Adept use of fertilizers is critical if sustainable development goal two of zero hunger and agroecosystem resilience are to be achieved for African smallholder agroecosystems. These heterogeneous systems are characterized by poor soil health mainly attributed to soil nutrient depletion. However, conventional methods do not take into account spatial patterns across geographies within agroecosystems, which poses great challenges for targeted interventions of nutrient management. This study aimed to develop a novel population-based farm survey approach for diagnosing soil nutrient deficiencies. The approach embraces principles of land health surveillance of problem definition and rigorous sampling scheme. The advent of rapid soil testing techniques, like infrared spectroscopy, offers opportune avenues for high-density soil and plant characterization. A farm survey was conducted on 64 maize fields, to collect data on soil and plant tissue nutrient concentration and grain yield (GY) for maize crops, using hierarchical and purposive sampling. Correlations between soil test values with GY and biomass were established. The relationship between GY, soil NPK, and the tissue nutrient concentrations was evaluated to guide the setting up of localized critical soil test values. Diagnosis Recommendation Integrated System (DRIS) indices for total nitrogen (N), total phosphorus (P), and total potassium (K) were used to rank and map the prevalence of nutrient limitations. A positive correlation existed between plant tissue nutrient concentration with GY with R2 values of 0.089, 0.033, and 0.001 for NPK, respectively. Soil test cut-off values were 0.01%, 12 mg kg-1, 4.5 cmolc kg-1 for NPK, respectively, which varied slightly from established soil critical values for soil nutrient diagnostics. N and K were the most limiting nutrients for maize production in 67% of sampled fields. The study demonstrates that a population-based farm survey of crop fields can be a useful tool in nutrient diagnostics and setting priorities for site-specific fertilizer recommendations. A larger-scale application of the approach is warranted.
Tag: agroecosystems
Microplastics as an emerging threat to plant and soil health in agroecosystems
Microplastics (MPs, <5 mm in diameter) have been widely recognized as a critical environmental issue due to their extensive use and low degradation rate. Based on current evidence, our aim is to evaluate whether MPs represent an emerging threat to plant-soil health in agroecosystems. We assess the ecological risks to plant-microbe-soil interactions associated with MPs and discuss the consequences of MPs on soil carbon (C), nutrient cycling, as well as greenhouse gas emissions in agroecosystems. We also identify knowledge gaps and give suggestions for future research. We conclude that MPs can alter a range of key soil biogeochemical processes by changing its properties, forming specific microbial hotspots, resulting in multiple effects on microbial activities and functions. Mixed effects of MPs on plant growth and performance can be explained by the direct toxicity of MPs or the indirect alteration in soil physical structures and microbial communities (i.e. symbiotic arbuscular mycorrhizal fungi). Because of the diverse nature of MPs found in soils, in terms of polymer type, shape and size, we also see differing effects on soil organic matter (SOM) decomposition, nutrient cycling, and greenhouse gases production. Importantly, increased bioavailable C from the decomposition of biodegradable MPs, which enhances microbial and enzymatic activities, potentially accelerates SOM mineralization and increases nutrient competition between plant and microbes. Thus, biodegradable MPs appear to pose a greater risk to plant growth compared to petroleum-based MPs. Although MPs may confer some benefits in agroecosystems (e.g. enhanced soil structure, aeration), it is thought that these will be far outweighed by the potential disbenefits.
Deciphering microplastic ecotoxicology: impacts on crops and soil ecosystem functions
Review on microplastic toxicity in agroecosystems is scarce. Thus, we develop a conceptual model (based on literature to date) that describes various microplastic effects using a size-scale. We also classify crops depending on their observed responses, and discuss several conceptual mechanisms of soil functions. The model shows that microplastic effects on crops can be positive, toxic, lethal and no-effect. Predominantly, microfibers in a wide range of sizes can positively affect crops. However, toxic effects of microplastics with/without other pollutants are more common at different sizes. Surprisingly, biodegradable plastic effects are lethal, calling into question their environmental friendliness. No-effect on crops is also possible but less observed. Unlike other crops (e.g., wheat, maize and bean), only onion seems resistant to microplastics. Crop uptake of micro/nanoplastic demands a clear benchmark to ensure food-safety. Furthermore, mixed effects are observed on soil functions. Alternation in soil enzymes and litter decomposition can affect nutrients and organic matter biogeochemistry. Hydrophobicity can be induced by increasing evaporation. Shifts in microbial community structure and activities are inevitable.
