Effect of temperature and soil moisture on the biodegradation of sheep manure in calcareous soils1- measurement of carbon dioxide evolution

الملخص EN

A three months laboratory incubation experiment was conducted at the department of soil and water sciences of the college of agriculture- University of Duhok to study the interactive effects of three levels of temperatures (5, 28, and 45°c) and three levels of soil moistures (25, 50, and 75%) of the soil water holding capacity (WHC) on the biodegradation of sheep manure added at three concentrations (zero, 1.5, and 3% w / w) to two calcareous soils differs mainly in the ratio between the active to total CaCO3 A / T (6.46 and 86.66 ).

The amounts of CO2-C evolved from the biodegradation of the manure-C were measured at 3, 6, 9, 15, 22, 45, 60, and 90 days of incubation, then converted to percentages of decomposition at 60 and 90 days.

Results indicated that the rate of decomposition was generally faster in the soil high in the ratio between A/T,(38%; 41.8; 36%) for the lower level of the added sheep manure, when the moistures of incubation were 25%; 50%; and 75% of WHC and (38.6% ; 39.8% ; 36.2%) for the higher level , respectively , in comparison with (37,4% ; 39.4% ; 34%), ( 38,3% ; 39.1% ; 35.5%), for the soil low in A / T, regardless of the temperature of incubation.

Maximum rate of decomposition was obtained at 45°c (43,3%) in the soil low in A / T when treated with 1.5% sheep manure, and (41.5%) for the soil high in A / T when treated with 3% sheep manure, regardless of the moisture of incubation.

The lowest rate of decomposition was in the soils incubated at 5°c (30,8% and 33,1%), while at 28°c was in between (39.1% and 38.9%), respectively.