Wheat-maize System Research Articles

Sustainable soil quality management for enhancing crop productivity in tribal areas of central India: A case study

The objectives of current investigation are to assess soil quality and sustainable management of soils for enhancing crop productivity in the tribal districts (Jhabua, Alirajpur and Dhar) of central India. Field trials were conducted in ten farmers’ fields for two years. Soybean-wheat system was adopted in six farmers’ fields and maize-wheat system in four farmers’ fields. Treatments were integrated plant nutrient supply (IPNS); soil test based nutrient management (STNM); recommended doses of fertilizers (RDF) and farmers’ practices (FP). Initial and post experiment soil samples were collected and analyzed. Soil quality changes were also studied. IPNS and STNM practices improved crop yield, farm income and soil quality compared to RDF and FP. Low organic carbon and deficiency of N, S and P are the major soil constraints in the region. Therefore, IPNS and STNM could be practiced to enhance crop productivity, farm income and to maintain soil health in the region.

The responses of soil enzyme activities, microbial biomass and microbial community structure to nine years of varied zinc application rates

Zinc (Zn) fertilizer application can certainly improve the production and nutritional quality of cereal crops. However, Zn accumulation in the soil may lead to some deleterious environmental impacts in agroecosystems. The effects of long-term Zn application on soil microbial properties remain unclear, but it is imperative to understand such effects. In this study, we collected soil samples from a nine-year field experiment in a wheat-maize system that continuously received Zn applied at various rates (0, 2.3, 5.7, 11.4, 22.7 and 34.1 kg ha−1) to evaluate the soil enzymes, microbial biomass and microbial community structure. The results showed that Zn application at the rate of 5.7 kg ha−1 significantly increased the activities of urease, invertase, alkaline phosphatase and catalase in the soil, while the rate of 34.1 kg ha−1 significantly decreased the evaluated enzyme activities. The microbial biomass carbon (C) and nitrogen (N) were not affected by Zn application rates, although an increase in the microbial biomass C was observed in the 11.4 kg ha−1 treatment. Moreover, the alpha diversity of the bacterial and fungal communities did not vary among the nil Zn, optimal Zn (5.7 kg ha−1) and excess Zn (34.1 kg ha−1) treatments. However, the bacterial communities in the soil receiving the optimal and excess Zn application rates were slightly changed. Compared to the nil Zn treatment, the other Zn application rates increased the relative abundances of the Rhodospirillales, Gaiellales and Frankiales orders and decreased the abundance of the Latescibacteria phylum. The redundancy analysis further indicated that the soil bacterial community composition significantly correlated with the concentrations of soil DTPA-Zn and total Zn. These results highlight the importance of optimal Zn application in achieving high production and high grain quality while concurrently promoting soil microbial activity, improving the bacterial community and further maintaining the sustainability of the agroecological environment.

Soil organic carbon, its fractions and soil organic carbon stocks under different land use systems in Typic Ustrochrepts of northwest India

A study was conducted to assess the impact of different land use systems on soil organic carbon (SOC), its fractions and soil organic carbon stocks under different land use systems in a mixed watershed in the submontane region of north-west India. Soil samples were collected up to a depth of 120 cm from three locations each from maize-wheat, agro-horticulture and agroforestry (3 and 6-year plantation) land use systems. The results revealed that the surface soils (0–15 cm) under agroforestry had significantly higher SOC (5.3 mg g− 1) than in soils under other cropping systems and varied from 4.3 to 5.3 mg g− 1. The labile carbon (LC), aggregate associated carbon (AAC), particulate organic carbon (POC) and mineralizable carbon (MC) were also significantly higher in surface soils under agroforestry 6-year plantation than other three cropping systems and thereafter exhibited significantly lower content of SOC and its fractions in each of the depth as compared to the surface soil in all the cropping systems except maize-wheat system where LC increased significantly in the second depth and decreased gradually in the subsequent lower depths. The proportion of these fractions in relation to the soil organic carbon was lowest in soils under maize-wheat (10–70%) than the tree-based cropping systems (20–100%). The typical decrease of SOC content in the 3rd depth (30–60 cm) was the sharpest and thereafter it stabilized in lower depths in maize-wheat system. The SOC stock followed the trend: agroforestry 6-year (38 Mg ha− 1) > agroforestry 3-year (30.5 Mg ha− 1) > agrohorticulture or maize-wheat system (27.5 Mg ha− 1). Up to 33% lower SOC stocks were recorded in maize-wheat or agrohorticulture cropping systems than under the agroforestry land use system, thereby suggesting that conversion of forest land to agroecosystems can contribute to losses of up to 10.5 Mg ha− 1 SOC over time. Overall conclusion from this investigation is that SOC levels are strongly influenced by the prevailing land use systems.

