Fallow Wheat Research Articles

Effects of fallow or planting wheat (Triticum aestivum L.) and fertilizing P or fertilizing P and N practices on soil carbon and nitrogen in a low-organic-matter soil

ABSTRACTSoil carbon (C) and nitrogen (N) are important for maintaining soil fertility, and they are considerably affected by soil use and management. In the present study, we conducted an 8-year field experiment on loessial dryland soil (Eum-Orthic Anthrosol, Food and Agriculture Organization of the United Nations (FAO)) in the southern Loess Plateau, China. We tested four soil management regimes—i.e., winter wheat (Triticum aestivum L.) cultivation with phosphorus (P) fertilization (WP), winter wheat cultivation with N and P fertilization (WNP), natural fallow (NF) and bare fallow (BF)—to evaluate their effects on soil C and N fractions. After 8 years, compared with the WNP treatment, the total soil organic nitrogen (SON) in the WP treatment decreased by 14.6% and 36.8%, and microbial biomass nitrogen (MBN) by 35.6% and 61.1%, at 0–20 and 20–40 cm soil depths, respectively. The soil heavy fraction nitrogen (HFN) and light fraction nitrogen (LFN) in the WP treatment also decreased by 36.6% and 39.4%, respectively. Furthermore, BF treatment decreased total soil organic carbon (SOC), heavy fraction carbon (HFC), LFN and MBN at both soil depths with average reductions of 43.4%. The NF treatment decreased light fraction carbon (LFC) by 17.0% at 0–20 cm soil depth, as well as MBN by 24.8% and 71.2%, and inorganic C by 29.1% and 23.8%, at 0–20 and 20–40 cm soil depths, respectively. There was no significant difference of microbial biomass C concentration among the WP, NF and BF treatments. These results confirmed that a lack of N fertilization decreased SON, BF reduced both SOC and SON, and NF decreased soil inorganic C. Therefore, the managements of a recommended rate of N fertilizer application and shortened time of bare fallow are critical for maintaining or increasing SON fraction sequestration, and natural fallow management is not a useful method for maintaining soil fertility in dryland in the Loess Plateau in China.Abbreviations: HFC: heavy fraction carbon; HFN: heavy fraction nitrogen; LFC: light fraction carbon; LFN: light fraction nitrogen; MBC: microbial biomass carbon; MBN: microbial biomass nitrogen; SOC: soil organic carbon; SON: soil organic nitrogen

Spring wheat response to nitrogen, tillage and cropping system under rainfed condition

AbstractThe objective of this research work was to assess the existing summer fallow elimination by growing short duration leguminous crop (mungbean) and reduction in number of plows could be a good substitute in recent shift of rainfall pattern. The traditional tillage frequencies (exceeding 4–5 plow + 2 harrows) of the summer fallow land without the addition of commercial fertilizers to wheat are the century-old practices in the project area. The rainfall efficiency is very low and is certainly related to the low and marginal fertility status. The existing wheat–fallow–wheat (W–F–W) where field remains without crop for five–six months in summer was compared with the proposed wheat–mungbean–wheat (W–Mb–W) cropping system by eliminating the summer fallow. Four tillage systems, i.e. no tillage (NT), conventional tillage (CT), reduced tillage (RT), and maximum tillage (MT), were employed before wheat sowing. Wheat (Triticum aestivum L., cv. Tatara) was sown at the residual moisture of the monsoon rainfall a...

Patterns of change in soil organic matter, physical properties and crop productivity under tillage practices and cropping systems in Bangladesh

