Retaining Crop Residues Research Articles

Optimizing yield and water productivity in summer mung bean (Vigna radiata L.) through crop residue management and irrigation strategies

A multi-season research trial entitled ‘crop residue management effects on yield and water productivity of summer mung bean (Vigna radiata L.) under different irrigation regimes in Indian Punjab’ was conducted at Punjab Agricultural University (PAU), Regional Research Station (RRS), Bathinda, during rabi 2020 and 2021. The field experiment was conducted in a split-plot layout with nine treatment combinations and replicated thrice. The treatments consisted of T1 (no wheat residue along with tillage), T2 (leftover wheat residue with zero tillage), and T3 (incorporated wheat residue along with tillage) in main plots and irrigation regimes viz., I1 (vegetative growth and flowering stage), I2 (vegetative growth, flowering, and pod filling stage) and I3 (vegetative growth, flowering, pod formation and pod filling stage) in sub-plots, respectively. The growth and yield attributing characters were significantly higher under T3 than T1 but statistically at par with T2 during both years. An increase of 24.1% and 19.0% in grain yield was found in residue incorporation (T3) and residue retention (T2) over residue removal (T1), respectively. Maximum crop and irrigation water productivity was observed under T3 due to reduced water use and increased yield. Among the irrigation regimes, the I3 recorded significantly higher grain yield (0.70 and 0.79 t ha− 1) than I1. It was at par with I2 during both years due to higher irrigation frequency at the pod formation and pod filling stage. Crop water productivity (CWP) was higher under I3, whereas irrigation water productivity (IWP) was higher under I1 during both years. Additional irrigation at the pod-filling stage increased the grain yield by 36.5%, and two additional irrigations at the pod-formation and pod-filling stage further increased yield by 46.2% compared to only two irrigations at the vegetative and flowering stages. The treatment combinations of T2I2 and T3I2 outperformed T1I3 in terms of growth and yield attributing characters viz. plant height, dry matter accumulation (DMA), leaf area index (LAI), pods plant− 1, seeds pod− 1, and 1000-seed weight, which resulted in higher grain yield in these treatment combinations over T1I3. Applying crop residue can help minimize water use and increase crop water productivity. So, retaining crop residue in summer mung bean resulted in saving irrigation water due to lesser evapotranspiration from the soil surface.

Effect of conservation agriculture on soil fungal diversity in rice-wheat-greengram cropping system in eastern Indo-Gangetic plains of South Asia.

Conservation agriculture (CA) is emerging as an eco-friendly and sustainable approach to food production in South Asia. CA, characterized by reduced tillage, soil surface cover through retaining crop residue or raising cover crops, and crop diversification, enhances crop production and soil fertility. Fungal communities in the soil play a crucial role in nutrient recycling, crop growth, and agro-ecosystem stability, particularly in agricultural crop fields. This study investigates the impact of seven combinations of tillage and crop residue management practices of agricultural production systems, including various tillage and crop residue management practices, on soil fungal diversity. Using the Illumina MiSeq platform, fungal diversity associated with soil was analysed. The results show that the partial CA-based (pCA) production systems had the highest number of unique operational taxonomic units (OTUs) (948 OTUs) while the conventional production system had the lowest number (665 OTUs). The major fungal phyla identified in the topsoil (0-15 cm) were Ascomycota, Basidiomycota, and Mortierellomycota, with their abundance varying across different tillage-cum-crop establishment (TCE) methods. Phylum Ascomycota was dominant in CA-based management treatments (94.9±0.62), followed by the partial CA (pCA)-based treatments (91.0 ± 0.37). Therefore, CA-based production systems play a crucial role in shaping soil fungal diversity, highlighting their significance for sustainable agricultural production.

Assessing the global warming potential impact of organic fertilizer strategies in rice cultivation in Sri Lanka.

