ABSTRACT
The study was carried out for two years in maize in succession to the wheat using no tillage system in a distroferric Red Latosol (Hapludox). Methods of management nitrogen fertilizer (120 kg ha-1) with ammonium sulphate were studied; the fertilizer was applied in maize sowing or in maize topdressing, and N with previous application in wheat sowing. In addition, leaf chlorophyll reading was used as an indicator for the need for topdressed nitrogen fertilizer. Nitrogen supply index (NSI) was shown to be effective at predicting need for topdressed nitrogen fertilizer for maize. The application of N improved the yield of the maize independent of the management system. The flowering stage was carried out at the appropriate time in order to estimate the nitrogen nutrition state and yield of maize using the relative chlorophyll level (RIC).
ABSTRACT
Com o desenvolvimento da soja resistente ao glifosato, Roundup Ready (RR), observa-se um aumento considerável no uso desse herbicida, com aplicações de três a quatro vezes durante o ciclo da cultura. Dessa forma, essas aplicações podem estar influenciando a nutrição mineral da cultura. Objetivou-se realizar este experimento para avaliar a influência do glifosato na eficiência nutricional de N, Mn, Cu, Zn e Fe pela soja transgênica cv. 'P98R31 RR'. O experimento foi realizado em casa de vegetação, na ESALQ/USP, Piracicaba (SP), em 2009. A unidade experimental foi constituída por vaso contendo 11kg de substrato (NITOSSOLO VERMELHO Eutroférrico latossólico), com duas plantas por vaso. Os tratamentos foram arranjados em um esquema fatorial 5X5, com cinco níveis do fator Mn (0, 20, 40, 60 e 80mg dm-3) e cinco de glifosato (0; 0,648; 1,296; 1,944 e 2,592kg i.a. ha-1), sendo que o Mn foi fornecido a partir do sulfato de manganês (MnSO4.H2O). O delineamento experimental foi em blocos casualizados, com quatro repetições. Não houve influência na resposta das plantas com relação ao fator Mn. A aplicação de glifosato interferiu de forma negativa na eficiência nutricional da planta e nos teores totais de N, Mn, Cu, Zn e Fe. A utilização de glifosato causou redução ao número de nódulos e redução na produção de massa seca.
After development of glyphosate-resistant (GR) soybean, there is a considerable raise in the use of this herbicide, with three to four applications during the culture cycle. Thus, these applications may be influencing the mineral nutrition of the crop. So, the aim of this research was evaluate the glyphosate influence on uptake, translocation and use efficiency of N, Mn, Cu, Zn and Fe by (GR) soybean 'P98R31' cultivar. The experiment was conducted in the greenhouse at ESALQ/USP, Piracicaba, State of São Paulo, Brazil, in 2009. The experimental unit was formed by 11kg vase-1 of soil (Rhodic Paleudult) with two plants in each vase. The treatments have been arranged in a factorial pathway 5X5, with five levels of the factor Mn (0, 20, 40, 60 and 80mg dm-3) and five of glyphosate drifts (0; 0,648; 1,296; 1,944 e 2,592kg e.a. ha-1) and the Mn was supplied by the manganese sulfate (MnSO4.H2O). The experimental design was randomized blocks, with four repetitions. There was no influence on response from plants concerning the levels of Mn used into the experiment. The application of glyphosate interfered on mineral nutrition of soybean and the total contents of N, Mn, Cu, Zn and Fe. The use of glyphosate has caused reduction of the nodules number and reduced the output of dry mass.
ABSTRACT
O melhor aproveitamento do P, tanto o aplicado no cultivo quanto o residual do solo, em razão do uso de calcário em solos argilosos cultivados e adubados por muitos anos, pode ser viável. Objetivando avaliar o efeito do aumento do pH do solo e da aplicação de adubo fosfatado e calcário na semeadura sobre a disponibilidade de P e o seu acúmulo em plantas de soja, realizaram-se dois experimentos em Latossolo Vermelho Distrófico-LVD e Latossolo Vermelho Distroférrico-LVDf, argilosos, com elevados níveis de fertilidade. O delineamento experimental foi blocos casualizados, num fatorial 4x2x2: quatro níveis de pH, duas doses de P e duas de calcário, com quatro repetições. Cultivaram-se plantas de soja em vaso até a floração. Avaliaram-se o peso da massa seca, teor e acúmulo de P na parte aérea; teor de P e P remanescente no solo. A disponibilidade de P nos solos aumentou com a elevação do pH. Para o LVdf, houve interação entre pH e doses de P, os teores de P no solo aumentaram com o pH e com a aplicação de P. Para o LVD, houve interação entre pH e doses de calcário. O P remanescente foi reduzido pelo aumento do pH em ambos os solos. Nos dois experimentos, com o aumento do pH do solo houve incremento na produção de massa seca e de P acumulado. Em solos argilosos e com alto teor de P, a elevação do pH aumenta a disponibilidade de P, proporcionando maior produção de massa seca de soja.
The best P employment, both applied in the culture as the P soil residual, is possible, due limestone use in clayey soils cultivated and fertilized for many years. Aiming at evaluating the pH increase in the soil and the effect of the application of phosphated fertilizer and lime on the sowing on the P availability and its accumulation in soybean plants, two experiments in oxisols, Haplortox (one LVD and the other LVDf), with high fertility levels, were carried out. The experimental design was random blocks, in a 4x2x2 factorial, being four pH levels, two P doses and two limestone doses, with four repetitions. Soybean plants were cultivated in vases up to flowering. The dry mass weight, P contents and accumulation in the area, P content and P remaining in the soil, were evaluated. P availability in soils increased with pH elevation. For the LVDf, there was an interaction between the pH and the P doses, the P contents in the soil increased with the pH and with the P application. For the LVD, there was an interaction between the pH and the doses of lime applied. The P remaining was reduced by the pH increase in both soils. In both experiments, with the pH increase in the soil, there was an increment in the dry mass production and P accumulated. In clayey soils with a high P content, the pH elevation increases the P availability, providing greater soybean dry mass production.