SUMMARYIn order to select soil management practices that increase the nitrogen-use efficiency (NUE) in agro-ecosystems, the different indices of agronomic fertilizer efficiency must be evaluated under varied weather conditions. This study assessed the NUE indices in no-till corn in southern Paraguay. Nitrogen fertilizer rates from 0 to 180 kg ha -1 were applied in a single application at corn sowing and the crop response investigated in two growing seasons (2010 and 2011). The experimental design was a randomized block with three replications. Based on the data of grain yield, dry matter, and N uptake, the following fertilizer indices were assessed: agronomic N-use efficiency (ANE), apparent N recovery efficiency (NRE), N physiological efficiency (NPE), partial factor productivity (PFP), and partial nutrient balance (PNB). The weather conditions varied largely during the experimental period; the rainfall distribution was favorable for crop growth in the first season and unfavorable in the second. The PFP and ANE indices, as expected, decreased with increasing N fertilizer rates. A general analysis of the N fertilizer indices in the first season showed that the maximum rate (180 kg ha -1 ) obtained the highest corn yield and also optimized the efficiency of NPE, NRE and ANE. In the 1642 second season, under water stress, the most efficient N fertilizer rate (60 kg ha -1 ) was three times lower than in the first season, indicating a strong influence of weather conditions on NUE. Considering that weather instability is typical for southern Paraguay, anticipated full N fertilization at corn sowing is not recommended due the temporal variability of the optimum N fertilizer rate needed to achieve high ANE.Index terms: Zea mays, plant nutrition, no-tillage, soil fertility.RESUMO: EFICIÊNCIA DA FERTILIZAÇÃO NITROGENADA APLICADA NA SEMEADURA DO MILHO, AVALIADA SOB CONDIÇÕES CLIMÁTICAS CONTRASTANTES NO PARAGUAI Visando selecionar práticas de manejo que incrementem a eficiência do uso de nitrogênio (EUN) em agroecossistemas, faz-se necessário avaliar vários índices agronômicos de eficiência da fertilização. O objetivo deste trabalho foi avaliar a EUN no milho, sob sistema plantio direto na região Sudeste do Paraguai. Neste trabalho, investigou-se a fertilização integral na semeadura do milho com doses variando de 0 até 180 kg de N, durante duas safras (2010 e 2011). O delineamento foi de blocos ao acaso, com três repetições. Com os dados de produtividade de grãos e matéria seca e o N absorvido, realizaram-se os cálculos dos seguintes índices: eficiência agronômica do uso de N (EAN), eficiência aparente da recuperação de N (ERN), eficiência fisiológica do N (EFN), produtividade parcial do fator (PPF) e balanço parcial do nutriente (BPN). As condições climáticas foram favoráveis ao desenvolvimento da cultura do milho na primeira safra e desfavoráveis na segunda. Os índices PPF e EAN, conforme esperado, apresentaram valores decrescentes em razão do incremento das doses de N. Na análise conjunta dos índices, observou-se, na p...
Despite its relevance, nitrogen is poorly utilized by the plants when improperly applied. Thus, the objective of this study was to evaluate the yield and nitrogen use efficiency (NUE) in corn in response to doses and split application of nitrogen fertilization. The experimental design was a randomized block design, with three replications. Doses of nitrogen of 0, 30, 60 and 180 kg ha -1 were applied at sowing in order to create different nutritional status of corn plants and to obtain different values of Normalized Difference Vegetation Index (NDVI) measured with "Greenseeker ® " optical sensor. The subplots with nitrogen doses in topdressing of 0, 30, 60 and 90 kg ha -1 at V8 and a dose of 60 kg ha -1 at V12 were placed in experimental plots with doses of 0, 30, 60 and 180 kg ha -1 of nitrogen at sowing. Moreover, NUE was calculated in the experiment using agronomic indexes determined by applications of nitrogen in late topdressing (V8 and V12) and contrasted to the possible combinations at doses of 60, 90 and 120 kg ha -1 of total N applied. The results showed the occurrence of a linear relationship between nitrogen fertilizer dose and NDVI at V8 as well as at V12 stages. Late topdressing fertilizations (V12) did not cause a decrease in grain yield when combined with nitrogen fertilization at sowing, moreover resulted in higher NUE. Split the nitrogen dose showed better NUE than the combinations where nitrogen was not applied at sowing or in topdressing. The delay of nitrogen topdressing can be an alternative for the planning of the moment of the N fertilization according to the climate forecast in each region. Key words: Produtividade e eficiência nutricional do milho em resposta a doses e parcelamentos da adubação nitrogenadaApesar de sua relevância, o nitrogênio apresenta reduzido aproveitamento pela planta quando aplicado de forma inadequada. Assim, objetivou-se avaliar a produtividade e a eficiência do uso de nitrogênio (EUN) no milho em resposta a doses e parcelamentos da adubação nitrogenada. O delineamento experimental utilizado foi de blocos ao acaso, com três repetições. Foram aplicadas doses de 0, 30, 60 e 180 kg ha -1 de nitrogênio em semeadura visando criar diferentes condições nutricionais das plantas de milho e assim obter diferentes níveis de Índice de Vegetação por Diferença Normalizada (NDVI) medidos com sensor óptico "GreenSeeker ® ". As subparcelas com doses de nitrogênio em cobertura de 0, 30, 60 e 90 kg ha -1 em V8 e uma dose de 60 kg ha -1 em V12 foram alocadas experimentalmente nas parcelas com doses de 0, 30, 60 e 180 kg ha -1 de nitrogênio em semeadura. Além disso, foi calculado no experimento a EUN através de índices agronômicos determinados a partir das aplicações de N em cobertura tardia (V8 e V12) e contrastado às possíveis combinações nas doses de 60, 90 e 120 kg ha -1 de nitrogênio total aplicado. Os resultados mostraram que houve relação 352Telmo Jorge Carneiro Amado et al.
This work aimed to develop two computerized systems, modeled to record and provide information about family farming activities within Itapúa Department-Paraguay. Meetings were held with Government members and municipal technicians to obtain all the requirements and to gather all the details that are relevant for the development of the application. Thus, with all the available information, it was possible to organize and structure the two proposed systems to collect data on rural producers, their properties, their production, family composition, livestock production, processed products, infrastructure, input use, etc. As a result an application for Android called C7-SustenLAF and a Web system was developed, where the main application’s function is to carry out the data registration of the rural producers, thus providing georeferenced data, in turn the Web system has the purpose of generating and structuring the information as well as enable data retrieval by giving a series of filter options for different characteristics that are registered from the application. Thus, it is expected that these systems, used specifically to give information, can help the Government of Itapúa - Paraguay to take strategic actions and give support to the Family Farming field, contributing to better management and technical assistance to producers.
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