Rice is the staple food in Sri Lanka, and over 15% of the national land is allocated for rice cultivation. Greenhouse gas (GHG) emissions from rice fields account for 10% of national GHG emissions. The country has committed to reducing its emissions by 14.5% between 2010 and 2030 and achieving net zero emissions by 2060. In 2021, the country banned agro-fertilizer imports and opted for organic fertilizers, leading to a notable decrease in production and posing challenges to food security. However, the impact of adopting compost fertilizers alone remains unexplored. This study evaluated the global warming impact of two organic fertilizer strategies: switching to compost fertilizer instead of urea and applying rice straw compost instead of retaining crop residue. We applied the Denitrification and Decomposition model (DNDC 95) to rice field management data from Sri Lanka's Mahaweli H agricultural region. Simulations suggest that both strategies would increase the global warming potential of rice fields, mainly owing to elevated N2O emissions. This outweighs the mitigation benefits of avoiding crop residue retention and adding organic carbon through compost. Overall, our results point to the potential risk of shifting exclusively to compost-based fertilizers.

A food-energy-water-carbon nexus framework informs region-specific optimal strategies for agricultural sustainability

Agricultural sustainability is threatened by pressures from water scarcity, energy crises, escalating greenhouse gas (GHG) emissions, and diminishing farm profitability. Practices that diversify crop rotations, retain crop residues, and incorporate cover crops have been widely studied for their impacts on soil organic carbon and crop production. However, their associated usage of natural resources and economic returns have been overlooked. Here, we employed a food-energy-water-carbon (FEWC) nexus framework to assess the sustainability of crop rotations plus various management strategies across three sub-regions of New South Wales (NSW) in Australia. We found that compared with residue burning and fallowing, residue retention and cover cropping contributed to GHG abatement, but the latter consumed more energy and water per hectare. The composite sustainability scores, calculated with the FEWC framework, suggested that legume-inclusive rotations were generally more sustainable. Furthermore, in northern NSW (with existing sorghum/wheat/chickpea/wheat rotation), residue retention with cover cropping was most suitable combination, while the use of residue retention with fallow yielded greater benefits in southern NSW (with existing wheat/field pea/wheat/canola rotation). Regional disparities in climate, soil, cropping systems, and on-farm costs prompted region-specific strategies to address the unbalanced distribution among FEWC domains. Our study provides assessments for identifying feasible management practices to advance agricultural sustainability.

Priorities for narrowing the yield gap and increasing farming systems resilience in the Fiji sugar industry

Sugarcane (Saccharum officinarum L.) is the single most important agricultural industry in Fiji and occupies half of the nation's cropped area while supporting 25% of the labour force. However, the industry is facing comprehensive challenges across the supply chain, underlain by declining productivity and changing climate. The purposes of this study were to: (1) use model simulation to determine the potential of conservation agriculture (CA) practices to narrow yield gaps in sugarcane production systems under historical and projected climates in a case study; (2) identify and rank candidate practices that would contribute to narrowing such yield gaps; and (3) identify the limitations of the modelling approach and make recommendations for improving it. We simulated nine scenarios of CA practices with potential to reduce the estimated yield gap (55 ​Mg ​ha-1) by increasing nitrogen (N) fertiliser rates (30 ​Mg ​ha−1), liming (25 ​Mg ​ha−1), improved weed control (5–9 ​Mg ​ha−1), replacing uncropped fallow with legume crops (2–3 ​Mg ​ha−1), crop cycle duration (0 ​Mg ​ha−1), and retaining crop residues (−2 ​Mg ​ha−1). The yield benefit of CA practices was similar under projected climates that were warmer and wetter or drier, or hotter and wetter. For a projected climate that was hotter and drier, the greatest yield benefit was obtained from liming, weed control, and retaining crop residues. The study was limited by the availability of daily weather data, and it would be complemented by additional studies incorporating more local crops, evaluation of barriers to mechanisation needed to implement new practices, and economic assessment of scenarios.

