Assessing the effect of crop residue removal on soil organic carbon storage and microbial activity in a no‐till cropping system

Changes in agricultural management strategies have received much attention in recent years with a view to increasing or maintaining the amount of carbon (C) sequestered as soil organic C (SOC). In many parts of the world, minimum or no‐till management has been promoted as a means of improving soil quality, reducing losses of erosion and potentially increasing SOC stocks. However, no‐till systems can become problematic and potentially disease‐prone, especially due to high crop residue loadings. Consequently, residue removal either by harvesting or burning off may be employed to reduce these pressures. Here, we examined the effect of crop residue removal on C storage in soil that had been under no‐till management for 20 yr. We predicted improved physical properties (i.e. lower bulk density) and greater microbial activity under the residue retention soils due to greater readily available C and nutrients derived from crop residues. In contrast, we predicted relative reductions in SOC in the no residue soils due to a lack of available residue‐derived C for microbial use. Residue removal caused a relative C loss from the soil, which was related to C input, amount of nutrient availability and microbial activity. We demonstrate the importance of maintaining crop residue cover in no‐till cropping systems for soil function and highlight the potentially deleterious effects of changing management strategy to increased residue harvesting or removal by burning.     

Impact of a no-till with mulch soil management strategy on soil macrofauna communities in a cotton cropping system

Systematic exportation, burning of crop residues and decreases in fallow periods have led to a large-scale depletion of soil organic matter and degradation of soil fertility in the cotton (Gossypium hirsutum L.) cropping systems of Cameroon. The present study tested whether soil management systems based on a no-till with mulch approach intercropped with cereals, which has been shown to restore cotton production, could boost the biological activity of soil macrofauna. The impacts of no tillage with grass mulch (Brachiaria ruziziensis Germain and Eward) (NTG) and no tillage with legume mulch (Crotalaria retusa L. or Mucuna pruriens Bak.) (NTL) on the abundance, diversity and functional role of soil invertebrates were evaluated during the third year of implementation in northern Cameroon (Windé and Zouana), compared to conventional tillage (CT) and no tillage (NT) without mulch. Macrofauna were sampled from two 30 cm × 30 cm soil cubes (including litter) at the seeding stage of cotton, and 30 days later. The collected organisms were grouped into detritivores, herbivores and predators. Examination of the soil macrofauna patterns revealed that the abundance and diversity of soil arthropods were significantly higher in NTG and NTL than in CT plots (+103 and +79%, respectively), while that of NT plots was in-between the no tillage groups and CT (+37%). Regarding major ecological functions, herbivores and predators were significantly more abundant in NTG and NTL plots than in CT plots at Windé (+168 and +180%, respectively), while detritivores, predators and herbivores were significantly more abundant in the NTG plots than in CT plots at Zouana (+92, +517 and +116%, respectively). Formicidae (53.6%), Termitidae (24.7%) and Lumbricidae (9.4%) were the most abundant detritivores while Julidae (46.1%), Coleoptera larvae (22.1%) and Pyrrhocoridae or Reduviidae (11.8%) were the dominant herbivores. The major constituents of the predatory group were Araneae (33.8%), Carabidae (24.6%), Staphylinidae (15.7%) and Scolopendridae (10.3%). Direct seeding mulch-based systems, NTG and NTL, favoured the establishment of diverse macrofaunal communities in the studied cotton cropping system.     

Temporal changes in the spatial distributions of some soil properties on a temperate grassland site

Abstract. Precision Agriculture seeks to match resource application and agronomic practice with soil and crop requirements as they vary in both space and time. Therefore, an understanding of both the temporal and the spatial components of variability is essential before decisions can be made about the feasibility of site-specific management. In the present study, the spatial and the temporal components of variability in certain key soil properties of a grassland field were evaluated to assess the likely feasibility of adopting a site-specific approach to grassland management. A 7.9 ha grassland field was selected for the study and soil samples were taken three times at regular 25 m intervals across the field over a two year period, and chemically analysed. Classical and geostatistical procedures were used to evaluate the spatial variability and the temporal stability of soil property distributions. Soil extractable P and K had the greatest within-field variability and soil pH the least. Soil K distributions were also highly unstable over time and it was concluded that the optimal risk aversion strategy would be to apply uniform dressings of this nutrient to the entire field. In contrast, soil pH, P, Mg and sulphate distributions were not only temporally stable, but were also spatially correlated over reasonably large ranges. It was concluded that these properties might be managed in a site-specific way based on the results of periodic soil testing in three clearly defined management sub-units within the field. Over the two year period, C and N accumulated in the soil at surprisingly high rates on certain parts of the field but not in others.     

