Produtividade agrícola de cana-de-açúcar irrigada com gotejamento em quatro ciclos de cultivo.

Abstract

Understand the water requirements of crops sugarcane is essential when seeking higher yields, since one of the main factors limiting agricultural productivity in Northeast Brazil rainfall is due to its uneven distribution which leads to soil water déficit. Therefore, to evaluate the response of sugarcane irrigation experiment was installed in the region of Rio Largo - AL with seven irrigation heights determined based on reference evapotranspiration: (ETo): 0% ETo 25% ETo, 50% ETo, 75% ETo, 100%, 125% and 150% ETo. During the experiment, the air temperature ranged from 20.77 to 29.19 ° C (average of 24.9 ° C). The total rainfall in the plant-cane cycle was 2.105 mm while the ETc was 1.684 mm in the 1st cycle of ratoom rain accumulated ETc and 2.002 mm in the same cycle was 1.516 mm. The total rainfall in 2nd ratoom was 2.017 mm and even at full ETc of 1.592 mm, there was 409 mm of water deficit in the cycle. The total rainfall in 2nd Ratoom was 2.017 mm and even at full ETc of 1.592 mm, there was 409 mm of water deficit in the cycle. The lowest rainfall was in the 3rd Ratoom (983 mm) and ETc cycle was 1.589 mm. In plant-cane, 1st ratoom, 2nd and 3rd ratoom, water deficit was 578, 409, 571, and 856 mm water surply was 998, 874, 976 and 229 mm, in the same order. The average productivity of agricultural crops was 160, 130, 101 and 92 t ha-1 for four cycles, respectively. The sugar cane irrigated with 150% of ETo, produced mean of 140.1 t ha-1 and the average productivity of rainfed was 94.1 t ha-1 in the four crop cycles, respectively. The height 150% ETo provided increase of agricultural productivity of 67% when compared to plots without irrigation and the height of 100% ETo was higher than 46% to the average of the upland. The reduction in yield due to water stress varied from 0.137 t-1 mm in plant cane to 0.050 t-1 mm 3rd ratoom (mean 0.07 t-1 mm). The polynomial regression curves of the second degree and represented the relationship between water deficit and yield of sugarcane.