Spatio-Temporal Variability of Soil Water Pressure Head in Crop Sequences Under No-till System.

No-till system is considered a conservation system of great importance to the sustainability of agriculture. Provides increase the aggregation of soil particles, greater infiltration and less evaporation. However, under tropical climate conditions of the main problems is the maintenance of soil cover in the offseason due to the high temperatures and lower water availability. However, under tropical climate conditions, the maintenance of soil cover in the offseason due to the high temperatures and lower water availability, becomes a problem. The objective was to evaluate the soil water pressure head and apply spatial and temporal analysis in field data, understand how soil water pressure head change in space and over time and establish the relationship with different crop sequences under no-till system. The field experiment was established in 2002 at Jaboticabal, SP, Brazil (21°15’22” S, 48°18’58” W and altitude of 595 m). The soil of the experimental area is an Oxisol (Rhodic Eutrudox). One transecta was analyzed. The transect consisted of twenty-one plots of a soybean/maize rotation, both intercropped every other year (summer) combined with seven winter crops, sown in February–March of each year in the same plots, were corn, sunflower, oilseed radish, pearl millet [Pennisetum americanum (L.) Leeke], pigeon pea, grain sorghum [Sorghum bicolor (L.) Moench]; and sunn hemp (Crotalaria juncea L.). The soil water pressure head was measured at 0,2 m, 0,4 m and 0,6 m using tensiometers, installed in the center of each plot and the line between the crops. Autocorrelograms and semivariograms was using to assess the structure of spatial and time correlation. The results show that the soil water pressure head showed a dependency structure in time and space. There is a greater dependency between the data considering the time-domain compared with the space-domain.