Crop residue retention increases greenhouse gas emissions but reduces chemical fertilizer requirement in a vegetable-rice rotation

Retaining crop residues on site after harvesting can maintain soil fertility, reduce fertilizer requirements and restore soil organic carbon on intensively cultivated land. However, how crop residue retention and reduced chemical fertilizer application affect greenhouse gas emissions and crop yield in vegetable-rice rotations is poorly understood. We studied the effect of chemical fertilizer application alone (control, without straw retention), straw retention with 100 % nitrogen fertilizer application (STF) or with three levels of reduced chemical fertilizer application (SFR1, SFR2 and SFR3) in a vegetable-rice rotation in a mesocosm system. In the vegetable season, crop yield was maintained but the agronomic efficiency (AE) was higher in SFR1, SFR2 and SFR3 as compared to STF and the control. In the rice season under flooded condition, the methanogens were higher in SFR1, SFR2 and SFR3 compared to the control, but not different between STF and SFR1. The STF showed higher methane and nitrous oxide emissions, but carbon dioxide emissions and AE remained unaffected compared to the control in the vegetable-rice rotation. The SFR2 and SFR3 treatments maintained crop yields, increased AE, and decreased N2O emissions as compared with STF, but the CH4 emissions were 29.8 % lower in SFR2 than SFR3 in the vegetable-rice rotation. We concluded that straw retention with reduced chemical fertilizer application can maintain crop yield in a vegetable-rice rotation but has the potential to increase CH4 emissions in the rice cultivation season.

Soil Autotrophic Bacterial Community Structure and Carbon Utilization Are Regulated by Soil Disturbance—The Case of a 19-Year Field Study

The roles of bacterial communities in the health of soil microenvironments can be more adequately defined through longer-term soil management options. Carbon dioxide (CO2) fixation by autotrophic bacteria is a principal factor in soil carbon cycles. However, the information is limited to how conservation tillage practices alter soil physiochemical properties, autotrophic bacterial communities, and microbial catabolic diversity. In this study, we determined the changes in autotrophic bacterial communities and carbon substrate utilization in response to different soil management practices. A replicated field study was established in 2001, with the following soil treatments arranged in a randomized complete block: conventional tillage with crop residue removed (T), conventional tillage with residue incorporated into the soil (TS), no tillage with crop residue removed (NT), and no tillage with residue remaining on the soil surface (NTS). Soils were sampled in 2019 and microbial DNA was analyzed using high-throughput sequencing. After the 19-year (2001–2019) treatments, the soils with conservation tillage (NTS and NT) increased the soil’s microbial biomass carbon by 13%, organic carbon by 5%, and total nitrogen by 16% compared to conventional tillage (T and TS). The NTS treatment increased the abundance of the cbbL gene by 53% in the soil compared with the other soil treatments. The cbbL-carrying bacterial community was mainly affiliated with the phylum Proteobacteria and Actinobacteria, accounting for 56–85% of the community. Retaining crop residue in the field (NTS and TS) enhanced community-level physiological profiles by 31% and carbon substrate utilization by 32% compared to those without residue retention (T and NT). The 19 years of soil management lead to the conclusion that minimal soil disturbance, coupled with crop residue retention, shaped autotrophic bacterial phylogenetics, modified soil physicochemical properties, and created a microenvironment that favored CO2-fixing activity and increased soil productivity.

Uneven crop residue distribution influences soil chemical composition and crop yield under long-term no-tillage

Conservation agriculture has three main components: crop residue retention; minimal soil disturbance; and diverse rotations. Whilst retaining crop residues on the soil surface is important to prevent erosion and conserve water, high residue amounts can also have negative effects. Residue spread behind harvesters is not always uniform, therefore, it is important to understand the impact of uneven residue spread on crop performance. These problems are likely to increase as more farmers windrow and burn residues for weed control, harvesters become larger and controlled traffic systems are implemented. The effect of residue distribution on soil properties and crop establishment and yield was studied under no-tillage and controlled traffic in cereal (wheat-wheat-barley) and diverse (wheat-legume-canola) rotations, over the final six years of a larger 12-year (2007–2018) rotation trial, in the Wheatbelt of Western Australia. Within each crop and rotation, residue management consisted of either spreading or windrow-burning and measurements were taken from three locations relative to the harvester wheel tracks: centre (between harvester wheel tracks), mid (2.25 m perpendicular) and outer (4.5 m perpendicular), representing the ~9 m working width of the machinery. In most years, the distribution of crop residue behind the harvester was uneven, with up to twice as much residue directly behind the harvester compared with mid and outer locations. Differences in residue amount had positive, negative or no effect on crop establishment and yield, depending on the crop and residue type and climatic conditions. Increasing residue amount had a positive effect on establishment and yield when conditions were dry around seeding and early crop growth stages, possibly associated with increased water availability with increased residue load. Conversely, there were negative effects when frost occurred at anthesis or under high rainfall conditions, the latter due to physical impairment, increased disease or lack of available nitrogen. Negative effects only occurred with cereal residue and could be minimised by growing more break crops, even under high residue loads. In the longer term, higher residue amounts resulted in increased soil nutrients behind the harvester, which increased yields in some years. Therefore, research to improve uniformity of residue spread behind harvesters is crucial. Otherwise, variation in crop performance will increase as harvesters get bigger and, in the long term, periodicities in soil chemistry under controlled traffic systems will occur.

