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At present, organic fertilizers are not widely used in intensive arable agriculture, and not much is known about their effects on crop nutrition. In a field experiment at Rothamsted, UK, anaerobic digestate (AD), compost, farmyard manure (FYM), straw, and mixes of amendment + straw, were applied at: 1, 1.75, 2.5 or 3.5 t carbon ha−1, with all plots receiving the same input of mineral fertilizer. After five seasons of application, plots receiving non-straw amendments had greater straw and grain yield of 28% and 18% respectively, and plots receiving the highest amendment rate had a 37% higher straw and 23% higher grain yield, compared to control plots. Whereas, the straw-only amendment did not increase yield compared to the control. The concentrations of secondary and micro nutrients in the crop, particularly P, Ca, and S in the straw, and P and Fe in the grain, were significantly greater in the crop receiving non-straw amendment compared to the control. Interestingly K, Fe, and Zn were greater in the crop straw treated with the straw-only amendment. Therefore ‘biomass dilution’ of secondary and micro nutrients did not occur in the higher-yielding amended plots after five seasons, and organic fertilizers would improve the quality of high-yielding, intensively produced crops. The study also demonstrates that portable x-ray fluorescence (pXRF) could be a reliable, cost-effective tool for screening potential organic fertilizers.

Soil fertility is at risk in intensive cropping systems when using an exclusive regime of inorganic fertilisers without returning sufficient organic matter to the soil. Our objective was to evaluate the long-term effects of commonly used organic amendments interacting with different rates of inorganic nitrogen fertiliser on crop yields of winter wheat. Yield data from winter wheat were collected for five seasons between 2013 and 2019 from a continuous field trial based at Rothamsted Research, SE England. Organic amendments (anaerobic digestate, compost, farmyard manure, and straw at a rate of 0 and 2.5 ton C per hectare) and five rates of inorganic nitrogen fertiliser (NH 4 NO 3 at 0, 80, 150, 190, 220 kg N ha −1 ) were applied to winter wheat grown in an arable rotation. At the same inorganic N rate, grain yields for the different organic amendment treatments (excluding the straw treatment) were statistically similar but significantly greater than the unamended control treatment. The nitrogen rate required for optimum yields tended to be lower in plots receiving a combination of organic amendments and mineral fertiliser. Based on the observed and modelled response functions, organic amendments excluding straw increased maximum achievable yields compared to non-amended controls. The size of the effect varied between seasons and amendments (+4.6 to +19.0% of the control yield), increasing the mean maximum achievable yield by 8.8% across four seasons. We conclude that the application of organic amendments can increase the yield potential in winter wheat substantially over what is achievable with inorganic fertiliser only.

A farmer's decision on whether to control a pest is usually based on the perceived threat of the pest locally and the guidance of commercial advisors. Therefore, farmers in a region are often influenced by similar circumstances, and this can create a coordinated response for pest control that is effective at a landscape scale. This coordinated response is not intentional, but is an emergent property of the system. We propose a framework for understanding the intrinsic feedback mechanisms between the actions of humans and the dynamics of pest populations and demonstrate this framework using the European corn borer, a serious pest in maize crops. We link a model of the European corn borer and a parasite in a landscape with a model that simulates the decisions of individual farmers on what type of maize to grow. Farmers chose whether to grow Bt-maize, which is toxic to the corn borer, or conventional maize for which the seed is cheaper. The problem is akin to the snow-drift problem in game theory; that is to say, if enough farmers choose to grow Bt maize then because the pest is suppressed an individual may benefit from growing conventional maize. We show that the communication network between farmers' and their perceptions of profit and loss affects landscape scale patterns in pest dynamics. We found that although adoption of Bt maize often brings increased financial returns, these rewards oscillate in response to the prevalence of pests.

Soil has supported terrestrial food production for millennia; however, agricultural intensification may affect its resilience. Using a systems-thinking approach, we reviewed the impacts of conventional-agriculture practices on soil resilience and identified alternative practices that could mitigate these effects. We found that many practices only affect soil resilience with their long-term repeated use. Lastly, we ranked the impacts that pose the greatest threats to soil resilience and, consequently, food and feed security.