冬小麦生长条件下改进遗传算法在根系水盐运移模型中的应用研究

应用改进遗传算法,优化人工神经网络模型的权值,对盐分存在下的冬小麦根系分布进行定量预报,将获得的根系分布参数与根系吸水模型以及水盐运移模型相结合,进行了水分、盐分分布的数值模拟。结果表明,应用改进遗传算法可以为根系吸水模型提供所需的根系参数,并且可以较好地对土壤中水分、盐分的运移分布情况进行模拟;该方法建模简单、实用,模型对于土壤次生盐渍化的防治与微咸水的灌溉利用等具有参考价值。     

Improved fallow with pigeon pea for soil fertility improvement and to increase maize production in a smallholder crop–livestock farming system in the subhumid zone of Ghana

Pigeon pea is cultivated by most smallholder crop–livestock farmers mainly as a border crop. It is quite often sparsely intercropped in cereal‐based cropping systems in the subhumid zone of Ghana. Management of pigeon pea and its biomass is a promising means of improving many abandoned arable fields but has not been consciously undertaken. The objective of this trial was to explore the use of pigeon pea and the management of its pruned biomass as part of an improved fallow for crop–livestock farming. Three pigeon‐pea management options and a natural fallow (two‐year fallow period) were compared in terms of maize grain yield and changes in soil organic carbon, total nitrogen and cation exchange capacity. Pigeon pea grain yield ranged between 615 and 678 kg ha⁻¹ and 527 and 573 kg ha⁻¹ in the first and second year of fallow, respectively. In the first year after fallow, maize grain yield ranged between 0·43 and 2·39 t ha⁻¹ and was significantly influenced by the fallow system. There was a marked decrease in maize grain on the pigeon pea fallow plots in the second year, ranging between 50 and 38·6 per cent in Kumayili and between 42·6 and 17·6 per cent in Tingoli. After the two‐year fallow period, increase of soil organic carbon on the pigeon pea fallow plot compared with the natural fallow plot was 30·5 per cent, and there was an improvement of total nitrogen (48·5 per cent) and CEC (17·8 per cent). Copyright © 2005 John Wiley & Sons, Ltd.     

Simulating the soil phosphorus dynamics of four long-term field experiments with a novel phosphorus model

Phosphorus is a nonrenewable resource, which is required for crop growth and to maintain high yields. The soil P cycle is very complex, and new model approaches can lead to a better understanding of those processes and further guide to research gaps. The objective of this study was to present a P-submodel, which has been integrated in the existing Carbon Candy Balance (CCB) model that already comprises a C and N module. The P-module is linked to the C mineralization and the associated C-pools via the C/P ratio of fresh organic material. Besides the organic P cycling, the module implies a plant-available P-pool (P_av), which is in a dynamic equilibrium with the nonavailable P-pool (P_na) that comprises the strongly sorbed and occluded P fraction. The model performance was tested and evaluated on four long-term field experiments with mineral P fertilization, farmyard manure as organic fertilizer and control plots without fertilization. The C dynamics and the P_av dynamics were modelled with overall good results. The relative RMSE for the C was below 10% for all treatments, while the relative RMSE for P_av was below 15% for most treatments. To accommodate for the rather small variety of available P-models, the presented CNP-model is designed for agricultural field sites with a relatively low data input, namely air temperature, precipitation, soil properties, yields and management practices. The CNP-model offers a low entry threshold model approach to predict the C-N and now the P dynamics of agricultural soils.     

Nitrogen turnover in a repeatedly manured arid subtropical soil: Incubation studies with 15N isotopes

Under the hot and moist conditions of irrigated agriculture in the arid subtropics, turnover of organic matter is high, which can lead to considerable carbon (C) and nitrogen (N) losses. Therefore, sustainable use of these soils requires regular manure application at high rates. To investigate the contribution of consecutive manure applications to an arid sandy soil to various soil N pools, goat manure was isotopically labeled by feeding ¹⁵N‐enriched Rhodes grass hay and applied to the soil during a two‐year field experiment. In the first year, soils received ¹⁵N‐labeled manure to distinguish between soil‐derived and manure‐derived N. In the second year, these plots were split for the application of either ¹⁵N‐labeled or unlabeled manure to discriminate N derived from previous (first year) and recent (second year) manure application. Soil samples (of control and ¹⁵N‐manured soil) were collected at the end of the first and the second year, and incubated in two laboratory experiments with labeled or unlabeled manure. At the beginning of Experiment 1, 7% of total N, 11% of K₂SO₄ extractable N, and 16% of microbial biomass N were derived from previously field‐applied manure. While the application of manure during incubation increased microbial biomass N by 225% and 410% in the control soil and the previously field‐manured soil, respectively, N₂O emissions were more affected on the control soil, releasing considerable amounts of the soil N‐pool (80% of total emissions). In Experiment 2, 4% of total N, 7% of K₂SO₄ extractable N, and 7% of microbial biomass N derived from previously applied manure, and 4%, 8%, and 3% from recently applied manure, respectively. Microbial biomass N and N₂O‐N derived from manure declined with time after manure application, whereas in Experiment 1 this tendency was only observed for microbial biomass N.     

