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Intercropping increases resource capture due to species complementarities, but it is not clear to which extent intercropping also affects the redistribution of carbohydrates and nitrogen (N) within the plant. Here, we examined in two years field experimentation the accumulation and translocation of dry matter and N in maize and peanut in pure stands and intercrops at five N input levels. Post-anthesis dry matter accumulation in the cob was on average 117 g plant−1 in sole maize and 159 g plant−1 in intercropped maize, of which post-anthesis dry matter translocation contributed 9 and 19 g plant−1, respectively. Intercropping increased post-anthesis N accumulation of maize from 0.77 to 1.29 g N plant−1 and N translocation to cobs from 0.94 to 1.16 g N plant−1, but it decreased the contribution of post-anthesis N translocation to grain from 54.0% in sole maize to 46.9% in intercropped maize. The kernel number was 486 per cob in sole maize and 609 per cob in intercropped maize, and the thousand-kernel weight was 320 g and 336 g, respectively. In peanut, intercropping decreased post-anthesis dry matter accumulation from 14.8 to 9.4 g plant−1, post-anthesis N accumulation from 0.37 to 0.24 g N plant−1 and N translocation to the pods from 0.25 to 0.14 g N plant−1. The pod number per plant in peanut decreased from 10.6 in the sole crop to 8.6 in intercropping. Nitrogen fertilization increased dry matter accumulation and translocation in intercropped maize, but had little impact in sole maize or in sole or intercropped peanut. In both species, dry matter translocation to the reproductive organs contributed slightly to the yield, while the post-anthesis contribution of N translocation was of the same order of magnitude as that of N uptake. • Retranslocation of dry matter made a small contribution to yield. • Retranslocation of nitrogen made a large contribution to nitrogen yield. • Intercropped maize increased nitrogen and dry matter accumulation and translocation. • Intercropped peanut decreased dry matter accumulation and translocation. • Nitrogen fertilizer effects were minor, except in sole maize. [ABSTRACT FROM AUTHOR]

Abstract: Most nutrient solution studies on the interactions between silicon (Si) and cadmium (Cd) are short term. Here we reported a long-term experiment in which rice (Oryza sativa L.) was cultured for 105 days and harvested at four different growth stages to measure biomass accumulation and Cd uptake and distribution in shoots and roots. Exogenous Si increased shoot biomass by 61–238% and root biomass by 48–173% when the culture solution was free of Cd. When 2μmolL−1 Cd was added, Si supply increased shoot and root biomass by 125–171% and by 100–106% compared to the zero-Si treatment. Increasing the Cd concentration to 4μmolL−1 decreased the beneficial effects of Si on root and shoot biomass. Silicon supply decreased shoot Cd concentrations by 30–50% and Cd distribution ratio in shoot by 25.3–46%, compared to the treatment without Si supply. Additionally, lower Si supply or more serious Cd stress would lead to roots with bigger biomass and higher Si concentration. Energy-dispersive X-ray microanalysis showed that both Si and Cd accumulated synchronously in the border and middle of phytoliths of the shoots. We conclude that Si enhances plant growth and decreases Cd accumulation in shoots and thereby helps to lower the potential risks of food contamination. [Copyright &y& Elsevier]

With labour migration to cities, Chinese agriculture is witnessing the emergence of business farming and an enlargement in farm sizes. Farm size enlargement triggers a wide range of managerial adjustments that may affect the sustainability of crop production practices. There is little empirical information on cropping practices and the sustainability of crop production of business farms as compared to traditional smallholder farms. Here, we made a comparison of cropping activities and sustainability performances between smallholder farms and business farms. Data on cropping activities and crop management were obtained by a survey among 486 smallholder farms and 19 business farms in 35 villages across Quzhou county on the North China Plain. After collecting data, we calculated sustainability indicators at the crop and farm scales. Business farms were about 15 times as large as smallholder farms (14.6 ha versus 0.8 ha) and they had more self-owned machinery. There was no significant difference in the number of crop species cultivated on smallholder or business farms. However, business farms allocated less area to grains and more area to cash crops with high economic benefit, such as stevia and vegetables, than smallholder farms did. Business farms showed some environmental benefits, e.g., business farms used 21% less irrigation water and had 28% lower N surplus. However, there were also trade-offs with business farms having 32% lower dietary energy output per unit area per year than smallholder farms. These differences were associated with better management and lower cropping index (number of crops per year) on business farms as compared to smallholder farms. These results indicate that business farms achieved improvements with respect to environmental externalities of agricultural production, when compared to smallholder farms, but the contribution to grain production was comparatively low. This study shows that scale enlargement of farming in a Chinese context is no panacea for achieving improved crop production sustainability. [Display omitted] • Smallholder farming in China is being replaced by business farming, but consequences for sustainability are not known. • We evaluate farm characteristics and crop management of smallholder and business farms on the North China Plain. • Smallholder farms had greater cereal production, while business farms focused on crops generating greater revenue. • Business farming resulted in improvement of some environmental characteristics, e.g. lower water use and N surplus. • Improved practices are needed to further enhance sustainability of both farm types. [ABSTRACT FROM AUTHOR]