Conservation agriculture for sustainable intensification in South Asia

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.

Dynamics of zinc under long‐term application of chemical fertilizers and amendments by maize–wheat cropping sequence in Typic Hapludalfs

AbstractThis present investigation took place on a continuing long‐term fertilizer experiment, initiated in 1972 at the experimental farm of the College of Agriculture CSK HPKV, Palampur, aimed at studying nutrient dynamics of micronutrients, especially Zn, after continuous use of chemical fertilizers and amendments over the previous 36 years in an acid Alfisol under a maize–wheat system. Treatments investigated were as follows: T1: Control; 100% N; 100% NP; 100% NPK (optimal application ‐ 120:26:33(maize)/25(wheat)); 100% NPK + FYM (10 t ha−1 to the maize crop); T6: 100% NPK + lime (900 kg ha−1); T7: 100% NPK + Zn (25 kg ha−1 as ZnSO4); T8: 100% NPK + Hand weeding; T9: 100% NPK (‐S); T10: 150% NPK (super‐optimal application); and T11: 50% NPK (sub‐optimal application). Different forms of zinc in soil were determined through a sequential extraction method. Results revealed that previous applications of high‐analysis fertilizers and amendments caused a marked depletion in the pools of Zn as compared to buffer plots. All pools of Zn as well as crop productivity and Zn uptake were noticeably greater in farmyard manure (FYM)‐amended plots compared with plots not receiving fertilizer. The residual fraction was the dominant form but organically bound and exchangeable forms were found to play major role in nutrient supply, crop productivity and nutrient uptake. Correlation and regression analysis studies showed that organic forms constituted the most important pool contributing towards variation in yield and uptake by maize and wheat crops. Exchangeable and organically bound forms contributed significantly towards the availability of DTPA‐extractable Zn in soil.

Impact of Conjunctive Nutrient Management Practices on Soil Quality Indicators and Soil Quality Indices under Maize (Zea mays)-Wheat (Triticum aestivum) Cropping System in Hill and Mountainous Inceptisol Soils of Northern India

A field experiment was conducted in the rainfed Inceptisol soils of Rakh Dhiansar in Kandi areas of Western Himalayas of South Kashmir and Kumaon from 2001 to 2005. The main focus of the present study was to quantify the impact of conjunctive nutrient management practices on soil quality parameters, to identify the key indicators of soil quality using data redundancy technique and to compute integrated soil quality indices (SQIs) and relative soil quality indices (RSQIs) as influenced by the conjunctive nutrient management treatments in hill and mountainous Inceptisol soils in Northern India under maize-wheat system. Out of the total 10 treatments, five treatments viz., T1: control, T2: FYM @ 10 t ha−1 + 20 kg N ha−1, T3: FYM @ 10 t ha−1 + 30 kg N ha−1, T4: FYM @ 10 t ha−1 + 40 kg N ha−1 and T5: green manuring with sunhemp + 20 kg N ha−1 were selected for the soil quality assessment studies. The nutrient management treatments significantly influenced the SQIs which varied between 3.69 to 5.66 across the management treatments, while the RSQIs varied between 0.63 to 0.96. Of all the nutrient management treatments, the application of FYM @ 10 t ha−1 + 40 kg N ha−1 maintained significantly highest SQI of 5.66, which was at par with the application of FYM @ 10 t ha−1 + 30 kg N ha−1 and green manuring with sunhemp + 20 kg N ha−1 both of which maintained SQI of 5.40. Irrespective of their statistical significance, the relative order of performance of the nutrient management treatments in maintaining the soil quality indices was: T4: FYM @ 10 t ha−1 + 40 kg N ha−1 (5.66) > T5: Green manuring with sunhemp + 20 kg N ha−1 (5.44) > T3: FYM @ 10 t ha−1 + 30 kg N ha−1 (5.40) > T2: FYM @ 10 t ha−1 + 20 kg N ha−1 (5.16) > T1: control (3.69). The percent contributions of each of these key indicators towards SQIs were also computed. It was observed that almost all the key indicators contributed more or less equally towards the SQIs except available N and available Fe, which contributed to a minimum extent of 2.27% and 1.90%, respectively. The percent contribution of the other key indicators was as follows: organic carbon (13.8%), available P (13.4%), available K (14.5%), available Zn (12.6%), microbial biomass carbon (13.7%), bulk density (15.2%) and mean weight diameter (11.6%).