SUMMARYConservation agriculture (CA) is inadequately developed for rice-based cropping systems widely practiced in Bangladesh. The current drawback is the implementation of CA for all crops including rice (Oryza sativaL., ecotype ‘transplanted aman’ [T. aman]) to increase rice–wheat (Triticum aestivumL.) rotation productivity. It is important to identify the best combination of tillage types and cropping systems to achieve a high yield of component crops and improve soil health. Three tillage practices, assigned to main experimental plots [namely, zero tillage (ZT), conventional tillage using a rotary tiller (CT) and deep tillage using a chisel plough (DT)] and three different cropping systems, assigned to sub-plots [namely, WFT: wheat–fallow–T. aman, WMT: wheat–mungbean (Vigna radiataL. Wilczek)–T. aman and WDT: wheat–dhaincha (Sesbania rostrata)–T. aman], were tested. After 4 years, ZT under WDT and WMT significantly increased soil organic matter (SOM) at 0–150 mm depth, and these replicates also held the highest levels of total organic carbon. Soil organic carbon (C) increased at a rate of 1.17 and 1.14 t/ha/y in ZT under WDT and WMT, respectively, while CT and DT under WFT were almost unchanged. After 4 years, SOM build-up by the three-crop system (WDT and WMT) under ZT helped conserve soil moisture and improve other soil properties, such as reduction in soil strength and bulk density and increase plant available water content, thus maintaining an optimum soil water infiltration rate. Zero tillage under WMT and WDT showed significant improvements in root mass density of rice and wheat at increased soil depth. The WDT and WMT plots under DT consistently gave the highest yield followed by WDT and WMT under CT, in contrast with ZT under WMT or WDT, which showed the highest improvement in crop yields over the years. In summary, minimum soil disturbance together with incorporation of a legume/green manure crop into the rice–wheat system as well as the retention of their residues increased soil C status, improved soil properties and maximized grain yields.

Least Shrews in North-Central Kansas: Habitat and Individual Characteristics

We captured least shrews (Cryptotis parva; n = 16) in native grassland, anthropogenic and woody habitats in north-central Kansas. Total effort was ca. 100,000 trap nights [TN] in >200 herbaceous sites and ca. 20,000 TN in >20 shrubby and woody sites. Least shrews were rare in both habitat types but slightly more abundant in herbaceous (ca. 0.15 individuals/1,000 TN) than woody sites (ca. 0.05 individuals/1,000 TN). We captured 15 least shrews in grazed native mixed grass prairie, post-harvest wheat fields and fallow wheat fields combined as well as one in a shelterbelt of deciduous trees. Body mass ranged from 2.6 g–6.0 g; body length explained ∼55% of the variation in body mass. Two pregnant females (4.9–5.0 g) were trapped; a litter size of five was observed for the one necropsied female. Finally, we document the first occurrence of the least shrew in Lincoln County, Kansas.

Dryland Soil Greenhouse Gases and Yield‐Scaled Emissions in No‐Till and Organic Winter Wheat–Fallow Systems

Core Ideas Dryland organic and no‐till wheat‐fallow systems impact GHG and wheat yields. The organic system produced more wheat grain yield than the no‐till system in a dry year. The organic system had greater GHG emissions during the fallow period. Concerted effort toward reducing tillage is needed to reduce overall GHG emission in dryland organic wheat–fallow systems. In the semiarid central Great Plains of the United States, cropping intensification beyond the traditional winter wheat (Triticum aestivum L.)–fallow rotation along with reduced tillage can lead to soil organic matter (SOM) conservation and offset greenhouse gas emission. Here, we quantified (i) soil greenhouse gas (GHG) carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes, and (ii) yield‐scaled GHG emissions from dryland no‐till (NT) and organic production systems in western Nebraska over a 2‐yr period. The systems evaluated were no‐till winter wheat–proso millet (Panicum miliaceum L.)–fallow (NT 3 yr), no‐till winter wheat–millet–fallow–winter wheat–sunflower (Helianthus annuus L.)–fallow (NT 6 yr), and organic winter wheat–millet or sunflower–fallow (Organic 3 yr). In 2012 and 2013, CO2 and N2O fluxes in the winter wheat phase were generally higher in the no‐till systems relative to the Organic 3‐yr system. In the fallow phase, however, these fluxes were higher in the Organic 3‐yr system than in the NT 6‐yr system, suggesting greater mineralization under the former. In 2013, fluxes of CH4 in the winter wheat phase tended to be higher in the Organic 3‐yr system than in the no‐till systems. Compared with the NT 6‐yr system, the Organic 3‐yr system had lower yield‐scaled emission in the winter wheat phase in 2012 (0.026 vs. 0.014 Mg [CH4 + N2O] in CO2 equivalent Mg−1 yield). More effort toward reducing tillage‐caused soil disturbance intensity is needed to further reduce CO2 and N2O emissions and SOM depletion in dryland organic winter wheat–fallow production systems.

