Trade-offs and synergies of conservation agriculture practices in the maize–wheat system: Improving yield, profitability, and soil resilience in a changing climate

Soil organic carbon sequestration in relation to organic and inorganic fertilization in rice–wheat and maize–wheat systems

Advantages of an Orychophragmus violaceus-maize rotation in reducing greenhouse gas emissions and reactive nitrogen losses and increasing net ecosystem economic benefits on the North China Plain

The proven significance of conservation agriculture (CA) in enhancing agronomic productivity and resource use efficiency across diverse agro-ecologies is often challenged by weed interference and nitrogen (N) immobilization. The collective effect of real-time N and weed management has been scarcely studied. To evaluate the appropriateness of sensor-based N management in conjunction with a broad-spectrum weed control strategy for the maize–wheat system, an experiment was conducted at ICAR—Indian Agricultural Research Institute—in New Delhi, India, during 2015–2016 and 2016–2017. Weed management in maize through Sesbania brown manure followed by post-emergence application of 2,4-D (BM + 2,4-D) in maize and tank-mix clodinafop-propargyl (60 g ha−1) and carfentrazone (20 g ha−1) (Clodi+carfentra) in wheat resulted in minimum weed infestation in both crops. It also resulted in highest maize (5.92 and 6.08 t ha−1) and wheat grain yields (4.91 and 5.4 t ha−1) during 2015–2016 and 2016–2017, respectively. Half of the N requirement, when applied as basal and the rest as guided by Optical crop sensor, resulted in saving 56 and 59 kg N ha−1 in the maize–wheat system, respectively, over 100% N application as farmers’ fertilizer practice during the two consecutive years. Interactive effect of N and weed management on economic yield of maize and wheat was also significant and maximum yield was obtained with 50% N application as basal + rest as per Optical crop sensor and weed management through BM+2,4-D in maize and Clodi+carfentra in wheat crop. The study concludes that real-time N management, complemented with appropriate weed management, improved growth, enhanced agronomic productivity and endorsed N saving under a CA-based maize–wheat system in Trans Indo-Gangetic Plains.

Intensive tillage-based production systems coupled with inefficient fertilizer management practices have led to increased production costs, sub-optimal productivity, and significant environmental externalities. Conservation agriculture (CA) is being increasingly advocated as a management strategy to overcome these issues but precision nutrient management under the CA-based maize-wheat system is rarely studied. Two year’s (2014–2015 and 2015–2016) research was conducted at the research farm of BISA, Pusa, Bihar, India to develop precision nutrient management practices for CA-based management in the maize-wheat system. Seven treatment combinations involving (i) tillage (conventional tillage; CT & permanent beds; PB) and (ii) nutrient management rates, application methods (farmers’ fertilizer practices; FFP, state recommended dose of fertilizer; SR and precision nutrient management using Nutrient Expert tool; NE and GreenSeeker; (GS), applied using two methods; broadcasting (B) and drilling (D)) were investigated for multiple parameters. The results showed that NE, NE+GS, and SR-based nutrient management tactics with drilling improved crop yields, nutrient-use efficiency (NUE), and economic profitability relative to NE-broadcasting, SR broadcasting, and FFP broadcasting methods. Maize-wheat system productivity and net returns under NE+GS-drilling on PB were significantly higher by 31.2%, 49.7% compared to FFP-broadcasting method, respectively. Total global warming potential (GWP) was lower in the PB-based maize-wheat system coupled with precision nutrient management compared to CT-based maize-wheat system with FFP. Higher (15.2%) carbon sustainability index (CSI) was recorded with NE-drilling compared to FFP-broadcasting method. Results suggests that PB-based maize-wheat system together with precision nutrient management approaches (NE+GS+drilling) can significantly increase crop yields, NUE, and profitability while reducing the emission of greenhouse gases (GHGs) from maize-wheat systems in eastern Indo Gangetic Plains (IGP).

Quantifying changes to the global warming potential of rice wheat systems with the adoption of conservation agriculture in northwestern India

A 3-year field experiment was setup to address the threat of underground water depletion and sustainability of agrifood systems. Subsurface drip irrigation (SDI) system combined with nitrogen management under conservation agriculture-based (CA) maize-wheat system (MWS) effects on crop yields, irrigation water productivity (WPi), nitrogen use efficiency (NUE) and profitability. Grain yields of maize, wheat, and MWS in the SDI with 100% recommended N were significantly higher by 15.8%, 5.2% and 11.2%, respectively, than conventional furrow/flood irrigation (CT-FI) system. System irrigation water savings (~ 55%) and the mean WPi were higher in maize, wheat, and MWS under the SDI than CT-FI system. There was saving of 25% of fertilizer N in maize and MWS whereas no saving of N was observed in wheat. Net returns from MWS were significantly higher (USD 265) under SDI with 100% N (with no subsidy) than CT-FI system despite with higher cost of production. The net returns were increased by 47% when considering a subsidy of 80% on laying SDI system. Our results showed a great potential of complementing CA with SDI and N management to maximize productivity, NUE, and WPi, which may be economically beneficial and environmentally sound in MWS in Trans-IGP of South Asia.