Effect of nitrogen point placement on energetic and soil enzymatic activities on long-term conservation agriculture based maize (Zea mays) - wheat (Triticum aestivum) system of western Indo-Gangetic plains

A field experiment was done in the long term conservation agriculture (CA)-based plots at ICAR-Indian Agricultural Research Institute (IARI) during 2018–19 with the treatments of nitrogen (N) point/line placement to compute the energy budgeting and soil enzymatic activity. There were four land management practices in main plots and in sub plots there were three nitrogen placement methods. Results of present study showed that the energy use efficiency was higher in the CA-based PB plots by 7.14% and 9.4% than CT plots in maize and wheat respectively. The energy output from the CA-based maize (Zea mays L.) and wheat (Triticum aestivum L.) plots was significantly higher by 9.1–11.2% and 8.8–14.4% than CT plots. However, N point placement treatments i.e. NPM3 and NPM2 had 14.8% and 8.8% higher energy output than NPM1 plots in maize respectively. Similarly in wheat, NPM2 and NPM3 plots had 4.2% and 7.0% higher energy output than NPM1. The CA-based plots recorded an increase in soil microbial biomass carbon (SMBC) by 8.7–15.6% in maize and 10.1–17.2% in wheat. The SMBC content remained statistically similar across N placement methods at flowering of maize and wheat crops. In maize and wheat, at the surface soil layer urease activity was found higher than CT by 11.7–20.2% and 13.2–22.4% in the CA-based plots. However, the urease activity was not affected by subsurface point or line placement of nitrogen at both the soil layers in both the crops. Therefore, the findings of present study suggest that the adoption of CA-based practices with point/line placement of split applied N in maize-wheat system of western Indo-Gangetic plains is favourable for improving the energy use efficiency and soil enzymatic activity.

Effect of long-term fertilization in maize-wheat cropping system on carbon mineralization in soil

Quantitative information on mineralization of soil organic carbon (SOC) under different long-term nutrient management practices is essential for better assessment of carbon (C) loss from soil. With an aim to evaluate long-term nutrient management effects on C mineralization kinetics in soils, a laboratory incubation study was conducted with soils collected from different depths (0–15, 15–30, 30–60, and 60–100 cm) of a 46-year old maize-wheat experiment. The treatments in the field involved long-term application of 100% N, 100% NP, 100% NPK, 150% NPK, 100% NPK + FYM (farmyard manure), and an unfertilized control. Long-term application of fertilizers significantly (p < 0.05) influenced organic C concentration and C mineralization kinetics in soil. Integrated application of inorganic fertilizers and organic manure (100% NPK + FYM) resulted in greater SOC accumulation and higher potentially mineralizable C in soil compared to other treatments. The microbial biomass carbon (MBC), basal soil respiration (BSR), carbon mineralization (Cmin), and microbial quotient (qMic) values were significantly higher under integrated application of NPK and FYM in maize-wheat system. The results showed that long-term application of FYM along with inorganic fertilizer enhanced SOC pool compared to solitary application of mineral fertilizers.

