Stubble Mulch Tillage Research Articles

Winter wheat grain yield stability under different tillage practices

AbstractGrain yield stability is vital for achieving yield consistency across a broad range of environments. The significance of this is well documented in crop genetic studies and may equally be relevant for tillage practices used in croplands. The objective of this study was to evaluate long‐term winter wheat (Triticum aestivum L.) grain yield stability under different tillage practices. The study was designed as a randomized complete block with three replications. The independent variable was tillage with three levels: no tillage (NT), stubble mulch (SM), and moldboard plow (MP). The experiment was established as a winter wheat–fallow under a dryland cropping system. Each phase of the wheat–fallow was present each year. The historical grain yield data from 1972 to 2010 were presented in this study. Yield stability was assessed using regression coefficients (βi) and squared deviation from regression (S2d). Grain yield had average stability because each tillage practice had a βi of 1.0. The SM tillage had an S2d of 0.03 (P = .90), which was not significant than zero (0), while NT and MP had an S2d of 0.06 (P = .04) and 0.07 (P = .01), respectively, that were significant than zero (0). This suggests that SM had a more stable yield under different environments when compared with NT and MP. In general, using minimum tillage, such as SM, that maintains residues on the soil surface could contribute to yield resiliency across different environments and enhance land sustainability in dryland cropping systems.

Soil organic carbon and nitrogen responses to occasional tillage in a continuous no-tillage system

No-tillage (NT) practice is increasingly adopted to improve soil health and sustainability. However, long-term NT may increase soil organic carbon (SOC) and nutrient stratification, soil acidification, compaction, and herbicide resistance in weeds. Targeted strategic disturbance of continuous no-tillage is occasionally practiced to overcome challenges of long-term no-tillage, yet limited information is available on their impacts on SOC and nitrogen (N) components. We evaluated the response of SOC and N fractions to different tillage practices after the imposition of one-time strategic minimum tillage operation (i.e., stubble mulch tillage: SMT) in a continuous NT system in semi-arid drylands. Tillage treatments included conventional tillage (CT), NT, SMT, and strip-tillage (ST). The CT, NT, and ST plots were established in 2013, and SMT plots were established with only one pass of stubble mulch tillage in september of 2019 in long-term NT plots. Soil samples were collected from 0 to 15 and 15–30 cm depth of each plot before SMT and 2-days, 7-months, 14-months, 19-months, and 26-months after SMT implementation. The CT management resulted in 12–27% and 11–16% lower SOC concentration than under NT, SMT, and ST in 0–15 and 15–30 cm depth, respectively. The CT and ST had 22–53%, 44–79%, and 43% greater soil inorganic N than NT and SMT after 2-days, 7-months, and 19-months, respectively, in 0–15 cm depth. The 3d-carbon dioxide-carbon (CO2-C) was 32–65%, 48–65%, 62–102%, and 122–195% greater under CT and ST than under NT and SMT after 2-days, 7-months, 19-months, and 26-months, respectively, in 0–15 cm depth. The microbial biomass carbon (MBC) showed varying responses, with 31–64% lower MBC after 2-days and 26-months, but it was 35–39% greater after 7-months under CT than under NT and SMT. There was no difference between NT and SMT systems on SOC and N fractions for most of the samplings. Further research may reveal how often SMT can be utilized in a long-term NT system without negative impacts on soil properties in semi-arid dryland cropping systems. This study showed one stubble mulch tillage after six years of continuous NT did not affect SOC and N concentrations in 0–30 cm depth.

Controlling Stormwater Runoff That Limits Water Availability and Dryland Crop Productivity