1. Focusing on food production, in this paper we define resilience in the food security context as maintaining production of sufficient and nutritious food in the face of chronic and acute environmental perturbations. In agri-food systems, resilience is manifest over multiple spatial scales: field, farm, regional and global. Metrics comprise production and nutritional diversity as well as socioeconomic stability of food supply. 2. Approaches to enhancing resilience show a progression from more ecologically based methods at small scales to more socially based interventions at larger scales. At the field scale, approaches include the use of mixtures of crop varieties, livestock breeds and forage species, polycultures and boosting ecosystem functions. Stress-tolerant crops, or with greater plasticity, provide technological solutions. 3. At the farm scale, resilience may be conferred by diversifying crops and livestock and by farmers implementing adaptive approaches in response to perturbations. Biodiverse landscapes may enhance resilience, but the evidence is weak. At regional to global scales, resilient food systems will be achieved by coordination and implementation of resilience approaches among farms, advice to farmers and targeted research. 4. Synthesis. Threats to food production are predicted to increase under climate change and land degradation. Holistic responses are needed that integrate across spatial scales. Ecological knowledge is critical, but should be implemented alongside agronomic solutions and socio-economic transformations.

AimsThe home-field advantage (HFA) hypothesis predicts faster decomposition of plant residues in home soil compared to soils with different plants (away), and has been demonstrated in forest and grassland ecosystems. It remains unclear if this legacy effect applies to crop residue decomposition in arable crop rotations. Such knowledge could improve our understanding of decomposition dynamics in arable soils and may allow optimisation of crop residue amendments in arable systems by cleverly combining crop-residue rotations with crop rotations to increase the amount of residue-derived C persisting in soil.MethodsWe tested the HFA hypothesis in a reciprocal transplant experiment with mesh bags containing wheat and oilseed rape residues in soils at three stages of a short-rotation cropping system. Subsets of mesh bags were retrieved monthly for six months to determine residue decomposition rates, concomitantly measuring soil available N, microbial community structure (phospholipid fatty acid analysis), and microbial activity (Tea Bag Index protocol) to assess how plants may influence litter decomposition rates via alterations to soil biochemical properties and microbial communities.ResultsThe residues decomposed at similar rates at all rotational stages. Thorough data investigation using several statistical approaches revealed no HFA within the crop rotation. Soil microbial community structures were similar at all rotational stages.ConclusionsWe attribute the absence of an HFA to the shortness of the rotation and soil disturbance involved in intensive agricultural practices. It is therefore unlikely that appreciable benefits could be obtained in short conventionally managed arable rotations by introducing a crop-residue rotation.

Bioenergy developments could lead to large-scale removal of cereal straw from fields, with consequences for soil organic carbon (SOC) and related properties. In 25 experiments of 6 to 56 yr duration there was a trend for SOC and total soil N content to increase where straw was incorporated annually. However the increases were only significant in six experiments and were <10% in the majority of cases. Increases in microbial biomass C or N were always proportionately greater than for SOC or N. In simulations of annual straw incorporation using the RothC model, 90% of the microbial biomass C increase in 100 yr was reached within 20 yr as biomass C moves toward a new equilibrium value more rapidly than total SOC. Simulations also showed that if straw was removed in 50% of years, SOC and biomass C increases were about 50% of those with annual straw incorporation. There is considerable evidence that small changes in total SOC have disproportionately large impacts on soil physical properties such as aggregate stability, water infiltration rate, and plow draft and that microbial activity is crucial in the formation of stable aggregates. We conclude that, although changes in SOC resulting from addition or removal of straw are small, it would be unwise to remove straw every year as this is likely to lead to deterioration in soil physical properties. Local assessments are required to determine the frequency of straw removal that is acceptable for soil functioning; this will influence the capacity of bioenergy installations.

