Precipitation Storage Efficiency Research Articles

No-tillage enhances soil water storage, grain yield and water use efficiency in dryland wheat (Triticum aestivum) and maize (Zea mays) cropping systems: a global meta-analysis.

Climate change significantly affects crop production and is a threat to global food security. Conventional tillage (CT) is the primary tillage practice in rain-fed areas to conserve soil moisture. Despite previous research on the effect of tillage methods on different cropping systems, a comparison of tillage methods on soil water storage, crop yield and crop water use in wheat (Triticum aestivum ) and maize (Zea mays ) under different soil textures, precipitation and temperature patterns is needed. We reviewed 119 published articles and used meta-analysis to assess the effects of three conservation tillage practices (NT, no-tillage; RT, reduced tillage; ST, subsoil tillage), on precipitation storage efficiency (PSE), soil water storage at crop planting (SWSp), grain yield, evapotranspiration (ET) and water use efficiency (WUE) under varying precipitation and temperature patterns and soil textures in dryland wheat and maize, with CT as the control treatment. Conservation tillage methods increased PSE, SWSp, grain yield, ET and WUE in both winter wheat-fallow and spring maize cropping systems. More precipitation water was conserved in fine-textured soils than in medium-textured and coarse-textured soils, which improved ET. Conservation tillage increased soil water conservation and yield under high mean annual precipitation (MAP) and moderate mean annual temperature (MAT) conditions in winter wheat. However, soil water conservation and yield were greater under MAP <400mm and moderate MAT. We conclude that conservation tillage could be promising for increasing precipitation storage, soil water conservation and crop yield in regions with medium to low MAPs and medium to high MATs.

Straw Residual Retention on Wheat Photosynthetic Characteristics, Utilization of Water and Nitrogen, and Reactive Nitrogen Losses

Straw residual retention is an emerging and promoted practice in rain-fed northwest China, but its effect on wheat photosynthetic characteristics, the utilization of water and nitrogen, and reactive nitrogen losses is poorly understood. A two-year consecutive field experiment was conducted to investigate the impacts of residual incorporation into soil and nitrogen application on wheat nitrogen and water utilization, yield and nitrogen losses during 2018–2020. The split-plot design of two tillage systems [conventional tillage (CT), and straw residue incorporated into soil (SR)] and three nitrogen rates [0 kg ha−1 (N0), 144 kg ha−1 (N144), 180 kg ha−1 (N180)] was implemented. Our results demonstrated that compared to CT, SR significantly influenced several key metrics. Compared with CT, SR increased the wheat photosynthetic rate (Pn), transpiration rate (Tr), leaf area index (LAI), leaf total chlorophyll (Chl-total), glutamine synthetase (GS) and nitrate reductase (NR) by an average of 5.38%, 12.75%, 8.21%, 5.79%, 16.21% and 20.08%, respectively (p &lt; 0.05). In addition, SR increased the wheat grain yield and nitrogen uptake accumulation (NUA), evapotranspiration (ET), precipitation storage efficiency (PSE), and mineral nitrogen residual after harvest (except for SR-N180 in 2019–2020), but decreased the apparent nitrogen recovery when compared with CT. However, there was an insignificant difference in the ammonia (NH3) volatilization and nitrous oxide (N2O) emissions of SR and CT. With an increase in the N-fertilization rate, the Pn and Tr, NH3 volatilization, N2O emission, mineral nitrogen residual (except for SR-N180 in 2019–2020), LAI, Chl-total (except for SR-N180 and CT-N180 in 2018–2019), GS, NR, grain yield, WUE, and NUA increased significantly; however, the ET, PSE, apparent nitrogen recovery (ANR), and nitrogen harvest index (NHI) decreased significantly. Furthermore, the differences between N144 and N180 in terms of the photosynthetic characteristics of wheat, the utilization of water and nitrogen, and yield were not significant. Overall, straw retention with N144 could be recommended as a resource-saving and environment-friendly management practice in a rain-fed winter wheat–fallow cropping system in northwest China.