Continued pumping for irrigation from the non-recharging Ogallala aquifer in Kansas and Texas is unsustainable. Reducing risks for dryland wheat (Triticum aestivum L ) and sorghum [Sorghum bicolor (L.) Moench] production, which depends exclusively on precipitation to meet water demand is critical for future adoption. Stormwater runoff reduces the amount of precipitation available to crops, but management practices to minimize runoff concomitantly increase the opportunity time for infiltration and improve precipitation storage as soil water for crop use. Our objectives in this study were to evaluate tillage, slope and the effects of contour or with-slope farming on runoff, soil water at planting, and the growth and yield of wheat and sorghum grown in the three year wheat-sorghum-fallow (WSF) rotation. Long-term, 1983 to present, runoff was measured from gauged terraced and contour farmed fields managed in the WSF rotation with no-tillage (NT) or stubble-mulch (SM) tillage. We found significantly greater mean cumulative runoff during fallow for NT than for SM but only for the 1.8% terrace slopes., The corresponding soil water with NT increased by a significant ~27 mm over SM due to reduced evaporation but generally did not differ due to slope. Wheat yield decreased significantly as slope decreased from 1.8% to 1.2% but exhibited no yield response tillage. In contrast, grain sorghum yields were greater with NT than SM tillage residue management. Farming along the contour or slope manifested no differences in soil water, crop grain yield, or water use; however, they did increased significantly with no tillage for sorghum but not wheat. We conclude that management of tillage was more effective than slope effects in increasing water availability to crops because of evaporation reduction with crop residue.

Efficiency of crop rotation under long-term application of basic tillage systems

An assessment is given of the long-term impact of basic tillage systems of various degrees of intensity on the yield and economic efficiency of production in the cultivation of cereals in grainfallow crop rotation. The study was carried out in 2017–2019 in a long-term stationary experiment on dark grey forest heavy loamy soil in Tyumen region. The experiments were carried out during the seventh rotation of the grain-fallow crop rotation: bare fallow – winter rye – spring wheat – spring wheat – spring barley, spread in time and space. In years with high temperatures and good rainfall, close to the average annual rainfall, resource-saving tillage systems with disk harrowing BDT-2.5 by 10-12 cm and stubble-mulch tillage by 12-14 cm with and without fertilizers led to a decrease in winter rye yield by 0.30-0.98 t/ha. Wheat yield against winter rye and barley was close to the variant with the moldboard tillage. There was a decrease in the yield of wheat sown repeatedly without the use of fertilizers by 0.04-0.40 t/ha. When fertilizers were used, the yield was equal to the control. The moldboard tillage without fertilizers was the most effective, with the net income of 14.92 thousand rubles/ha. Combined and surface soil tillage systems were similar in efficiency to the moldboard tillage (inferior by 4.3-6.6%). The most effective cultivation of cereals with the use of fertilizers was by minimum combined tillage with alternating plowing and disk harrowing, with the net income of 17.74 thousand rubles/ha, which was 13.4% higher compared to moldboard plowing. Differentiated, stubble-mulch and combined tillage brought the net income close to the control. In the remaining options studied, the net income was lower than with the moldboard tillage: without fertilizers – by 1.26-2.44 thousand rubles/ha (8.5-16.3%), with the use of fertilizers – by 1.02-1.78 thousand rubles/ha (6.5-9.0%).

Precipitation, runoff, and yields from terraced drylands with stubble‐mulch or no tillage1

AbstractDryland crops rely on precipitation as their exclusive water source, but storm water runoff decreases the amount available for biomass and grain production. Management practices that minimize runoff often increase the opportunity time for infiltration and improve precipitation storage as soil water. Our objective was to quantify storm water runoff from contour farmed terraces in relation to precipitation and field characteristics and then relate runoff to soil water at planting and yields of wheat (Triticum aestivum L.) and sorghum [Sorghum bicolor (L.) Moench] grown in a 3‐yr wheat–sorghum–fallow (WSF) rotation. Comparisons of long‐term (1984–2010) runoff observations indicated mean annual runoff for both uncropped periods of the WSF rotation were significantly greater with no‐tillage (NT) than stubble‐mulch (SM) tillage. By contrast, soil loss was greater for SM than NT because residue cover of undisturbed NT soil was less subject to entrainment and loss. Increasing field slope from 1.2 to 1.8% produced greater fallow runoff, which is water lost from dryland production. Nevertheless, soil water was significantly greater with NT, which reduced evaporative losses during fallow compared with SM. Long‐term wheat yields exhibited no difference due to tillage, but NT grain sorghum yields increased significantly over SM tillage. The data show that while runoff with NT was typically greater than SM, profile soil water at planting was also greater for NT and increased grain sorghum yields significantly. We conclude that decreasing evaporative water losses with NT residues is the primary factor affecting soil water conservation.

