production costs in the fallow-wheat rotation system were considered in the analysis. Among the practices, Gross Production Value (GPV) was obtained the most from the (509.63$ ha-1) practice. This practice was followed by Direct Seeding (486.13$ ha-1) and Minimum Tillage (421.92$ ha-1) practices, respectively. The profit threshold was exceeded in all practices, and production activities’ variable and total costs were fulfilled. The highest relative profit rate was obtained in Direct Seeding (1.77) practice, and it was followed by Conventional Tillage (1.30) and Minimum Tillage (1.08) practices, respectively. In order to obtain an income of $1 in wheat production, the lowest production cost was obtained in the Direct Seeding practice. With the Direct Seeding application, it can be ensured that economic wheat production, preservation of soil structure, reduction of input costs, and less economic damage to the farmer in changing climate conditions can be achieved.

Addressing the soil carbon dilemma: Legumes in intensified rotations regenerate soil carbon while maintaining yields in semi-arid dryland wheat farms

Semi-arid regions support the majority of global wheat production, but they are threatened by continued soil erosion and increased risk of drought and extreme temperatures from climate change. Enhancing soil organic matter (SOM) is a key adaptation strategy for sustaining agriculture in these regions because it can improve water retention and nutrient cycling. When seeking to increase SOM, growers face a dilemma, known as the ‘soil carbon (C) dilemma’ (Janzen, 2006): How can SOM be increased, while also increasing the release of nutrients that accompanies decomposition? Our observational study examined whether growers could address this dilemma through intensification with diverse grain crops. We specifically tested whether incorporating legumes into a continuous rotation influences the form and amount of SOM as well as productivity in farms of the central Great Plains region of the U.S. by contrasting three, no-till rotation systems: 1) conventional wheat-fallow; 2) continuous grain-only rotations, and 3) continuous grain rotations that incorporate a legume crop. We sampled on-farm fields and experimental agricultural research station plots that had received one of these rotations for at least eight years. We compared yield, soil organic C (SOC), and nitrogen (N) stocks in bulk soil to 1 m, as well as SOC and N in particulate organic matter (POM) and mineral-associated organic matter (MAOM) in surface soils (0–10 cm) among the different rotations. We also estimated the long-term effects of the rotations on SOC fractions through a simulation of each rotation with the MEMS 1.0 model, verified with measured data.We found that intensifying the rotation with continuous grains led to 1.5-fold increase in aggregate size but did not change SOC stocks. Incorporating a legume to the continuous grain rotation resulted in 1 Mg C ha-1 more SOC on average in surface soil compared to wheat-fallow rotations. No significant soil changes among rotations were observed at depth. Longer-term simulations of these cropping systems suggest that including legumes could allow for 10% greater SOC gains over time compared to wheat-fallow. Since legume incorporation also increased crop yields across the full rotation cycle, our results support our hypothesis that growers can solve the ‘soil C dilemma’ by simultaneously increasing the quantity and N-content of soil input through continuous cropping with both grains and legumes.

Simulation of wheat yield using CERES-Wheat under rainfed and supplemental irrigation conditions in a semi-arid environment

Wheat-fallow rotation is the major land-use system in the rainfed cropping system of Pakistan. Crop production in rainfed cropping systems is often jeopardized due to the scare and erratic seasonal patterns of rainfall. Climate change is further threatening the extent and productivity of rainfed agriculture in Pakistan. Climatic risk reduction strategies such as supplemental irrigation (SI) can assist in sustaining the productivity of rainfed agriculture. However, little has been done to investigate the potential of SI in sustaining the productivity of the rainfed cropping system of Pakistan despite the recent water resource developments in the rainfed regions of the country. For this purpose, a four-year (2010–2014) study was conducted to assess wheat yield and water productivity under rainfed and SI using a crop modeling approach. Calibrated CERES-Wheat was evaluated for its ability to simulate soil moisture dynamics, water productivity, canopy growth, in-season biomass, phenology, grain yield, and biomass at harvest based on soil water balance. Results showed a good to excellent performance of CERES-Wheat during evaluation. For example, combined values of soil moisture content between different layers, root zone soil moisture, seasonal crop evapotranspiration, in-season biomass growth, and canopy cover showed NRMSE values ranging from 13%–89%, 5–11%, 2–17%, 12–26%, and 13–22%, respectively. The NRMSE values of rainfall productivity of biomass and grain yield and water productivity of biomass and grain yield ranged from 18%, 16%, and 17%, 6%, respectively. The model was also applied to determine favorable management practices (appropriate planting dates from 15 October to 15 December at 15-day intervals and SI of 50 mm either at planting or 30 days after planting) as their determination under actual field conditions is laborious. Simulations for the best combination of planting date and SI suggested that higher crop yield and water productivity can be achieved with planting in November with irrigation applied 30 days after planting.