Effects of conservation tillage with straw mulching on annual yield and water utilization in a winter wheat‐summer maize cropping system on the North China Plain

AbstractUnderstanding the combination of conservation tillage and straw mulching on water utilization is important for developing water management strategies in arid and semiarid areas. Few studies have investigated the effects of different tillage treatments on precipitation efficiency in winter wheat (Triticum aestivum L.)‐summer maize (Zea mays L.) cropping systems. A 3‐year field experiment with five treatments, that is, conventional tillage (CT), no‐tillage, no‐tillage with straw mulching (NT + S), subsoiling tillage, and subsoiling tillage with straw mulching (ST + S), was conducted. The objective was to investigate how conservation tillage with straw mulching affected soil water storage (SWC), precipitation storage efficiency (PSE), water consumption, grain yield, water use efficiency (WUE), and precipitation use efficiency (PUE) in a winter wheat‐summer maize cropping system. The results indicated that the ST + S treatment increased SWC by 10.1% and 8.3% in 2014–2015 and 2015–2016, respectively. The average PSE over the 3 years under the ST + S treatment was significantly higher, by 9.1% and 6.6%, than that under the CT treatment during the respective wheat and maize seasons. Compared with CT, the average annual yield under the NT + S treatment and ST + S treatment increased by 8.5% and 14.4%, respectively. In the winter wheat‐summer maize system, the NT + S and ST + S treatments significantly increased the annual WUE and PUE. The annual average PUE under the ST + S treatment was significantly higher, by 14.1%, than that under CT over the 3 years. Therefore, the ST + S treatment was more beneficial than the other treatments for increasing yield, WUE and PUE in sandy loam soil on the North China Plain.

Wheat stubble height effects on subsequent corn and grain sorghum crops

AbstractFor sustainable productivity, a winter wheat (Triticum aestivum L.)–summer crop (corn [Zea mays L.] or grain sorghum [Sorghum bicolor L.])–fallow (W‐SC‐F) cropping system could benefit from optimal wheat stubble cutting height management, but only limited information is available. The objective of this study was to evaluate the effect of wheat stubble height on subsequent corn and grain sorghum yields, available soil water, crop water use, and precipitation storage efficiency in a W‐C‐F and W‐S‐F cropping system. This study was conducted from 2006 through 2020 at the Kansas State University Southwest Research‐Extension Center near Tribune, KS. The experimental design was a randomized complete block with three wheat stubble heights (high, low, and strip). Average across all years, there was a 9%–10% corn yield and 7%–11% corn biomass advantage from high and stripper harvested wheat stubble compared with low cut stubble, and a 5% sorghum yield advantage from high cut stubble compared with low cut stubble. Kernel weight of corn was the only yield component that significantly differed among stubble height treatments. Water productivity of corn in the high and stripper harvested stubble treatments (15.3 kg ha−1 mm−1) was significantly greater compared with the low cut stubble (14 kg ha−1 mm−1). Water productivity of sorghum in the high cut stubble treatment (18.9 kg ha−1 mm−1) was also significantly greater compared with low cut stubble (17.7 kg ha−1 mm−1). Total available soil water at planting (ASWP) and available soil water at harvest (ASWH) of corn were both greater for high cut stubble compared with stripper harvested stubble but total ASWP and ASWH of grain sorghum were not significantly different among stubble height treatments. We concluded that low cut wheat stubble decreased subsequent corn and grain sorghum yields in a W‐C/S‐F cropping system.

Plow layer management during the fallow season can enhance the wheat productivity and resource utilization in a semi-arid region

