Wheat-maize System Research Articles

Conservation agriculture and precision nutrient management practices in maize-wheat system: Effects on crop and water productivity and economic profitability

Excessive pumping of groundwater over the years to meet the high irrigation water requirement of rice-wheat system has resulted in over exploitation of groundwater in the Indo-Gangetic plains (IGP) of India. Replacement of traditional rice with less water crops such as maize under conservation agriculture (CA) based management (tillage, crop establishment and residue management) practices are required to promote sustainable intensification. Furthermore, inefficient nutrient management practices are responsible for low crop yields and nutrient use efficiencies in MW system. A 3-year field experiment was conducted in farmer’s participatory strategic research mode at Taraori, Karnal, India to evaluate the effects of tillage and crop establishment (TCE) methods, residue management, mungbean integration, and nutrient management practices on crop yields, water productivity and profitability of MW system. The main plot treatments included four combinations of TCE, residue and mungbean integration [conventional tillage (CT), conventional tillage with mungbean (CT + MB), permanent bed (PB) and permanent bed with MB (PB + MB] with three nutrient management practices [farmer’s fertilizer practice (FFP), recommended dose of fertilize (RDF) and site specific nutrient management (SSNM)] using Nutrient Expert® as sub plot treatments. System productivity, water use efficiency (WUE) and net returns under PB + MB were significantly increased by 28.2–30.7%, 27.8–31.0% and 36.8–40.5% compared to CT respectively, during three years of experimentation. Integration of MB in MW system contributed 24.9 and 27.6% increases in system productivity and net returns compared with no MB, respectively. SSNM based nutrient management increased the mean (averaged across 3 yrs) system productivity, WUE and net returns of MW system by 13.4%, 13.3% and 15.3% compared with FFP, respectively. Study showed that conservation agriculture based sustainable intensification (PB + MB) and SSNM approach provided opportunities for enhancing crop and water use efficiency, and profitability of MW system in North-West IGP of India.

Improving soil organic carbon pools through inclusion of summer mungbean in cereal-cereal cropping systems in Indo-Gangetic plain

ABSTRACTLong-term effect of mungbean inclusion in lowland rice-wheat and upland maize-wheat systems on soil carbon (C) pools, particulate organic C (POC), and C-stabilization was envisaged in organic, inorganic and without nutrient management practices. In both lowland and upland systems, mungbean inclusion increased very-labile C (Cfrac1) and labile C (Cfrac2) in surface soil (0–0.2 m). Mungbean inclusion in cereal-cereal cropping systems improved POC, being higher in lowland (107.4%). Lowland rice-based system had higher passive C-pool (11.1 Mg C ha−1) over upland maize-based system (6.6 Mg C ha−1) indicating that rice ecology facilitates the stabilization of passive C-pool, which has longer persistence in soil. Organic nutrient management (farmyard manure + full crop residue + biofertilizers) increased Cfrac1 and carbon management index (CMI) over inorganic treatment. In surface soil, higher CMI values were evident in mungbean included cropping systems in both lowland and upland conditions. Mungbean inclusion increased grain yield of cereal crops, and yield improvement followed the order of maize (23.7–31.3%) > rice (16.9–27.0%) > wheat (lowland 7.0–10.7%; upland 5.4–16.6%). Thus, the inclusion of summer mungbean in cereal-cereal cropping systems could be a long-term strategy to enrich soil organic C and to ensure sustainability of cereal-cereal cropping systems.

Agronomic productivity, nitrogen fertilizer savings and soil organic carbon in conservation agriculture: efficient nitrogen and weed management in maize-wheat system

ABSTRACTConservation agriculture (CA) practice increases agronomic productivity and soil fertility, yet CA stimulate nitrogen (N) immobilization and weed interference during the early periods of implementation. This study focuses on efficient N management by soil testing and optical sensor (GreenSeekerTM) information; and weed management using brown manuring (Sesbania aculeata co-culture) and herbicide mixtures under CA-based maize (Zea mays L.) – wheat (Triticum aestivum L. emend Fiori & Paol) system in the Indo-Gangetic Plains. Fertilizer N application guided by the optical sensor increased grain yields of maize and wheat up to 20 and 14% (average of two years), respectively, compared to whole N application at sowing. Weed management using brown manuring in maize and herbicide mixtures in wheat increased the grain yields up to 10 and 21%, respectively, over the weedy check. The optical sensor-based N management saved up to 45 and 30 kg N ha–1 of the optimized N fertilizer rate in maize and wheat, respectively, over whole N application. Fertilizer N management coupled with brown manuring resulted in 5 and 4% higher soil organic carbon accumulation. Implementing efficient N fertilizer and weed management in the early years of CA can improve agronomic yield, fertilizer savings, and soil organic carbon content.