Effects of conventional versus no-tillage systems on the population dynamics of elaterid pests and the associated damage at establishment of maize crops

No-till agriculture, combined with the practices of continuous soil cover by retaining crop residues and of crop rotation, including cover crops, represents a relatively widely adopted management system that aims to increase soil organic matter content as well as long-term sustainability. However, its impacts on wireworm populations in the soil and risk of damage to crops are uncertain, and current recommendations may unjustifiably limit grower options. Consequently, this study examined the effects of no-tillage soil management on the population dynamics of Agriotes wireworm pests (Coleoptera: Elateridae) by bait sampling, maize plant damage assessments, and pheromone trapping (adults) within three farms in northeastern Italy, from 2011 through 2016, as compared to conventional tillage. The four-year cropping rotation consisted of winter wheat (Triticum aestivum), oilseed rape (Brassica napus), maize (Zea mays), and soybean (Glycine max) under both tillage treatments. The nature and intensity of damage caused by wireworms to maize early stages was assessed each year. Wireworms and beetles comprised of four different species (A. brevis, A. sordidus, A. ustulatus, and A. litigiosus) were captured, with the numerically dominant species (A. sordidus) accounting for over 90% of all captures. All species responded similarly to tillage practices. No effects of tillage operations were associated with beetle captures (P > 0.28) and larval densities (P > 0.45). No differences were observed between tillage treatments in wireworm feeding maize damage scores (P > 0.17; means for no-till and conventional tillage maize were 3.82 and 4.14 percent damage, respectively). These results suggest that switching from a conventional tillage system to a no-till maize production may not cause an increase of wireworm damage to maize, even though no-till conditions have been historically associated with increased wireworm damage risk. Possible causes of these results are discussed.

Simulation of nitrogen dynamics in lowland polders using a new coupled modelling approach: Insights into management

A new modelling framework, the Polder Hydrology and Nitrogen modelling System (PHNS), was developed to simulate the nitrogen dynamics and processes in polder systems. PHNS is a mass-balance model that simulates water and nitrogen dynamics in soil and surface water systems through integrating the WALRUS-paddy, MUSLE, and INCA models. The model explicitly considers the interactions among surface water, groundwater, and vadose water, as well as irrigation, pumping, and fertilizer application, which are the key processes controlling the nitrogen cycle in polders. The sensitivity analysis, calibration, and validation of the developed model were conducted in a Chinese agricultural polder by using three years of measured hydro-meteorological data. The calibrated and validated results proved that the model has a good performance with an R2 of 0.748 and a Nash-Sutcliffe (NS) efficiency coefficient of 0.619 for total nitrogen (TN) concentration during the validation period. The nitrogen budget results (net export of 40.4 kg/ha/yr) revealed that the polder is a nitrogen source for downstream freshwater systems. Reducing the amount of fertilizers, retaining crop residues, and restoring aquatic plants in surface water are effective countermeasures for reducing nitrogen export from polders. This study provides an efficient modelling tool and useful insights into polder management.