Elements of fertility and productivity of arable land depending on the soil tillage system

The effect of basic tillage systems on fertility elements and arable land productivity in the cultivation of crops was studied. Research took place in 2017–2019 in a stationary experiment on the dark grey forest loamy soil of the Northern Trans-Urals. The observations were carried out during the seventh rotation of the grain-fallow crop rotation, namely bare fallow – winter rye – spring wheat – spring wheat – spring barley, spread in time and space. Moldboard, non-moldboard, combined, differentiated, minimum combined, stubble-mulch and surface soil tillage systems were studied. Various basic tillage systems did not affect significantly the agrophysical properties of soil during the research period with favorable precipitation conditions. At a very low N–NO 3 content, tillage did not have a large effect on the availability of the arable layer. Favorable conditions for phosphorus nutrition in the soil layer of 0–20 cm were formed by combined and surface soil tillage systems. The Р 2 О 5 content with these systems was higher than with moldboard tillage, in the spring by 20.6–24.4%, in the autumn by 6.6–14.3%. Non-moldboard and stubblemulch tillage systems reduced the content of Р 2 О 5 compared to the moldboard by 19.0–23.3%. The most stable positive results for grain yield from 1 ha of crop rotation area without fertilizers were obtained with moldboard (1.88 t/ha) and combined (1.84 t/ha) tillage systems. The yield of grain with the use of resource-saving tillage systems and with fertilizers was almost equal to moldboard system. The difference in productivity generally did not exceed 5%. Moreover, grain yield was 0.03–0.17 t/ ha higher when applying minimum combined tillage alternated with plowing and disk plowing, or when using stubble-mulch tillage than with moldboard system.

Efficiency of the Erosion Protection Methods Involving Biologizing Agriculture in the Steppe and Forest-steppe Areas of Cultivated Land in Siberia

The research has been carried in the steppe zone of the Minusinsk Hollow and forest-steppe of the Altai Ob Region. The paper presents the results of studying the efficiency of erosion protection methods using biologizing agriculture and technologies of soil treatment. The authors have analyzed long-term data provided by numerous research institutions located in different agro-ecological conditions in the forest-steppe and steppe areas of cultivated land. Long-term field experiments carried out to study and make a comparative analysis of soil treatment technologies in green manure fallows have shown different soil conservation efficiencies in various soil climatic conditions of the Middle Siberia. In the steppe area of cultivated land, in the case of erosion-hazard soil, it is worth using stubble mulch tillage treatment, which allows preserving plant residues on the soil surface in order to increase the soil protection efficiency of green manure fallows. After this type of treatment no removal of fine soil by wind was observed on black soil, while in the case of tillage the soil removal amounts to 2,5 - 8,1 tons per hectare per year. In the steppe area on slope lands, winter stubble residues allow one to completely prevent the soil wash out in spring. The number of days with dust storms after the Virgin Lands Campaign in Khakassia in 1961 – 1965 amounted to 5 – 13. At present, with the decreased areas of strongly eroded plough land and increased volume of fallow land, dust storms do not occur. A fallow grown crop (summer planted oats) and, on the slope lands, mulching with rape completely prevented the spring wash out. The grain yield from a hectare of the crop rotation area in the case of sweet clover tillage and stubble mulch plowing was almost the same: 1,64 and 1,76 tons per hectare, respectively. Treatment of the deposit land followed by spraying with Tornado herbicide in August reduces soil erosion 2.2 times compared to its introduction in June.

Contrasting tillage effects on stored soil water, infiltration and evapotranspiration fluxes in a dryland rotation at two locations