Building effective policies to conserve pollinators: translating knowledge into policy
Pollination management recommendations are becoming increasingly precise, context-specific and knowledge-intensive. Pollination is a service delivered across landscapes, entailing policy constructs across agricultural landscapes. Diversified farming practices effectively promote pollination services. Yet it remains difficult to secure large-scale uptake by farming communities. A strong foundation upon which to base policy formulation stems from respecting the perspective of farmers and local communities on the need to conserve pollinators, alongside scientific understanding. Ecological intensification resonates with both indigenous knowledge, local communities and scientific understanding. It emphasizes that the regulating functions of nature require both landscape-level agroecosystem design and recognition of the complexity of agricultural systems. Facilitating ecological intensification across landscapes requires collective decision-making, with institutional innovation in local structures and food system governance.
Unraveling consequences of soil micro- and nano-plastic pollution on soil-plant system: Implications for nitrogen (N) cycling and soil microbial activity
Micro- and nano-plastics have widely been recognized as major global environmental problem due to its widespread use and inadequate waste management. The emergence of these plastic pollutants in agroecosystem is a legitimate ecotoxicological concerns for food web exchanges. In agriculture, micro/nano plastics are originated from a variety of different agricultural management practices, such as the use of compost, sewage sludge and mulching. A range of soil properties and plant traits are affected by their presence. With the increase of plastic debris, these pollutant materials have now begun to demonstrate serious implications for key soil ecosystem functions, such as soil microbial activity and nutrient cycling. Nitrogen (N) cycle is key predictor of ecological stability and management in terrestrial ecosystem. In this review, we evaluate ecological risks associated with micro-nano plastic for soil-plant system. We also discuss the consequence of plastic pollutants, either positive or negative, on soil microbial activities. In addition, we systematically summarize both direct and hypothesized implications for N cycling in agroecosystem. We conclude that soil N transformation had showed varied effects resulting from different types and sizes of plastic polymers present in soil. While mixed effects of microplastic pollution on plant growth and yield have been observed, biodegradable plastics have appeared to pose greater risk for plant growth compared to chemical plastic polymers.
Biochar producing gasifier cooking system for enhanced fuelwood efficiency, women’s wellbeing and sustainable agroecosystems in Kenya
Gasifier cookstoves produce heat for cooking through gasification of dry biomass at high temperature and produce charcoal as a by-product, which is used for further cooking or as biochar for soil amendment. Compared to conventional cooking practices, the gasifier is a cleaner cooking option that improves efficiency, and reduces exposure to smoke and need for firewood collection, a tiring and time-consuming exercise. The cookstove is suitable for fuelling with small pieces of wood, such as prunings from agroforestry trees reducing need for collection of forest residues allowing their accumulation into soil organic matter consequently enhancing biodiversity. When applied to soil, biochar helps to improve the crop yields and when used as fuel, households save money on the purchase of alternative fuels. Users, however, have faced challenges with fuel preparation, lighting and reloading fuel, especially when the fuel chars before the food is ready.
Monitoring Behaviour Change of Farmers to Support Ecologically Friendly Agricultural Management Program in Peatland Ecosystems
Conserving peatland areas requires the commitment and the capacities of all stakeholders, including farmers living within the areas. Two business models, agro-silvo-fishery and Trigona apiculture, have been established in a demonstration plot in the peatland ecosystem of Baru Village, Banyuasin, South Sumatra, as new options for farmers to improve livelihoods while also managing peatland sustainably. Trainings on sustainable production, post-harvest, and markets were provided to the rice-based farmers to help them manage new livelihood options. Monitoring the behavioural transformation of farmers engaged in the two business model pilots is a crucial aspect of the program. This is accomplished using the ADKAR approach, which posits that attaining long-term behavioural change involves progressing through stages of Awareness, Desire, Knowledge, Ability, and Reinforcement. A survey instrument was created to monitor farmers behaviour changes in (i) collective action, and (ii) managing agroecosystems sustainably, reflecting collaborative effort required to conserve peatland. Prior to the intervention program, a baseline survey (n=43) was conducted to record farmers’ current knowledge. The findings revealed that most farmers (60%) never joined a group but motivated to actively participate, whereas 25% of farmers had actively participated in groups and were eager to urge other farmers to join. Most farmers (52%) acknowledge the significance of safeguarding peatland areas but lack the knowledge to do so, whereas 25% have implemented ecologically friendly agricultural management in peatland areas. When the program began, none of the farmers were involved in agro-silvo-fishery or Trigona apiculture. According to a mid-program assessment aimed at recording the performance of the business models, 3 farmers have adopted apiculture with a total of 101 beehives. While none of the farmers adopt agro-silvo-fishery individually, 5 farmers produced organic fertilizer individually using the training program’s new competence. However, producing organic fertilizer as collective action was halted, suggesting farmers partiality to work individually rather than collectively. A final survey to assess behavioural changes is planned towards the end of the program next year. The ADKAR approach for monitoring farmers’ behavior change is useful for evaluating the performance of intervention programs and seek solutions to ensure it is aligned with the landscape level NRM goals.