Semi-Automated Roadside Image Data Collection for Characterization of Agricultural Land Management Practices

Land cover management practices, including the adoption of cover crops or retaining crop residue during the non-growing season, has important impacts on soil health. To broadly survey these practices, a number of remotely sensed products are available but issues with cloud cover and access to agriculture fields for validation purposes may limit the collection of data over large regions. In this study, we describe the development of a mobile roadside survey procedure for obtaining ground reference data for the remote sensing of agricultural land use practices. The key objective was to produce a dataset of geo-referenced roadside digital images that can be used in comparison to in-field photos to measure agricultural land use and land cover associated with crop residue and cover cropping in the non-growing season. We found a very high level of correspondence (>90% level of agreement) between the mobile roadside survey to in-field ground verification data. Classification correspondence was carried out with a portion of the county-level census image data against 114 in-field manually categorized sites with a level of agreement of 93%. The few discrepancies were in the differentiation of residue levels between 30–60% and >60%, both of which may be considered as achieving conservation practice standards. The described mobile roadside image capture system has advantages of relatively low cost and insensitivity to cloudy days, which often limits optical remote sensing acquisitions during the study period of interest. We anticipate that this approach can be used to reduce associated field costs for ground surveys while expanding coverage areas and that it may be of interest to industry, academic, and government organizations for more routine surveys of agricultural soil cover during periods of seasonal cloud cover.

Assessing Soil Cover Levels during the Non-Growing Season Using Multitemporal Satellite Imagery and Spectral Unmixing Techniques

Growing cover or winter crops and retaining crop residue on agricultural lands are considered beneficial management practices to address soil health and water quality. Remote sensing is a valuable tool to assess and map crop residue cover and cover crops. The objective of this study is to evaluate the performance of linear spectral unmixing for estimating soil cover in the non-growing season (November–May) over the Canadian Lake Erie Basin using seasonal multitemporal satellite imagery. Soil cover ground measurements and multispectral Landsat-8 imagery were acquired for two areas throughout the 2015–2016 non-growing season. Vertical soil cover photos were collected from up to 40 residue and 30 cover crop fields for each area (e.g., Elgin and Essex sites) when harvest, cloud, and snow conditions permitted. Images and data were reviewed and compiled to represent a complete coverage of the basin for three time periods (post-harvest, pre-planting, and post-planting). The correlations between field measured and satellite imagery estimated soil covers (e.g., residue and green) were evaluated by coefficient of determination (R2) and root mean square error (RMSE). Overall, spectral unmixing of satellite imagery is well suited for estimating soil cover in the non-growing season. Spectral unmixing using three-endmembers (i.e., corn residue-soil-green cover; soybean residue-soil-green cover) showed higher correlations with field measured soil cover than spectral unmixing using two- or four-endmembers. For the nine non-growing season images analyzed, the residue and green cover fractions derived from linear spectral unmixing using corn residue-soil-green cover endmembers were highly correlated with the field-measured data (mean R2 of 0.70 and 0.86, respectively). The results of this study support the use of remote sensing and spectral unmixing techniques for monitoring performance metrics for government initiatives, such as the Canada-Ontario Lake Erie Action Plan, and as input for sustainability indicators that both require knowledge about non-growing season land management over a large area.

Innovative Pro-Smallholder Farmers’ Permanent Mulch for Better Soil Quality and Food Security Under Conservation Agriculture

Soil degradation is the greatest threat to agricultural production globally. The practice of applying or retaining crop residues in the field as mulch is imperative to prevent soil erosion, maintain soil quality and improve crop productivity. However, smallholder farmers resort to maximizing profit by removing crop residues after harvest to sell or use them as feed for livestock. Agrimats are innovative pro-smallholder farming mulching materials that are manufactured using cheap or freely available organic waste materials. These materials include forestry waste, grasses, etc., therefore allowing smallholder farmers to make more profit through improved crop productivity for better food security. The most notable attributes of agrimats include their ability to prevent soil erosion, increase and sustain soil organic matter, suppress weeds, and conserve soil moisture. Food security challenge can be addressed by adopting agrimat technology as a sustainable permanent soil cover to improve soil quality and crop productivity. Agrimat incorporation in conservation agriculture practice could produce more food from less input resources (chemical fertilizers, water, etc.) with minimal or no adverse effect on the environment. This study aims to advocate permanent soil cover using agrimat as an innovative pro-smallholder farmer technology to improve soil quality for better food security.