整建制全要素全链条农业面源污染综合防治的思考及实践

加强农业面源污染综合防治是加快推进中国农业发展全面绿色转型,实现乡村全面振兴的重要任务。近年来,在多方的共同努力下,中国生态环境改善取得了一定成效,但重点流域的农业面源污染问题仍然突出。该研究在分析中国农业面源污染现状的基础上,通过资料收集、现场调研、专家座谈等多种方式梳理和分析了农业面源污染综合防治在治理主体、投入要素、技术体系与产业链条方面的瓶颈,解析了整建制全要素全链条农业面源污染综合防治的内涵,阐述了国家农业绿色发展先行区浙江平湖在践行整建制全要素全链条农业面源污染综合防治方面的先进做法及应用效果。总结了典型案例在网格化健全污染综合防治“整建制”、特色化延伸综合防治“全链条”、以及全方位保障污染综合防治“全要素”三个方面开展的相关工作,以期为探索形成农业面源污染综合防治整体解决方案,示范带动农业发展全面绿色转型提供支撑。     

Producing nitrogen (N) uptake maps in winter wheat by combining proximal crop measurements with Sentinel-2 and DMC satellite images in a decision support system for farmers

Responsive fertilisation of winter wheat (Triticum aestivum L.) is often adopted, with N applied two or three times between the developmental stages of tillering and booting. Satellite-based decision support systems (DSS) providing vegetation index maps calculated from satellite data are available to aid farmers in adjusting the topdressing nitrogen (N) rate site-specifically to the current season and to variations in growth conditions within the field. One example is the freely available CropSAT DSS used in Scandinavia, which provides farmers with raster maps of the modified soil-adjusted vegetation index (MSAVI2) calculated mainly from data obtained from satellites Sentinel-2 (ESA, EU) and DMC (DMCii Ltd, Guildford, UK). This study investigated the possibility of calibrating MSAVI2 maps with data from handheld proximal sensor measurements of N uptake covering the main agricultural regions in Sweden during growth stages Z30-45 on the Zadok scale, in order to facilitate farmers’ decisions on N rate. More than 200 N-sensor measurements acquired during 2015 and 2016 in seven different winter wheat cultivars were combined with MSAVI2 values from CropSAT. It was found that N uptake could be predicted in a general, national model, i.e. for sites and dates other than those for which the calibration model was parameterised, with a mean absolute error of 11–15?kg?N?ha^?1. A cultivar-specific model performed better than this general model, but a regional model showed no improvement compared with the model parameterised with national data. Vegetation indices calculated from the two narrow bands of Sentinel-2 in the red edge-near infrared region of the crop canopy reflectance spectrum proved to be promising alternatives to the broadband index MSAVI2. Based on the results, we suggest that data from a monitoring programme involving handheld N sensor measurements can be integrated with a satellite-based DSS to upscale N uptake information.     

Applicability of a combined staining method with fluorochromes for the visualization of microbial cells in a soil thin section

Staining of microbial cells in a soil thin section provides useful information about the role of soil as an ecological niche by relating the in situ distribution of microorganisms to the state of pores under undisturbed conditions. For technical improvement, we developed a procedure consisting of a combined staining method with 5-sulfofluorescein diacetate (SFDA), a metabolic type fluorochrome, and magnesium salt of l-anilino-8-naphthalene sulfonic acid (Mg-ANS), an adsorption type fluorochrome, in order to detect and differentiate the living microbial cells from the dead ones in a single soil thin section. Using images under a fluorescence microscope, we also examined the applicability of SFDA for staining microbial cells embedded in soil thin sections, which had seldom been attempted. Through this study, we confirmed the following facts: i) combined staining with SFDA and Mg-ANS can be achieved without major modification of the general procedure for thin section preparation, ii) staining with SFDA can be applied to soil thin sections, and iii) detection of in situ distribution and differential identification of the living and dead microbial cells may be possible by the proposed combined staining method.     