Sustainable intensification influences soil quality, biota, and productivity in cereal-based agroecosystems

Monotonous rice-wheat cropping system with conventional management practices have resulted in declining soil quality and biota in addition to low input factor productivity and farmer’s profitability in western Indo-Gangetic plains (IGP) of India. Conservation agriculture (CA) based sustainable intensification (SI) is required to improve the soil quality while improving the productivity and profitability. A field experiment was conducted to evaluate the effects of CA based management practices such as zero tillage (ZT), direct seeding of rice (DSR), crop diversification, residue recycling and legume integration for SI in comparison to conventional management on soil quality and biota in cereal (rice and maize) based cropping systems. Fourteen treatments were included in which four treatments (T1–T4) with rice–wheat and two treatments (T11–T12) with maize-wheat system were based on conventional management, while six treatments (T5–T10) with rice–wheat and two (T13–T14) with maize-wheat were based on CA management practices. Conservation agriculture based SI of maize-wheat-mungbean (T14) recorded lower soil bulk density (1.33 Mg m−3). Soil organic carbon (OC) was increased by 83% and 72% with CA based rice-wheat-mungbean (T10) and maize-wheat-mungbean (T14) system, respectively and it was at par with T9 and T12 compared to farmer’s practice (T1) (4.6 g kg−1). Mean microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) were 213% and 293% higher with T14 over T1 (646 and 201 µg g−1 dry soil), respectively. However, T10 recorded 117% and 171% higher MBC and MBN, respectively compared to T1. Dehydrogenase activity (DHA) and alkaline phosphatase activity (APA) were improved by 210% and 49% under T14; 140% and 42% under T10 compared to T1 (180 µg TPF g−1 soil 24 h−1 and 144 µg p-nitrophenol g−1h−1), respectively. Mean number of bacteria, fungi and actinomycetes were increased by 28%, 68%, 98% respectively, under T14 relative to T1, and at par with T12 and T10. Most abundant micro-arthropod group belonged to Collembola followed by Acari and Protura, irrespective of treatments. Higher soil quality index (SQI) was observed in T10 (0.82), followed by T14 and T6 treatment (0.76). Sustainable intensification of rice and maize based systems (T10 and T14) recorded 39% higher system yield compared to T1 (11.12 Mg ha−1). CA-based sustainable intensification of rice/maize systems improved soil quality and biota, hence resulted higher system yield in alluvial soils of IGP. Conservation agriculture based SI of maize-wheat-mungbean system was found to be the best alternative option than rice–wheat system to achieve sustainable productivity while improving the soil quality index (35%) and conservation of natural resources.

Effects of fertilization on soil aggregation, carbon distribution and carbon management index of maize-wheat rotation in the north-western Indian Himalayas

Abstract The impacts of the resource conservation practices can be evaluated in short-term through carbon management index (CMI) that conceptualizes the carbon lability and soil aggregation. To test this hypothesis, we investigated the labile organic carbon (LOC) pool and CMI in relation to runoff, soil loss and maize-wheat system productivity on 2% sloping crop lands of Indian Himalayan region in a study (2009–2014) where different nutrient management practices were adopted. Results showed that all integrated nutrient management (INM) practices (mineral fertilizers with different organic sources like farmyard manure (FYM), vermi-compost (VC), green manure (GM) and poultry manure (PM) enhanced soil aggregation compared with only mineral fertilization (NPK). Among all the treatments, the highest water-stable macroaggregates (+25%) in the 0–5 cm soil layer were recorded in 50% NPK + 50% FYM (7.5 t ha−1) treatment. Aggregate size of >2000, 250–2000, 53–250 and 2000 to

Impacts of tillage and herbicide mixture on weed interference, agronomic productivity and profitability of a maize – Wheat system in the North-western Indo-Gangetic Plains