• A global meta-analysis was conducted on maize/soybean intercropping. • Average land equivalent ratio (LER) was 1.32 ± 0.02. • The average value of fertilizer nitrogen equivalent ratio (FNER) was 1.44 ± 0.03. • Intercropping saved fertilizer due to concentrating production on less land with similar fertilizer N input per unit land. • Increasing N input scarcely changed LER and pLER maize but significantly reduced intercropped soybean yield. Intercropping exploits species complementarities to achieve sustainable intensification by increasing crop outputs per unit land with reduced anthropogenic inputs. Cereal/legume intercropping is a classical case. We carried out a global meta-analysis to assess land and fertilizer N use efficiency in intercropping of maize and soybean as compared to sole crops, based on 47 studies reported in English and 43 studies reported in Chinese. The data were extracted and analyzed with mixed effects models to assess land equivalent ratio (LER) of intercropping and factors affecting LER. The worldwide average LER of maize/soybean intercropping was 1.32 ± 0.02, indicating a substantial land sparing potential of intercropping over sole crops. This advantage increased as the temporal niche differentiation between the two species was increased by sowing or harvesting one crop earlier than the other as in relay intercropping, i.e. with only partial overlap of the growing periods of the two species The mean fertilizer N equivalent ratio (FNER) was 1.44 ± 0.03, indicating that intercrops received substantially less fertilizer N than sole crops for the same product output. These fertilizer savings are mainly due to the high relative maize yield and the lower N input in the intercrop compared to the input in sole maize. This meta-analysis thus shows that exploiting species complementarities by intercropping maize and soybean enables major increases in land productivity with less fertilizer N use. Both LER and FNER increased as the difference in growth duration increased for maize and soybean, but were not affected by fertilizer N rate. LER increased when soil organic matter increased but FNER did not change with soil organic matter. [ABSTRACT FROM AUTHOR]

Intercropping is becoming an attractive and profitable agricultural practice, and a growing body of literature investigate on the plant–plant interaction between intercrops. However, little is known on how sowing date alters interspecific interaction causing a yield difference between the intercropped and sole crop. A two-year field experiment was undertaken to investigate the impacts of varying competitive interaction on plant growth and grain yield of a maize/watermelon intercropping system. Both intercropped and sole maize were sown 28 days, 33 days and 38 days after a consistent transplanting date for watermelon to generate varying intensities of asymmetric competition between species in the maize/watermelon intercropping system. Growth patterns were monitored over two years and described with logistic growth curves. Compared with conventional sowing date, changes in maize sowing date significantly enhanced the intercropped maize grain yield by 21%–42%, but barely affected the sole maize yield, consequently reducing the yield difference between intercropped and sole maize. An earlier sowing date empowered the intercropped maize to reach the maximum absolute growth rate 11 days earlier, producing greater aboveground biomass and larger growth rate over its growing period, and thereby enhanced the maize resilience towards size-asymmetric competition derived from the presence of watermelon. Changes in the maize sowing date did not alter the fruit yield of intercropped watermelon in the most cases, but overmuch improvement in the aggressivity and growth rate of the maize sown on 13 June in 2014 caused a 16% reduction in fruit yield. We concluded that the yield difference can be reduced by adjusting the sowing date to manipulate plant–plant interaction between intercrops, and an optimal sowing date not only enhances crop growth but also brings on no penalty on companion crop yield. [ABSTRACT FROM AUTHOR]