There are significant uncertainties in partitioning growing season precipitation into the water balance components that determine water available for dryland crop yield across a range of environments and tillage practices. We evaluated profile soil water contents at a high temporal resolution during phases of a dryland wheat (Triticum aestivum L.) –sorghum (Sorghum bicolor L.) -fallow rotation under no tillage (NT)1 and stubble-mulch tillage (ST) management at Bushland, Texas and Tribune, Kansas to assess event-based soil water balance components. Cumulative infiltration and evaporation were estimated based on hourly changes in stored soil water using a water balance approach and a drainage model. Estimated deep drainage comprised a small proportion of the soil water budget averaging five percent of annual precipitation in Bushland. Tillage did not significantly influence cumulative infiltration during summer fallow and growing season periods at Bushland. In contrast, NT at the Tribune location exhibited significantly greater (P = 0.023) cumulative infiltration compared to ST during the wheat fallow period just prior to sorghum planting. At both locations during summer fallow periods, NT was not more efficient in increasing stored soil water over that obtained with ST. Evaporation during summer fallow periods was more a function of the soil water content near the surface than the tillage practice. Effective infiltration expressed as a fraction of precipitation averaged 0.55 and 0.57 under NT and ST, respectively, at Bushland compared with 0.83 and 0.52 under NT and ST, respectively, at Tribune. Observations of effective infiltration elucidate historical results of the incremental sorghum grain yield response of NT over ST that averaged 12 percent at Bushland and 35 percent at Tribune. Partitioning of growing season precipitation to transpiration was insufficient in Bushland to generate yield increases under NT of similar magnitude to that observed in Tribune demonstrating that NT does not perform similarly across all environments.

Grazing and Tillage Effects on Soil Properties, Rain Infiltration, and Sediment Transport during Fallow

Core Ideas Soil loss tended higher (>40%) with grazing, but tillage increased soil loss significantly. Infiltration increased with tillage and did not vary with grazing during either fallow phase. Combined grazing and NT management decreased infiltration without tillage to disrupt compaction. Depletion of the High Plains Aquifer that supplies irrigation water for the semiarid Southern Great Plains may necessitate dryland production of crops like wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] using the wheat–sorghum–fallow (WSF) rotation. Reduced crop productivity without irrigation can be offset by intensifying the WSF rotation with cattle (Bos taurus) grazing. Biomass removal and soil trampling without tillage, however, may reduce rain infiltration and storage during fallow that increases with no‐tillage (NT) over stubble‐mulch (SM) tillage. Our objective was to quantify grazing and tillage effects on infiltration, sediment transport, and aggregate stability during fallow periods after sorghum and wheat. Using a split plot randomized complete block design, we compared wet aggregate size distribution of a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll; 0.0–0.05 m) and sediment yield in runoff of simulated rain during the fallow‐like idle period after wheat and the sorghum fallow. Sediment concentration and yield for both fallows were numerically larger (>40%) with grazing. Sediment concentration from SM tillage increased significantly over NT for either fallow, but soil loss differed only for wheat fallow. Mean final infiltration rate (IRf) and amount (IA60) did not differ significantly with grazing during either fallow, but IA60 was usually 20% lower for grazed than for ungrazed paddocks. Because SM tillage after grazed wheat significantly (P < 0.01) increased IRf and IA60 over NT, occasional SM tillage to disrupt compaction from trampling may increase water conservation for dryland cropping systems combining grazing with NT residue management.

The reduction of partitioned wind and water erosion by conservation agriculture

Soil loss due to wind and water erosion degrades the soil on-site and results in environmental problems due to deposition in off-site areas downstream and downwind of the source field. Wind and water erosion may both occur to varying extents particularly in semi-arid environments. Soil conservation strategies require information about the processes of soil redistribution to mitigate its impact. However, very few studies have partitioned soil erosion between contributions of wind and water. We quantified wind and water erosion on six graded terraces under a uniform crop rotation since 1949 and two tillage management practices begun in 1981. Detailed runoff and sediment yield data have been recorded on all the terraces since 1984. We used a stratified random sampling design to collect soil which were then bulked to form six composites for each terrace. From an adjacent undisturbed native prairie, soil cores were collected and composited similarly to provide a reference. The cores were composited by 15cm layers in the terraces and, in the reference area, the upper 15cm layer was subdivided into 5cm layers and all were measured for 137Cs activity which was converted to 137Cs inventory. We then employed an established computer model that equates loss of 137Cs inventory with soil loss and direct measurement of water-borne sediment loss to estimate 30year mean wind erosion losses on the terraces by tillage type. We found that no-till management reduced total soil loss by one-third compared with stubble mulch tillage, reduced water-borne sediment loss by about the same amount, and that for both tillage systems, wind erosion was responsible for about 75% of the total soil loss.