The soil quality is poor in the arid areas of Northwest China and planting green manure can improve the soil quality but it also increases the soil water consumption. Straw mulching in the wheat (Triticum aestivum L.) fallow season can improve the soil water content. It is unclear whether green manure can be planted in addition to straw mulching to improve the soil water content and quality. Therefore, a field experiment was conducted in the semi-arid area of the Loess Plateau in China from 2009 to 2017 with the following treatments; (1) traditional bare land in fallow season after plowing (CK), (2) no-tillage with straw mulching (NTSM), (3) and no-tillage with straw mulching and planting soybean as green manure (NTSGM). We determined the effects of these three treatments on the soil water, nutrients, and wheat productivity. Compared with CK, the average soil water contents in 0–100 cm soil depth increased by 11.1% and 3.6% under NTSM and NTSGM, respectively, during the soybean full bloom stage, and by 13.06% and 6.6% before wheat sowing. Compared with CK, the decomposition of green manure increased the NO3–-N contents in the 0–100 cm soil depth by 6.6% and 5.3% under NTSGM before wheat sowing and after harvesting, respectively, and NTSM and NTSGM significantly improved the soil nutrients, microbial biomass contents, and enzyme activities. The superior soil quality and water content under NTSM and NTSGM increased the fertilizer uptake and partial factor productivity. Compared with CK, the average precipitation storage efficiency, water use efficiency during the whole year, biomass, and wheat yield were 32.6%, 23.2%, 16.2%, and 21.6% higher under NTSGM, respectively. Therefore, NTSGM is an effective method for improving the soil water storage and NO3–-N contents before sowing wheat, as well as the water use efficiency, soil quality, utilization of nutrients, and wheat productivity in semi-arid areas of the Loess Plateau.

Deep ploughing in the summer fallow season and optimizing nitrogen rate can increase yield, water, and nitrogen efficiencies of rain-fed winter wheat in the Loess Plateau region of China.

BackgroundAbout 60% of the annual precipitation in the Loess Plateau occurs during the summer fallow season, and does not align with the wheat growing season. In addition, the nitrogen use efficiency is low in this area because nutrient availability is affected by drought. As a result, rainwater storage during the summer fallow season is very important to increasing nitrogen use efficiency, and to the stable production of dryland wheat in the Loess Plateau.MethodsA 3-year field experiment in the eastern part of the Loess Plateau was conducted with two tillage methods (no tillage (NT) and deep ploughing (DP)) and five N rates (0, 120, 150, 180, and 210 kg N ha−1) to study the effect of tillage on soil water utilization, plant nitrogen utilization, and wheat yield.ResultCompared to NT, DP showed a larger increase in soil water storage (SWSf) and precipitation storage efficiency (PSEf) during the two dry summer fallow seasons than in the normal summer fallow season. DP substantially increased the pre-anthesis soil water consumption (SWCpre) and N translocation. The average yield under DP was 12.46% and 14.92–18.29% higher than under NT in the normal and dry seasons, respectively. A 1 mm increase in SWCpre could increase grain yield by 25.28 kg ha−1, water use efficiency (WUE) by 0.069 kg ha−1 mm−1, and nitrogen utilization efficiency (NUtE) by 0.029 kg kg−1. DP could reduce the N rate by 11.49–53.34% in the normal seasons and 40.97–65.07% in the dry seasons compared to the same highest point of yield, WUE, and NUtE under NT.ConclusionDeep ploughing in the summer fallow season, paired with optimized N application, could help increase wheat yield and nitrogen efficiency in dryland.

Cover crops to improve soil health in the North American Great Plains

AbstractRotating cereal crops (e.g., wheat [Triticum aestivum L.] with a 10‐ to 21‐mo summer fallow period [fallow]) is a common farming practice in dryland (rainfed) agricultural regions. Fallow is associated with several challenges including low precipitation storage efficiency, depletion of soil organic carbon (SOC), loss of soil fertility, little crop residue retention and soil erosion, and few control options for herbicide‐resistant (HR) weeds. The inability to effectively control HR weeds poses a major challenge to maintaining soil and water conservation practices such as no‐tillage, as some producers are considering tillage to control weeds. Cover crop (CC) integration into wheat‐based production systems to replace portions of the fallow period provides an opportunity to increase SOC, improve soil fertility, suppress weeds, and increase profitability of dryland crop production, especially when CCs are used as forage. This forum paper used the North American Great Plains as a model region to review information on (a) challenges of dryland agriculture; (b) integrating CCs in dryland agriculture; (c) benefits, challenges, and limitations of CCs in dryland crop production; (d) management options for CC integration in dryland grain systems; and (e) recommendations for future research efforts.

