ABSTRACT
Over the past 20 years, the use of center-pivot irrigation has increased tomato (Solanum lycopersicum L.) yields in Brazil from 42 Mg ha-1 to more than 80 Mg ha-1. In the absence of field trials to support fertilizer recommendations, substantial amounts of phosphorus (P) have been applied to crops. Additional P dosing has been based on an equilibrated nutrient P budget adjusted for low-P fertilizer-use efficiency in high-P fixing tropical soils. To document nutrient requirements and prevent over-fertilization, tissue samples and crop yield data can be acquired through crop surveys and fertilizer trials. Nevertheless, most tissue diagnostic methods pose numerical difficulties that can be avoided by using the nutrient balance concept. The objectives of this study were to model the response of irrigated tomato crops to P fertilization in low- and high-P soils and to provide tissue diagnostic models for high crop yield. Three P trials, arranged in a randomized block design with six P treatments (0-437 kg P ha-1) and three or four replications, were established on a low-P soil in 2013 and high-P soils in 2013 and 2014, totaling 66 plots in all. Together with crop yield data, 65 tissue samples were collected from tomato farms. We found no significant yield response to P fertilization, despite large differences in soil-test P (coefficient of variation, 24%). High- and low-yield classes (cutoff: 91 Mg fruits ha-1) were classified by balance models with 78-81% accuracy using logit and Cate-Nelson partitioning models. The critical Mahalanobis distance for the partition was 5.31. Tomato yields were apparently not limited by P but were limited by calcium. There was no evidence that P fertilization should differ between center-pivot-irrigated and rain-fed crops. Use of the P budget method to arrive at the P requirement for tomato crops proved to be fallacious, as several nutrients should be rebalanced in Brazilian tomato cropping systems.
ABSTRACT
The objective of this work was to accomplish the nutritional diagnosis in conilon coffee crop cultivated in organic and conventional systems in the North of the Espírito Santo State to compare different limit indexes of diagnose in order to consider the lower and upper nutrient levels by use of foliar contents and the yield of 40 coffee crops under the conventional cultivation and 56 coffee crops under the organic cultivation. The calculations of the indexes were made through the method DRIS including the incorporation of the dry matter. Four indexes of diagnose were used for considering the nutrient as limiting. The nutrients that showed deficiency in the organic coffee crops were Mn, P, Fe and Cu. In the conventional coffee crop, Mn, N and P were the nutrients limiting. Lower index of absolute value will be able to identify with accuracy the nutrients as limiting. The first limit nutrient does not have its position modified when using different indices thresholds.
O objetivo deste trabalho foi realizar o diagnóstico nutricional em cafeeiros conilon cultivados de forma orgânica e convencional na região Norte do Espírito Santo e comparar diferentes índices limiares de diagnóstico para considerar o nutriente como sendo limitante ou excessivo, empregando os teores foliares e produtividade de 40 lavouras sob o cultivo convencional e 56 lavouras sob o cultivo orgânico. Para os cálculos dos índices, utilizou o método DRIS com incorporação da matéria seca. Quatro índices limiares de diagnóstico foram utilizados para considerar o nutriente como sendo limitante. Os nutrientes que ocorreram mais vezes, nas lavouras orgânicas, como sendo deficientes foram Mn, P, Fe e Cu. Nas lavouras convencionais o Mn, N e P foram os nutrientes considerados mais limitantes. Índice de menor valor absoluto afere mais nutrientes como sendo limitante. O primeiro nutriente mais limitante não tem sua posição alterada ao utilizar diferentes índices limiares.
ABSTRACT
The objective of this work was to accomplish the nutritional diagnosis in conilon coffee crop cultivated in organic and conventional systems in the North of the Espírito Santo State to compare different limit indexes of diagnose in order to consider the lower and upper nutrient levels by use of foliar contents and the yield of 40 coffee crops under the conventional cultivation and 56 coffee crops under the organic cultivation. The calculations of the indexes were made through the method DRIS including the incorporation of the dry matter. Four indexes of diagnose were used for considering the nutrient as limiting. The nutrients that showed deficiency in the organic coffee crops were Mn, P, Fe and Cu. In the conventional coffee crop, Mn, N and P were the nutrients limiting. Lower index of absolute value will be able to identify with accuracy the nutrients as limiting. The first limit nutrient does not have its position modified when using different indices thresholds.
O objetivo deste trabalho foi realizar o diagnóstico nutricional em cafeeiros conilon cultivados de forma orgânica e convencional na região Norte do Espírito Santo e comparar diferentes índices limiares de diagnóstico para considerar o nutriente como sendo limitante ou excessivo, empregando os teores foliares e produtividade de 40 lavouras sob o cultivo convencional e 56 lavouras sob o cultivo orgânico. Para os cálculos dos índices, utilizou o método DRIS com incorporação da matéria seca. Quatro índices limiares de diagnóstico foram utilizados para considerar o nutriente como sendo limitante. Os nutrientes que ocorreram mais vezes, nas lavouras orgânicas, como sendo deficientes foram Mn, P, Fe e Cu. Nas lavouras convencionais o Mn, N e P foram os nutrientes considerados mais limitantes. Índice de menor valor absoluto afere mais nutrientes como sendo limitante. O primeiro nutriente mais limitante não tem sua posição alterada ao utilizar diferentes índices limiares.