Weeds comprising of annual monocotyledons, dicotyledons and perennial Cyperus rotundus L. (hereafter referred to as nutsedge) are important constraints in maize-wheat production system in India. They can cause yield losses of 25–30% in maize and 10–25% in wheat. Recently, continuous use of selective herbicides has led to an increase of nutsedge and other annual weeds in maize. There is need for a broad-spectrum weed control strategy that includes control of nutsedge in maize. Herbicide mixtures, containing a nutsedge killer partner herbicide may prove to be more effective for this. Imazethapyr among herbicides available in India possesses nutsedge-killing action, but the tolerance of maize to this herbicide, which is usually recommended for application as post-emergence in soybean and groundnut, is variable. We observed dose-dependent selectivity/tolerance of maize to imazethapyr when applied as post-emergence in a previous trial. Imazethapyr’s pre-emergence application may prove more useful in offering selectivity to maize, but is hardly studied. In addition, its residual/carry-over effect may lead to weed control in following wheat crops grown in sequence with maize, economizing production costs of the maize-wheat system. Therefore, this experiment was designed to evaluate the efficacy of imazethapyr against weeds including nutsedge, and its selectivity in maize crops when applied as pre-emergence in tank-mixture with pendimethalin; to compare these tank-mixtures effects with that of the sequential applications of pendimethalin (pre-emergence) and imazethapyr (post-emergence) in maize; and to evaluate their residual actions combined with tillage and crop residue in wheat under a maize- wheat system. The application of pre-emergence tank-mixture of pendimethalin 0.75 kg a.i. ha−1 + imazethapyr 0.050 kg a.i. ha−1 caused significant reductions in densities of broad-leaved (30%), nutsedge (45.2%), grassy (79.7%) and total weeds (49.1%) compared with un-weeded control (UWC) in maize. It reduced total weed dry weight by 58.3% and gave 56.1% higher maize yields than UWC. Among the tillage treatments adopted in the wheat crop, zero tillage (ZT) + residue (R) resulted in 14.0% greater reductions in weed dry weight and 6.9% higher wheat yields than conventional tillage (CT). It increased maize-wheat system productivity by 5.4% and 7%, respectively over CT and ZT without residue. The application of a tank-mixture of pendimethalin + imazethapyr gave 2.9% lower system productivity, but 8.2% higher net returns than the weed-free control, reducing the weed seed bank by 65% at 0–15 cm soil layer in two years. The application of this tank-mixture (in maize), followed by ZT + residue (in wheat) was more remunerative and could lead to better weed control with 25% and 50% lower doses of pendimethalin and imazethapyr, respectively, and 50% reduction in application cost. This practice can be adopted in maize-wheat system under irrigated conditions in the North-western Indo-Gangetic Plains of India, and in similar agro-ecologies of the tropics and sub-tropics. This result can also be applicable to cropping systems like maize – mustard, maize – barley/oat, subject to further evaluation and refinement under field conditions.

Evaluating alternatives to rice-wheat system in western Indo-Gangetic Plains: Crop yields, water productivity and economic profitability

Serious water deficits, diminishing profitability and deteriorating natural resources are threatening agricultural sustainability in many regions of South Asia. High water input and low water productivity of conventional irrigated rice–wheat (RW) systems has led to the depletion of surface water and ground waters in northwest India. Conservation agriculture (CA) practices with precision irrigation management and replacing rice with low water requiring maize crop may help to achieve sustainable crop production in the western Indo-Gangetic Plains (IGP) of India. A three-year field experiment was conducted to evaluate the effect of CA-based management (tillage, crop establishment, residue management mungbean integration), precision water management on crop and water productivity, and economic profitability in RW and maize-wheat (MW) systems. The treatments for RW systems included: i) conventional till rice-wheat with irrigation scheduling at critical growth stages (CTRW); ii) CTRW + mungbean (CTRW + MB); iii) Zero-till RW with residue retention (+R) scheduling precise irrigation (PI) based on soil matric potential approach (ZTRW + R + PI); and iv) ZTRW + MB + R + PI. A similar set of treatments was evaluated for MW systems, except the crops were established on raised fresh beds (FB) and permanent beds (PB). Treatment PBMW + MB + R + PI recorded 38% higher system productivity, saved 1660 mm of irrigation water, increased irrigation + rainfall water productivity (WPI+R,) by 270% and increased net returns by 84% compared to CTRW. ZTRW + MB + R + PI recorded 24, 41 and 37% (3 yrs’ mean) higher system productivity, WPI+R and net returns, respectively, compared to CTRW. System productivity was increased by 19 and 33%, WPI+R by 223 and 29% and net returns by 84 and 57% with ZTRW and PBMW compared to CTRW, respectively irrespective of MB integration and residue management. On average, inclusion of MB in cereal systems (RW/MW) contributed an 18% increase in system productivity and a 15% increase in net returns. CA based sustainable intensification of MW systems (PBMW + MB + R + PI) is a better alternative to RW system (ZTRW + MB + R + PI) as it provides opportunities for saving 79% of precious water, enhancing crop and water productivity by 12 and 145%, respectively along with high (34%) economic benefits thereby helping to arrest decline in ground water table in the North-West IGP of India.