The experimental field study was conducted at Borlaug Institute for South Asia (BISA) Research Farm, Lakhanwada, Jabalpur, Madhya Pradesh, India to evaluate the soil carbon fractions (very labile, labile, less labile and non-labile or recalcitrant carbon) in different land use practices with soil depths under cropping systems in Vertisols after harvest of Kharif and Rabi season crops of year 2015-16 and 2016-17. The experiment was conducted under Split plot design considering land use practices as main plot treatments [L1: Uncultivated, L2: rice-wheat system with conventional agriculture (CT), L3: rice-wheat system with conservation agriculture (CA), L4: soybean-wheat system with CT, L5: soybean-wheat system with CA, L6: maize-wheat system with CT and L7: maize-wheat system with CA] and depth (0-5 cm, 5-15 cm and 15-30 cm) as sub-plot treatments replicated thrice. Very labile carbon fraction was obtained highest in L3 (rice-wheat system with CA) and lowest under L6 (maize -wheat system with CT) treatment after harvest of Kharif and Rabi season crops during 2015-16 and 2016-17and it was significantly higher at 0-5 cm soil depth than those in 5-15 cm and 15-30 cm soil depths. Similar trends were also obtained in case of labile, less labile and non-labile fraction of carbon i.e. the applied land use practices had significant effect on all the carbon fractions under study and found to be maximum under L3 (R-W system with CA) and minimum in L6: (M-W system with CT) treatment after harvest of both the season crops during both years of experiment. Whereas, the interaction effect of land use practices and soil depths on the carbon fractions was found statistically non-significant during both the seasons and years.

Soil acts as the integrator of processes operating within the biological and hydrological landscapes and responds to external disturbances and processes on varying time scales. The impact of any change results in a corresponding response in the system; which is dependent on the resistance of the soil system to the disturbance. Irreversible permanent change results when the soil system shifts over a threshold tipping point; with the soil system experiencing a regime shift with associated structural and functional collapse. Climate change is the most important external disturbance or stressor on these systems due to changes in precipitation, temperature and moisture regimes. Our research at Mt Grand is focused on approaches to increasing land use resiliency in the face of environmental change. Our purpose is to select and apply soil quality indices which can be used to assess soil resilience to external disturbance events for Mt Grand Station in New Zealand. We will identify biophysical variations and landscape drivers in soil resilience; and use these results to match land management practices with variations in soil resilience. For example, soils with low resilience will only have land management practices that have a low impact on the soil resource. We selected soil attributes that represented indicators of resistance, used to quantify the capacity of a soil to recover its functionality. We mapped this soil resilience framework against a national database of soil and landscape attributes for Mt Grand Station. The output from this research is to posit a conceptual framework of soil quality indices which relates to soil resilience, and thus to create a spatial map of soil resilience for Mt Grand Station.

The food supply is being increasingly challenged by climate change and water scarcity. However, incremental changes in traditional cropping systems have achieved only limited success in meeting these multiple challenges. In this study, we applied a systematic approach, using model simulation and data from two groups of field studies conducted in the North China Plain, to develop a new cropping system that improves yield and uses water in a sustainable manner. Due to significant warming, we identified a double-maize (M-M; Zea mays L.) cropping system that replaced the traditional winter wheat (Triticum aestivum L.) –summer maize system. The M-M system improved yield by 14–31% compared with the conventionally managed wheat-maize system, and achieved similar yield compared with the incrementally adapted wheat-maize system with the optimized cultivars, planting dates, planting density and water management. More importantly, water usage was lower in the M-M system than in the wheat-maize system, and the rate of water usage was sustainable (net groundwater usage was ≤150 mm yr−1). Our study indicated that systematic assessment of adaptation and cropping system scale have great potential to address the multiple food supply challenges under changing climatic conditions.

Agriculture’s contribution to the Sustainable Development Goals requires climate-smart and profitable farm innovations. In the past decade, attention has been given to conservation agriculture as a ‘sustainable intensification’ strategy, although a lack of evidence-based consensus on the merits of conservation agriculture prevails in the context of intensive smallholder farming in South Asia. A meta-analysis using 9,686 paired site–year comparisons representing different indicators of cropping-system performance suggest significant (P < 0.05) benefits when conservation-agriculture component practices are implemented either separately or in tandem. For example, zero tillage with residue retention had a mean yield advantage of 5.8%, a water use efficiency increase of 12.6%, an increase in net economic return of 25.9% and a reduction of 12–33% in global warming potential, with more-favourable responses on loamy soils and in maize–wheat systems. Results suggest that there are opportunities to maximize expected benefits, and policymakers and development practitioners should continue to be appraised of the potential of CA for contributing to the Sustainable Development Goals in South Asia. Conservation agriculture prioritizes soil health and diverse cropping systems. This meta-analysis finds multiple benefits, including for water conservation and profitability, from conservation-agriculture practices in South Asia.

