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Crop management recommendations that are tailored to local conditions offer promise for improved farmer livelihoods, input use efficiency, and crop output. An important step towards achieving localized recommendations is to establish repeatable, low-cost approaches to diagnosing nutrient constraints. Satellite remote sensing is particularly attractive in this context for its ability to monitor crop conditions and provide yield estimates at much lower expenses than extensive field measurements. Here we evaluate nutrient constraints for maize yields in central Mexico by utilizing an extensive field dataset on soil properties, fertilizer practices, and yields that were collected as part of the MasAgro program. We also compare insights from satellite-based yield estimates to those derived from crop-cut yields. Overall we find strong positive associations between maize yields and fertilizer inputs for N, P, and K in farms at lower elevations, characterized by larger, commercial farms. In higher elevations where farms are typically smaller and use less responsive varieties, we still find significant but slightly less positive associations with N and P. In both regions, we observe significant negative associations between yield and soil pH, consistent with an unmet need for micronutrient fertilizers in the region. Satellite-based yields were able to reproduce the positive associations and large yield response to fertilizer N and P, but were not sensitive enough to detect significant effects of secondary factors, namely fertilizer K and soil pH. We conclude by suggesting specific interventions that could be experimentally tested in the region. [ABSTRACT FROM AUTHOR]

Abstract: This article reports on field experiments with 4 different rotations that are commonly used throughout Haryana in NW India (rice–wheat, cotton–wheat, pearl millet–wheat, cluster bean–wheat), where we assess wheat yield and chapatti quality measures with different crop establishment methods and input of micronutrients. In a series of experiments conducted on farmers’ fields in 2007–2008 and 2008–2009 winter seasons, the addition of micronutrients and sulphur to wheat crops was used alongside the use of a common farmer practice, the use of farmyard manure (FM) and best practice inputs of N-fertilizer (150kgNha−1), P-fertilizer (26kgPha−1) and K-fertilizer (33kgKha−1). The application of FM with the recommended NPK treatment produced 9–13% more grain yield in the rice–wheat rotation when compared with the recommended NPK only treatment. Given that the farm sites used here had low levels of soil P, this may suggest that the recommended rate of 26kgPha−1 for the rice–wheat rotation is too low. The addition of FM did not improve any grain quality outcomes at any of the sites. There were no yield responses with S application with any of the rotations but the S input resulted in more wheat protein from all sites (average 8%). The addition of S also gave similar increases in grain hardness and the chapatti score. The inclusion of micronutrients (boron, copper, iron, zinc and manganese) with the recommended NPK treatment did not increase the grain yield at any of the sites when compared with the recommended NPK treatment, and sometimes, but not consistently, gave small responses with protein, grain hardness and chapatti score. In concurrent experiments wheat growth and chapatti quality were compared in zero till and conventionally sown systems, and with and without S fertilizer amendment. Here too there were no grain yield responses to S, and the protein, grain hardness and chapatti score were increased with S addition. Grain yields with zero till and conventional wheat were similar in the rice–wheat system and zero till sowing resulted in small increases in yield at all of the non-rice sites. The grain from the zero till treatments had higher protein (1–3%), grain hardness (3–10%) and chapatti score from all 4 rotations. Zero till has substantial adoption in the rice–wheat districts of Haryana but little farmer awareness and adoption in the areas where the other rotations are used. The data given here show that with zero tillage and an integrated practice of nutrient management farmers in Haryana can maintain grain yields of wheat whilst improving quality outcomes. [Copyright &y& Elsevier]

Abstract: In aerobic rice, adapted varieties are grown in non-flooded and non-saturated soil. In the Philippines, occasional poor crop growth and yield failures have been reported. To investigate the underlying causes, we conducted 3 pot experiments using the aerobic rice variety Apo and so-called “sick soil” from a field where aerobic rice failed in four successive dry seasons. The (experimental) aerobic rice crop replaced the farmer''s practice of wet-season lowland rice and dry season sweet potato cropping. We hypothesized that abiotic factors, especially the inter-relationship between high soil pH and impaired micronutrient uptake, restrict plant growth, and that ammonium sulfate has an ameliorating effect. Experiment 1 used “sick soil” collected from around yellowing and dying plants in a field experiment with aerobic rice yield failure, and “healthy soil” collected from around well-growing plants in the same field. We used three N fertilizer treatments (ammonium sulfate, urea, no application) and two soil water conditions (well drained and water-logged). In experiment 2, the treatments were a combination of sick and healthy soil, N fertilizer, soil acidification, and foliar application of Fe. Experiment 3 compared the irrigation water used at the experimental field site with reverse-osmosis water. Irrigation with water from the field site increased soil pH, impaired plant growth, and induced chlorosis. The application of ammonium sulfate reduced soil pH to values below 6 and increased plant micronutrient (Fe, Mn and Zn) contents and plant growth. In early vegetative plant growth, the high soil pH appeared to be the key determinant of “sick soil”, while root knot nematodes were most likely secondary causes for poor plant growth. [Copyright &y& Elsevier]