Índice de estresse “soma do excesso de água (SEW30)” na cultura do milho em solo de várzea sob sistema de drenagem subterrânea.

Abstract

The excess, the of lack water and the nutritional deficiency, usually produces decreases in the yield of the cultures. The meadows areas, usually, meet close to bodies of water, which have big influences in the flotation of water table regulating the tenor of O2 in the macro and microspores. The aim at work was of quantifying the effect of the flotation of the water table and of the growing doses of N in the productivity of the culture of the corn, using the excessive soil water SEW30 in meadow soil. The experiment was conduct in a meadow belonging ESALQ/USP, with drainage system implanted with 19 underground drains, spaced of 10 m. The experimental design was randomized complete blocks, with 5 treatments and 3 repetitions. Each treatment possessed an underground drain and an observation well (OW) installed. The depth of OW varies inversely to the values of the rains. The relative productivity (%) of the corn in function of the index SEW30 presented a model of growing lineal regression (P<0,05). The yield of the culture was not committed by the excess of humidity of the soil. It conclude that (1) the stress index SEW30 answered in a increase lineal way the relative productivities of the corn grains; (2) the elevations of OW in function of the rains along the cycle of the culture of the corn contributed to the increase of the productivity of the culture of the corn