Balanço de 15N em sistemas de produção de milho para adoção do plantio direto no Oeste baiano / 15N balance in maize production systems for no-till in the west State of Bahia

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

In Cerrado of the west of Bahia state the climate difficulties the formation of vegetable residue for no-tillage. Intercropping cultures is an alternative for climate limitation, for producing biomass to the system. Cotton producers from this region use maize culture for rotation and, in some cases, for formation of straw, with fertilization done exclusively during sowing in sandy soils, with low level of organic matter and an average precipitation of 1500 mm. Two researches were performed: (i) maize productivity and remaining residues due to production system and nitrogen dosage and (ii) nitrogen (15N) balance in maize single crop systems and intercropped with Brachiaria ruziziensis. The objective of the first research was to evaluate the use N doses, in sowing, in maize single crop and intercropped at São Desidério, BA; to establish no-till. It was adopted the randomized block design, with 10 treatments and four repetitions: T1 maize without nitrogen; T2 maize-brachiaria without N; T3 maize with 50 kg ha-1 of N; T4 maize- brachiaria with 50 kg ha-1 of N; T5 maize with 100 kg ha-1 of N; T6 maize- brachiaria with 100 kg ha-1 of N; T7 maize with 150 kg ha-1 of N; T8 maizebrachiaria with 150 kg ha-1 of N; T9 maize with 200 kg ha-1 of N; T10 maizebrachiaria with 200 kg ha-1 of N. Productivity was evaluated, nitrogen extraction and exportation, biomass production and N extraction by the brachiaria and the correlation between determined and estimated N grain quantity. Intercropping was efficient for formation of straw (5.056 kg ha-1) intending to adopt of no-till; maize responded to 50 kg ha-1 of nitrogen, independently of cropping system and brachiaria did not respond to fertilization; nitrogen extraction in the cropping systems was harmed only in the absence of N; while the exportation was reduced in the intercropped system, only in the absence of nitrogen; the estimative of N exportation can be obtained by the expression: NGE = PG x 0,09 x 0,16. The second research had objective of evaluate dynamics of N with 150 kg ha-1 of 15N-urea application in the sowing of maize single crop and intercropped with brachiaria in the same place. The randomized blocks design was adopted, with two treatments and four repetitions. Treatments were: T1 single crop maize and T2 maize- brachiaria, with 150 kg ha-1 of 15N urea at sowing. It was evaluated the accumulation of 15N by aboveground and roots; the EUFN by maize crop and brachiaria and the residual amount in the soil derived from the fertilizer. The brachiaria intercropped with maize did not restrict N avaibility. The EUFN varied between 60,4 % for intercropped and 64,8 % for single crop. Brachiaria recovered 1,4 % of the 15N applied. The RFNS were of 18% and 25% for single crop and intercropped maize. The 15N not recovered from urea was 25,5 kg ha-1 of N in the maize single crop and 19,5 kg ha-1 in the intercropped maize.

ASSUNTO(S)

brachiaria isótopos estáveis stable isotopes plantio direto. fertilizantes nitrogenados milho no-till. palhada straw brachiaria nitrogen fertilizers maize

ACESSO AO ARTIGO

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