Simulation of wheat biomass yield by thermal time, rainfall and nitrogen/Simulacao da produtividade de biomassa do trigo pela soma termica, precipitacao e nitrogenio

Wheat biomass yield focused on the production of quality silage is dependent on rainfall, temperature and nitrogen (N). The objective of the study was to validate the use of rainfall, thermal time and N as potential variables for the composition of the multiple linear regression model and simulation of wheat biomass yield for silage production under N supply conditions during the cycle, in the systems of succession. The study was conducted in 2012, 2013 and 2014, in randomized blocks with four replicates in 4 x 3 factorial, for N-fertilizer doses (0, 30, 60, 120 kg [ha.sup.-1]) and forms of N supply [single application (100%) in the stage [V.sub.3] (third expanded leaf); split application (70%/30%) in the stages [V.sub.3]/[V.sub.6] (third and sixth expanded leaves); split application (70%/30%) in the stages [V.sub.3]/E (third expanded leaf and beginning of grain filling)], respectively, in the systems soybean/wheat and maize/wheat. Rainfall and N are potential variables in the composition of the multiple linear regression model. Multiple linear regression models are efficient in the simulation of wheat biomass yield for silage under the N supply conditions during the cycle in the succession systems. Key words: Triticum aestivum N dose split N application residual N silage A producao de biomassa de trigo voltada para a elaboracao de silagem de qualidade e dependente da precipitacao, da temperatura e do nitrogenio. O objetivo no estudo foi validar o uso da precipitacao, soma termica e nitrogenio como variaveis potenciais para composicao do modelo de regressao linear multipla e a simulacao da produtividade de biomassa do trigo na elaboracao de silagem nas condicoes de fornecimento de nitrogenio durante o ciclo, nos sistemas de sucessao. O estudo foi conduzido em 2012, 2013 e 2014 em blocos ao acaso com quatro repeticoes em fatorial 4 x 3, para doses de N-fertilizante (0, 30, 60, 120 kg [ha.sup.-1]) e formas de fornecimento [unico (100%) no estadio [V.sub.3] (terceira folha expandida); fracionado (70%/30%) no estadio [V.sub.3]/[V.sub.6] (terceira e sexta folha expandida) e fracionado (70%/30%) no estadio [V.sub.3]/E (terceira folha expandida e inicio do enchimento de graos)] respectivamente, no sistema soja/trigo e milho/trigo. A precipitacao e o nitrogenio sao variaveis potenciais na composicao do modelo de regressao linear multipla. Os modelos de regressao linear multipla sao eficientes para simulacao da produtividade de biomassa do trigo para silagem nas co