Organic mulch decomposition kinetics in semiarid environment at bare and crop field conditions

Scantly available knowledge of organic mulch decomposition kinetics is impo rtant to determine the best choice of mulching materials, and their applica tion rate and frequency for crop production and soil protection in arid are as. The kinetics was studied in two field experiments. In Experiment I, it was tested for sugarcane trash mulch (6 Mg ha(-1)) with and without enrichi ng it with Mussoorie rock phosphate (MRP) at 600 kg ha(-1) (obtained from M ls pyrites, Phosphates and Chemicals Ltd., Dehradun, India) and with indust rial glue waste (GW) at 4 Mg ha(-1), a solid granular waste material of sub cutaneous animal origin, rich in N (obtained from Glue Industry, Juglan, Ha ryana, India) at ratoon sugarcane (Saccharum officinarum) on fine loamy soi l for two years (1997-1998 and 1998-1999) at Hisar (29 degrees 05 'N, 75 de grees 38 'E, 222 m elevation). The GW and MRP were manually broadcast over the sugarcane trash mulch at the time of mulch application. Experiment II w as conducted from December 1998 to April 1999 on sandy soil at Balsamand (2 9 degrees 07 'N, 75 degrees 28 'E, 225 m elevation), 35 km west of Hisar, a t bare field conditions wherein three different types of mulches were teste d: farmyard manure (FM), green neem (Azadiracta indica) leaves GM, and whea t straw (Triticum. aestivum) (WM), with two mulch thicknesses (20 and 40 mm ). Wheat straw mulch (WM) placed at surface was compared with wheat straw m ixed into 0.0-0.10 m soil depth (W-mixed) for decomposition kinetics. The l oss in dry weight of mulches was taken as a measure for mulch decomposition as a function of time (t). First-order decomposition kinetics was followed in all the treatments at varying field moisture conditions in Experiments I and II. The decomposition percentage in 4 months (d4) was 40% higher at e nriched sugarcane trash (ESM) than that at sugarcane trash mulch (SM). It w as higher at 20 mm mulch thickness than at 40 mm for all the types of mulch in Experiment II and followed the order GM > WM > FM. The d4 value of W-mi xed was two times higher than that of wheat straw mulch WM at 20 mm mulch t hickness. Mulch decomposition rate constant k was 0.0071 d(-1) for SM and 0 .0115 d(-1)for ESM averaged over the two years. The k values were 0.0021 d( -1), 0.0032 d(-1), and 0.0037 d(-1) for FM, WM, and GM respectively at 20 m m mulch thickness and it was 0.0066 d(-1) for W-mixed in Experiment II. The practical implications were: (a) enriched dry mulch should be preferred ov er dry mulch for annual crops in order to enhance their nutrient recycling and decomposition, and (b) dry mulch should be preferred over green mulch i n the perennial fruit trees for their long persistence and durability in or der to protect soils against wind erosion in and areas.