A meta-analysis on cover crop impact on soil water storage, succeeding crop yield, and water-use efficiency

Cover cropping is practiced to enhance soil health and sustain succeeding crop yield; however, the effect of cover crop on soil water storage, succeeding crop yield, and water-use efficiency (WUE) may not be consistent in all regions. A meta-analysis was carried out to evaluate the effect of cover crop on precipitation storage efficiency (PSE, the percent of precipitation that is stored in the soil during the fallow period), soil water storage at succeeding crop planting (SWSP), succeeding crop yield, and WUE from data collected from 117 studies across the world. Cover crop decreased PSE by 33.4% and soil water storage for the whole profile (SWSPT) at soil depth by 13.2%, but increased water storage to a depth of 30 cm (SWSP30) by 6.0% (P < 0.05) compared to no cover crop. Cover crop did not affect succeeding crop yield, but decreased evapotranspiration (ET) by 6.2% and increased WUE by 5.0% (P < 0.05) compared to no cover crop. The effect of cover crop on these parameters varied by soil and climatic conditions of various regions. Leaving cover crop residue at the soil surface or incorporating into the soil reduced PSE, SWSPT, and ET, but increased SWSP30 and WUE compared to residue removal. Maintaining cover crop biomass at 5Mgha−1 and leaving a 20-d interval between cover crop termination and succeeding crop planting, also enhanced PSE and SWSP30. Although cover crop had minimal impact on succeeding crop yield, WUE of succeeding crops can be increased with cover cropping by decreasing evapotranspiration.

Higher precipitation storage efficiency in nongrowing season ensures the success of dryland rain‐fed agricultural system

AbstractIn arid and semi‐arid regions, ridge‐furrow with plastic mulch (RFM) is an innovative approach to promote crop productivity and enhance food security. The long‐term effect of the RFM system on soil water is not known. A 7‐yr maize (Zea mays L.) field experiment was conducted between 2012 and 2018 in the Chinese Loess Plateau to estimate the spatial and temporal variation of soil water. The objectives were to (a) understand how RFM affects soil water status during and between growing seasons; and (b) investigate whether RFM causes the formation of dry soil layers and threaten the sustainability of the agricultural system. In the nongrowing season, the average precipitation storage efficiency (PSE) of the plastic mulching treatment was 78.2%, compared to just 17.7% for no film mulching treatment. Higher PSE means that the RFM system stored more precipitation during the nongrowing season. In addition, 2‐ and 5‐m soil profile water status showed that the film mulching did not overuse deep soil water and would not lead to the formation of dry soil layers. Our research indicated that the RFM was beneficial for increasing crop production and sustainability of agriculture in semi‐arid regions. Higher PSE during the nongrowing season played an important role in the success of RFM system. We recommend that farmers adopted year‐round plastic mulch management method to make fuller use of water resources.

Plastic Film Mulching Sustains High Maize (Zea mays L.) Grain Yield and Maintains Soil Water Balance in Semiarid Environment

Ridge–furrow cultivation with plastic film mulching has been widely used for many years to increase crop yields in semiarid regions. The long-term effects of plastic mulching on crop yield and soil water balance need to be seriously considered to assess the sustainability of this widely used field management technique. A seven-year maize field experiment was conducted during 2012–2018 to estimate the yield sustainability and soil water balance with two treatments—mulching (yes; no) and nitrogen fertilization (yes; no). This resulted in the following four groups—no film mulching, no N application (M0N0); film mulching, no N application (M1N0); no film mulching, N application (M0N1); film mulching and N application (M1N1). Our results show that plastic mulching significantly increased maize yield. A combination of mulching and nitrogen application had the highest sustainability yield index (SYI) of 0.75, which was higher than the other three treatments, with SYI values of 0.31, 0.33, and 0.39, respectively. Plastic film mulching increased soil water content and water storage in both the sowing and harvesting periods and did not cause the formation of dry soil layers. Precipitation storage efficiency (PSE) in the nongrowing season played a key role in maintaining the soil water balance and it was positively affected by plastic film mulching. Our research indicates that plastic mulching and N application could maintain maize yield sustainability and the soil water balance of agriculture in semiarid regions. In addition, we highlight the importance of nongrowing season precipitation, and thus, we suggest that mulching the field land with plastic film throughout the whole year should be adopted by farmers to store more precipitation, which is important to crop growth.