Evaluation of N fertilization management strategies for increasing crop yields and nitrogen use efficiency in furrow-irrigated maize–wheat system under permanent raised bed planting

ABSTRACT Information on the effect of N management on crop yields and N use efficiency (NUE) under furrow irrigations is scarce for conservation agriculture (CA)-based annual maize–wheat (MW) system in South Asia. A 2-year (2013–2015) field experiment was conducted to evaluate the effects of residue management in main plots and combinations of two rates and three methods of N fertilizer application plus no N control treatment in subplots on the yield, N uptake and NUE of permanent raised bed (PB) MW system in north-western India. Residue retained on surface significantly increased grain yields by 7.7% and 4.3% in maize and wheat compared to no residue, respectively. Results showed that while uniformly broadcast method (B) required 120 kg N ha−1, similar maize and wheat yields can be achieved with 90 kg N ha−1 using deep placement on beds (DB) thereby saving 30 kg N ha−1. DB increased maize yield by 5.4% and 10.9% compared with DF and B, respectively. In wheat, DB and DF significantly increased grain yield by 4–7% compared to B. At 120 kg N ha−1, NUE of 61% and 74% with B was increased to 73% and 98% with DB in wheat and maize, respectively.

Effect of phosphorus fertilization and microbial inoculants on yield, phosphorus use-efficiency and available phosphorus in maize (Zea mays)- wheat (Triticum aestivum) cropping system

A field experiment was conducted between 2012-14 to investigate the effect of different phosphorus levels (control-no P, 33% P, 50% P, 100% P and 100% P in 3-splits of the recommended dose of P) and microbial inoculants (un-inoculated control, arbuscular mycorrhizal fungi, AM phosphate solubilising bacteria, PSB and AM+PSB) in maize-wheat system. The study revealed that the maize and wheat grain yields were increased by 20% and 40%, respectively, under 100% P which were significantly higher over control. The total P uptake by maize and wheat varies from 11.7–20.7 kg/ha and 17.7–32.4 kg/ha, respectively. The highest apparent recovery (AR) in both the crops was recorded when 50% P was added with AM+PSB inoculation whereas, a significant reduction in AR was recorded with increase in fertilizer P beyond 50% of recommended P. Agronomic efficiency was highest under 50% P averaged across microbial inoculants in both maize (32.5 kg grain/kg P) and wheat (78.5 kg grain/kg P). Grain yield of both maize and wheat was significantly and positively correlated with Olsen P content at tasseling (r = 0.30*) and panicle emergence (r = 0.35**). The higher P use-efficiency under 50% recommended P along with microbial inoculants suggests applying lower doses of P fertilizer along with microbial inoculants to achieve optimum yield in maize-wheat system without any adverse impact on soil fertility.

Drip irrigation and nitrogen management for improving crop yields, nitrogen use efficiency and water productivity of maize-wheat system on permanent beds in north-west India

The traditional flood irrigation system has led to overexploitation of ground water and low nitrogen (N) use efficiency. In north-western India, maize-based systems with lower irrigation requirement are being advocated as an alternate to rice-based systems to address the issues of declining water table. Bed planting of crops, straw mulching and drip irrigation are known to save precious irrigation water, and improve N use efficiency and grain yields. To this effect a two-year field experiment was conducted with annual wheat-maize rotation on permanent bed system to evaluate the effect of surface drip irrigation, residue management, and N application on crop and water productivity. Maize and wheat under drip irrigation with residue retention system showed significant grain yield increase of 13.7% and 23.1% compared to furrow irrigation with no residue, respectively. Surface drip irrigation with residue retention saved 88 mm and 168 mm of water and increased water productivity by 66% and 259% in wheat and maize on permanent beds compared to the conventional furrow irrigation system with residue removal, respectively. Similarly, fertigation at 10-day interval with five splits in wheat and seven splits in maize under drip irrigation system increased the mean N recovery efficiency by 16.5% and 29% compared to furrow irrigation in wheat and maize, respectively.

