Using Hermetia illucens to process Ugandan waragi waste

Waragi, a form of homemade gin, is produced throughout Uganda in both legal and illegal breweries. Waste produced during the illegal brewing process is predominantly disposed of via indiscriminate dumping into surrounding environments and reports from local communities have indicated this to be harmful to crops and livestock. The larvae of Hermetia illucens are documented to consume a wide range of otherwise unappealing waste products. In addition to this, the prepupal stages of the larvae can serve as a high-quality protein feed for animal livestock. Therefore, the feasibility of the larvae of H. illucens to digest waragi waste was evaluated. A dietary toxicity trial was run to establish an LC50 value for waragi inclusion in larval diets. This was followed by a larger scale trial utilising waragi waste in combination with various in situ available feed stuffs to further assess the viability of processing waragi waste using H. illucens. Larvae were able to eat diets composed of up to 85% waragi waste without any significant impact on survival or growth. When combined with locally available feed sources, e.g. chicken offal, cottonseed cake, sunflower meal or groundnut cake, larvae showed high survival and growth rates on diets including 25% waragi waste. Results indicate that H. illucens larvae may be a useful tool in processing waragi waste

The effect of an initial high-quality feeding regime on the survival of Gryllus bimaculatus (black cricket) on bio-waste

Previous studies have led to claims that insects can offer a solution to several food security hurdles, one of which is the processing of food waste. However, although it has been demonstrated that some insects survive well on bio-waste (e.g. Hermetia illucens), no study, has to date, demonstrated success rearing species more commonly used for human consumption, such as crickets, on biowaste from hatching. This trial aimed to establish if the black cricket, Gryllus bimaculatus, can be reared successfully on bio-waste from hatching. Since, in other livestock sectors it has been established that nutritional requirements vary with age and that diet must be altered accordingly to achieve the best growth, e.g. chick feed to layer mash in chickens, the present trial used a similar feeding regime of an initially high-quality feed to see if this allowed the subsequent survival of crickets on low quality bio-waste products. Pilot trials have demonstrated poor to no survival on beer waste and cow manure and mid-level survival on unprocessed vegetable waste with chicken feed as the control. Based on this, feed regimes of either 1 or 2 weeks high quality feed (chicken feed) and then either 2 or 3 weeks of low quality feed (beer waste or vegetable waste) were tested. Results showed that even 1 week of high quality feed makes a significant difference in survival and end size of crickets subsequently reared on low-quality bio-waste

Impact of heat processing on the nutritional content of Gryllus bimaculatus (black cricket)

Insects are increasingly suggested as a potential novel solution to global nutrition challenges. However, limited research is available on what impact varied rearing and processing methods ultimately have on the nutritional content of edible insects. This trial examines the impact of six distinct diets, some based on bio-waste, on the nutritional content of the commonly consumed cricket, Gryllus bimaculatus. Results showed a significant impact of diet on the protein, micronutrient and fatty acid content of crickets. However, the majority of these relationships were not distinctly linear; in general, an increase in a certain area in the diet did not equate to the same increase in the crickets. The only nutritional element with a direct dietary relationship was α-linolenic acid, which increased as dietary content did. Following on from this the effect of various levels of heat processing on subsequent nutritional profile was studied. Results showed that different temperatures, from freeze drying up to 120℃ had no significant impact on protein or micronutrient content. However, the fatty acid content was significantly impacted by higher temperature processing. Freeze-drying crickets conserved significantly more of the longer chained polyunsaturated fatty acids than drying at 120℃. It is evident from ongoing research that insects hold potential as a source of essential nutrients and fatty acids, but when reared on low-quality feed and processed at high temperatures they are unlikely to be of any more nutritional benefit than foods presently used in nutritional interventions

High-Yielding Corn Response to Applied Phosphorus, Potassium, and Sulfur in Nebraska