Potassium (K) is an essential macronutrient for crop growth but it catches less attention than either nitrogen or phosphorus regarding their role in escalating crop yield. However, increasing evidences support the fact that K application enables crop to enhance resistance to lodging, but little is known about how maize resistance to lodging is affected by K distribution in shoot. We conducted a two-year field experiment including 6 levels of K application, monitored K uptake and distribution in different parts of shoot, and examined the effect of K application on stalk bending resistance of maize. K application significantly enhanced above-ground K uptake of maize. Across growing season, maize increased K uptake in the vegetative period while leveled off after anthesis. Stalk contained greater proportion of K than other parts, and stalk increased but ear rarely altered the K proportion with K application increase. K application significantly enhanced the bending resistant strength of maize stalk. The bending resistant strength was positively correlated with the diameter/length ratio, dry matter linear density and stalk K concentration, but those two internode morphological traits played more important role. We concluded that K application promoted K allocation to stalk and enhanced maize resistance to stalk lodging by modifying the internode traits. The study provides evidence for the importance of K application in maize production on soils with high stalk lodging risk. [ABSTRACT FROM AUTHOR]

Intercropping is a promising model for ecological intensification of modern agriculture. Little information is available on how species growth patterns are affected by size-asymmetric above- and belowground competitive interactions, especially in intercrops with more than two species. We studied plant growth and competitive interactions in a novel intercropping system with three species: wheat, watermelon and maize. Wheat and maize are grown sequentially (as a double cropping system) in narrow strips while watermelon is grown between the cereal strips, with partial overlap in growing period with the two cereals. Growth patterns were monitored over two years and described with logistic growth curves. Root barriers were used to study the effect of belowground interactions. Wheat produced 31% greater yield per plant in the intercrop than in the sole crop but 24% lower yield per unit total (inter)crop area. Wheat yield increase per plant was associated with faster growth and substantial overyielding in the outer rows of wheat strips. Watermelon did not competitively affect wheat. Watermelon biomass was substantially reduced at the time of wheat harvest. However, compensatory growth after wheat harvest and greater allocation to fruits resulted in a good yield of intercropped watermelon, 92% of monoculture yields, at final harvest. Intercropped maize produced 32% lower grain yield per plant and per unit area than sole maize, as a consequence of later sowing and a changed plant configuration in the intercrop as compared to the sole crop, and competitive effects of watermelon, as shown by comparison with a skip-row maize system without watermelon. Root barriers did not affect yield of any of the species, indicating that aboveground competitive interactions in this case played a more important role in shaping the observed growth responses than belowground interactions. Plant interactions in this tripartite intercrop system are consistent with the hypothesis of size-asymmetric competition for light. [ABSTRACT FROM AUTHOR]