Is Rainwater Harvesting an Option for Designing Sustainable Cropping Patterns for Rainfed Agriculture?

AbstractRainwater harvesting in small dams has good potential to provide supplementary agricultural irrigation during critical crop growth stages. Field experiments were conducted to evaluate cropping patterns: fallow–wheat (FW), mash–wheat (MaW), sorghum–wheat (SW), maize (grain)–wheat (MW), maize (grain)–gram (MG) and mung–canola (MuC); under two conditions: irrigated (Command area of Pira Fatehial small dam) and rainfed (Un‐command area) on sandy loam soil during three years (2009 to 2011). Treatments were arranged in a randomized complete block design, three factor factorial (cropping patterns, irrigated/non‐irrigated conditions and years) using four replications. The highest grain yield of wheat (5.6 Mg ha−1) was obtained from the MaW cropping pattern as compared to those from MW, FW and SW cropping patterns. Summer crops (sorghum fodder, maize grain and mash) performed excellent under irrigated conditions. Water use efficiency of wheat (14.3 kg ha−1mm−1) following mash under both the conditions exhibited higher values than when compared with those from SW, FW and MW cropping patterns. However, nutrient use efficiency in SW cropping pattern surpassed the others. Performance of all crops remained better under the irrigated condition during both all seasons and years, as rainfall deficiency was compensated by supplementary irrigations. Hence, this study concluded that farmers having water resources for supplemental irrigation should adopt the MW cropping pattern, based on grain yield, efficient utilization of available supplemental water and better utilization of nutrients. Similarly, based on improved nutrient utilization and monitory outputs, the MaW sequence should be followed in rain‐fed areas for better resource management. Copyright © 2015 John Wiley & Sons, Ltd.

Productivity and soil fertility of the rice–wheat system in the High Ganges River Floodplain of Bangladesh is influenced by the inclusion of legumes and manure

Productivity of the rice–wheat system is critical to the food security of Bangladesh. However, many concerns about the sustainability of this system exist because of low soil organic matter (SOM). In this context, an experiment was performed in the agro-ecological zone of the High Ganges River Floodplain (HGRF) at the Regional Wheat Research Centre (RWRC), Rajshahi of the Bangladesh Agricultural Research Institute (BARI) over two consecutive years, 2009–2010 and 2010–2011. The experiment evaluated the productivity and changes in soil fertility of the wheat–rice cropping sequence as influenced by an integrated plant nutrition system (IPNS) and through the inclusion of legume crops. Two factors were considered: cropping sequence and IPNS treatment. A legume crop was fitted to the existing wheat–rice sequence, resulting in four cropping sequences: wheat–mungbean–rice, wheat–blackgram–rice, wheat–dhaincha–rice and wheat–fallow–rice. There were six fertilizer/manure treatments: 100% recommended artificial fertilizer, farmers’ practice (FP) and four IPNS treatments. The IPNS treatments comprised two rates of poultry manure (PM; 3 and 6tha−1) and cowdung (CD; 5 and 10tha−1). For the IPNS treatments, 100% nutrient rates were adjusted with manure (PM and CD) and artificial fertilizers. The inclusion of legumes in the wheat–rice cropping sequence, particularly the use of mungbean, resulted in the highest productivity. This system rendered 57% higher wheat equivalent yield (WEY) than the wheat–fallow–rice cropping sequence. The incorporation of legume residues into the soil increased SOM, total N, available P and available Zn, but exchangeable K and available S were depleted under all crop rotations. The simultaneous use of chemical fertilizer and organic manure (OM; PM and CD) with the IPNS approach resulted in higher crop productivity and system WEY as well as higher rates of OM, especially IPNS with 6tha−1 PM. This indicates that chemical fertilizers alone could not provide adequate and balanced nutrition for potential yield of the tested crops. SOM, total N, available P and available Zn improved in treatments that included OM (both PM and CD) but the increment was greater in the combination of IPNS with higher rates of both OMs in the wheat–dhaincha–rice cropping sequence. K and S decreased in all nutrient treatments compared to initial soil. The wheat–mungbean–rice cropping sequence under IPNS with OM (especially 3–6tha−1 PM) resulted in best crop productivity (wheat, 4.55; rice, 5.48; WEY of mungbean, 4.54 and system WEY, 13.19tha−1) in both years.