Improving soil microbiological properties in typic ustochrepts through tree-based cropping system

Anthropogenic interference in natural ecosystem due to intensive agriculture has led to deterioration of soil fertility, productivity and quality. The soil microbiological properties are very important means of assessing soil health and productivity of agricultural ecosystems. The purpose of this study was to investigate the impact of tree-based cropping systems on soil microbiological activity in Shiwalik region of lower Himalayas. A study was conducted in a mixed watershed comprising of agroforestry, agrohorticulture and maize-wheat cropping systems. The soil samples were collected from three cropping systems and were analyzed for soil microbiological and basic physicochemical properties. The soil microbiological properties significantly improved in agroforestry and agrihorticultural systems compared to maize-wheat cropping systems. Soil respiration rate and polysaccharide carbon content were also higher in soils under tree-based cropping system (agroforestry and agrihorticulture) than in soils under maize-wheat system. The soil microbiological properties were positively correlated with soil organic carbon, available N and Olsen P. The higher soil microbiological activity under tree-based cropping system as compared with sole agriculture shows the propitious role of trees for the ecosystem functioning in north-west region of India.

Effect of farmyard manure and Jeevamrit in maize-wheat organic production system in Punjab

A field study on maize-wheat system was conducted at Punjab Agricultural University, Ludhiana for three years to evaluate different sources of nutrition under organic production. The experiment was laid out in split plot design with main plots consisting of recommended doses of chemical fertilizers (RDF), farmyard manure (FYM200) to supply 200 kg N ha−1, to supply 100 kg N ha−1 (FYM100) to each crop and one unfertilized control. The sub plots consisted of application of Jeevamrit (cow dung and urine culture) as soil application, soil & foliar application and a control without Jeevamrit. Maize grain yields with FYM200 and FYM100 were significantly lower than RDF by 53.5 and 59.6; 35.8 and 38.1; 12.7 and 18.7% during 1st, 2nd and 3rd year, respectively. FYM200 resulted in 15.1, 3.7 and 7.4% higher grain yield than FYM100 during 1st, 2nd and 3rd year, respectively. The wheat grain yield decrease with FYM200 and FYM100 from RDF was 40.7 and 44.2; 16.6 and 30.1; 11.0 and 21.5% during 1st, 2nd and 3rd year, respectively. Thus, maize and wheat grain yields under organic farming failed to compete with recommended fertilizers even with FYM200 to both the crops. Therefore, application of single source of manures should not be recommended under organic farming. Jeevamrit was not effective in influencing the grain yields of maize and wheat indicating its inability to contribute to the nutrition of these crops. Soil organic carbon improved with FYM at both the rates compared to RDF. The soil microbial population increased with application of Jeevamrit but it did not influence the productivity of crops.

Increasing Soil Organic Carbon Through Crop Diversification in Cereal–Cereal Rotations of Indo-Gangetic Plain