&amp;lt;p&amp;gt;How climate change will affect soil functioning is a major concern, especially in Mediterranean agrosystems, where, according to climate change projections, the occurrence of extreme temperatures and drought events will be increased. The main objective of our experiment was to evaluate the effect of land management (tillage system) on soil resilience against a simulated dry-rewetting cycle. Soil samples were collected from an in-situ field experiment established in 2008 in the Guadalquivir Valley, where conservation agriculture practices have been tested. Three different land management practices under a typical Mediterranean wheat-legume rotation system were compared: 1) traditional tillage (TT), 2) minimum tillage (MT) and 3) no-tillage (NT). Following our hypothesis, conservation agriculture practices (reduced tillage and no-tillage) may allow a more mature soil microbial community by reducing soil perturbation, and this would result in higher resistance of soil functioning against drought periods. Soil enzyme activities (&amp;amp;#946;-glucosidase, phosphatase, acetylglucosaminidase, aminopeptidase, and dehydrogenase activities), microbial functional diversity (Microresp method), and soil DNA concentration (as an index of microbial biomass) were analyzed in a base-line sampling. Afterwards, a dry-rewetting cycle was simulated under controlled conditions. 8 subsamples of 50g from each soil sample were hydrated to reach 70% of each soil water holding capacity (WHC) and kept in those conditions for a pre-incubation period of 15 days. After this period, half of the replicates were let dry for 12 days (drought), while the others were maintained at 70% WFC (controls). Finally, all replicates were rehydrated again to the initial water content during a 14 days rewetting period. During this cycle, soil respiration rates were periodically measured to study the evolution of soil microbial activity. Our results showed that initial respiration rates were slightly higher in MT compared to NT (p&amp;lt;0.1), likely due to higher organic C and N content in the MT soils. Drought extremely reduced respiration rates in the three treatments, but the results did not show a clear pattern among treatments. During the rewetting period, respiration rates were significantly higher in drought samples in comparison with the controls, while no significant differences were found for the land management treatments. Besides, land management practices did not have a significant effect on soil DNA concentration, functional diversity of the microbial community, or enzyme activities. To conclude, the absence of a clear effect of land management practices on soil resilience to drought may be due to the experimental conditions. An in-situ experiment will allow us to determine if tillage reduction enhances soil resilience to moisture stress.&amp;lt;/p&amp;gt;

Conservation agriculture practices impact on biological and microbial diversity in earthworm cast under maize-wheat system

A meta-analysis of economic and environmental benefits of conservation agriculture in South Asia

SUMMARYRice (Oryza sativaL.), wheat (Triticum aestivumL.) and maize (Zea maysL.) are the main crops grown in China. Applying organic manures is an important practice in sustaining soil fertility and agricultural productivity in these cropping systems. The current paper presents the effects of manure application on grain yields in nine long-term experiments that consist of one continuous maize, four wheat–maize and four rice-based cropping systems across a wide range of agro-ecological regions in China. The study shows that regular manure application can increase soil organic carbon (SOC) and grain yield across all the sites. Overall, regular use of manure results in larger increases in SOC in the maize and wheat–maize systems than in the rice-based systems. Application of manure tends to increase the grain yield in the maize and wheat–maize systems during the final years, but increases the grain yield in the rice-based systems during the initial years of the long-term experiments. There is only one site that shows significant improvement in the yield trend in association with the application of manure. The effects of manure on yield trends are probably determined by the initial yield and/or the ‘organic C effect’ that may cause gradual improvements in SOC and soil physical properties.

The growing popularity of nano-fertilization around the world for enhancing yield and nutrient use efficiency has been realized, however its influence on soil microbial structure is not fully understood. The purpose of carrying out this study was to assess the combined effect of nano and conventional fertilizers on the soil biological indicators and crop yield in a wheat–maize system. The results indicate that the at par grain yield of wheat and maize was obtained with application of 75% of recommended nitrogen (N) with full dose of phosphorus (P) and potassium (K) through conventional fertilizers along with nano-N (nano-urea) or nano-N plus nano-Zn sprays and N100PK i.e. business as usual (recommended dose of fertilizer). Important soil microbial property like microbial biomass carbon was found statistically similar with nano fertilizer-based management (N75PK + nano-N, and N75PK + nano-N + nano-Zn) and conventional management (N100PK), during both wheat and maize seasons. The experimental data indicated that the application of foliar spray of nano-fertilizers along with 75% N as basal is a sustainable nutrient management approach with respect to growth, yield and rhizosphere biological activity. Furthermore, two foliar sprays of nano-N or nano-N + nano-Zn curtailed N requirement by 25%, furthermore enhanced soil microbial diversity and the microbial community structure. The specific microbial groups, including Actinobacteria, Bacteroidia, and Proteobacteria, were present in abundance and were positively correlated with wheat and maize yield and soil microbial biomass carbon. Thus, one of the best nutrient management approaches for sustaining productivity and maintaining sound microbial diversity in wheat–maize rotation is the combined use of nano-fertilizers and conventional fertilizers.