Long‐Term Crop Residue and Nitrogen Management Effects on Soil Profile Carbon and Nitrogen in Wheat–Fallow Systems

Intensive cultivation of native grassland for dryland agriculture continuously depleted soil organic carbon (SOC) and nutrients. In 2010, we evaluated the influence of 80 yr of crop residue and nutrient management practices on SOC and N in 0‐ to 60‐cm soil depth profiles in conventionally tilled winter wheat (Triticum aestivum L.)–summer fallow (WW–SF) system. Residue and N treatments, no N addition with fall burning (FB0), spring burning (SB0), and no burning (NB0), 45 kg N ha−1 with SB (SB45) and NB (NB45), 90 kg N ha−1 with SB (SB90) and NB (NB90), manure (MN, 5.32 Mg dry mass ha−1 yr−1), and pea vines (PV, 0.99 Mg dry mass ha−1yr−1), were in ordered arrangement, and an undisturbed grassland (GP) was used as a reference. All WW–SF treatments had less SOC and N stocks than GP. The SOC stocks were lowest under FB0 with 50% less SOC than GP. The WW–SF treatments have depleted up to 63 and 26% of SOC and N from surface soil since 1931. Fall burning and MN treatments depleted SOC at rates of 0.64 and 0.17 Mg ha−1yr−1. Nitrogen stocks decreased at a rate of 0.02 Mg ha−1yr−1 in FB, SB, and NB treatments, and 0.01 Mg ha−1yr−1 in PV treatment. Reduction in tillage, application of low C/N ratio residues, and elimination of burning can improve sustainability of winter wheat production in the summer fallow region of the Pacific Northwest (PNW).

Dryland Soil Carbon and Nitrogen after Thirty Years of Tillage and Cropping Sequence Combination

Little is known about the long‐term management impact on soil C and N contents in the northern Great Plains. We evaluated the 30‐yr effect of tillage and cropping sequence combination on dryland crop biomass yield and soil bulk density, soil organic carbon (SOC), soil inorganic carbon (SIC), soil total nitrogen (STN), NH4–N, and NO3–N contents at the 0‐ to 120‐cm depth in a Dooley sandy loam (fine loamy, mixed, frigid Typic Argiboroll) in eastern Montana. Treatments were no‐till continuous spring wheat (Triticum aestivum L.) (NTCW), spring till continuous spring wheat (STCW), fall and spring till continuous spring wheat (FSTCW), fall and spring till spring wheat–barley (Hordeum vulgare L., 1984–1999) followed by spring wheat–pea (Pisum sativum L., 2000‐2013) (FSTW–B/P), and spring till spring wheat–fallow (STW–F, traditional system). Mean annualized crop biomass returned to the soil was 23 to 30 % greater in NTCW, STCW, FSTCW, and FSTW–B/P than STW–F. At 0 to 7.5 cm, bulk density was 13 to 21% greater in STW–F, but SOC, SIC, and STN were 12 to 98% greater in STCW than other treatments. Ammonium‐N and NO3–N contents were 25 to 74 % greater in FSTCW than other treatments. At other depths, SOC, SIC, STN, NH4–N and NO3–N contents varied among treatments. Reduced tillage with increased crop residue returned to the soil increased soil C and N storage in NTCW and STCW, but increased tillage intensity increased mineral N content in FSTCW compared with STW–F. Improved management practices, such as NTCW and STCW, may be adopted to improve dryland soil C and N stocks.