Nutrient management recommendations may change as yield levels and efficiency of crop production increase. Recommendations for P, K, and S were evaluated using results from 34 irrigated corn (Zea mays L.) trials conducted in diverse situations across Nebraska. The mean yield was 14.7 Mg ha-1 with adequate fertilizer applied. Th e median harvest index values were 0.52, 0.89, 0.15, and 0.56 for biomass, P, K, and S, respectively. Median grain yields were 372, 49, and 613 kg kg-1 of above-ground plant uptake of P, K, and S, respectively. The estimated critical Bray-1 P level for corn response to 20 kg P ha-1 was 20 mg kg-1 when the previous crop was corn compared with 10 mg kg-1 when corn followed soybean [Glycine max (L.) Merr.]. Soil test K was generally high with only three site-years kg-1. Over all trials, application of 40 kg K ha-1 resulted in a 0.2 Mg ha-1 mean grain yield decrease. Application of 22 kg S ha-1 did not result in significant yield increase in any trial. Soil test results accounted for twice as much variation in nutrient uptake when soil organic matter (SOM) and pH were considered in addition to the soil test nutrient values. The results indicate a need to revise the current recommendation for P, to maintain the current K and S recommendations, and to use SOM and pH in addition to soil test nutrient values in estimating applied nutrient requirements for irrigated high yield corn production

High-Yielding Corn Response to Applied Phosphorus, Potassium, and Sulfur in Nebraska

Nutrient management recommendations may change as yield levels and efficiency of crop production increase. Recommendations for P, K, and S were evaluated using results from 34 irrigated corn (Zea mays L.) trials conducted in diverse situations across Nebraska. The mean yield was 14.7 Mg ha-1 with adequate fertilizer applied. Th e median harvest index values were 0.52, 0.89, 0.15, and 0.56 for biomass, P, K, and S, respectively. Median grain yields were 372, 49, and 613 kg kg-1 of above-ground plant uptake of P, K, and S, respectively. The estimated critical Bray-1 P level for corn response to 20 kg P ha-1 was 20 mg kg-1 when the previous crop was corn compared with 10 mg kg-1 when corn followed soybean [Glycine max (L.) Merr.]. Soil test K was generally high with only three site-years kg-1. Over all trials, application of 40 kg K ha-1 resulted in a 0.2 Mg ha-1 mean grain yield decrease. Application of 22 kg S ha-1 did not result in significant yield increase in any trial. Soil test results accounted for twice as much variation in nutrient uptake when soil organic matter (SOM) and pH were considered in addition to the soil test nutrient values. The results indicate a need to revise the current recommendation for P, to maintain the current K and S recommendations, and to use SOM and pH in addition to soil test nutrient values in estimating applied nutrient requirements for irrigated high yield corn production

The nitrogen economy of rice-livestock systems in Uruguay

Over many decades there has been a global trend away from mixed farming and integrated crop-livestock systems to more-intensive single commodity systems. This has distorted local and global nutrient balances, resulting in environmental pollution as well as soil nutrient depletion. Future food systems should include integrated crop-livestock systems with tight nutrient budgets. For nitrogen (N), detailed understanding of processes, fluxes – including of gaseous forms – and budgets at a component level is needed to design productive systems with high N use efficiency (NUE) across the full nutrient chain. In Uruguay, a unique rice-livestock system has been practiced for over 50 years, attaining a high production level for rice (mean grain yields > 8 Mg ha−1) and an average level for livestock (120 kg liveweight gain ha−1 y−1). The aim of this study was to quantify the components of the N balance and NUE of this system, so as to understand its long-term sustainability, and draw conclusions for other regions. Analysis of country-level statistics for each component over the last 16 years shows tight N balances of +3.49, +2.20 and +2.22 kg N ha−1 yr−1 for rice, livestock and the whole system, respectively. Based on average values of N retained in edible food products, NUE values were 65.7, 13.2 and 23.1% for rice, livestock and the whole system, respectively. While NUE of livestock was unchanged over the period, NUE of the rice component decreased due to increasing fertiliser use. Further gains in N efficiency are possible by better integrating the system components. Actions to increase system level NUE include raising pasture and livestock productivity and controlling the increasing use of N fertilisers in rice. Tightly integrated crop-livestock systems can play a significant role in re-shaping global agriculture towards meeting food security, environmental and socioeconomic sustainability targets

Fertilizing Nature: A Tragedy of Excess in the Commons

Why has nitrogen fertilizer use declined in some countries while increasing in others, despite significant environmental harm? Proper crop management strategies offer environmental and economic benefits without sacrificing yields