Effects of sorghum residue in presence of pre-emergence herbicides on emergence and biomass of Echinochloa colonaand Chloris virgata.

In conservation agriculture systems, farmers gain many advantages from retaining crop residue on the soil surface, but crop residue retention in these systems may intervene with the activity of pre-emergence herbicides. A pot study was conducted to evaluate the effect of different rates of pre-emergence herbicides [imazethapyr (100 and 150 g a. i. ha-1), isoxaflutole (100 and 200 g a. i. ha-1), metolachlor (1.5 and 2.25 kg a. i. ha-1), pendimethalin (2.25 and 3.38 kg a. i. ha-1) and prosulfocarb + metolachlor (2.5 and 3.75 kg a. i. ha-1)] on seedling emergence and biomass of Echinochloa colona and Chloris virgata when applied in the presence of sorghum residue at rates equivalent to (0, 3 and 6 t ha-1). When seeds of E. colona and C. virgata were not covered with sorghum residue, the seedling emergence and biomass of both weeds was inhibited by 93–100% and 56–100%, respectively, with the application (both rates) of isoxaflutole, metolachlor, pendimethalin and prosulfocarb + metolachlor. Using sorghum residue resulted in lower herbicide efficacy on both weeds. At 3 t ha-1 sorghum residue, E. colona emergence and biomass reduced by 38–100% and 30–100%, respectively, with application of isoxaflutole, metolachlor and pendimethalin (both rates) in comparison with the no-herbicide treatment. Similarly, the emergence and biomass of C. virgata was also reduced by 92–100% and 25–100%, respectively. The results of this study suggest that crop residue may influence efficacy of commonly used pre-emergence herbicides and that the amount of crop residue on the soil surface should be adjusted according to the nature of the pre-emergence herbicides to achieve adequate weed control.

Effects of crop residue retention on soil carbon pools after 6 years of rice–wheat cropping system

Enhancing soil organic carbon (SOC) is an important strategy to sustain and improve the soil quality, mitigate climate change and increase crop productivity under intensive tillage-based rice–wheat (RW) system in the Indo-Gangetic Plains (IGP) of South Asia. Therefore, the effects of tillage, crop establishment, and residue management practices on total as well as different pools of SOC in a sandy loam after 6 years of RW system were studied. The imposed three main plot treatments to the rice plots were: (1) ZTDSR, zero till dry seeded rice; (2) CTDSR, conventional till dry seeded rice; and (3) PTR, conventional puddled transplanted rice, and the three sub-plot treatments in succeeding wheat were (i) CTW − R, conventional tillage (CT) wheat with both rice and wheat residues removed; (ii) ZTW − R, zero tillage (ZT) wheat with both the residues removed and (iii) ZTW + R, ZT wheat with rice residue. Total soil organic content increased by 6.5–12.5% and 3.1–12.9% in different soil layers up to 0–60 cm depth in ZTDSR followed by ZTW + R over PTR followed by CTW − R practices, respectively. The corresponding increase of the oxidizable C was 4.2–28.2% and 8.2–8.5%, respectively. Significant enhancement in all the carbon pools (non-labile, less labile, labile, very labile pools, water soluble and microbial biomass carbon) and glomalin content were also recorded in ZTW + R treatment. The carbon management index was significantly higher in ZTW + R than ZTW − R and CTW − R treatments. In conservation-based agriculture systems, the principal component analysis revealed that passive pools of SOC and microbial biomass carbon were the most promising and reliable indicators for assessing soil quality. This study showed that adoption of ZTDSR followed by ZTW + R was the better crop production strategy for increasing C-sequestration, improving and sustaining the soil quality and crop productivity in the RW system. This practice also provides an opportunity to retain crop residues as an alternative to burning, which causes severe air pollution in the RW system in the IGP of South Asia.