Intensification of dryland cropping systems for bio-feedstock production: Evaluation of agronomic and economic benefits of Camelina sativa

Camelina (Camelina sativa L. Crantz) is a promising bioenergy crop, but a sustainable production system for this crop has not yet been well developed. There is also concern about competing land use between crop productions for bioenergy or food use. One approach to overcoming this concern and developing sustainable production systems for bioenergy crops is potentially replacing the fallow period in wheat-based cropping systems with bioenergy crops. The agronomic and economic benefits of growing camelina in rotation with winter wheat were evaluated in a replicated rotation study from 2008 to 2011 in the Northern Great Plains (NGP), focusing on the effects on wheat yield and overall profitability of the cropping system. Average winter wheat yields were 2401 and 1858kgha−1 following camelina and barley, respectively, representing a 13.2 and 32.8% winter wheat yield reduction compared to the fallow–winter wheat rotation (2766kgha−1). Lower winter wheat yield in the alternative systems were offset by 907kgha−1 camelina and 1779kgha−1 barley yields. Economic analyses revealed that at existing market prices and production costs, the traditional fallow–winter wheat rotation provides greater net returns to growers due to substantially lower variable costs of the system. Scenario analyses that use more optimized, lower cost camelina production practices show that the net profits of camelina–wheat system could be closer to those in the fallow–wheat system. However, higher grain price and/or greater grain yield of camelina are essential to attract producers to include camelina in their cropping systems. Although the fallow–wheat system resulted in higher short-run net returns, the total biomass production and crop residue return to soil is much greater in camelina–wheat than fallow–wheat rotation, which is likely to improve soil quality and productivity in the long run.

Depth Distribution of Soil Organic Carbon Fractions in Relation to Tillage and Cropping Sequences in Some Dry Lands of Punjab, Pakistan

AbstractDepth distribution of soil organic carbon (SOC) fractions depends on the efficiency of agro‐technical managements. Information on depth distribution of SOC fractions mostly confined to the plow layer and scant in dry lands of Punjab, Pakistan. Therefore, a field experiment was laid out with moldboard plow (MP) (control), tine cultivator (TC), and minimum tillage (MT) as main plots, and cropping sequences fallow wheat (Triticum aestivum L.), (FW, control), mungbean (Vigna radiata L.) wheat (MW), sorghum (Sorghum bicolor L.) wheat (SW), green manure wheat (GW), and mungbean‐chickpea (MC) (Cicer arietinum L.) as sub‐plots. Treatment effects were assessed for microbial biomass carbon (MBC), potentially mineralizeable carbon (PMC), particulate organic carbon (POC), dissolved organic carbon (DOC), HCl insoluble carbon (HIC), and stratification ratio (SR) in Rawal series: Udic Haplustalf. Alfisols. The MBC concentration was the highest in MT system, at 15 to 30‐cm depth under MW and PMC concentration was highest under SW with MT at 45–60 cm. MP had higher POC in FW sequence. The highest DOC was at 0 to 15‐cm depth under MC with TC and stock of HIC was more under TC with FW sequence. The highest SR of PMC was under MT with FW at 0–15:15–30 and POC was under TC and MP with FW at depths of 0–15:45–60 cm. The highest SR for DOC was under MP with GW at 0–15:45–60 cm and HCl insoluble C was under MT with SW at 0–15:45–60. In broad‐spectrum, labile organic fractions revealed differential sensitivity, and POC stocks are also a sensitive indicator to detect the short‐management effects. Copyright © 2015 John Wiley & Sons, Ltd.

