A VON LIEBIG MODEL FOR WATER AND NITROGEN CROP RESPONSE

The century-old “law of the minimum” proposed by von Liebig was tested using five independent sets of crop response data on wheat, corn, cotton, silage, and sugar beets. The rival models were polynomial functions reported in the literature as the most suitable models for interpreting those data. Overall, the von Liebig model performed very well. While the nonnested hypothesis test was inconclusive with regard to silage and sugar beets, the von Liebig model rejected the polynomial specifications for wheat, corn and cotton.Crop Production/Industries,

A VON LIEBIG MODEL FOR WATER AND NITROGEN CROP RESPONSE

The century-old "law of the minimum" proposed by von Liebig was tested using five independent sets of crop response data on wheat, corn, cotton, silage, and sugar beets. The rival models were polynomial functions reported in the literature as the most suitable models for interpreting those data. Overall, the von Liebig model performed very well. While the nonnested hypothesis test was inconclusive with regard to silage and sugar beets, the von Liebig model rejected the polynomial specifications for wheat, corn and cotton

Soybean fertilization, liming and sustainable yields on a latosol in the state of Santa Catarina, Brazil

Neste trabalho é apresentado um método para estimar efeitos residuais de adubação e calagem, diretamente sobre a função de resposta de cultivos seqüenciais. O método permite fazer previsões das quantidades de adubos, requeridas para a manutenção de rendimentos sustentáveis a longo prazo. Um estudo de caso foi feito com base em dados experimentais de onze anos, com aplicações e reaplicações de PA, Kz0 e calcário dolomítico em soja. Os resultados foram satisfatórios e dão suporte ao método proposto. O trabalho é complementado com uma análise econômica em condições de equilíbrio estacionário do caso estudado.A method to estimate fertilizer residual effects directly upon the response function of sequential crops is presented. The method allows for the prediction of fertilizer quantities that are demanded to support different levels of sustained yields in the long run. A case study has been made based upon a series of eleven years of experimental results from the application and reapplication of P205, K20 and limestone on soybeans. The statistical fits obtained were satisfactory and support the proposed method. The study also includes an economic analysis of fertilizer applications under conditions of stationary equilibrium of the case studied