Continuous practices of cereal–cereal rotations in Indo-Gangetic plain (IGP) region have emerged with several soil related issues including depletion of soil organic carbon (SOC). Crop diversification remains a conceivable option to address this issue. Here, the authors envisaged the long-term alternate-year inclusion of chickpea in upland maize–wheat and lowland rice–wheat systems on SOC, C-dynamics and C management indices under organic, inorganic, and control nutrient management. Inclusion of chickpea in rice–wheat and maize–wheat systems increased total organic C (TOC) by 6.5 and 13.4%, and particulate organic C (POC) by 94.7 and 41.3% in the surface soil (0–0.2 m), respectively. In both the production systems, enrichment of very-labile C (Cfrac1) and labile C (Cfrac2) fractions were apparent with inclusion of chickpea. Very-labile (Cfrac1) (36.6–37.9%) in upland and less-labile (Cfrac3) (29.1–31.7%) in lowland were the dominant C-fractions. Subsequently, upland conditions had higher active C-pool; conversely, lowland ecosystem enriched passive C-pool, which is desirable for long-term persistence of soil C. The higher values of TOC, POC, and C-fractions were registered in organic nutrient treatment over inorganic and control treatment. In lowland, chickpea residue C had a low rate of stabilization as compared to cereal residue. In lowland, crop diversification with chickpea increased lability-index and C-management index; however, the effect was marginal in upland. Thus, inclusion of chickpea in the cereal–cereal rotations of IGP would be a potential long-term strategy to improve SOC and to ensure production sustainability.

Conservation agriculture effects on crop and water productivity, profitability and soil organic carbon accumulation under a maize-wheat cropping system in the North-western Indo-Gangetic Plains

The Indo-Gangetic Plains (IGP) of India is dominated with rice − wheat cropping system that occupies almost 10.5 million ha area. The sustainability of rice-wheat system is under threat due to numerous water-, nutrients-, weeds- and environment-related problems, mainly, due to the cultivation of rice. Suitable crop and soil management practices with a bias to conservation agriculture (CA) that can sustain soil and environmental health as well as improve crop and water productivity, are required for the Indian IGP. Maize can be a viable alternative to rice and a potential driver for diversification of rice-wheat system. The acreage of maize is on the increase in conventional and conservation agriculture-based cereal systems of India in recent years. Therefore, a field experiment, involving a maize (Zea mays L.)-wheat cropping system was undertaken on a sandy clay loam soil for three years (2010–11 to 2012-13) in New Delhi to evaluate the impacts of CA on crop and water productivity, profitability and soil organic carbon (SOC) accumulation. There were five CA-based treatments in first year, and two treatments were introduced in second year (2011-12) onwards. The experiment was laid out in a randomized complete block design with three replications. In all the residue retention plots, wheat residue was retained in maize crop and maize residue was retained in wheat crop under zero till conditions. Results showed that the plots under permanent broad bed with residue (PBB+R) and without residue (PBB) resulted in ∼29 and ∼26% higher maize grain yield, respectively than conventional tillage (CT) (2.6tha−1), but wheat grain yields were comparable in all the treatments in first year. Maize grain yield in second year under PBB+R and zero tillage with residue (ZT+R) were 55 and 43% higher than CT plots (2.8tha−1). Three-year mean maize yields due to PBB+R and permanent narrow bed with residue (PNB+R) were 28 and 15% higher than that in CT plots (3.3tha−1). The PBB+R resulted in 11% higher two-year mean water productivity in maize than PBB (∼without residue), but both these treatments were comparable in this regard in wheat. The ZT+R plots resulted in 14% and 22% higher two-year mean water productivity, respectively in maize and wheat than ZT plots. Overall, the plots under PBB+R had 57% and 19% higher mean water productivities in maize and wheat, respectively compared with CT plots. Again, the PBB+R plots gave 12% higher two-year mean net returns compared with CT plots. With regard to net returns, the plots under permanent narrow bed with and without residue (PNB+R; PNB) were inferior to PBB, PBB+R, ZT and ZT+R plots. Retention of both-season crop residues could significantly improve SOC concentration in surface (0–5cm) soil. The PBB+R resulted in highest SOC pool at 0–30cm soil layer, which was significantly higher than that in CT. This system showed maximum carbon sequestration potential. Thus, this CA practice, which involves PBB+R is superior to other practice. This would save water through higher water-use efficiency, and lead to accumulation of more carbon in soil with higher sequestration potential, besides giving sustainable production through maize-wheat system over the years. This can be adopted across the IGP regions of India, where irrigated rice-wheat system is in practice, and in similar agro-ecologies of the tropics and sub-tropics under irrigated conditions.