Long-Term Changes in Soil Organic Carbon and Nitrogen under Semiarid Tillage and Cropping Practices

Understanding changes in soil organic C (SOC) and total soil N (TSN) is important for evaluating C fluxes and optimizing N management. We evaluated long-term SOC and TSN changes under dryland rotations for historical stubble-mulch (HSM) and graded terrace (GT) plots on a clay loam soil in Bushland, TX. Compared with adjacent grassland with no history of cultivation, stored SOC in the surface 0.30 m of HSM declined by 41% after 86 yr of cultivation, with half of the estimated changes occurring during the first 20 yr. In the HSM plots under a winter wheat (Triticum aestivum L.)–fallow rotation, SOC and TSN (0.0–0.152 m) were significantly greater with decreasing tillage intensity (P < 0.05) in 1977 for treatments imposed in 1941. On GT plots under a winter wheat–sorghum [Sorghum bicolor (L.) Moench]–fallow rotation, SOC and TSN storage under no-till were not significantly (P = 0.396 and P = 0.261, respectively) different from stubble-mulch tillage 30 yr after treatments were imposed in 1984. Calculated export of N in wheat and sorghum grain from 1927 to 2013 from GT (1.6 Mg ha−1) accounted for 80% of the difference between TSN in grassland and GT plots. From 1927 to 1960, TSN decline exceeded N in exported grain by 1.2 Mg ha−1 and may explain present-day accumulation of NO3–N at 1 to 6 m in the unsaturated zone. Since 1966, crops have probably been assimilating NO3–N located deeper in the soil profile to supplement N requirements.

Residue and Long-Term Tillage and Crop Rotation Effects on Simulated Rain Infiltration and Sediment Transport

Increased precipitation storage as soil water is crucial to dryland production of wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] on the semiarid southern Great Plains. At the USDA-ARS Conservation and Production Research Laboratory at Bushland, TX, surface runoff from a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll) is typically greater with no-till (NT) than stubble-mulch (SM) tillage under the 3-yr wheat–sorghum–fallow (WSF) dryland crop rotation. Our objective was to quantify the effects of NT or SM tillage with bare or retained residue on infiltration of simulated rain, sediment transport, and related aggregate stability for continuous wheat (CW) and WSF rotation plots established in 1983. Compared with bare soil, the retained wheat residue cover increased mean 60-min cumulative infiltration across all tillage and rotation combinations by >25 mm and decreased soil loss. Cumulative rain infiltration and total soil loss did not vary significantly (P < 0.05) with tillage, but the mean infiltration rate at 60 min was 15.0 mm h−1 less for NT than SM. The CW rotation typically increased infiltration regardless of residue cover or tillage compared with the WSF rotation, which we attributed to greater aggregate stability. The greater aggregate stability for CW may have decreased soil loss compared with WSF, which was greatest for bare SM tilled sites. We conclude that residue cover significantly increases rain infiltration over bare soil conditions independent of any tillage or rotation treatment effects. Nevertheless, increased rain infiltration due to residue cover was not sustained in the absence of soil disturbance for NT.

Tillage and Cattle Grazing Effects on Soil Properties and Grain Yields in a Dryland Wheat–Sorghum–Fallow Rotation

Cattle (Bos taurus) grazing intensifies production of the dryland wheat (Triticum aestivum L.)–sorghum [Sorghum bicolor (L.) Moench]–fallow (WSF) rotation in the U.S. Southern High Plains. Stubble‐mulch (SM) tillage controls weeds and counteracts soil compaction. No‐till (NT) increases soil water at planting and dryland crop yields, but added grazing effects are unknown. Our objectives were to quantify dryland winter wheat and sorghum yield responses to grazing and tillage practices. At the USDA‐ARS Conservation and Production Research Laboratory, Bushland, TX, we established all WSF rotation phases in triplicate ungrazed and grazed paddocks beginning 1999 on a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll) using SM tillage. During spring 2004, NT or SM tillage were superimposed within grazing main plots. Cattle gain, soil water after fallow, and crop yield were compared during 2005 to 2009 using a split‐plot randomized complete block design. Cattle, stocked at 1.8 Mg ha−1, grazed sorghum stover and growing wheat an average of 29 d for a mean gain of 147 kg ha−1 Soil water at planting was unaffected by grazing, but increased from 14 to 28 mm with NT. Although grazing seldom reduced yield of wheat or sorghum, NT in ungrazed plots increased crop yields sufficiently (0.96–2.6 Mg ha−1) in 2008 and 2009 to offset any value added by grazing. We conclude that cumulative grazing effects in NT plots reduced soil water storage and depressed yield. We recommend post‐wheat‐harvest SM tillage to disrupt soil compaction and restore grazed soil productivity.