Long-term effects of tillage and straw management on soil organic carbon, crop yield, and yield stability in a wheat-maize system

A long-term experiment for testing different tillage methods and straw management practices was carried out in the Northern China Plain (NCP) since 2002 in a double cropping system (winter wheat and summer maize) rotated annually. Data for 11 yr (2005–2015) was collected to compare the long-term effects of six agricultural practices on soil organic carbon (SOC) storage, crop yield, and yield stability. The six agricultural methods comprised of two main factors (i) tillage practices with three modalities—conventional tillage (CT), no-tillage (NT), and subsoiling (ST); and (ii) straw management with two modalities—straw return (S) and straw removal (0). Here, straw was usually defined as crop residue cut and removed with harvest. Finally, the six treatment combinations were represented as CT0, NT0, ST0, CTS, NTS, and STS. The SOC storage showed similar dynamic changing trends under all treatments, but was higher in NT and ST and straw return plots than in CT0 plots. Average SOC storage under STS and NTS reached 14.1, and 13.1 g kg−1, respectively. After 2005, both tillage practice and residue management affected SOC storage significantly. Cumulative yields for 11 yr with maize and wheat were higher for ST than NT and CT both with straw removal and straw return. Average crop yield increased by 6.2 and 20.1% in winter wheat and by 11.0 and 21.6% in summer maize, respectively, in ST0 and STS, when compared to CT0. NT, ST, and straw return increased crop yield stability, with STS being the most stable. Variability in STS was only 11.3% for winter wheat and 8.8% for summer maize. Pearson correlation analysis showed that winter wheat and summer maize yields were significantly and positively correlated with SOC storage. Subsoiling with straw return (STs) did not result in higher SOC than NTs after 11 yr, but it resulted in the highest cumulative yield for wheat and maize, and the highest yield stability for wheat. When straw was removed, SOC after 11 yr was highest for NT, but cumulative yields for wheat and maize were highest for ST. STS is firstly an optimal method to improve SOC storage, crop yield, and yield stability in the NCP.

Long-term tillage and nitrogen management for improving productivity and profitability of a rainfed maize-wheat system in north western Himalaya

Long-term tillage and nitrogen management for improving productivity and profitability of a rainfed maize-wheat system in north western Himalaya

Productivity, energetics and economics of wheat-maize system as affected by tillage and nitrogen levels

Productivity, energetics and economics of wheat-maize system as affected by tillage and nitrogen levels

Improved yield and water storage of the wheat-maize rotation system due to double-blank row mulching during the wheat stage

Mulching techniques have been widely used in dryland regions in northern China. It is necessary to develop water-saving cultivation techniques in irrigation regions in northern China to relieve water scarcity. Planting and mulching on separate rows has been widely used to improve wheat yield and involves a pattern of a double row of planting and a blank row of mulching. However, whether the mulching pattern during the wheat season can be applied to the wheat-maize system to increase the yield of both crops and to reduce the use of irrigation water remains unclear. Three mulching practices (conventional planting (CP), conventional planting with mulching (CPM) and double-blank planting with mulching (DPM)) during the wheat season were conducted to verify the potential roles of DPM in increasing wheat and maize yields, improving soil temperature and enhancing water storage under the DPM practice. The results show that the DPM practice significantly increased the efficiency spike number, aboveground biomass and grain yield (7.8% higher than CP and 11.3% higher than CPM) of wheat. The heat conservation effect of the DPM practice was stronger in the early stage of growth and was more effective in minimizing fluctuations in soil temperature in the wheat season compared with CPM. The development and yield of maize that was sowed in the mulching lines of DPM were less improved, although the amount of aboveground biomass at the maturity stage was higher. Additionally, the soil temperature of the maize season under DPM showed a narrowing trend of changes during the early stage with slight effects in the middle stage and a resumption of heat conservation in the late stage. Compared with CP, both mulching patterns decreased soil evaporation during the two crops’ seasons by an average 5.3% in CPM and 7.8% in DPM, which is particularly evident when the crops’ leaf area index was low. Therefore, the DPM pattern could more effectively optimize soil temperature and water storage. Furthermore, this pattern may have positive effects on the yields of winter wheat and on reducing the soil water requirement of the maize season.