Long-Term Effect of Fertilizers and Amendments on Depth-Wise Distribution of Available NPK, Micronutrient Cations, Productivity, and NPK Uptake by Maize-Wheat System in an Acid Alfisol of NorthWestern Himalayas

ABSTRACTThe present study was undertaken in the ongoing long-term fertilizer experiment initiated during 1972 at experimental farm of Department of Soil Science, Himachal Pradesh Agricultural University, Palampur (India). Soil samples collected from three depths (0–0.15, 0.15–0.30, and 0.30–0.45 m) were analyzed for pH; organic carbon; CEC; available N, P, and K; and micronutrients cations. Continuous use of optimal dose of fertilizers and FYM-influenced pH, organic carbon, CEC, available NPK, and DTPA extractable micronutrient cations significantly. The contents of organic carbon, available N, P, K, Fe, Mn, Zn, and Cu were higher in top soil layer (0–0.15 m) compared to lower depths (0.15–0.30 and 0.30–0.45 m). Highest productivity of wheat (89.89 q ha−1) and maize (156.52 q ha−1) was recorded under 100% NPK + FYM, which was at par with 100% NPK + lime. Application of 100% NPK along with amendments (FYM/lime) recorded significantly higher NPK uptake over other treatments.

Effects of tillage, mulching and N management on yield, water productivity, N uptake and residual soil nitrate in a long-term wheat-summer maize cropping system

A thorough understanding of coupled effects of soil management (tillage), mulch and N rate on the wheat-maize system is crucial for achieving sustainable agriculture in the southern Loess Plateau of China. This study was based on a 12-year (2003–2015) field experiment and aimed to evaluate the impact of three wheat-maize systems (S) which varied in terms of tillage, mulch, wheat row spacing and irrigation management (CT, conventional tillage with no mulch; RFM, ridge-furrow with plastic film-mulched ridges and straw-mulched furrows; CTM, conventional tillage with straw mulch) combined with N fertilizer rates (0, 120 and 240kgNha−1) on crop yield, water productivity (WP, kg grain per kg of water input), N uptake, residual soil nitrate (RSN) and soil physicochemical properties. Results demonstrated that RFM significantly increased maize yield in comparison with CT in all 12 years, while CTM increased yield in comparison with CT from year 3 onwards. By contrast, wheat yield was not strongly influenced by RFM and CTM from 2004 to 2012 (except for 2008). Maize yields of RFM were significantly higher than those of CTM from the third year onwards. Compared with CT, the other two practices, and more so RFM, showed beneficial effects on crop yield, the amount of stored water, WP, N uptake and RSN. N fertilization significantly increased crop yield, WP and N uptake, while no significant difference was observed between the N120 and N240 treatments. Notably, considerable buildup of RSN to∼490kgNha−1 at maize harvest and ∼340kgNha−1 at wheat harvest were observed in 0–200cm soil depth when 240kgNha−1 was applied. These results suggest that the conventional N rate of 240kgNha−1 is excessive, and risks serious contamination of the groundwater as a result of NO3−-N leaching. The N120 treatment was characterized with considerably lower RSN accumulation after harvest, while maintaining crop yield. Thus, we concluded that the RFM practice with 120kgNha−1 application could reduce irrigation water and fertilizer inputs and increase crop land and water productivity, and is a promising strategy for developing sustainable agriculture in the southern Loess Plateau and other areas with similar climate and cropping systems.

Effect of Continuous Application of Fertilizers, Farmyard Manure and Lime on Soil Fertility and Productivity of the Maize-Wheat System in an Acid Alfisol

ABSTRACTA study on the long-term effect of fertilizers and amendments on crop productivity and changes in soil fertility in maize-wheat cropping system in an acid Alfisol was carried out in randomized block design (RBD) with 11 treatments. Continuous application of chemical fertilizers along with farmyard manure (FYM) or lime significantly influenced the grain and straw/stover yield and the uptake of nutrients by wheat and maize crops significantly. The organic carbon content increased from 7.9 to 12.1 g kg−1, cation exchange capacity (CEC) from 12.1 to 14.6 cmol (p+) kg−1 and available phosphorus from 21.9 to 75.2 kg ha−1 through the integrated use of organic and fertilizers for the last 42 years while the status of available nitrogen (N) and potassium (K) declined over the years in all the treatments. Continuous application of urea alone resulted in a drastic decline in soil pH at both depths. Imbalanced use of fertilizers led to a significant reduction in the productivity of both crops and depleted the soil fertility.