Conservation tillage increases yield and precipitation use efficiency of wheat on the semi-arid Loess Plateau of China

Drought is a major limiting factor for rainfed spring wheat production on the semiarid Loess Plateau of China. Suitable tillage practices are important for improving precipitation use efficiency (PUE), which is the ratio of grain yield to annual precipitation. To obtain a better understanding of the effects of conservation tillage practices on PUE on the semiarid Loess Plateau, PUE was divided into five steps: precipitation storage efficiency, farmland water consumption rate, ratio of transpiration to evapotranspiration, crop transpiration efficiency, and harvest index. Six tillage practices were assessed in this paper, including conventional tillage with no straw (T), no-till with straw cover (NTS), no-till with no straw (NT), conventional tillage with straw incorporated (TS), conventional tillage with plastic mulch (TP), and no-till with plastic mulch (NTP), based on a long-term experiment initiated in 2001. The impact of tillage practices on soil quality, soil water storage, soil evaporation, biomass yield, and grain yield of spring wheat were monitored in 2015 and 2016. The results show that NTS improved soil quality and soil water storage before sowing. No-till with plastic mulch and NTS increased evapotranspiration but decreased evaporation, thus optimizing precipitation storage efficiency, the farmland water consumption rate, the ratio of transpiration to evapotranspiration, and crop transpiration efficiency, which gave rise to greater aboveground dry matter accumulation and more dry matter accumulation in grain. As a result, grain yield under NTS and NTP was significantly increased by 45 and 41 % compare to T, respectively, with corresponding improvements in PUE of 43 and 39 %. Therefore, both NTS and NTP have potential to substantially increase grain yield of spring wheat and PUE. However, for sustainable intensification in the long-run, NTS is the best combination of tillage and soil surface management for spring wheat production on the semi-arid Loess Plateau of China.

Influence of plastic film mulch on maize water use efficiency in the Loess Plateau of China

Water is the main limiting factor for crop growth in dryland farming areas. Plastic film mulch (PM) is widely used to improve water use efficiency (WUE) and increase crop yield over conventional methods (no mulch, NM) in China. To get a better understanding about PM influence on water use process in the field, we defined WUETWI as the ratio of yield (Y) to the total water input (TWI), and divided WUETWI into 4 steps by means of a systematic and quantitative approach. The 4 steps included ratio of available soil water (SW) to TWI (SW0+P, where SW0 is available soil water at the sowing, P is seasonal precipitation), ratio of crop evapotranspiration (ETC) to SW, ratio of crop transpiration (T) to ETC and transpiration efficiency (WUET, Y/T). Three field experiments were conducted to analyze the influence of PM on soil moisture content, water consumption, and the grain yield of dryland spring maize (Zea mays L.). Results showed that, compared with NM, spring maize yield of PM was increased by 28.6%, and the WUETWI of PM was increased by 26.4% on average in the experiment 1. Since ETc with PM was slightly higher than that with NM, the ETC/SW was increased by 3.9%. In the experiment 2, the T/ETC with PM was 77.7% on average, 30.6% higher than that with NM; the Y/T increased by 13.6% from NM to PM. Precipitation storage efficiency increased linearly with the percentage of PM. Improved crop growth under PM led to higher crop biomass and higher leaf area index, which might result in higher transpiration rate. The T/ETC under PM was also increased.