勺夹式花生小区单粒精量播种单体设计与试验

针对花生小区播种机播种尺寸差异较大种子时存在适应性差、单粒精播粒距合格率低等问题,该研究设计了一种基于STM32单片机控制的勺夹式花生小区单粒精量播种单体。采用先充种后投种的模式,利用夹持空间可调节的勺夹式排种器向双格盘播种总成内单粒排种,由STM32单片机控制光电传感器、增量式编码器以及步进电机等元件,实现有序充种和投种。根据播种时花生种子的运动轨迹,确定影响机具作业性能的主要参数为机具作业速度和投种口离地高度。以提高单粒精播粒距合格率,降低播种漏播率、重播率、破损率为目标,对机具作业参数进行单因素与双因素数值模拟分析,探究了机具作业速度、投种口离地高度以及二者交互作用对播种性能的影响。试验结果表明,机具作业速度0.9 m/s、投种口离地高度15 cm时的播种效果最佳：粒距合格率为96.20%、重播率为2.97%、破损率为0.50%、漏播率为0.33%,整机通过性和适用性良好,能够满足小区育种试验要求。该研究可为花生小区精量播种技术研发提供参考。     

Soil physical responses to novel rice cultural practices in the rice–wheat system: Comparative evidence from a swelling soil in Nepal

Soil puddling in advance of rice (Oryza sativa L.) transplanting disperses surface aggregates and generates compaction at depth. As a management scheme for rice, puddling is typically considered advantageous for maximizing resource availability and yield. However, some experimental findings suggest a conflict between edaphic conditions created by this establishment technique and the performance of subsequent non-rice crops like wheat (Triticum aestivum L.). At a site in the mid-hills region of Nepal on a silt loam soil with vertic characteristics, we compared the impact of six rice tillage (surface tillage—T₁, shank subsoiler—T₂, shank subsoiler + moldboard plough—T₃) and establishment (soil puddling + transplanting—TPR, direct seeding—DSR) combinations on soil physical properties over two cycles of the rice–wheat rotation. For the rice season, 0–20 cm saturated hydraulic conductivity (K_sat) in the DSR plots was 2.6 and 4.3 times higher than their TPR counterparts in the first (Y₁) and second (Y₂) years, respectively (TPR-Y₁ = 93 mm day⁻¹, DSR-Y₁ = 241 mm day⁻¹, TPR-Y₂ = 133 mm day⁻¹, DSR-Y₂ = 582 mm day⁻¹), whereas tillage method did not significantly influence K_sat in this soil layer. The impact of rice establishment method was reflected in higher TPR bulk densities in the 5–10 (DSR = 1.19 g cm⁻³, TPR = 1.24 g cm⁻³) and 10–15 cm (DSR = 1.24 g cm⁻³, TPR = 1.29 g cm⁻³) depth increments in the wet season. Although none of the treatments significantly influenced the position or thickness of the plough sole, penetration resistance profiles suggest that vertical fractures with reduced soil strength were created within the pan region by deep tillage (T₂ and T₃), although these features were not associated with higher hydraulic conductivities from 20 to 50 cm. As the soils dried at the end of the rice season, crack propagation in the deep tilled plots (T₂ and T₃) was more pervasive. During the wheat season, comparable bulk density profiles and soil moisture retention characteristics across the treatments suggest that many of the edaphic changes induced by contrasting rice tillage and establishment practices did not persist in the self-mulching, vertic soils at our site. Conversely, significant increases in K_sat among the DSR plots from Y₁ to Y₂ (Y₁ = 241 mm day⁻¹, Y₂ = 582 mm day⁻¹) imply a temporal element to soil structural regeneration with adoption of direct seeding.     

因地制宜地发展聚流型农业──以党家水流域为例谈干旱草原区小流域综合治理的方式与途径

干旱草原类型区在我国北部黄土高原地区占有相当大的面积，其主要特点是干旱，风沙，水土流失，地广人稀。如何在这类地区开展以小流域为单元的水土保持综合治理工作，促使群众早日脱贫致富，是一项十分迫切的任务，但以往还没有一个较成熟的办法。党家小水流域经过５年的水土保持综合治理试点，根据本区的特点，因地制宜和科学地用洪用沙，发展聚流型农业，取得十分显的效果，为干旱草原类型区开展小流域水土保持综合治理提供了新     

Soil quality and fertility in sustainable agriculture,with a contribution to the biological classification of agricultural soils

Soils and crops are particularly vulnerable to climate change and environmental stresses. In many agrosystems, soil biodiversity and ecosystem services provided by soils are under threat from a range of natural and human drivers. Agricultural soils are often subject to agronomic practices that disrupt soil trophic networks and make soils less productive in the long term. In this scenario, sustainable soil use aimed at improving plant/root status, growth and development plays a crucial role for enhancing the biological capacity of agricultural soils. This commentary paper is divided into the following four main sections: (i) the contentious nature of soil organic matter; (ii) soil biological quality/fertility; (iii) soil classification; and, (iv) which agricultural practices can be defined as sustainable? The published literature was analyzed within a holistic framework, with agrosystems considered as living systems where soil, vegetation, fauna and microorganisms co-evolve and are reciprocally influenced. Ultimately, this article will suggest a better stewardship of agricultural soils as a natural capital.