Nitrification inhibitor's effect on mitigating N2O emissions was weakened by urease inhibitor in calcareous soils

The application of nitrification or urease inhibitors together with nitrogen (N) fertilizer has been proposed to reduce N losses, including nitrous oxide (N2O) emissions, from agricultural soils. We measured N2O fluxes, crop yield and plant N content over 3 years (2012–2015) to evaluate the long-term effects of nitrification and/or urease inhibitors on N2O emissions, crop production and N use efficiency (NUE) in an intensively farmed wheat–maize system in northern China. The experiment consisted of the following five treatments: 1) CK, no N fertilizer; 2) U, urea; 3) NI, urea with 3,4-dimethylpyrazole phosphate (DMPP); 4) UI, urea with N-(n-butyl) thiophosphoric triamide (NBPT); and 5) NIUI, urea with combined DMPP and NBPT. Compared with the U treatment, the NI, NIUI and UI treatments mitigated cumulative N2O emissions by 55%, 40% and 21% in the maize season, respectively, and 47%, 40% and 33% in the wheat season, respectively. The annual direct emission factors of N2O for the U, NI, UI and NIUI treatments were 0.4%, 0.1%, 0.3% and 0.2%, respectively. The NIUI, NI and UI treatments increased the annual crop yield (7%, 6% and 4%) and the NUE (15%, 10% and 7%) relative to the U treatment. The NI treatment showed the best effect on mitigating N2O emissions, but its efficacy was reduced when applied together with UI. This indicates that more studies are required focusing on the performances and mechanisms of these two inhibitors in alkaline and low organic carbon soils.

Increasing farmer’s income and reducing soil erosion using intercropping in rainfed maize-wheat rotation of Himalaya, India

Humankind faces the need to achieve sustainable agriculture production, meanwhile increasing crop yields and reducing soil and water losses. Soil conservation through intercropping or crop canopy management is widely accepted as one of the ways of diversifying crop yields in rainfed agriculture in sloping landscapes. Field experiments were conducted between 2009 and 2014 to evaluate the effects of one or two rows of cowpea/okra intercropped with maize (planted either in 90 or 150 cm row spacing) on productivity, profitability, and resource conservation on 4% sloping crop land in the Himalayas. During five years of experimentation, a total of 110 runoff events were observed in the maize crop grown in rainy months of June to September. The results showed that by growing one row of cowpea in between two rows of maize (90 × 20 cm), no effect was observed on the productivity of rainfed maize. Productivity of the succeeding wheat crop was enhanced by 13% which resulted in a higher net return (117 US$ ha−1) than in a maize-wheat system. This system also reduced runoff and soil loss by 26% and 43%, respectively, compared to only a maize cropping system. Regression analysis revealed as runoff in maize crop increases, grain yield of succeeding rainfed wheat crop decreases due to the less availability of soil moisture.

Value of groundwater used for producing extra grain in North China Plain

Irrigation has led to increased crop productivity in the North China Plain (NCP) in the past three decades, but also caused quick depletion of groundwater resources with potentially severe hydrological consequences. Future policy development needs to balance crop production and groundwater use for increased sustainability. This requires an understanding of how crop production can be impacted by reduced irrigation and the value of the groundwater used for producing extra grains across NCP. We used cropping systems modelling to assess how the productivity of the wheat-maize system are influenced by spatial climate variability and changes in irrigation water supply across a north-south rainfall gradient in NCP. Our results show that irrigation has minimised the north-south difference in crop productivity, leading to a production gain as large as 9t/ha/year grain with a total value of up to 19,000 CNY/ha/year in the north. The high water use efficiency (WUE) of irrigation water in the north was similar to the WUE of natural rainfall in the south, allowing the farmers at dry sites to obtain very similar production value to those at the wet sites. The value of groundwater used for producing the extra grains was estimated to be 1.8–8.6 CNY m−3 water. The results provide the scientific basis for the design of future policies for water pricing and sustainable agricultural development in NCP.