No‐Till Diversified Cropping Systems for Efficient Allocation of Precipitation in the Southern Great Plains

Core Ideas Precipitation allocation increased from 45 to 85% when using diversified crop rotations. Shifting timing of fallow periods increased growing season precipitation allocation. Diversified crop rotations exhibited lower total water losses during fallow periods than continuous wheat rotations. Conventional till continuous winter wheat (Triticum aestivum L.) is a common cropping system in the portion of the Southern Great Plains (Kansas, Oklahoma, and Texas) with &gt;600 mm annual precipitation. This cropping system contributes to soil erosion and uses resources such as precipitation, land, and time inefficiently. Therefore, new cropping strategies are needed. The objective of this research was to determine how no‐till diversified cropping systems affect precipitation allocation and precipitation storage efficiency relative to conventional till continuous wheat. Five crop rotations of varied diversity were studied including the following crops: winter wheat, corn (Zea mays L.), sunflower (Helianthus annus L.), grain sorghum [Sorghum bicolor (L.) Moench.], and soybean [Glycine max (L.) Merr.]). The experimental design was a randomized complete block in two location and 2 yr. Soil water content (SWC) to a 2‐m depth was measured weekly with a neutron probe. Regardless of the cropping system, nearly 80% of precipitation during fallow periods was lost. Eighty‐five percent of the annual precipitation was received during the crop growing seasons in the diversified cropping systems compared with 48% in continuous wheat. Fallow periods were inefficient regardless of cropping intensification and shifting fallow periods from summer to winter months resulted in more efficient use of precipitation in the diversified cropping systems.

Straw mulching increases precipitation storage rather than water use efficiency and dryland winter wheat yield

Straw mulching is widely used to conserve soil water and increase crop yields. The effects of wheat straw mulching rate and method on dryland soil water storage, winter wheat (Triticum aestivum L.) growth and yield, and water-use efficiency (WUE) were examined from 2008 to 2015 in the Loess Plateau of China. Treatments included wheat straw mulching at a high rate of 9000 kg ha−1 (HSM) and low rate of 4500 kg ha−1 (LSM) throughout the year, straw mulching at a rate of 9000 kg ha−1 during summer fallow (FSM), and no mulching (CK). Soil water storage at wheat planting and precipitation-storage efficiency (PSE) were greater with straw mulching than without. Soil water storage at harvest was greater with HSM than CK and FSM. Wheat yield components such as number of wheat seedling, plant, tiller, and spike and thousand-grain weight varied with treatments and years, but wheat aboveground biomass and grain yields were usually greater with mulching than without during years with below-average precipitation. Harvest index and WUE were lower with LSM and HSM than other treatments in most years, but evapotranspiration did not vary with treatments. Overall, the increased PSE due to straw mulching did not increase yield and WUE, and straw mulching could sustain dryland wheat grain yield only in dry years.

Effects of film mulching regime on soil water status and grain yield of rain-fed winter wheat on the Loess Plateau of China

Shortages and fluctuations in precipitation are influential limiting factors for the sustainable cultivation of rain-fed winter wheat on the Loess Plateau of China. Plastic film mulching is one of the most effective water management practices to improve soil moisture, and may be useful in the Loess Plateau for increasing soil water storage. A field experiment was conducted from July 2010 to June 2012 on the Loess Plateau to investigate the effects of mulching time and rates on soil water storage, evapotranspiration (ET), water use efficiency (WUE), and grain yield. Six treatments were conducted: (1) early mulching (starting 30 days after harvest) with whole mulching (EW); (2) early mulching with half mulching (EH); (3) early mulching with no mulching (EN); (4) late mulching (starting 60 days after harvest) with whole mulching (LW); (5) late mulching with half mulching (LH); and (6) late mulching with no mulching (LN). EW increased precipitation storage efficiency during the fallow periods of each season by 18.4 and 17.8%, respectively. EW improved soil water storage from 60 days after harvest to the booting stage and also outperformed LN by 13.8 and 20.9% in each growing season. EW also improved spike number per ha by 13.8 and 20.9% and grain yield by 11.7 and 17.4% during both years compared to LN. However, EW decreased WUE compared with LN. The overall results of this study demonstrated that EW could be a productive and efficient practice to improve wheat yield on the Loess Plateau of China.