Water use efficiency of dryland cowpea, sorghum and sunflower under reduced tillage

Drought-adapted, early maturing crops combined with reduced tillage systems have the potential to stabilize and increase dryland crop yields in semiarid regions of the world. The objectives of this research were to evaluate soil water use and dryland grain yield response of cowpea [ Vigna unguiculata (L.) Walp], sorghum [ Sorghum bicolor (L.) Moench], and sunflower [ Annus helianthus (L.)] under no tillage (NT) and stubble mulch tillage (SMT) systems. The study was carried out on a Torrertic Paleustoll in the high plains of Texas, USA from 2000 to 2001 when growing season precipitation totaled 47 and 62%, respectively, of the historical mean (317 mm). The experimental design was a split plot, with tillage as the main plot and crop type as the subplot. Soil water contents were measured weekly throughout two growing seasons, from 0.10 to 2.30 m depth at 0.20-m intervals using a neutron moisture meter. Crop water use was calculated as the change in stored soil water plus measured precipitation and assuming negligible runoff and drainage beyond 2.3 m. In 2000, after a 10-month fallow following winter wheat, soil water content at planting was 53 mm greater ( P = 0.012) under NT compared with SMT. At harvest, soil water content was greater under cowpea compared with sorghum and sunflower in both tillage systems ( P < 0.001). However, greater soil water content at harvest under cowpea did not always result in significantly greater plant available water content the following year compared with sorghum. Differences in water use were dominated by a crop effect ( P < 0.028) largely as a result of lower water use by cowpea compared with sorghum and sunflower. Water use of sorghum and sunflower averaged 97 and 29 mm greater than that of cowpea across tillage treatments, respectively. Mean grain water use efficiency (WUE) was greatest for sorghum (1.03 kg m −3), followed by cowpea (0.52 kg m −3) and sunflower (0.32 kg m −3). Sorghum under NT had similar or slightly greater water use, yet consistently greater grain yields compared with SMT. This suggests that a larger fraction of evapotranspiration was diverted to transpiration under NT compared with SMT. Greater residual soil water under cowpea at harvest may increase plant available water the following year provided that the soil has a high soil water storage capacity and slow drainage rates. Tillage effect on soil water use depended on the crop and year, however only sorghum exhibited a significant yield response to increased soil water storage afforded by NT.

Tillage effects on soil water redistribution and bare soil evaporation throughout a season

Abstract Tillage-induced changes in soil properties are difficult to predict, yet can influence evaporation, infiltration and how water is redistributed within the profile after precipitation. We evaluated the effects of sweep tillage (ST) on near surface soil water dynamics as compared with an untilled (UT) soil during a 7-month period. Plots were established in a fallow field devoid of residue under stubble–mulch tillage management on a clay loam soil. Soil water contents were monitored using time-domain reflectometry at 0.05–0.3 m and using a neutron moisture gage to a depth of 2.3 m. Soil temperature and net radiation was also monitored. During a 114-day period from April through July, tillage with a sweep (0.07–0.1 m) significantly decreased net water storage above 0.3 m soil depth by an average of 12 mm ( P = 0.002) as compared with UT plots. After tillage, soil water contents at 0.05 and 0.1 m were significantly ( P P −1 ) despite the greater near-surface water contents of UT plots. Although ST plots exhibited 19 mm greater cumulative evaporation from July through October, this was offset by 26 mm greater infiltration compared with UT. A more advanced surface crust development and greater initial water contents were likely responsible for lower cumulative infiltration of UT compared with ST plots. Immediately after tillage, cumulative daily net radiation averaged 22% greater for ST compared with UT surfaces and these differences diminished with time. Increased evaporation under tillage was likely a result of enhanced vapor flow near the surface and greater absorption of radiation by a tilled surface with reduced albedo.