Legume, cropping intensity, and N-fertilization effects on soil attributes and processes from an eight-year-old semiarid wheat system

In the North American northern Great Plains (NGP), legumes are promising summer fallow replacement/cropping intensification options that may decrease dependence on nitrogen (N) fertilizer in small grain systems and mitigate effects of soil organic matter (SOM) losses from summer fallow. Benefits may not be realized immediately in semiarid conditions though, and longer-term effects of legumes and intensified cropping in this region are unclear, particularly in no-till systems. We compared effects of four no-till wheat (Triticum aestivum L.) cropping systems–summer fallow–wheat (F–W), continuous wheat (CW), legume green manure (pea, Pisum sativum L.)—wheat (LGM–W), and pea–wheat (P–W)—on select soil attributes in an 8-year-old rotation study, and N fertilizer effects on C and N mineralization on a duplicate soil set in a laboratory experiment. We analyzed potentially mineralizable carbon and nitrogen (PMC and PMN) and mineralization trends with a nonlinear model, microbial biomass carbon (MB-C), and wet aggregate stability (WAS). Legume-containing systems generally resulted in higher PMC, PMN, and MB-C, while intensified systems (CW and P–W) had higher WAS. Half-lives of PMC were shortest in intensified systems, and were longest in legume systems (LGM–W and P–W) for PMN. Nitrogen addition depressed C and N mineralization, particularly in CW, and generally shortened the half-life of mineralizable C. Legumes may increase long-term, no-till NGP agroecosystem resilience and sustainability by (1) increasing the available N-supply (~26–50 %) compared to wheat-only systems, thereby reducing the need for N fertilizer for subsequent crops, and (2) by potentially mitigating negative effects of SOM loss from summer fallow.

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

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

Pea in Rotation with Wheat Reduced Uncertainty of Economic Returns in Southwest Montana

Pea (Pisum sativum L.) is increasingly being rotated with wheat (Triticum aestivum L.) in Montana. Our objective was to compare economic net returns among wheat‐only and pea–wheat systems during an established 4‐yr crop rotation. The experimental design included three wheat‐only (tilled fallow–wheat, no‐till fallow–wheat, no‐till continuous wheat) and three no‐till pea–wheat (pea–wheat, pea brown manure–wheat, and pea forage–wheat) systems as main plots, and high and low available N rates as subplots. Net returns were calculated as the difference between market revenues and operation and input costs associated with machinery, seed and seed treatment, fertilizer, and pesticides. Gross returns for wheat were adjusted to reflect grain protein at “flat” and “sharp” discount/premium schedules based on historical Montana elevator schedules. Cumulative net returns were calculated for four scenarios including high and low available N rates and flat and sharp protein discount/premium schedules. Pea–wheat consistently had the greatest net returns among the six systems studied. Pea fallow–wheat systems exhibited greater economic stability across scenarios but had greater 4‐yr returns (US$287 ha−1) than fallow–wheat systems only under the low N rate and sharp protein discount schedule scenario. We concluded that pea–wheat systems can reduce net return uncertainties relative to wheat‐only systems under contrasting N fertility regimes, and variable wheat protein discount schedules in southwestern Montana. This implies that pea–wheat rotations, which protected wheat yield and/or protein levels under varying N fertility management, can reduce farmers’ exposure to annual economic variability.

Estimation of soil carbon change from rotation cropping of rapeseed with wheat in the hydrotreated renewable jet life cycle