Water use and environmental parameters influence proso millet yield

Proso millet (Panicum miliaceum L.) is a short-season, drought-tolerant C4 species capable of making use of limited available water supplies and is suitable for dryland crop rotations in the Central Great Plains. Previously published water use/yield production functions for proso millet have slopes lower than reported for other C4 species in this region. The objectives of this experiment were to determine the water-limited yield relationship for proso millet and to identify environmental factors that cause yields to be lower than predicted by the water-limited yield relationship. Water use and yield data were obtained from a long-term crop rotation experiment conducted under dryland conditions in northeast Colorado from 1995 to 2016. Stepwise linear regression analysis was used to determine important environmental factors influencing yield. The water-limited yield relationship had a slope consistent with other C4 species in this region (32.57kgha−1 per mm of water use). A relationship based on growing season water use, plant available soil water at planting, precipitation received from 12 to 18 August, number days in July and August with maximum temperature greater than 36°C, daily average wind run and maximum wind gust during the week before swathing explained 88% of yield variability. The results of this analysis suggest that closing the yield gap for proso millet production could likely result from efforts to breed for enhanced shattering resistance and heat tolerance and from production methods that improve precipitation storage efficiency during the non-crop period prior to millet planting and increase available soil water at millet planting.

Seven rainfed wheat rotation systems in a drought-prone Mediterranean climate

Increasing cropping intensity and use of no-till fallow (NTF) has been successful in many rainfed Mediterranean agricultural regions around the world, including of the Inland US Pacific Northwest (PNW) where annual precipitation exceeds 290mm. However, in the low-precipitation (<290mm annual) region east-central Washington and north-central Oregon, these practices have not been widely adopted and a 2-year winter wheat (Triticum aestivum L.)-tilled summer fallow rotation is practiced by the vast majority of farmers. The objective here was to evaluate the productivity of seven wheat rotation systems that reduce or eliminate tillage and increase cropping intensity in a 6-year study at Lind, WA. The study included: (i) soft white, hard red, and hard white market classes of wheat; (ii) both NTF and undercutter conservation-tillage summer fallow (UTF), and; (iii) continuous annual no-till cropping of wheat. Crop-year (September 1–August 31) precipitation over the six years averaged just 217mm. Across years, market class, and rotation system, spring wheat (SW) grain yield was only 33% of winter wheat (WW) after UTF. Thus, although only one crop was produced every other year with WW-UTF, this system had water use efficiency (WUE) of 5.5 grain/mm precipitation versus as low as 3.0kg grain/mm precipitation for SW with no preceding fallow year. Possible mechanisms for differences in grain yield and WUE among rotations were: (i) Russian thistle (Salsola tragus L.) weed infestation was at least eleven times greater in the various SW systems and much greater still with WW after SW with no fallow year compared to in WW after NTF and UTF, and; (ii) precipitation storage efficiency (PSE) in the 180cm soil profile during fallow for NTF-WW-SW was only 30% compared to 39 and 42% for the UTF-WW-SW and UTF-WW treatments, respectively. Critically, the seed zone of NTF was too dry for early planting of WW in most years whereas adequate seed-zone water was present every year in the UTF systems. Primarily due to late planting necessitated from lack of seed-zone water, grain yield of WW after NTF was reduced 35% compared to WW after UTF. Optimum grain yields and soil conservation are both required for sustainable agriculture, and WW with the UTF method was the clear winner of systems evaluated in this study.

Long-term analysis of soil water conservation and crop yield under different tillage systems in Mediterranean rainfed conditions

