Additives incorporated into urea to reduce nitrogen losses after application to the soil.

The objective of this work was to develop urea-based fertilizers with internal incorporation of urease inhibitors and other additives in the granule. The effects of the incorporation of NBPT, copper (Cu+2), boric acid (H3BO3), elemental sulphur (Sº), and a clay mineral from the zeolite group in powder urea - with ten different combinations of these additives - were evaluated as to N losses by volatilization and leaching. The losses in laboratory-developed formulations were compared with those of commercial fertilizers coated with the same additives (Super N, FH Nitro Mais, and FH Nitro Gold). The evaluations were made in greenhouse conditions, using a Ultisol accommodated in PVC columns. Nitrate and ammonium leaching was evaluated in the solution percolated through the soil columns. Ammonia volatilization was measured with a semi-open static chamber. The incorporation of urease inhibitors (NBPT, H3BO3, and Cu+2) into the urea granules was efficient to reduce N volatilization. Ammonia volatilization in the laboratory-developed ureas was lower than in commercial fertilizers coated with the same additives, while ammonium sulfate losses by leaching were similar. The addition of zeolite does not reduce N volatilization. Mineral N leaching in the soil profile is not affected by urease inhibitors.Título em português: Aditivos incorporados à ureia para reduzir perdas de nitrogênio após aplicação ao solo

Pesquisas apontam o aumento da eficiência do uso de rochas fosfatadas pela associação com microrganismos solubilizadores.

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A geometric statement of the Harnack inequality for a degenerate Kolmogorov equation with rough coefficients

We consider weak solutions of second-order partial differential equations of Kolmogorov-Fokker-Planck-type with measurable coefficients in the form ∂tu + (v,∇xu) = div(A(v,x,t)∇vu) + (b(v,x,t),∇vu) + f, (v,x,t) ϵ2n+1, where A is a symmetric uniformly positive definite matrix with bounded measurable coefficients; f and the components of the vector b are bounded and measurable functions. We give a geometric statement of the Harnack inequality recently proved by Golse et al. As a corollary, we obtain a strong maximum principle

Fertbrasil: an innovative network for the development of tropical soils fertilizers.

This paper aims to present the FertBrasil network, a network leaded by the Brazilian Agricultural Research Corporation ? Embrapa, that includes more than three hundreds of researchers in more than fifty institutions, among public agents, universities and private companies. First, we introduce the subject of network innovation and a little background on tropical fertilizers. Then, we present the FertBrasil network, since its creation, passing by its leadership, partners and the products the network intends to develop. After, a little is discussed about the innovative control mechanism of the network and the product development flow, as well as the interaction between FertBrasil and other governmental initiatives or public policies about the same subject. At least, we discuss about the results of the network until now, in terms of products, technologies and political impacts and mobilization in fertilizers research for tropical regions. Then, we conclude presenting some challenges for FertBrasil network as well as reinforcing the important role assumed by this network in contributing to Brazil keeps its high position in agricultural production and productivity