Rapeseed is being considered as a potential feedstock for hydrotreated renewable jet (HRJ) fuel in the USA through its cultivation in rotation with wheat. The goal of this research was to determine the impact of soil C changes, induced through replacing the fallow period with rapeseed in rotation with wheat, and the effects it would have on emission of greenhouse gases (GHG) of rapeseed HRJ. The Intergovernmental Panel on Climate Change (IPCC) (Tier 1) method was used with modifications to determine the changes in soil C of wheat–wheat–rapeseed (WWR) relative to the reference wheat–wheat–fallow (WWF) rotation for 20 years of cultivation. The 27 case scenarios were conducted to study the impacts of changes in management practices (tillage practice and residue input) on changes in soil C for WWR rotation in multiple locations in 10 US states. The CO2 emissions resulting from soil C changes were incorporated into the rapeseed HRJ pathway in order to evaluate the GHG emissions. Introducing rapeseed to replace the fallow period with wheat could either increase or decrease changes in soil C, depending on management practices. Soil C is predicted to increase with increased residue input and reduced tillage. The greatest gain of soil C was found when using high residue input for wheat and rapeseed under no tillage, resulting in the best management practice. Conversely, adding low residue input to both crops with full tillage created the highest loss of soil C, referring to as the worst management practice. Soil C changes varied across locations from −0.22 to 0.32 Mg C ha−1 year−1. Consequently, the GHG emissions of rapeseed HRJ ranged from 4 to 70 g CO2 eq./MJ, comparing to 46 g CO2 eq./MJ for excluding soil C change. The rapeseed HRJ exhibited the GHG savings of 65–96 % for the best practice and 20–42 % for the worst practice when compared to petroleum jet fuel. Based on results using the modified IPCC method, adoption of high residue input with no tillage for the rotation cropping of rapeseed with wheat had the potential to increase soil C. However, the method has limitations for predicting soil C changes regarding crop management practices. Biogeochemical-based models that have a potential to capture processes of C and N dynamics in soil and yield may be better suited to quantify regional variations in soil C changes for the rotation cropping of rapeseed with wheat.

Yield and profitability of fallow and fertilizer inputs in long-term wheat rotation plots at Lethbridge, Alberta

Smith, E. G., Janzen, H. H. and Krobel, R. 2015. Yield and profitability of fallow and fertilizer inputs in long-term wheat rotation plots at Lethbridge, Alberta. Can. J. Plant Sci. 95: 579–587. A long-term, 42-yr study was used to determine the impacts of crop rotation and fertility management on wheat yield and profitability. Crop rotations included continuous wheat (W), fallow–wheat (FW), and fallow–wheat–wheat (FWW). Original plots were split for nitrogen (N) and phosphorus (P) fertility treatments, a two-factor factorial for N (0 and 45 kg ha−1) and P (0 and 20 kg ha−1). Phosphorus increased yield during the first half of the period, but had little impact during the last half. Nitrogen had no yield impact on fallow crops during the first half of the period, but had a positive impact during the last half, and throughout for wheat after wheat. The soil became incapable of releasing adequate N for wheat after fallow. Simulated distributions of net returns determined the W rotation with N and P fertilize...

Active Soil Organic Carbon Fractions and Aggregate Stability Effected by Minimum Tillage and Crop Rotations on a Marginal Dryland Soil in Punjab, Pakistan

Conservation Agriculture (CA) is an important technique for enhancing soil organic carbon (SOC) content in the surface layer and improving structural stability. CA is not widely practiced in dryland soils of developing countries where marginal farming practices are extensively used. Therefore, a field study was conducted in dryland region of Punjab, Pakistan to compare minimum tillage and intensified cropping systems effects on active SOC fractions and aggregate stability. The experiment was laid out in a split-plot design having moldboard plough (MP) and minimum tillage (MT) as main plots, and crop sequences as sub-plots. The latter comprised of fallow–wheat (Triticum aestivum L.), (FW, control), mungbean ( Vigna radiate L.) –wheat (MW), sorghum (Sorghum bicolor L.)–wheat (SW), green manure–wheat (GW) and mungbean-chickpea (MC) (Cicer arietinum L.). Tillage systems had more pronounced effects than cropping sequences on microbial biomass carbon (MBC), potentially minerlizeable carbon (PMC) and particulate organic carbon (POC). The PMC in second year was significantly more in the soil under MT than that under

Integrating Sheep Grazing into Cereal‐Based Crop Rotations: Spring Wheat Yields and Weed Communities

