RESUMOA adubação nitrogenada é de suma importância para a cultura do trigo, já que o nitrogênio constitui um dos nutrientes mais exigidos por essa cultura e o rendimento desta é função direta da quantidade de nutrientes acumulados pela planta. Foram testados os adubos nitrogenados: sulfonitrato de amônio com inibidor de nitrificação, sulfato de amônio e uréia, na dose de 70 kg de N ha -1 ; em duas épocas de aplicação, na linha de semeadura ou em cobertura, além da testemunha que não recebeu nitrogênio como tratamento, em quatro cultivares de trigo irrigado: EMBRAPA 21, EMBRAPA 22, EMBRAPA 42 e IAC 370. O experimento foi conduzido sob irrigação por aspersão em dois anos (2005 e 2006) em área experimental pertencente à Faculdade de Engenharia de Ilha Solteira -UNESP/São Paulo -Brasil. As fontes de nitrogênio sulfonitrato de amônio com inibidor de nitrificação, sulfato de amônio e uréia não diferiram entre si, porém foram superiores à testemunha, em relação à produtividade de grãos. A aplicação do N todo em cobertura proporcionou aumento na produtividade de grãos. O comportamento das cultivares quanto aos componentes de produção e produtividade foram dependentes do ano em estudo. Termos para indexação:Triticum aestivum L., uréia, sulfato de amônio, sulfonitrato de amônio. ABSTRACTNitrogen fertilization is very important to wheat crop, since nitrogen constitutes one of the most demanded nutrients by this crop, which yield is directly related to the amount of nutrients accumulated in the plant. Three nitrogen sources were tested at 70 kg N ha -1 : ammonium sulfonitrate with nitrification inhibitor, ammonium sulfate, and urea in two applications (at sowing or at side dressing), besides a control that did not receive nitrogen as treatment. Four wheat cultivars were tested: EMBRAPA 21, EMBRAPA 22, EMBRAPA 42, and IAC 370. The experiment was carried out under irrigation in two years (2005 and 2006) at Experimental Station of UNESP/São Paulo -Brazil. The N sources ammonium sulfonitrate, ammonium sulfate, and urea did not differ among them; however, they were higher than the control regarding the grain yield. N applied at side dressing provided an increase in grain yield. The cultivar performance concerning the production and grain yield depended on the environmental condition of the year. Index terms:Triticum aestivum L., nitrogen fertilizer, urea, ammonium sulfate, ammonium sulfonitrate. (Recebido em 6 de maio de 2008 e aprovado em 12 de fevereiro de 2009) INTRODUÇÃOA nutrição mineral tem efeito na produtividade de grãos, sendo o nitrogênio o nutriente quantitativamente mais importante (Lamothe, 1998;Sylvester-Bradley et al., 2001). A deficiência de nitrogênio pode reduzir a evapotranspiração e a eficiência do uso da água na cultura do trigo (Nielsen & Halvorson, 1991) interceptação da radiação, diminuindo a eficiência do uso da radiação (Abbate et al., 1995). Todos os componentes do rendimento do trigo podem beneficiar-se em maior ou menor grau com o nitrogênio, exceto a população de plantas (Zagonel et al., 2002). As...
sUmmAry the quantification of ammonia (nH 3 ) losses from sugarcane straw fertilized with urea can be performed with collectors that recover the nH 3 in acid-treated absorbers. thus, the use of an open nH 3 collector with a polytetrafluoroethylene (ptfe)-wrapped absorber is an interesting option since its cost is low, handling easy and microclimatic conditions irrelevant. the aim of this study was to evaluate the efficiency of an open collector for quantifying nH 3 -n volatilized from urea applied over the sugarcane straw. the experiment was carried out in a sugarcane field located near piracicaba, são paulo, brazil. the nH 3 -n losses were estimated using a semi-open static collector calibrated with 15 n (reference method) and an open collector with an absorber wrapped in ptfe film. Urea was applied to the soil surface in treatments corresponding to rates of 50, 100, 150 and 200 kg ha -1 n. Applying urea-n fertilizer on sugarcane straw resulted in losses nH 3 -n up to 24 % of the applied rate. the amount of volatile nH 3 -n measured in the open and the semi-open static collector did not differ. the effectiveness of the collection system varied non-linearly, with an average value of 58.4 % for the range of 100 to 200 kg ha -1 of urea-n. the open collector showed significant potential for use; however, further research is needed to verify the suitability of the proposed method. index terms: Saccharum spp., nitrogen, n fertilization, volatilization, collection system.(1) part of msc. thesis of the first author. received for publication in June 9, 2011 and approved in december 22, 2011.
SUMMARYThe great difficulty of incorporation of N fertilizers into the "green sugarcane" system causes concern and since urea is the most commonly used source, there is the risk of loosing NH 3 through volatilization. For this reason, a field experiment was undertaken (in a Hapludox Typic) with the objective of evaluating the agronomic efficiency of ammonium chloride on stubble of the second ratoon (SP89 1115), as well as its residual effect on the subsequent cycle (third ratoon).
Produtividade de colmos e atributos tecnológicos na colheita da cana soca (segunda rebrota) relacionados com a adubação nitrogenada ... 4.2 Efeito do N-residual no ciclo da cana soca de terceira rebrota ............ 4.2.1 Concentrações de macronutrientes na folha-diagnóstico e características químicas do solo .
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