This study focuses on the quantification of soil water storage and crop yield under different tillage systems in dryland semiarid Mediterranean conditions. Three long-term tillage experiments based on cereal production were initiated in 1987, 1990 and 1992, at three different locations in the Ebro river valley (NE Spain): El Canós, Selvanera and Agramunt, with an increasing degree of aridity. Different tillage intensities were compared in each experiment using different implements: no tillage (NT), minimum tillage (MT), chisel (Ch), subsoiler up to 25cm depth (Sub-25) and up to 50cm (Sub-50), and mouldboard plough (Mb). Soil water content (SWC) up to 100cm, soil water storage (SWS), precipitation storage efficiency (PSE) and crop yield were quantified during 8 (El Canós) and 19 years (Selvanera and Agramunt). The use of MT (at Selvanera) and NT (at El Canós and Agramunt) led to the highest SWC after the storage period (i.e., from previous harvest to crop tillering), with a major role played by the storage of water at deep soil layers. At Agramunt, Mb presented the lowest SWS when compared to Ch, Sub-50 and NT, and, consequently, the lowest post-tillering evapotranspiration. On the contrary, no differences were found between tillage systems on SWS at El Canós or at Selvanera. Significant yield differences were found at Agramunt being: NT>Sub-50>Ch=Mb. These differences were especially important in years with mean yield below 2000kgha−1, in which NT obtained the highest productions. At Selvanera yield was greater under conservation tillage (NT, MT) than under intensive tillage (Sub-50). Contrarily, no yield differences were found between tillage systems at El Canós, the site with the lowest water deficit, where crop residues were removed. A strong linear relationship was found between SWS and yield at Agramunt and Selvanera. At Agramunt the relationship presented a greater slope under Mb. In this site, in years with previous harvest-to-tillering SWS below 100mm and with precipitation over 100mm between tillering and anthesis, yields were, as an average, 1245kgha−1 higher than in standard years. This study demonstrates that under semiarid rainfed conditions, soil water storage increases with the use of conservation tillage systems, being amplified with the degree of aridity of the site. The relationship between water stored in the soil and crop yield and its reliability is site-specific. Once determined, it could be used to predict yield at the end of the vegetative phase of the crop to help take management decisions.

Cover Crop Effect on Subsequent Wheat Yield in the Central Great Plains

Crop production systems in the water‐limited environment of the semiarid central Great Plains may not have potential to profitably use cover crops because of lowered subsequent wheat (Triticum asestivum L.) yields following the cover crop. Mixtures have reportedly shown less yield‐reducing effects on subsequent crops than single‐species plantings. This study was conducted to determine winter wheat yields following both mixtures and single‐species plantings of spring‐planted cover crops. The study was conducted at Akron, CO, and Sidney, NE, during the 2012–2013 and 2013–2014 wheat growing seasons under both rainfed and irrigated conditions. Precipitation storage efficiency before wheat planting, wheat water use, biomass, and yield were measured and water use efficiency and harvest index were calculated for wheat following four single‐species cover crops (flax [Linum usitatissimum L.], oat [Avena sativa L.], pea [Pisum sativum ssp. arvense L. Poir], rapeseed [Brassica napus L.]), a 10‐species mixture, and a fallow treatment with proso millet (Panicum miliaceum L.) residue. There was an average 10% reduction in wheat yield following a cover crop compared with following fallow, regardless of whether the cover crop was grown in a mixture or in a single‐species planting. Yield reductions were greater under drier conditions. The slope of the wheat water use–yield relationship was not significantly different for wheat following the mixture (11.80 kg ha−1 mm−1) than for wheat following single‐species plantings (12.32–13.57 kg ha−1 mm−1). The greater expense associated with a cover crop mixture compared with a single species is not justified.

Fallow Replacement Crop (Cover Crops, Annual Forages, and Short-Season Grain Crops) Effects on Available Soil Water

Producers are interested in growing cover crops and reducing fallow. Limited information is available on growing crops in place of fallow in the semiarid Great Plains. Between 2012 and 2015, spring cover, annual forage, and grain crops were grown in place of fallow in a no-till wheat-grain sorghum-fallow (WSF) rotation in southwest Kansas. Growing a cover, hay, or grain crop in place of fallow reduced the amount of stored soil moisture at wheat planting. On average, cover crops stored slightly more moisture than hay crops, but this soil moisture difference did not affect wheat yields. Soil moisture after grain crops was less than after cover or hay crops, and this difference resulted in reduced wheat yields. These results do not support claims that cover crops increase soil moisture compared to fallow. Soil moisture storage from fallow crop termination to wheat planting was greatest among those treatments that were most dry at termination and produced the most aboveground biomass. On average, cover crops had a 28% precipitation storage efficiency (PSE) and hay crops had a 22% PSE between termination and wheat planting. Fallow during the full-fallow period (sorghum harvest to wheat planting) had an 18% PSE. Crops grown in place of fallow must compensate for the expense of growing the crop plus the reduction in soil moisture for the next crop.