Rainfall infiltration and runoff from an Alfisol in semi-arid tropical India. I. No-till systems¹

Abstract

Alfisols, which are abundant in the semi-arid tropics, are fragile and subject to crusting, resulting in high runoff amounts and large soil losses. A field experiment was conducted at the International Crops Research Institute for the Semi-Arid Tropics, Hyderabad, India, over a 6-year period to study the runoff from Alfisols under no tillage without amendments, and with the addition of farmyard manure (15 Mg ha⁻¹yr⁻¹) and rice straw (Oryza sativa) (5 Mg ha⁻¹ yr⁻¹). Each treatment had three replicates. A total of 211 runoff events were recorded for each plot. For runoff from no-till systems without any plant or straw cover, the infiltration rate was controlled by the surface crust. Infiltration rate through a surface crust was 9.6 mm h⁻¹ and showed little change over time. Infiltration rates measured with a ring infiltrometer and disc permeameter were five to six times higher than that observed under natural rainfall. The data was divided into four groups with similar amounts of rain during the preceding 2 days and percent soil cover. The regression analysis found that the amount of precipitation, 30 min intensity, soil cover, and time since the beginning of the experiment were all significant factors in determining the runoff. More than 75% of the variation in runoff was explained by these variables for the zero tillage system without amendments and with farmyard manure applied. Straw amended systems were more difficult to predict. For events with less than 15 mm of rain during the previous 2 days, runoff was mainly related to the amount of rainfall when surface cover was less than 30% and to the product of rainfall amount and 30 min intensity when surface cover was greater than 30%. For events with more than 15 mm of rain during the previous 2 days, infiltration rates were generally higher than for dry soil. Runoff was related to a number of variables. Implication for management practices on Alfisols are that adding organic residue to no-till systems could significantly lower the runoff and increase the amount of water available for the crop.