Effect of tillage practices on least limiting water range in Northwest India

Abstract Tillage practices affect mechanical and hydrological characteristics of soil and subsequently the least limiting water range. This quality indicator under the wheat-maize system of northwest India has not been studied yet. The treatments included four tillage modes, namely conventional tillage, no-tillage without residue, no-tillage with residue, and deep tillage as well as three irrigation regimes based on the irrigation water and pan evaporation ratio i.e. 1.2, 0.9, and 0.6. The experiment was conducted in a split plot design with three replications. At the end of cropping system, the mean least limiting water range (m3 m-3) was found to be highest in deep tillage (0.26) and lowest in notillage without residue (0.15). The field capacity was a limiting factor for the upper range of the least limiting water range beyond soil bulk density 1.41 Mg m-3 and after that 10% air filled porosity played a major role. However, for the lower range, the permanent wilting point was a critical factor beyond soil bulk density 1.50 Mg m-3 and thereafter, the penetration resistance at 2 MPa becomes a limiting factor. Thus, deep tillage under compaction and no-tillage with residue under water stress is appropriate practice for achieving maximum crop and water productivity.

Yield, phosphorus use efficiency and balance response to substituting long-term chemical fertilizer use with organic manure in a wheat-maize system

The over-application of mineral phosphorus (P) fertilizer has become common in the North China Plain, meanwhile, most of organic manure cannot be recycled into the soil. To make full use of organic manure and decrease the applied rate of mineral P fertilizer, a 20-year fertilization experiment in a continuous wheat-maize rotation was carried out to assess the long-term effects of substituting mineral fertilizer with organic manure on the yield, P use efficiency, and P balance. Treatments included organic compost (OM), half compost in combination with half mineral fertilizer NPK (1/2 OM), mineral fertilizer NPK (NPK), mineral fertilizer NK (NK), and an unfertilized control (CK). The results showed that the grain yield in the NK plots was less than 1.0t ha-1 for both wheat and maize. The highest grain yield was obtained for the NPK treatment, which was slightly higher than the yields of the 1/2 OM treatment over all the years. The effects of the compost application were greater on the maize yield than on the wheat yield. Compost addition can significantly increase the P content and P uptake. The mean P fertilization use efficiencies were 53.7, 59.9 and 61.7% in the NPK, 1/2 OM and OM treatments for the wheat-maize system, respectively. In considering the P from the fertilizer, seed and irrigation as inputs and P uptake from crops and P storage in the 0–20cm soil layer as outputs, no significant P loss was observed in all the treatments. The results indicated that an application of mineral fertilizer alone at a reasonable level could result in a high crop yield and a relatively high P use efficiency. Considering the improvements in the P use efficiency and the benefits of soil fertility, replacing less than half the chemical fertilizer with organic fertilizer might be a promising alternative in the North China Plain.

Straw return reduces yield-scaled N2O plus NO emissions from annual winter wheat-based cropping systems in the North China Plain

Straw return in combination with synthetic N fertilizer is considered to be beneficial to soil fertility and crop yield. Such practice, however, can considerably modify soil microbial activity and relative C and N availability, both of which are known to regulate soil nitrous oxide (N2O) and nitric oxide (NO) emissions. Minimizing these emissions per unit of crop yield is a prerequisite to minimize the environmental footprint of agricultural production and thus, a policy objective. In our study, we quantified N2O and NO emissions and determined fertilizer-N use efficiencies (NUE) and crop yields of two double-cropping (summer maize/Welsh onion-winter wheat) systems with and without straw incorporation in the North China Plain. Relative to the fertilized treatment without straw amendments, straw incorporation showed a significant inhibitory effect on annual N2O emissions from the maize-wheat system (−31%), but no significant effect was observed for the Welsh onion-wheat system. However, straw return significantly reduced annual NO emissions by >30% for both systems. Meanwhile, straw return in both systems significantly increased the NUE and crop yields by 34–47% and 7–16%, respectively, as compared to the treatment without straw additions. Across the double-cropping systems, annual direct emission factors of N2O, NO and N2O+NO were 0.37–0.57%, 0.08–0.78% and 0.57–1.36%, respectively. Furthermore, a negative relationship between direct emission factors of N2O+NO and crop NUE was observed, highlighting the importance of optimizing NUE for reducing environmental risks of a cropping system. When expressing emissions on a yield basis, straw return significantly reduced annual yield-scaled N2O+NO emissions by 15–42% for both systems. Overall, our results show that the combined application of crop straw and synthetic N fertilizer is a promising N management strategy for maximizing crop yields while mitigating N-trace gas emissions.