Sustainable cropping systems need to balance productivity and profitability with resource and environmental conservation. Within a population of cropping system observations, there might be positive deviants that outperform others in terms of sustainability, which could serve as "model systems" for future development. Wheat-maize double cropping is the dominant system in the North China Plain, which is facing multiple economic, societal, and environmental sustainability challenges. Identifying exemplary positive deviants out of a multitude of wheat-maize observations might provide solutions to enhance overall sustainability. We aimed to 1) identify exemplary wheat-maize systems that reached optimal performance across seven sustainability indicators, 2) determine which factors regarding management practices and farming contexts resulted in the sustainability gaps between exemplary and other systems, and 3) propose a sustainable wheat-maize prototype. Based on a farmer survey dataset (n = 344), we developed a cropping system-level positive deviance approach, including multi-criteria assessment, positive deviant identification (Pareto ranking) and positive deviant clustering, to identify exemplary wheat-maize systems. We then compared exemplary and other systems to quantify the sustainability gaps and identify the key variables explaining sustainability gaps. Sixteen percent of wheat-maize cases were Pareto-optimal and were classified as positive deviants. These were sorted into seven clusters representing contrasting sustainability patterns. Among these clusters, one comprised exemplary systems due to the best compromise over the indicator set. Compared to remaining wheat-maize cases, exemplary systems, on average, resulted in 49% and 17% higher gross margin and dietary energy output, respectively, and 33–51% lower labor use, groundwater depletion, N loss, net greenhouse gas emission, and pesticide use. Key practices conferring exemplary system performance included higher maize seeding density, lower fertilizer N input in wheat, partial substitution of inorganic fertilizer with manure, a smaller number of irrigation events, and a lower frequency of pesticide and herbicide application. No significant difference in farming context was found between exemplary and other systems. Since the practices of exemplary systems were already locally adopted and proven, we expect that farmers in the region can increase the sustainability of their wheat-maize production by adjusting their management to resemble the exemplary systems. The positive deviance approach thus provides a pragmatic bottom-up approach to identify practices that can improve the sustainability of cropping systems, and can be used for other cropping systems elsewhere. [Display omitted] • A positive deviance approach was used to identify exemplary sustainable cropping systems. • Exemplary wheat-maize systems reached the best compromise across seven indicators. • Exemplary wheat-maize systems were supported by several efficient practices but not farming contexts. • Sustainability gaps could be closed if local wheat-maize systems resembled exemplary ones. • The positive deviance approach is a promising way to inform sustainability improvement of cropping systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Soil organic C remains the most important indicator for soil quality assessment. • The nonlinear scoring and weighted additive integration method is the best SQI tool. • The soil quality in the wheat-maize and vegetable systems is higher than that in the cotton system. • High soil quality depends on high inputs of straw residues, organic and inorganic fertilizers. • Application of agrochemicals decreases soil quality. Soil quality on smallholder farms is progressively declining due to inappropriate land management and agricultural inputs. Assessing soil quality at the field scale and evaluating the contributions of agricultural inputs to soil quality is therefore important in the formulation of policies and technologies for improving the land management practices of smallholders. The objectives of this study were to analyze the effects of smallholder agricultural inputs (fertilizer input, agrochemical input, organic fertilization and straw incorporation) on soil quality under three dominant planting patterns (wheat-maize, vegetable and cotton) in Quzhou County on the North China Plain. Six soil indicators (soil organic carbon, available zinc, fungal species richness, carbon pool activity, total chromium content and acid phosphatase activity) were identified as the minimum dataset (MDS). The SQI calculated using nonlinear weighted additive integration (SQI-NLWA) had the best discrimination under different planting patterns. The SQIs in the wheat-maize and vegetable systems were significantly higher than those in the cotton system. The overall spatial pattern of soil quality was related to the distribution of the planting patterns throughout the county. Organic fertilization, fertilizer input and straw incorporation increased the SQI, while agrochemical input decreased the SQI. Our study provides a quantitative tool for assessing soil quality at the field-scale and creatively analyzes the effects of smallholder agricultural inputs on soil quality. Our findings suggest that resource input and allocation determine soil quality and agricultural sustainability in smallholder-dominated agricultural systems. [ABSTRACT FROM AUTHOR]

• We analyse the effects of cover crops (CCs) on subsequent crop yield in China. • On average over whole China, CCs significantly increased subsequent crop yield by ca. 10 % compared to fallow. • CC type, CC season and N input were key factors influencing the effect of CCs on crop yield. • Results provide a basis for advising farmers on the use of CCs for increasing crop yields. Inclusion of cover crops (CCs) in cropping systems can improve soil quality, reduce agricultural inputs, and improve environmental sustainability. While CCs have been widely promoted in China in recent years, a quantitative assessment of CC effect on crop yield across China is lacking. There is also no overarching analysis on factors explaining variation in yield effects. Here, we carried out a meta-analysis to evaluate the effects of CCs on subsequent primary crop yield in China, based on 53 published studies reporting 442 yield ratios with and without CCs. We found that CCs increased subsequent primary crop yields by 9.7 % on average when compared with fallow across China. The effects of CC varied with different factors related to climatic zone, field management and soil properties. CC type (legume or not), CC season (growing in winter or summer) and nitrogen input were factors substantially influencing primary crop yield. We identified high yield benefits in subtropical rice systems with winter CCs (12.9 ± 3.9 %) but no significant yield benefits in temperate wheat systems with summer CCs (1.9 ± 6.6 %). Within subtropical rice systems, both legume and non-legume CCs were tested widely, and the effects of legume CCs (14.6 ± 4.0 %) on primary crop yield were greater than those of non-legume CCs (7.9 ± 3.7 %). The yield benefits of CCs decreased with increasing fertilizer inputs. These results may be used for developing policy recommendations to improve primary crop yield by integrating targeted CCs associated with nitrogen management into cropping systems in China. [ABSTRACT FROM AUTHOR]