To manage agricultural landscapes more sustainably, we must understand and quantify the synergies and trade-offs between environmental impact, production, and other ecosystem services. Models play an important role in this type of analysis as generally it is infeasible to test multiple scenarios by experiment. These models can be linked with algorithms that optimise for multiple objectives by searching a space of allowable management interventions (the control variables). Optimisation of landscapes for multiple objectives can be computationally challenging, however, particularly if the scale of management is typically smaller (e.g. field scale) than the scale at which the objective is quantified (landscape scale) resulting in a large number of control variables whose impacts do not necessarily scale linearly. In this paper, we explore some practical solutions to this problem through a case study. In our case study, we link a relatively detailed, agricultural landscape model with a multiple-objective optimisation algorithm to determine solutions that both maximise profitability and minimise greenhouse gas emissions in response to management. The optimisation algorithm combines a non-dominated sorting routine with differential evolution, whereby a ‘population’ of 100 solutions evolves over time to a Pareto optimal front. We show the advantages of using a hierarchical approach to the optimisation, whereby it is applied to finer-scale units first (i.e. fields), and then the solutions from each optimisation are combined in a second step to produce landscape-scale outcomes. We show that if there is no interaction between units, then the solution derived using such an approach will be the same as the one obtained if the landscape is optimised in one step. However, if there is spatial interaction, or if there are constraints on the allowable sets of solutions, then outcomes can be quite different. In these cases, other approaches to increase the efficiency of the optimisation may be more appropriate—such as initialising the control variables for half of the population of solutions with values expected to be near optimal. Our analysis shows the importance of aligning a policy or management recommendation with the appropriate scale.

Crop residues are valuable soil amendments in terms of the carbon and other nutrients they contain, but the incorporation of residues does not always translate into increases in nutrient availability, soil organic matter (SOM), soil structure, and overall soil fertility. Studies have demonstrated accelerated decomposition rates of chemically heterogeneous litter mixtures, compared to the decomposition of individual litters, in forest and grassland systems. Mixing high C:N ratio with low C:N ratio amendments may result in greater carbon use efficiency (CUE) and nonadditive benefits in soil properties. We hypothesised that nonadditive benefits would accrue from mixtures of low-quality (straw or woodchips) and high-quality (vegetable waste compost) residues applied before lettuce planting in a full factorial field experiment. Properties indicative of soil structure and nutrient cycling were used to assess the benefits from residue mixtures, including soil respiration, aggregate stability, bulk density, SOM, available N, potentially mineralisable N, available P, K, and Mg, and crop yield. Soil organic matter and mineral N levels were significantly and nonadditively greater in the straw–compost mixture compared to individual residues, which mitigated the N immobilisation occurring with straw-only applications. The addition of compost significantly increased available N, K, and Mg levels. Together, these observations suggest that greater nutrient availability improved the ability of decomposer organisms to degrade straw in the straw–compost mixture. We demonstrate that mixtures of crop residues can influence soil properties nonadditively. Thus, greater benefits may be achieved by removing, mixing, and reapplying crop residues than by simply returning them to the soils in situ.

Although it is well-known that high soil strength is a constraint to root and shoot growth, it is not clear to what extent soil strength is the main physical stress that limits crop growth and yield. This is partly because it is difficult to separate the effects of soil drying and high soil strength, which tend to occur together. The aim of this paper is to test the hypothesis that for two different soil types, yield is closely related to soil strength irrespective of difference in soil water status and soil structure. Winter (Triticum aestivum L., cv. Hereward) and spring wheat (cv. Paragon) were grown in the field on two soils, which had very different physical characteristics. One was loamy sand and the other sandy clay loam; compaction and loosening treatments were applied in a fully factorial design to both. Crop growth and yield, carbon isotope discrimination, soil strength, water status, soil structure and hydraulic properties were measured. The results showed that irrespective of differences in soil type, structure and water status, soil strength gave a good prediction of crop yield. Comparison with previous data led to the conclusion that, irrespective of whether it was due to drying or compaction (poor soil management), soil strength appeared to be an important stress that limits crop productivity.