Bruno L. Santoro

Alterations in attributes of a Red-yellow Latosol irrigated with reuse water

The reuse of treated sewage effluent to water bodies to supply water for irrigation has been of great advantage to agriculture, and the use if not regimented could bring changes in physical and chemical properties of soil. This paper aimed the evaluation of the physical and chemical properties alteration of a Red-yellow Latosol after the application of reuse water from an effluent treatment station of wetlands. The experiment was accomplished in laboratory using a soil column. First, 15 L of distilled water were applied in the soil column and after 15 L of reuse water and at interval of 5 L of water a sample was collected for analysis. The results showed decrease of nitrate, potassium and saturated hydraulic conductivity values and an increase in sodium, iron, manganese, zinc and electrical conductivity of the soil after water application. In this way, it may be concluded that the use of waste water for agronomic activities must be used in a rational way, mainly checking the elevation of sodium.

Utilização da TDR para monitoramento da solução de nitrato de potássio em Latossolo Vermelho-Amarelo

Knowledge of water distribution in soil is of great importance to agriculture, since water is one of the factors that most influence the yield of crops. There are many techniques used for monitoring of soil water content, the Time Domain Reflectometry (TDR) has been widespread among researchers to present several advantages, among which the determination in real time and possibility of automated readings. The main goal of this research was to evaluate the KNO3 solution distribution in a profile of a Dystrophic Red-Yellow latossol. Time domain reflectometry (TDR) probes were used to monitor the soil solution distribution from drippers discharging at constant flow rates of 2, 4 and 8 L h-1 in soil. Considering the results from different profiles, we observed greater solute storage near the dripper decreasing gradually towards the wetting front. About half of the applied KNO3 solution (65%) was stored in the first layer (0-0.10 m) for all experiments and 22 % was stored in the next layer (0.10-0.20 m). Comparing different dripper flow rates, we observed higher solution storage for 4 L h-1, with 60, 72 and 63 % of the applied KNO3 solution accumulated in the first layer (0-0.10 m) for dripper flow rates of 2, 4 and 8 L h-1, respectively. The results suggest that based on the volume and frequency used in this experiment, it would be advantageous to apply small amounts of solution at more frequent intervals to reduce deep percolation losses of applied water and solutes.

Distribuição de água no solo aplicado por gotejamento enterrado e superficial

Studies of sub-surface water movement is an interesting topic in irrigation but, in spite of the its importance, there is little literature. One of the purposes of this study was to contribute to this subject and evaluate the distribution of water applied by both subsurface drip irrigation (SDI) and conventional irrigation. Experiments were conducted at the Department of Rural Engineering (ESALQ/USP), located at Piracicaba, SP. Trenches were opened and 17 three-rod TDR probes were installed, placed at 0.05, 0.15, 0.25, 0.35 and 0.45 m depths, and to 0.05, 0.15, 0.25, 0.35 m intervals. This procedure was repeated using a dripper buried at 0 and 0.10 m for each discharge rate of 2 and 4 L h-1 tested. Wetted soil volume was observed with 1 L of water applications at intervals (total 10 L). The saturated disc around the dripper and the advance of the wetting front on the soil surface were measured with a ruler. Also, a central control volume was established inside the wetted soil volume where the uniformity of application was evaluated. The results suggest that SDI presented smaller wetted soil surface area and it reached larger distance and depth with greater storage of solution adjacent to the dripper.

Wetted Soil Volume as a Design Criteria in Drip Irrigation

The principal objective of a drip system design is to choose the appropriate layout and components to obtain adequate soil solution distribution throughout a field. In addition to maximizing crop production, modern fertigation practices must consider environmental sustainability and rigorous water management. These often conflicting considerations require significant changes in irrigation system design and operation (relative to traditional designs for maximum crop production). We conducted experiments to characterize dynamics and patterns of soil solution within the wet bulbs formed by drip fertigation for pepper (Capsicum annum, L). Time domain reflectometry (TDR) probes were used to monitor the distribution of potassium nitrate (KNO3) and water distribution from drippers discharging at constant flow rates of 2 and 4 L h-1 under field conditions. Considering results from different profiles, it was observed greater (large) solute storage near the dripper decreasing gradually towards the wetting front. About half of the applied KNO3 solution (65%) was stored in the first layer (0-0.10 m) for all experiments and 22% was stored in the next layer (0.10-0.20 m). Comparing different dripper flow rates higher solution storage was found for 4 L h-1 by means of 72% of applied KNO3 solution was accumulated in the first layer (0-0.10m) compared with 60% for 2 L h-1. The chemical analysis of leaf showed no differences between N and K concentrations for different flow rates. These results suggest that based on the volume and frequency used in this experiment, it would be advantageous to use flow rate of 4 L h-1 to reduce deep percolation losses of applied water and solutes.