Sustainable crop production on aeolian sandy semi-arid soils in South Africa

Large areas of the soils under rainfed crop production in the semi-arid climate regions Southern Africa are of Aeolian origin with a sandy texture. These soils are prone to wind erosion, soil compaction and drought, which hamper sustainable crop production. Field experiments were conducted over three years in which 3 tillage practices were combined with 3 cropping practices. The tillage practices were: i) conventional mouldboard ploughing, ii) stubble mulch tillage, both in combination with deep ripping and controlled traffic, and iii) no-tillage with chemical weed control. Every tillage practice was combined with three cropping practices viz. i) continuous maize, ii) wheat with a 5-month fallow, and iii) maize and wheat in rotation allowing a 10-month fallow. It was found that continuously grown maize and wheat with conventional tillage gave the highest rainfall use efficiency. Conventionally grown maize and wheat in rotation with a longer fallow gave the highest yields, whereas no-tillage with continuous maize and wheat gave the lowest yields. The yields on stubble mulching were lower than those on conventional tillage.

Economics of spring wheat production systems using conventional tillage management in the Brown soil zone – Revisited

Producers in the semiarid Brown soil zone of the Canadian Prairies have historically used fallow (F)-based cropping systems with mechanical tillage methods to produce spring wheat (Triticum aestivum L.) (W). However, in the past two decades government policies and programs have changed, as have cropping practices, market opportunities, and weather patterns. This study re-examines the economic merits of these conventional cropping systems under today’s conditions in regard to the optimal cropping frequency, value of applying N and P fertilizer at soil test rates, and the possible advantage of replacing monoculture wheat with lentil (Lens culinaris Medikus) (Lent) or flax (Linum usitatissimum L.) (Flx) grown in mixed rotations. The analysis draws on data from a long-term crop rotation experiment that was established in 1967 on an Orthic Brown Chernozem at the Semiarid Prairie Agricultural Research Centre at Swift Current, Saskatchewan. All cropping systems were managed using conventional tillage practices, which attempted to conserve as much surface crop residue as possible (i.e., stubble mulch tillage techniques were used). The findings for 1985–2002, a period characterized by above normal precipitation, were compared with those reported previously for the 1967–1984 period when growing conditions were less favorable but more typical for this area. Net returns during 1985–2002 were highest for W-Lent ($93 ha-1 yr-1) and lowest for F-Flx-W ($38 ha-1 yr-1). Net returns for well-fertilized F-W, F-W-W, F-W-W-W-W-W, and Cont W during this same period were similar, averaging about $52 ha-1 yr-1 or 44% less than for W-Lent. These results contrast with those reported for the previous 18-yr period when F-W and F- W-W generally produced higher net returns than Cont W. Within the F-W-W systems, the application of both N and P fertilizer increased the 18-yr (1985–2002) mean net returns by $18 ha-1 yr-1 compared with application of N only, and by $32 ha-1 yr-1 compared with application of P only. For Cont W the application of N and P fertilizer increased the mean net returns by $71 ha-1 yr-1 compared with application of P only. These economic benefits from N and P fertilization were much higher than those reported in 1967–1984 due to the more humid growing conditions and the increased rate of N fertilizer prescribed by the soil testing lab since 1991. Further, our findings showed that only if producers were highly risk averse, do not subscribe to all-risk crop insurance , or if the price for wheat was high or price for lentil low, would the monoculture wheat systems be preferred to W-Lent. However, producers who are highly risk averse would still opt for the cropping systems that included some summerfallow. Our findings support the recent trends in land use practices by area producers towards more diversified and intensive cropping systems which are less reliant on frequent fallowing. Key words: Crop rotations, wheat, lentil, flax, summerfallow, production costs, net returns, income variability