Long-term effects of biochar addition and straw return on N2O fluxes and the related functional gene abundances under wheat-maize rotation system in the North China Plain

To evaluate long-term effects of biochar addition and straw return (SR) on N2O fluxes in wheat-maize rotation system, a 2-year field experiment following a 7-year biochar addition and SR was investigated in an intensively managed agricultural soil in the North China Plain (NCP). Four treatments were included: 1) no biochar addition (CK); 2) biochar treatment with 4.5 t ha−1 yr−1 (C1); 3) biochar treatment with 9.0 t ha−1 yr−1 (C2); and 4) all the wheat/maize straw return (SR). The results showed the annual cumulative N2O emissions from C1 treatment were increased by 15.9–16.5%, while C2 treatment suppressed the annual cumulative N2O emissions by 22.8–26.3%. In comparison, straw return suppressed N2O emissions by 13.4–43.6% in the wheat season but increased N2O emissions remarkably by 45.3–53.9% in the maize season. Biochar addition enhanced the copies of AOA, AOB, nirK, nirS, and nosZ genes, while straw return decreased the copies of AOB, nirK, nirS, and nosZ genes at the high N2O emission period in the maize season. The production of N2O in the maize season was mainly driven by the AOB and nosZ genes, and by AOB gene in the wheat season. These results suggest that application of 9.0 t ha−1 yr−1 biochar is a more optimum agricultural strategy for reducing N2O emission in the wheat-maize system.

Comparisons of weed community, soil health and economic performance between wheat-maize and garlic-soybean rotation systems under different weed managements.

This study compared the impacts of different weed managements on weed community, soil health and economic performance between the wheat–maize (WM) and garlic–soybean (GS) rotations. A total of four treatments (H0T, tillage without herbicide; H0T0, without both herbicide and tillage; HT, both herbicide and tillage; HT0, herbicide without tillage) were designed for both rotations. A total of 16 weed species were recorded in the WM rotation, with life forms of 62% for annuals, 12% for annual + perennial and 20% for perennials. While in the GS rotation, there were 17 weed species, with 71% being annuals. When crop rotation changed from WM to GS, the topsoil layer seed bank (0–5 cm) decreased by 137%. GS rotation always had higher earthworm densities than that of WM under the same condition. Organic weed control (H0T, H0T0) from both WM and GS added more soil organic matters than the chemical methods (HT and HT0). Economically, up to 69% higher net profit had been achieved in the GS than WM for their organic products. This study provides an ecological basis to guide organic farming practices, especially for weed management in the future.

Aggregate-associated N and global warming potential of conservation agriculture-based cropping of maize-wheat system in the north-western Indo-Gangetic Plains

