4R Nutrient Stewardship for Improved Nutrient Use Efficiency

AbstractFertilizers play a significant role in securing the production of food crops around the world. In fact, it is estimated that fertilizers currently support 40-60% of all crop production currently. Meeting future food security targets requires the responsible use of fertilizer nutrients. The 4R Nutrient Stewardship guidelines were developed by the fertilizer industry as a process to guide fertilizer Best Management Practices (BMP) in all regions of the world. This approach was required to address the growing concern that fertilizers are applied indiscriminately to the detriment of the environment. Given that farmers purchase fertilizers at world prices in most regions, and these prices have been steadily increasing over time, most users are very cautious about the rates of nutrients they apply. To avoid unnecessary policy intervention by governments, the fertilizer industry needs to be unified in their promotion of BMPs that support improved nutrient use efficiency and environmental sustainability, while supporting the farmer's profitability. This ultimately comes down to developing appropriate recommendations that match crop nutrient requirements fertilizer additions and minimize nutrient losses from fields. This lead to the 4R Nutrient Stewardship concept, applying the Right Source of nutrients, at the Right Rate, at the Right Time and in the Right Place. Right source means matching the fertilizer to the crop need and soil properties. A major part of source is balance between the various nutrients, a major challenge globally in improving nutrient use efficiency. Finally, some fertilizer products are preferred to others based on the soil properties, like pH. Right rate means matching the fertilizer applied to the crop need – simple as that. However, this is far from being a simple concept when you consider the variations in yield goals, previous crop management, crop residue management, influence of legume crops in rotation, etc. Adding too much fertilizer leads to residual nutrients in the soil and losses to the environment. Ultimately, striking a balance between the crop needs, environmental conditions and the farmers economic situation is required. Right time means making fertilizer nutrients available to the crop when they are needed. Nutrient use efficiency can be increased significantly when their availability is synchronized with crop demand. Split time of application, slow and controlled release fertilizer technology, stabilizers and inhibitors are just a few examples of how fertilizer nutrients can be better timed for efficient crop uptake. Right place means making every effort to keep nutrients where crops can use them. This is an issue which poses the greatest challenge in small holder agricultural systems, where most fertilizer is broadcast applied, and in many cases without incorporation. Research indicates that fertilizer placement can not only improve crop response, but also improve fertilizer use efficiency significantly by lowering nutrient application rates. Adaptation to non-mechanized agriculture have been made in certain regions which clearly support efforts to modify fertilizer placement as a BMP

Transforming soil phosphorus fertility management strategies to support the delivery of multiple ecosystem services from agricultural systems

Despite greater emphasis on holistic phosphorus (P) management, current nutrient advice delivered at farm-scale still focuses almost exclusively on agricultural production. This limits our ability to address national and international strategies for the delivery of multiple ecosystem services (ES). Currently there is no operational framework in place to manage P fertility for multiple ES delivery and to identify the costs of potentially sacrificing crop yield and/or quality. As soil P fertility plays a central role in ES delivery, we argue that soil test phosphorus (STP) concentration provides a suitable common unit of measure by which delivering multiple ES can be economically valued relative to maximum potential yield, in $ ha−1 yr−1 units. This value can then be traded, or payments made against one another, at spatio-temporal scales relevant for farmer and national policy objectives. Implementation of this framework into current P fertility management strategies would allow for the integration and interaction of different stakeholder interests in ES delivery on-farm and in the wider landscape. Further progress in biophysical modeling of soil P dynamics is needed to inform its adoption across diverse landscapes. © 2018 Elsevier B.V

Suitability of peanut residue as a nitrogen source for a rye cover crop Resíduos da cultura de amendoim como fonte de nitrogênio para uma cultura de cobertura de centeio

Leguminous winter cover crops have been utilized in conservation systems to partially meet nitrogen (N) requirements of succeeding summer cash crops, but the potential of summer legumes to reduce N requirements of a winter annual grass, used as a cover crop, has not been extensively examined. This study assessed the N contribution of peanut (Arachis hypogaea L.) residues to a subsequent rye (Secale cereale L.) cover crop grown in a conservation system on a Dothan sandy loam (fine-loamy, kaolinitic, thermic Plinthic Kandiudults) at Headland, AL USA during the 2003-2005 growing seasons. Treatments were arranged in a split plot design, with main plots of peanut residue retained or removed from the soil surface, and subplots as N application rates (0, 34, 67 and 101 kg ha-1) applied in the fall. Peanut residue had minimal to no effect on rye biomass yields, N content, carbon (C) /N ratio, or N, P, K, Ca and Zn uptake. Additional N increased rye biomass yield, and N, P, K, Ca, and Zn uptakes. Peanut residue does not contribute significant amounts of N to a rye cover crop grown as part of a conservation system, but retaining peanut residue on the soil surface could protect the soil from erosion early in the fall and winter before a rye cover crop grows sufficiently to protect the typically degraded southeastern USA soils.<br>Culturas leguminosas de inverno tem sido utilizadas em sistemas conservacionistas para suprimento parcial das necessidades de nitrogênio (N) de culturas subseqüentes de verão, mas o potencial destas culturas leguminosas de verão no sentido de reduzir as necessidades de N de gramíneas anuais de inverno, utilizadas como culturas de cobertura, ainda não foi extensivamente estudado. Este trabalho avaliou a contribuição dos resíduos de uma cultura de amendoim (Arachis hypogaea L.) sobre as necessidades de N de uma cultura subsequente de centeio (Secale cereale L.) como cobertura desenvolvida dentro de um sistema conservacionista, em um solo limo-arenoso Dotham (limoso fino, caulinítico, Plinthic Kandiudults térmico) de Headland, AL EEUU, durante 2003-2005. Os tratamentos foram arranjados de acordo com um esquema split-plot, com parcelas principais de resíduos de amendoim retido ou retirado da superfície do solo e, parcelas secundárias de taxas de aplicação de N (0, 34, 67 e 101 kg ha-1) aplicadas no outono. O resíduo de amendoim teve efeito mínimo ou nenhum sobre a produtividade de matéria seca do resíduo, conteúdo de N, relação carbono (C)/N, ou absorção de N, P, K, Ca e Zn. O N adicional aumentou a produção de biomassa do centeio e as absorções de N, P, K, Ca e Zn. Os resíduos de amendoim não contribuem com quantidades significativas de N para a cultura de cobertura de centeio desenvolvida como parte do sistema conservacionista, mas a retenção dos resíduos na superfície podem proteger o solo da erosão no início do outono e inverno, antes que a cultura de cobertura de centeio pudesse proteger os solos tipicamente degradados do sudoeste dos EEUU