Dr. Kamaruzaman Jusoff of the Universiti Pertanian Malaysia, performed a study to determine the effects of animal/crop integration on soil properties and tree growth. The study was conducted in a rubber plantation on a small-holder's mini estate at bukit Mahang in the state of Kelantan, Malaysia. The study period lasted from August 1986 to November 1986. The soil texture is loamy sand. The climate there is tropical humid, the annual rainfall is 3,175 mm, the mean annual temperature is 24 degrees Celsius, and the relative humidity is approximately 96%. The wet season begins in November, and the dry season runs from February to August.
Two treatment plots of 50m by 100m were randomly established at the study site. One was grazed while the other was left ungrazed. Soil was taken from depths of 0 to 10 cm at random in the inter-row areas, and analyzed using 'ELE' augers. Tree girth at 0.5 m height was used as a measure of growth of 100 randomly selected rubber trees in each plot.
The soil tests revealed the following positive results:
The increased N was probably due to the increased input of organic matter from sheep manure. The increase in P, Ca, and Mg uptake is, however, not significant when compared to the increase in N and Na in the grazed plot. The uneven distributon of soil nutrients observed in the grazed plot may be due to the variation in the amount of sheep manuer in the soil and leaching losses. Large amounts of ammonia produced from the hydrolysis of urea in sheep urine, and cations deposited from the sheep manuer could account for the increase in pH of the grazed soil.
The larger girth of trees in areas grazed by sheep relative to the ungrazed plot indicates that trees under grazing conditions take up more nutrients. According to Tajuddin  an adult sheep can produce about 186g (dry matter basis) of manure, containing 2.40% N, 0.40% P, 2.89% K, 1.84% Ca, 0.54% Mg, and 507 ppm Na, each day. Apart from the addition of organic matter, suppression of weeds by sheep may reduce competition for nutrients and water, thus enhancing tree growth.
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