Interação entre os estresses de nitrogênio e disponibilidade hídrica no fracionamento isotópico de 13C e na produtividade em soqueira de cana-de-açúcar / Interaction between nitrogen and water availability over isotopic discrimination of 13C and ratoon sugarcane production

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

09/05/2012

RESUMO

The sugarcane crop has an important contribution in sub tropical and tropical regions around the world, which Brazil the major producer of sugarcane crop, sugar and ethanol. However, the sugarcane yield is still very low in many regions of this country, mainly due to water stress and nitrogen supply. Understand the loss sugarcane production related with water and nitrogen stress using experimental classical methodology not always has obtained conclusive results. This work has evaluated the impact of water and nitrogen (N) stress by discrimination of 13C (\ delta\ 13C) and sugarcane production in a ratoon over fertirrigation system, where 2 water supply and 5 N level were applied. The results of isotopic technique (\ delta\ 13C) were correlated with a several parameters like sugarcane production, biomass accumulation (tops, stalks and dry leaves), and, others physiologic parameters (SPAD index, foliar area, diameter, tillering and height) evaluated throughout crop cycle. The research was performed in Jaú county, São Paulo State, Brazil (22°17\ S 48°34\ O), over Rhodic Eutrudox condition. The randomized block design was used with 4 replication per treatment. The sugarcane cultivar SP80-3280 was submitted a 5 N rates (0, 50, 100, 150 e 200 kg ha-1 N) which were applied by fertirrigation system. Further, 4 treatments were used to estimate the N and water stress, such as: T1- without water irrigation and N application; T2 - water irrigation without N supply; T3 - without water irrigation but with N application; T4 - with water irrigation and N fertilization. The results showed linear increase in physiologic, morphologic parameters and biomass production related N rates applied. The N content and SPAD index of leaf +1 correlated a linear decreasing model. The elevation of dose of 100 to 200 kg N ha-1 no increased dry matter accumulation of aboveground in 20 Mg ha-1, and N in 95 kg ha-1, increments also observed in dry matter production rates and rates of accumulation of N. The data of 13C (\ delta\ 13C) had a negative correlation between sugarcane production (R2= 0.69, p<0.05) and biomass (R2= 0.69, p<0.05) and N rates. Verified an increase linear in productivity of stalks and sugar with an increment respectively of 60 and 8 Mg ha-1 as a function of applied doses of N along the irrigation. The higher value of 13C (\ delta\ 13C) were observed when took place N and water stress (T1), whilst the treatment with N application and water irrigation (T4) showed the lowest value of 13C discrimination (\ delta\ 13C). The 13C discrimination (\ delta\ 13C) was efficient to evaluate stress in sugarcane crop, can be used as an indicator of water deficit and deficiency of N to in this culture

ASSUNTO(S)

delta 13c delta 13c disponibilidade hídrica doses de n n rates saccharum sp saccharum sp water stress

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