Effect of tillage systems and organic manure on bromide leaching under corn cropping

Tillage and organic matter management have some impact on soil physical, chemical and biological properties, therefore they influence water and solute transport in soil. This study was performed in two consecutive years. Different tillage treatments including disk harrowing + two disk harrowings as reduced tillage (15 cm plowing depth) and moldboard plowing + two disk harrowings as conventional tillage system (30 cm plowing depth) were used. Also, three levels of 0, 30 and 60 tons per hectare farmyard manure were also used as organic manure treatments. The above mentioned treatments were done in a split block design with 3 replications and under corn cultivation for two years. In order to determine solute transport, potassium bromide was added to soil at concentration of 16.67 g/l. Soil sampling from furrow was conducted after 126, 315 and 630 mm irrigation, respectively. Sampling depth were 0-15, 15-30, 30-60, 60-90 and 90-120 cm. The results showed that bromide leaching and transport was significantly lower under reduced tillage (T1) in comparison to conventional tillage (T2) irrespective to water irrigation content. This is due to higher soil loosing by T2 compared to T1. The results indicated that manure had no significant effect on bromide transport. With increasing irrigation water content, bromide leaching to lower layers increased as well. Under T1, after 126 and 315 mm water, most of bromide has remained at depth of 0-15 cm. However, by adding 630 mm of water, bromide concentration reduced considerably at surface layer. Although bromide leaching was higher at T2 than T1 treatment, but due to low permeability of subsoil layers, bromide concentration (tracer) at topsoil was considerable. But, by adding 630 mm water in the last stage of sampling, the bromide concentration at surface layer (0-15 cm) showed a reduction, therefore a great amount of trace element has escaped from this layer.