• Soil biodiversity is positively related to agroecosystem multifunctionality. • Management practices are most important driving factors of multifunctionality. • High multifunctionality depends on high inputs of straw residues, organic and inorganic fertilizers. • Management practices are determined by smallholders' socioeconomic factors. Agroecosystems provide multiple goods and services that are important for human welfare. Despite the importance of field management practices for agroecosystem service delivery, the links of socioeconomic factors, management practices and ecosystem multifunctionality have rarely been explicitly evaluated in agroecosystems. Here we used a county-scale database with 100 farmer households and their farmlands, and analyzed the relative importance of management practices, soil abiotic environment and soil biota on multifunctionality under three distinct ('smallholder's viewpoint', 'sustainable soils' and 'equal weight') scenarios. Furthermore, we also analyzed the effect of smallholders' socioeconomic factors on management practices. Our results found that smallholders' high inputs of fertilizers and agrochemicals were associated with their high agricultural income and less farmland area, but total land area had a positive effect on straw incorporation. Total soil biota index was positively related to multifunctionality, however, management practices (fertilizer input, agrochemical input, organic fertilizer amount and straw incorporation) had stronger effect on multifunctionality than that of soil biota or the abiotic environment. Their strength varied with distinct scenarios. Our work suggests that increasing organic materials (organic fertilizers and crop residues) and decreasing agrochemicals are beneficial for maintaining or increasing ecosystem multifunctionality in smallholder-dominated agroecosystems. Moreover, improving management practices of smallholders needs to take into account the effects of their socioeconomic factors. [ABSTRACT FROM AUTHOR]

• Intercropping grain crops in China provides a yield gain of 2.14 Mg grain ha−1. • This net effect (NE) is mostly due to the complementarity effect (CE). • CE increases but selection effect (SE) decreases with temporal niche differentiation. • Inclusion of maize in the intercrop is a key factor contributing to yield gain. • Intercrops with or without legumes have similar yield gains. • Intercrops without legumes respond to N input with greater NE, CE and SE. • NE, CE and SE of intercrops with legumes do not respond to N input. • NE, CE and SE were independent of P fertilizer input. Intercropping is known to increase the efficiency of land use, but no meta-analysis has so far been made on the yield gain of intercropping compared to sole cropping in terms of absolute yield per unit area. Yield gain could potentially be related to a relaxation of competition, due to complementarity or facilitation, and/or to the competitive dominance of the higher yielding species. The contributions of competitive relaxation and dominance were here estimated using the concepts of complementarity effect (CE) and selection effect (SE), respectively. We compiled a dataset on intercropping of grain-producing crops from China, a hotspot of strip intercropping in the world. We quantified the yield gain and its components and analysed the contribution to yield gain of species traits (C3, C4, legume, non-legume), complementarity in time and nutrient input. Total yield in intercrops exceeded the expected yield, estimated on the basis of sole crop yields, by 2.14 ± 0.16 Mg ha−1 (mean ± standard error). Ninety percent of this yield gain was due to a positive CE while the remaining 10 % was due to SE. The net yield gain increased with temporal niche differentiation (TND) which is the proportion of the total growing period of the crop mixture during which species grow alone. The mechanism underlying yield gain shifted from competitive dominance of the higher yielding species when there was more overlap in growth period between the two species, to competitive relaxation when there was less overlap, while competitive relaxation remained the major component of the yield gain. The yield gain was substantially greater in intercrops with maize than in intercrops without maize, but there was no difference in yield gain between systems with and without legumes. The yield gain increased with nitrogen (N) input in maize/C3-cereal intercrops but not in cereal/legume intercrops, illustrating the ability of legumes to compensate for low N input, and highlighting the need for N input for high productivity in intercropping systems without legumes. Yield gain did not respond to phosphorus (P) input. We conclude that competitive relaxation is the main contributing factor to yield gain in the investigated Chinese intercropping systems, which were mostly relay strip intercropping systems. The underlying drivers of yield gain were related to presence of maize and species complementarity in time, but we did not find strong evidence for the selection effect. [ABSTRACT FROM AUTHOR]