AVAILABILITY OF MAJOR NUTRIENTS IN AN ULTISOL IN SOUTHERN SRI LANKA TREATED WITH SELECTED ORGANIC AMENDMENTS INTERMIXED WITH HYDROPHOBIC ORGANIC MANURE

Abstract

The addition of a small amount of hydrophobic organic manure blended with commonly used organic amend ments is found to induce slight water repellency, improve aggregate stability, and reduce organic matter decom position without detrimentally affecting hydrophysical properties of tropical Ultisols. The present study was con ducted to explore any negative impacts of this strategy on the availability of soil nutrients. A field experiment was conducted using Cattle (CM) and Goat manure (GM), and Gliricidia sepium (GL) leaves amended with soils in 5% rate. Separate plots were prepared by mixing 2% of Casuarina equisetifolia (CE) leaves which shows hydrophobic characteristics, with 5% of each manure (CM, GM, GL) separately to induce slight water repellency. Bush bean was established in the field and the major nutrients (N, P, and K) were tested at initial, vegetative, flowering, and harvesting stages. Data were statistically analyzed using SAS 9.1 statistical software. The results revealed that the highest and the least N contents were at the initial (40-130 mg/kg) and vegetative stages (8-20 mg/kg), respectively. The P contents were high at initial and vegetative stages (1-55 mg/kg) compared with other stages (<6 mg/kg). The highest and the least K contents were at flowering (370-600 mg/kg) and vegetative (40-210 mg/kg) stages, respec tively. The nutrient contents of the samples with intermixed 2% CE were statistically the same or higher than those without 2% CE in most of the growth stages. The yields of the plots with GL and GM with 2% CE were sig nificantly higher than those with only 5% GL and GM. The harvest index was significantly high in the treatment with 5% GM intermixed 2% CE. It can be concluded that the addition of extra 2% CE would not be unfavorable on nutrient availability and it would result in higher yields and harvest indices.