Despite conservation agriculture (CA) is being promoted as a climate resilient technology, limited information is available on its impacts on N storage within soil aggregates vis a vis global warming potential (GWP) under tropical agro-ecosystems. Hence, this study assessed the effects of a medium-term (5-years) CA on total soil N (TSN) changes in bulk soils and aggregates, N2O and CO2emission, GWP and total C fixed in soils under maize (Zea mays L.)- wheat (Triticum aestivum L.) system on the Indo-Gangetic Plains (IGP). The treatments were: conventional tillage (CT), zero tillage (ZT) with planting on permanent narrow beds (PNB), PNB with residue (PNB + R), ZT with planting on permanent broad beds (PBB), PBB with residue (PBB + R), ZT on flat land/plains without crop residue (ZT) and with crop residue retention (ZR + R). Soil samples were collected after five years of a maize–wheat system and TSN in bulk soils and their aggregates of the 0–5 and 5–15 cm soil layers were measured along with N2O and CO2 emissions during the fifth year (2014–15).The soils under PBB + Rhad 37 and 9% more macro-aggregate-and micro-aggregate-associated N concentrations in topsoil (0–5 cm layer) than CT (248 and 299 kg N ha−1). However, topsoil soil aggregation and aggregate-associated N contents of PNB + R and ZT + R were similar to CT plots. The dehydrogenase and fluorescein diacetate activities and TSN, microbial biomass N, NO3-N and NH4-N concentrations were also highest in PBB + R plots in topsoil. The topsoil dehydrogenase activity was significantly correlated (r = 0.426, n = 21, p < 0.05) with CO2emission and with N2O emission (r = 0.770, n = 21, P < 0.01) during wheat (2014–15). However, topsoil FDA activities and MBN concentrations were only significantly correlated with N2O emission in wheat. In the maize–wheat system, highest N2O emission was observed in PNB + R plots and least in CT plots. But, PBB + R and PNB + R plots had similar CO2 emissions to CT plots in both crops. Despite GWP of ZT + R and PBB + R plots in the maize-wheat system were ∼5% higher than CT, greenhouse gas (GHG) intensities in the CT, PBB + R and ZT + R plots were similar. Thus, PBB + R practice is a better management alternative for soil N improvement (and a reduced fertilizer N dose could be adopted in future) than CT since this practice also had 36% and 8.2% higher biomass productivities of maize and wheat, respectively in the maize-wheat cropping system and similar GHG intensity to CT plots.

Integrated assessment of economic and environmental consequences of shifting cropping system from wheat-maize to monocropped maize in the North China Plain

Abstract Monocropped maize is being discussed as a possible alternative to the conventional wheat-maize cropping system in order to conserve water in the North China Plain. To evaluate the economic and environmental consequences of converting cropping systems, wheat-maize, monocropped maize systems with and without irrigation are compared through a joint use of economic analysis, emergy evaluation and life cycle assessment in this study. According to the economic analysis results, the wheat-maize system has higher grain yield and levels of economic profit but a lower ratio of income to costs compared to monocropped maize systems with and without irrigation. The emergy evaluation results show that monocropped maize systems have higher levels of sustainability. Their environmental loading ratios are 8.16%–26.7% lower and the emergy sustainability indexes are 10.20%–30.52% higher than those of wheat-maize system, respectively. The life cycle assessment results reveal lower potential environmental impacts for monocropped maize systems and their total potential environment impact indexes are 39.59%–40.30% lower than that of wheat-maize system. These results indicate monocropped maize will be an effective measure to resolve the current issue of environmental pressures caused by the conventional wheat-maize system in the North China Plain.

Response of the soil microbial community to different fertilizer inputs in a wheat-maize rotation on a calcareous soil

The combined use of inorganic fertilizers with organic manures has recently attracted increasing interest in China in attempts to mitigate the deleterious environmental impacts of excessive rates of chemical fertilizers in agroecosystems. However, questions remain concerning temporal change and how the soil microbiome responds to different fertilizer inputs in intensively managed crop rotations. Here, we collected soil samples from a wheat–maize system to investigate the response of the soil microbiome to four years of application of inorganic fertilizer only (NPK), NPK plus either cattle manure or straw, NPK plus both manure and straw, or a zero fertilizer control. The soil bacterial and fungal populations and community composition, nitrogen functional genes (amoA) and carbon utilization patterns were assessed. Sampling time had a much greater influence on the soil microbiome than did fertilizer regime, and the effect of fertilization was mostly significant at the wheat harvest. Fertilization increased amoA gene copy numbers but only AOB abundance showed differences among fertilizer treatments. In June the community composition of both bacteria and fungi was clearly separated between the organic matter additions and the zero organic matter treatments. Microbial carbon source utilization was significantly affected by fertilization regime and sampling time. By contrast, at the maize harvest neither microbial populations nor microbial community composition were altered. Our results suggest that the entire soil microbiome is more responsive to organic inputs than to chemical fertilizers in the short term. Temporal shifts in microbial community composition in the crop rotation imply that crop species and environmental conditions need to be carefully integrated into nutrient management strategies.