Crop diversification and integration of livestock into cropping systems may improve the economic and environmental sustainability of agricultural systems. However, few studies have examined the integration of these practices in the semiarid areas of the Northern Great Plains (NGP). A 3‐yr experiment was conducted near Bozeman, MT, to compare the effects of crop rotation diversity and weed management practices imposed during fallow periods [sheep (Ovis aries) grazing, reduced tillage, and conventional tillage] on spring wheat (Triticum aestivum L.) yields and weed pressure. Management treatments were applied to replicated whole plots, within which the split‐plots received crop rotation treatments [continuous spring wheat (CSW) and a 3‐yr rotation of annual forage, fallow, and spring wheat, where each phase was present in each year]. In the initial 2 yr, the realized rotational treatments were wheat–fallow and CSW. In the final year, wheat was grown following all phases of the diversified rotation. Yields were similar among management treatments within the wheat–fallow and CSW rotations. Weed pressure was generally low but perennial weeds were more abundant in grazing‐managed, wheat–fallow systems. The integration of livestock into the annual hay crop–fallow–spring wheat rotation was associated with a nearly 30‐fold increase in weed pressure and a yield reduction of 51.2% compared to conventional management. The results suggest that although targeted sheep grazing is a viable alternative to conventional fallow management in CSW and wheat–fallow rotations, successful integration of livestock in diversified cropping systems requires more effective weed management practices.

Potential legume alternatives to fallow and wheat monoculture for Mediterranean environments

Growing populations and intensification of land-use in West Asia and North Africa (WANA) are prompting a need for viable alternatives to fallow and cereal mono-cropping systems common in dry areas of this region. The sustainability and economic viability of such rotations can only be assessed accurately by using long-term trials. A two-course rotation experiment was established in 1986 in north-eastern Syria, comparing yields and profitability of wheat (Triticum aestivum L.) when grown after wheat, fallow, a grazed mixture of medic species (Medicago spp.) and common vetch (Vicia sativa L.) cut for hay, over 10 growing seasons. Lentils (Lens culinaris Medik.) were introduced into the experiment in 1990. On average over the course of the experiment, the highest wheat grain yields were obtained following fallow (2.57 t ha–1), the lowest in continuous wheat (1.14 t ha–1), and intermediate following medic and vetch (1.90–2.01 t ha–1). Compared with wheat grown after fallow, wheat grain yields declined following vetch, medic and lentils in only three of the 10 seasons, which were drier than average. Yields of wheat after lentils were generally lower (2.22 t ha–1) than after vetch (mean 2.56 t ha–1) and after medic (2.40 t ha–1). Inclusion of grain legumes in the rotations boosted profits considerably because of their high grain prices and valuable straw. Replacing fallow with vetch for hay production increased the average gross margin by US$126 ha–1 year–1, and growing vetch for hay in rotation with wheat produced greater profit than continuous wheat, by $254 ha–1 year–1. The wheat–vetch-for-grain and wheat–lentil rotations were especially profitable, at least twice as profitable as wheat–fallow and three times continuous wheat. This experiment adds to the growing body of field data in Syria and in Australia showing that forage and grain legumes are excellent alternatives to wheat–fallow rotation and continuous wheat production in areas that experience a Mediterranean-type climate, and help support more efficient and sustainable cropping systems.

Diffuse-reflectance mid-infrared spectroscopy reveals chemical differences in soil organic matter carried in different size wind eroded sediments

Abstract Soil organic matter (SOM) is essential for soil water holding capacity, aggregation, and biodiversity. Little information is available regarding the carbon (C) functional groups carried away in wind eroded sediments away from the source soil. Mid-infrared (MidIR) spectroscopy was used on wind tunnel-blown sediments eroded from a loam soil during the fallow period of different cropping systems and tillage managements in Akron, Colorado. The soil was managed as fallow-winter wheat ( Triticum aestivum L.) under conventional tillage (F–Wct) or no tillage (F–Wnt) and fallow–wheat–corn under no tillage (F–W–Cnt). Two wind eroded sediments were evaluated: fine dust ( −1 ), and clays (3690–3620 cm −1 ). The saltation-sized material showed higher absorbance for quartz from 2000–1800 cm −1 and reduced absorbance from 1250–1050 cm −1 . Both wind eroded sediments showed higher absorbance for –OH/NH groups and aliphatic CH from no-till soil. Finer dust sediments, which travel greater distances from the source soil than saltation size material, can carry away higher levels of aliphatic-carbon compounds and clays with potential negative impacts on SOM quantity and quality, and consequently the sustainability of these agroecosystems.