Fertilizer and Soil Health in Africa The Role of Fertilizer in Building Soil Health to Sustain Farming and Address Climate Change

Summary Soil health is commonly defined as the ability to generate sufficient crop yields while maintaining the future productive capacity of soils and the ecosystem services soils regulate and deliver. However, less consensus exists on indicators to assess soil health and its changes over time and space, although soil organic carbon (SOC) is generally acknowledged as a key indicator. In the context of this paper, soil health status is equated with SOC status. Current SOC conditions are influenced by soil properties and climate. Under smallholder farming conditions, SOC is variable and affected by past crop and soil management practices, which are influenced by farmer typology. Although SOC content under cropland is a maximum of 60-70% of that under natural vegetation, there is substantial scope to increase it in smallholder farming conditions. A conceptual framework relating to fertilizer, crop productivity, and soil health is presented here. While fertilizer application commonly results in a substantial increase in crop yield at various scales, a key indicator of fertilizer use, agronomic efficiency (AE), is often observed to be lower than relatively easily achievable values under well-managed conditions, caused by a diversity of factors. Low AE values do not necessarily result in greater greenhouse gas (GHG) emissions because of the low fertilizer application rates in sub-Saharan Africa (SSA), though increases in GHG emissions are likely with increases in fertilizer use. Crop response to organic inputs is substantially lower although organic inputs increase SOC content, which usually results in greater AE values relative to sole application of fertilizer. Increases in crop productivity are associated with increases in SOC, though the relationship is weak and efforts besides fertilizer application itself are required. That said, N(PK) fertilizer has had a positive effect on SOC in most parts of the world except SSA, an observation corroborated by an analysis of past and ongoing long-term experiments, likely related to the low and erratic use of fertilizer in the region. While fertilizer use can be an entry point to increasing soil health, this will not likely happen on degraded soils where responses to fertilizer are limited. In such cases, investments to rehabilitate degraded soils should come first. Several approaches can be followed to determine best fertilizer recommendations, while recognizing nutrients needs by crops and soil-specific properties. Site-specificity commonly requires an assessment of the soil fertility status of a particular field, and analytical tools now allow for the development of locally relevant recommendations at scale with some early successes. While organic inputs do positively impact SOC, attractive options to increase organic inputs in smallholder farming systems are limited and mostly related to in-situ production, with an important emphasis on multi-purpose legumes. Climate adaptation is facilitated by healthy Fertilizer and Soil Health in Africa 2 soils and requires fertilizer to be combined with other crop, soil, and water management practices (Wortmann and Stewart, 2021). While low yields are linked to the ecological yield gap, whereby the potential productivity of crops is set by biological factors, input and output prices determine the economic yield gap, which is usually quite lower than the former because of unfavourable ratio of fertilizer prices to crop product prices. Even though profitability is a key driver of impact, many other factors affect the adoption of appropriate fertilizer and soil health recommendations, including farmers’ production objectives, resource endowment, land tenure, and access to markets. A main bottleneck in engaging smallholder farmers in soil health-restoring practices is the relatively large amount of time such practices take to deliver benefits that are visible to farmers. In the absence of incentive programs, farmers require short-term benefits, generated within their farming systems. Furthermore, associated advice on complementary practices to fertilizer use increases the complexity of information to be conveyed to farmers. Scaling models have moved toward the delivery of bundled services, often digitally enabled, to address challenges with communicating complex information and the necessary complementary crop and soil management practices. Targeted policy interventions can support the delivery of broad digitally enabled fertilizer management recommendations and the creation of conditions that enable smallholder farmers to implement these recommendations at scale. A number of recommendations have been generated from the scientific information, covered under the following headings: (1) key elements of a Fertilizer and Soil Health Action Plan; (2) development of quantitative indicators and targets of soil health; (3) addressing climate change requires choices; (4) incentivizing farmers; (5) soil health investments, which require localized actions (think global, act local); and (6) not only fertilizers, but also auxiliary interventions, as defined by the Integrated Soil Fertility Management (ISFM) approach. Action is needed today to reverse the downward spiral of low and inefficient fertilizer use, resulting in low yields and declining soil health