Exploring long-term impacts of different crop rotation systems on sustainable use of groundwater resources using DSSAT model

Groundwater depletion has been a global concern due to unreasonable agricultural water managements. Identifying long-term impacts of crop rotation systems on hydrological parameters and crop yields can help to alleviate groundwater depletion. The Decision Support System for Agro-technology Transfer model was applied to simulate impacts of nine crop rotation systems (H1: continuous spring maize; H2: continuous potato; H3: continuous spring wheat; H4:potato-maize rotation; H5:maize-wheat rotation; H6: wheat-potato rotation; H7: two year fallow-maize rotation; H8: two year fallow-potato rotation; H9: two year fallow-wheat rotation) on crop evapotranspiration, percolation, yields, water use efficiency, net water use and groundwater table depth changes in Zhangjiakou, China from 1985 to 2018. The results showed DSSAT model performed well in simulating crop ET, yields (R2>0.9, RMSE<500 kg ha−1) and soil water content (R2>0.9 and RMSE<10.1 mm). The long-term two year fallow with one single crop rotation systems (H7 to H9) had lower total accumulative groundwater table depth changes (2.8–14.4 m) than others (12.7–52.3 m) from 1985 to 2018. Also, cropping rotation systems H7 to H9 obtained the lower annual average net water use (14–70 mm) compared to other cropping rotation systems (62–253 mm). The significant difference of net water use, crop yields, water use efficiency and accumulative groundwater table depth changes of nine different cropping systems indicated H4 and H8 is suitable in the study region. Our results is useful for selecting suitable cropping systems based on the water use for local farmers.

Influence of crested wheatgrass on soil water repellency in comparison to native grass mix and annual spring wheat cropping

Crested wheatgrass (CWG) [Agropyron cristatum (L.) Gaertn.] is a commonly introduced grass in the Canadian prairies, but concerns remain about its possible long-term effects on soil quality, and its influence on soil water repellency (SWR) has not been determined. The long-term (24 yr) effects of CWG on SWR in comparison to seeded native grasses and annual cropping were determined for a clay loam soil in southern Alberta, Canada by measuring SOC concentration and SWR using soil hydrophobicity (SH) and soil water repellency index (RI) methods. The cropping treatments were CWG, seeded native grass mix (NGM), continuous wheat, and wheat–fallow rotation, each with fertilized (nitrogen) and non-fertilized subplots, replicated four times. Mean SOC concentration, SH, and RI in samples of surface soil were similar (P &gt; 0.05) for CWG and seeded NGM, and they did not support our hypothesis (seeded NGM &gt; CWG). Mean SOC was significantly greater for seeded perennial grasses than annual crops by 1.7–2 times and SH by 2.1–2.5 times, which supported our hypothesis, but RI was similar among treatments. As expected, nitrogen fertilization significantly increased SOC concentrations, but the effects on SH and RI were undetectable. A strong positive correlation occurred between SOC concentration and SH (r = 0.92) but not for RI (r = 0.10). Our findings suggested that SWR was similar for CWG and seeded NGM. The SWR as measured using SH was greater for seeded perennial grasses than annual cropping but was similar using RI.

Long-term biosolids land application influences soil health

Soil health assessments associated with organic amendment applications have primarily focused attention on manure or composts. Yet, quantifying specific changes in soil health associated with biosolids land applications has yet to be determined. Our objectives were to evaluate the changes in various soil indicators, and utilizing the Soil Management Assessment Framework (SMAF), quantify changes in soil indicator scores and soil health indices as affected by either increasing inorganic N fertilizer (0 up to 112 kg N ha−1) or biosolids (0 up to 11.2 dry Mg ha−1) applied every other year over 22 years. Soils were sampled (0 to 20 cm depth) following 22 years of N fertilizer or biosolids inputs to a dryland wheat-fallow (Triticum aestivum L.) rotation, 11 soil health indicators were monitored under SMAF guidelines, and indicators, indicator scores, and soil health indices were analyzed statistically. In general, increasing N fertilizer application rates had little effect on soil indicators, SMAF indicator scores or soil health indices. Increasing biosolids application rates increased soil organic C (SOC) and potentially mineralizable N (PMN). The SMAF indicator scores showed upward trends for soil pH, SOC, PMN, and microbial biomass C (MBC) associated with increasing biosolids application rates; discussing trends are important as these indicator scores are combined to provide soil health indices. Indeed, increasing biosolids application rates increased soil chemical and biological health indices, leading to an improvement in the overall soil health index. When comparing the overall N fertilizer to biosolids effect, biosolids applications significantly improved the soil biological health index. Results indicate that long-term biosolids land application to semi-arid, dryland wheat fallow rotations, similar to those studied, improve various aspects of soil health. These findings suggest that biosolids may play a pivotal role in dryland agroecosystem sustainability.

Residue management changes soil phosphorus availability in a long-term wheat-fallow rotation in the Pacific Northwest

Crop residue management strategies have exhibited significant effects on crop growth and soil properties, which in turn may influence soil phosphorus (P) transformation and availability. In this study, the effect of long-term (83-year) crop residue management treatments (straw plus 45 or 90 kg N ha−1; straw burning in fall or spring; straw plus manure) on soil P availability and storage capacity in the surface (0–0.3 m) and subsurface (0.3–0.6 m) were investigated relative to straw incorporated into soil (control) in a wheat-fallow rotation in the Pacific Northwest. Compared to the control, N application significantly decreased soil available P by 37–49%, measured as Olsen-P, due to the higher P removal by the wheat crop. The significant decrease in NaOH-extractable inorganic P (Pi) by 31–42% and Oxalate-extractable Fe by 20–27% suggests N application induced Fe associated-Pi release to supply crop growth. Straw burning had no significant effect on soil P balance but decreased available P by 20–36%, which can be attributed to the transformation of labile Pi and/or moderately labile Pi to stable Pi and P downward transport due to the increased pH of 0.4–0.9 and the loss of organic carbon. Fall burning appeared to have a greater effect on soil properties and P chemistry than spring burning. Manure application significantly increased soil available P by 245% in surface soil in 2014 while resulted in obvious negative soil P storage capacity (− 103 mg P kg−1) and high potential of P downward transport due to long-term positive P surplus together with the increase in soil pH of 1.2.