New methods to quantify NH3 volatilization from fertilized surface soil with urea

Gaseous N losses from soil are considerable, resulting mostly from ammonia volatilization linked to agricultural activities such as pasture fertilization. The use of simple and accessible measurement methods of such losses is fundamental in the evaluation of the N cycle in agricultural systems. The purpose of this study was to evaluate quantification methods of NH3 volatilization from fertilized surface soil with urea, with minimal influence on the volatilization processes. The greenhouse experiment was arranged in a completely randomized design with 13 treatments and five replications, with the following treatments: (1) Polyurethane foam (density 20 kg m-3) with phosphoric acid solution absorber (foam absorber), installed 1, 5, 10 and 20 cm above the soil surface; (2) Paper filter with sulfuric acid solution absorber (paper absorber, 1, 5, 10 and 20 cm above the soil surface); (3) Sulfuric acid solution absorber (1, 5 and 10 cm above the soil surface); (4) Semi-open static collector; (5) 15N balance (control). The foam absorber placed 1 cm above the soil surface estimated the real daily rate of loss and accumulated loss of NH3N and proved efficient in capturing NH3 volatized from urea-treated soil. The estimates based on acid absorbers 1, 5 and 10 cm above the soil surface and paper absorbers 1 and 5 cm above the soil surface were only realistic for accumulated N-NH3 losses. Foam absorbers can be indicated to quantify accumulated and daily rates of NH3 volatilization losses similarly to an open static chamber, making calibration equations or correction factors unnecessary

Chemical properties of soils treated with biological sludge from gelatin industry

The impact of agro-industrial organic wastes in the environment can be reduced when used in agriculture. From the standpoint of soil fertility, residue applications can increase the organic matter content and provide nutrients for plants. This study evaluated the effect of biological sludge from gelatin industry on the chemical properties of two Ultisols (loamy sand and sandy clay) and an Oxisol (clay). The experiment lasted 120 days and was carried out in laboratory in a completely randomized design with factorial arrangement, combining the three soils and six biological sludge rates (0, 100, 200, 300, 400, and 500 m³ ha-1), with three replications. Biological sludge rates of up to 500 m³ ha-1 decreased soil acidity and increased the effective cation exchange capacity (CEC) and N, Ca, Mg, and P availability, without exceeding the tolerance limit for Na. The increase in exchangeable base content, greater than the effective CEC, indicates that the major part of cations added by the sludge remains in solution and can be lost by leaching

Dry matter production and nutrient accumulation after successive crops of lettuce, tomato, rice, and andropogongrass in a substrate with zeolite Produção de matéria seca e acúmulo de nutrientes após cultivos sucessivos com alface, tomate, arroz e capim andropogon em substrato com zeólita

Zeolites are hydrated crystalline aluminosilicate minerals of natural occurrence, structured in rigid third dimension net that can be used as slow release plant-nutrient source. The main objective of this study was to evaluate the effects of plant growth substrate under zeolite application, enriched with N, P and K, on dry matter yield and on nutrient contents in consecutive crops of lettuce, tomato, rice, and andropogon grass. The experiment was carried out in a greenhouse, with 3 kg pots with an inert substrate, evaluated in a randomized block design with three replications. Treatments consisted of four types of enrichment of concentrated natural zeolite: concentrated zeolite (Z) only, zeolite + KNO3 (ZNK), zeolite + K2HPO4 (ZPK) and zeolite + H3PO4 + apatite (ZP), and a control grown in substrate fertilized with a zeolite-free nutrient solution. Four levels of enriched zeolite were tested: 20, 40, 80, and 160 g/pot. Four successive crops were grown on the same substrate in each pot: lettuce, tomato, rice, and andropogon grass. Results indicated that N, P and K enriched zeolite was an adequate slow-release nutrient source for plants. The total dry matter production of above-ground biomass of four successive crops followed a descending order: ZP > ZPK > ZNK > Z.<br>Zeólitas são minerais aluminossilicatos cristalinos hidratados de ocorrência natural, estruturados em redes cristalinas tridimensionais rígidas que podem ser usados como fonte de liberação lenta de nutrientes para as plantas. O objetivo deste trabalho foi avaliar o efeito da adição de zeólita enriquecida com N, P e K ao substrato de cultivo sobre a produção de matéria seca e o acúmulo de nutrientes pelas culturas sucessivas de alface, de tomate, de arroz e de capim-andropogon. O experimento foi conduzido em vasos em casa de vegetação, em vasos contendo 3 kg de substrato inerte. O delineamento experimental foi o de blocos ao acaso, com três repetições. A zeólita natural estilbita foi concentrada e enriquecida com nutrientes N, P e K obtendo-se os seguintes tratamentos: zeólita concentrada (Z), zeólita + KNO3 (ZNK), zeólita + K2HPO4 (ZPK) e zeólita + H3PO4 + apatita (ZP), além de um tratamento testemunha sem adição de zeólita, mas com solução nutritiva. Utilizaram-se quatro doses de zeólita enriquecida: 20, 40, 80 e 160 g/vaso. Foram realizados quatro cultivos sucessivos no mesmo substrato de cada vaso: alface, tomate, arroz e capim-andropogon. Os resultados indicaram que a zeólita enriquecida com N, P e K funcionou como fonte de nutrientes de liberação lenta. A produção de matéria seca total da parte aérea dos quatro cultivos sucessivos seguiu a seguinte ordem decrescente: ZP > ZPK > ZNK > Z