To burn or retain crop residues on croplands? An integrated analysis of crop residue management in China

Crop residue burning influences human health and global climate change. In China—the world's largest crop residue producer—farmers burn almost one quarter of their crop residues in the field after harvest, despite the government providing financial incentives such as subsidies to retain crop residues. This study combined economic analyses with simulations of soil carbon accumulation and carbon emission reduction associated with different residue management practices to determine the minimum level of incentives needed for Chinese farmers to shift from burning to retaining crop residues for generating carbon benefits. Simulation results showed that [1] the density of topsoil organic carbon in China's croplands would have increased from about 21.8 t ha−1 in 2000 to 23.9 t ha−1 in 2010, and soil organic carbon sequestration would have reached 24.4 Tg C yr−1 if farmers had shifted from burning to retaining crop residues on croplands during this period; and [2] retaining crop residues would have avoided about 149.9 Tg of CO2 emission per year. Economic analyses showed that [1] existing subsidies in all regions of China, except Northeast China, only accounted for 18–82% of the incentives required for farmers to shift from burning to crop residue retention; [2] Northeast China required the lowest incentive (287 CNY ha−1), while eastern China required the highest (837 CNY ha−1); and [3] the prevailing market prices (1.4–60.2 CNY tCO2e−1) in China's seven pilot carbon markets seem to be below the required incentives (39.6–189.1 CNY tCO2e−1). Our study suggests that the Chinese government should increase subsidies or seek innovative incentive schemes to encourage farmers to change their crop residue management practices for global climate change mitigation and health benefits.

Crop residue removal and nitrification inhibitor application as strategies to mitigate N2O emissions in sugarcane fields

Nitrous oxide (N2O) emission estimates are important to ascertain the greenhouse gas balance of ethanol produced from sugarcane. We quantified N2O emissions in the presence of sugarcane crop residues, N fertilizer (ammonium sulfate), and a nitrification inhibitor (NI, dicyandiamide). Two field experiments were conducted to evaluate the implications of N fertilizer application during dry and wet seasons at two locations in southeast Brazil. Treatments consisted of four levels of crop residue (0, 5, 10, and 15 Mg ha−1) and three of N fertilizer (0 and 120 kg ha−1 and 120 kg ha−1 plus NI). N2O emission was measured using the closed chamber method and sugarcane yield via mechanical harvest. N2O emissions were higher in wet than in dry seasons following N fertilizer application, albeit affected by crop residue and NI in both. Retaining crop residues on the soil increased N2O emission and sugarcane yield. The N2O emission factor from N fertilizer ranged from 0.12% to 1.44% of N applied. NI reduced N2O emissions (by 87% and 63% in dry and wet seasons, respectively). Sugarcane yield varied from 42 to 92 Mg ha−1 of fresh matter stalk and emission intensity from 3.7 to 22.9 kg of CO2eq. Mg of stalk−1. The lowest greenhouse gas intensity was recorded with 5 Mg ha−1 crop residue and 120 kg ha−1 N supplemented with NI. Therefore, partial crop residue removal and NI addition to N fertilizer may be effective strategies to improve the sustainability index of biofuel from sugarcane and reduce N2O emissions and intensity.

The Directional Components of Splash Erosion at Different Raindrop Kinetic Energy in the Chinese Mollisol Region

Core Ideas Directional components of splash erosion and effects of raindrop kinetic energy were investigated. Lateral splash erosion played a significant role in supplying detached particles to adjacent areas. We fit equations for total and net splash erosion to rainfall physical parameters. We used cross‐validation to test the equations. Splash erosion is an important process of hillslope erosion. However, there is little information available in the literature to show how rainfall physical parameters affect the directional components of splash erosion. Therefore, the objectives of this study were to investigate the effects of rainfall physical parameters (rainfall intensity [RI], raindrop kinetic energy [KE], and raindrop diameter) on the directional components (upslope, lateral, downslope) of splash erosion characteristics in the Chinese Mollisol region. A specially designed soil pan, which can measure the directional components of splash erosion, was subjected to designed rainfall intensities of 50 and 100 mm h−1 and varying raindrop KE. The results showed that the total splash erosion (downslope plus upslope plus lateral splash erosion), directional components of splash erosion, and net splash erosion (downslope minus upslope erosion) on hillslopes significantly increased as RI and raindrop KE increased (p < 0.05). Furthermore, splash erosion from downslope, lateral slope, and upslope contributed 32.2, 26.3, and 14.5%, respectively, of total splash erosion. Additionally, raindrop KE and raindrop median volume diameter (D50) were the key indicators affecting both total and net splash erosion. The equations between total and net splash erosion with both parameters of raindrop KE and raindrop D50 were fitted. The cross validation results showed that the two equations had acceptable accuracy. Therefore, preventing raindrop impact by using conservation tillage methods, such as retaining crop residue or mulch cover, can effectively reduce splash erosion in the Mollisol region of Northeast China.