Wheel traffic and tillage effects on runoff and crop yield

Traffic and tillage effects on runoff, soil water and crop production under rainfall were investigated over a period of 6 years on a heavy clay vertosols (vertisols) in Queensland, Australia. A split plot design was used to isolate traffic effects, while the cropping program and treatments were broadly representative of extensive grain production practice in the northern grain region of Australia. Treatments subject to zero tillage and stubble mulch tillage each comprised pairs of 90 m 2 plots, from which runoff was recorded. A 3 m wide controlled traffic system allowed one of each pair to be maintained as a non-wheeled plot, while the complete surface area of the other received a single annual wheeling treatment from a working 100 kW tractor. Mean annual runoff from controlled traffic plots was 81 mm (36.3%) smaller than that from wheeled plots, while runoff from zero tillage was reduced by 31 mm (15.7%). Traffic and tillage effects appeared to be cumulative, so the mean annual runoff from controlled traffic and zero tillage plots, representing best practice, was 112 mm (47.2%) less than that from wheeled stubble mulch plots, representing conventional cropping practice. Rainfall infiltration into controlled traffic zero tillage soil was thus 12.0% greater than into wheeled stubble mulched soil. Rainfall/runoff hydrographs show that wheeling produced a large and consistent increase in runoff, whereas tillage produced a smaller increase. Treatment effects were greater on dry soil, but were still present in large and intense rainfall events on wet soil. Plant available water capacity (PAWC) in the 0–500 mm zone increased by 10 mm (11.5%) and mean grain yields increased by 337 kg/ha (9.4%) in controlled traffic plots, compared with wheeled plots. Mean grain yield of zero tillage was 2–8% greater than that of stubble mulch plots for all crops except for winter wheat in 1994 and 1998. Increased infiltration and plant available water were probably responsible for increased mean grain yields of 497 kg/ha (14.5%) in controlled traffic zero tillage, compared with wheeled stubble mulch treatments. Dissipation of tractive and tillage energy in the soil is the apparent mechanism of deleterious effects on the soils ability to support productive cropping in this environment. Controlled traffic and conservation tillage farming systems appear to be a practicable solution.

Soil Water Depletion and Root Distribution of Three Dryland Crops

Characterization of plant uptake of soil water at different points in time and space are important in evaluating seasonal water use as well as rotational dryland cropping strategies. The objective of this study was to characterize root length density (RLD) and soil water depletion patterns of cowpea [Vigna unguiculata (L.) Walp.], grain sorghum [Sorghum bicolor (L.) Moench], and sunflower (Halianthus annuus (L.)] under no tillage (NT) and stubble mulch tillage (SMT) systems in a Torrertic Paleustoll. Root length density of crops was measured from scanned images of washed root samples obtained from soil cores extracted several times during each of two growing seasons. Soil water contents were measured with a neutron moisture meter to a depth of 2.3 m at weekly intervals throughout each growing season. The RLDs of sorghum and sunflower near the soil surface increased rapidly after planting but thereafter declined whereas subsoil RLD increased throughout the growing season. Residual water contents at harvest were 28 to 93 mm greater (P < 0.05) under cowpea as compared to sorghum. As compared to the other crops, most of the additional residual water under cowpea was confined to soil depths between 0.5 and 1.7 m. Soil depths of 1.0 to 1.8 m were the most important source of stored water for sorghum and sunflower towards the end of the season. Deeper rooting and greater soil water extraction below 1.2 m depth were observed for NT as compared to SMT (P < 0.05). Results suggest that a rotation of cowpea with sorghum or sunflower would permit the stratified use of soil water and that the storage and crop use of water deep in the profile would be optimized under NT.

Factors affecting runoff and soil loss under simulated rainfall on a sandy Bainsvlei Amalia soil

This study was conducted on a long-term tillage experiment that was designed to evaluate appropriate tillage practices for sustainable dryland crop production. Measurements of runoff and soil loss were conducted on a sandy Bainsvlei Amalia soil (88.0% sand, 3.6% silt, and 8.4% clay) with a rainfall simulator on three tillage practices, namely no-tillage (NT), stubble mulch (ST) and conventional tillage (CT), each combined with four levels of wheat residue cover. The measurements were replicated twice for each of the three tillage practices on 1 m2 area plots. The simulator used for the study produced raindrops at a constant intensity of 60 mm h-1 with a veejet type nozzle, which had kinetic energy comparable to natural rainfall. A sharp decline in runoff and soil loss occurred with an increase in residue ground cover from bare to about 70%, above which the effect was less dramatic. Generally, runoff and soil loss was higher on NT plots compared with ST and CT plots. It is recommended that a crop residue covering at least 70% should be maintained on the soil surface when conservation tillage is practiced to ensure higher infiltration and lower runoff on this type of soil. Tilling the soil to a depth of at least 150 to 250 mm below the mulch gave the lowest runoff and soil loss.