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The aim of this study was to evaluate the phosphorus (P) extraction ability of the methods Mehlich 1 (M-1), Mehlich 3 (M-3), anion exchange resin in strips (AER-ST), and anion exchange resin in spheres (AER-SP), as a function of clay content, P rates, and incubation time. Experimental units were built with 20%, 40%, 60%, and 80% of clay and five different phosphorus rates as follows: 0, 100, 200, 400, and 600 mg P kg −1 , with subsequent incubation for 0, 30, and 90 days. After that, the samples were subjected to the analysis of extractable P using the M-1, M-3, AER-ST, and AER-SP extractors. All P extraction methods evaluated were sensitive to clay content and to the amount of added P. The input of P increased the recovery of this nutrient by all extractors, but this was less effective when the clay content of the soil was increased. In general, the ability of phosphorus extraction from the soil followed the order: M-1 > AER-SP > M-3 > AER-ST. The longer contact time of P with the soil, lower is the extracted P content, regardless of the extraction method, this being more evident in clayey soils. All extraction methods tested are sensitive to clay content, incubation time, and to the P concentration applied.

The use of organomineral fertilizers in agriculture instead of mineral fertilizers is a way to add organic compounds to the soil, potentially improving its properties and crop production. Our objective was to evaluate the agronomic efficiency of an organomineral fertilizer manufactured from poultry litter and mineral fertilizers. The experiment was carried out in a Humic Cambisol in the subtropical region of Brazil, with high organic matter content, low phosphorus content, and very high potassium content. The study consisted of six treatments: mineral fertilizer (monoammonium phosphate, KCl, and urea), at rates of 100 and 150% of the technical recommendation; organic fertilizer (poultry litter), at 100% rate; organomineral fertilizer (poultry litter + monoammonium phosphate), at rates of 100 and 150%; and control treatment (without fertilization). Between 2015 and 2017, common bean (Phaseolus vulgaris), wheat (Triticum aestivum L.), and corn (Zea mays L.) were sequentially cultivated. Before performing the experiment and at the end of the fourth crop, chemical properties of the soil were analyzed in the 0‐ to 10‐ and 10‐ to 20‐cm layers. The use of fertilizers increased crop yield, but there was no difference between the three fertilizer sources or between the 100 and 150% rates of the technical recommendation. Chemical properties of the soil were altered in a similar manner with fertilization, regardless of the fertilizer source used. According to the results, the organomineral fertilizer can replace mineral fertilizers with equivalent performance.

The volatilization of ammonia (NH3) and nitrate leaching (NH3-) are the main processes of nitrogen (N) loss in the soil. The objective of the study was to evaluate N losses by NH3 volatilization and mineral N transformations in the soil with urea coated with poultry litter (urea + litter) compared with other sources of N, under two moisture conditions. The experiment was conducted in a controlled environment with a 5 x 2 factorial arrangement with four replicates, five N sources (urea, SuperN®, Kimcoat®, urea + litter and control without fertilizer) and two moisture contents [80 and 100% of field capacity (FC)]. The total volatilized NH3 did not differ between the sources, regardless of the soil moisture condition, ranging from 10.8 to 13.2% of the total N applied. The transformation of NH4+ into NH3- did not vary between the sources, except for the control, but it differed between soil moisture contents, with equilibrium estimated at 31 and 38 days, in the treatments with 80 and 100% FC, respectively. The urea + litter has N losses by NH3 volatilization and speed of transformation of the soil mineral N similar to those of the other sources, and can be used to substitute them.