Seven years resource-conserving agriculture effect on soil quality and crop productivity in the Ethiopian drylands

Resource-conserving agriculture (RCA) aims at improving soil quality and crop yield whilst maintaining or improving soil health by minimizing soil disturbance, retaining crop residue, using crop rotations and adding in situ soil and water conservation tillage practices (terwah and derdero) in crop fields. In Ethiopia, intensive mining of soil resources using repeated tillage, complete crop residue removal at harvesting, overgrazing and biomass burning in croplands have aggravated soil degradation. We studied the impact of two RCA (derdero+ (DER+) and terwah+ (TER+) on long-term soil quality and crop productivity in permanently kept plots in northern Ethiopia 7 years after its inception. The two RCA practices: (i) DER+ is a bed and furrow planting system, where beds remain unploughed, furrows are tilled once at planting time and 30% of crop residue is retained. (ii) TER+ is ploughed once at planting, furrows are made at 1.5m intervals, creating fresh broad beds, and 30% crop residue is retained. These RCA practices were compared against conventional tillage (CT) characterized by a minimum of three tillage operations and complete removal of crop residues. Among the several assessed soil properties, soil organic C (SOC), total soil N, available P, soil microbial biomass C (SMBC), time of ponding, aggregate stability index (SI), consistency index (CI), cone index, air capacity and macroporosity were shown to increase significantly in soils subjected to DER+ planting system compared to CT. On average, crop yields under DER+ and TER+ increased by 30 % and 16 %, respectively, as compared to CT. Thus, from an agro-ecological point of view, adopting improved local practices such as DER+ and TER+ planting systems that employ conservation agriculture principles proved to be sustainable, resource conserving alternatives and incentives should be provided to facilitate larger adoption by farmers in Ethiopia.

The influence of the type of crop residue on soil organic carbon fractions: An 11-year field study of rice-based cropping systems in southeast China

Retaining crop residue is an important agronomic practice in sustainable agriculture, particularly to maintain soil organic carbon (SOC). To evaluate the effect of the retention of different types of crop residues on SOC and labile fractions, a long-term rice-based crop rotation experiment was established with five different winter cropping practices: (1) rice-fallow (RF), (2) rice–wheat (RW), (3) rice–potato with rice straw mulch (RP), (4) rice–green manure (Chinese milk vetch; RG), and (5) rice–oilseed rape (RO). The results showed that the annual rice yields in the RP, RO, RG, and RW treatments were not significantly different from each other, but 13.3%, 10.2%, 10.3%, and 8.4% higher, respectively, than in the RF treatment. Furthermore, the soil properties in the RP system improved significantly compared with those at the initiation of the study, with increases of 14.7% in total N, 17.5% in total P, 77.2% in available K, and 13.9% in SOC content. Considering the slight rice yield increase and superiority in the annual net income, the RP treatment seems to be a promising rotation system to meet the sustainability requirements for the agro-ecosystem. The responses of the labile SOC fractions (i.e., microbial biomass C (MBC), dissolved organic C (DOC), hot-water extractable C (HWC), permanganate-oxidizable C (KMnO4-C), and particulate organic C in the 0–20cm layer) to the crop rotation systems with the retention of different crop residues over the period of 11 years were specific to the types of the rotation system and closely related to the soil fertility properties. The RP treatment had comparatively higher content of DOC, HWC, MBC, and KMnO4-C than the other treatments in both 0–10cm and 10–20cm depths. The RW treatment had higher KMnO4-C content but lower MBC and POC content than the other treatments. The RO treatment had lower MBC content compared to the other treatments, while the opposite results were found in the RG treatment. Furthermore, the DOC content was improved by the winter crop growth. The changes in labile SOC might be attributable to the types of residues retained.