Nutrient dynamics of a seven-year old yemane (Gmelina arborea Roxb.) hedgerow intercropping system at Claveria, Misamis Oriental, Philippines

This study was conducted to evaluate the nutrient status of the crops, soil and hydrologic inputs to seven-year old yemane intercropping system vis-a-vis crop removal and soil erosion of the site. Specifically it aimed to determine the nitrogen (N), phosphorous (P), potassium (K) contents of the soil, before, after and at the end of each cropping period including organic matter content, soil pH and soil bulk density. Leaf litter production and decomposition studies were also included which are considered the primary source of nutrients within the hedgerow-intercropping system. The study had three treatments, T1 (1 x 3 m hedgerow spacing), T2 (1 x 9 m hedgerow spacing) and T3 (pure maize or control) with two replicates. It was found that N had the highest input from stemflow, throughfall, maize residue and leaf litter fall with 5.71-16.14, 5.37-6.83, 18.73-82.62 and 105.65-133.05 kg/ha/yr, respectively. P inputs were; 6.54-11.51, 1.05-2.37, 0.94-5.73 and 6.34-7.19 kg/ha/yr for stemflow, throughfall, maize residue and leaf litter fall, respectively. On the other hand, K inputs (kg/ha/yr) were as follows: stemflow (14.08-62.47), throughfall (2.10-4.58), maize residue (17.79-121.05) and leaf litter fall (10.78-11.77). For nutrient outputs (kg/ha/yr), N had 6.99-15.53 in soil erosion, 3.64-6.86 in surface runoff and 6.16-27.54 in crop harvest. On the other hand, P outputs (kg/ha/yr) were 0.02-0.03, 1.03-1.22 and 0.31-1.91 for soil erosion, surface run-off and crop removal, respectively. K outputs were 0.18-1.65, 0.29-0.39 and 5.86-40.36 respectively. Total monthly leaf production (kg/ha) of the site totalled to 7,187 (1 x 3 m) and 9,051 (1 x 9 m) with a decomposition rates of 44 percent and 60 percent for 1 x 3 and 1 x 9 m hedgerow spacing, respectively. Generally, it was observed that soil pH slightly change from 5.29 to 5.60 before the first cropping and at the end of the second cropping period as well as with the soil bulk density from 1.37 to 1.22 g/cu cm. Increase in organic matter content from 2.83 percent to 3.70 percent was noted in the study before the first cropping and at the end of the second cropping periods, respectively. Moreover, both N and total P also increased from 0.14 percent to 0.19 percent and 0.006 to 3.32 ppm correspondingly while available K increased from 36.50 to 51.13 ppm before the first cropping period but decreased after second cropping period from 51.13 to 44.88 ppm. Net balances (kg/ha/yr) of the nutrients were as follows: N (33.86-163.80), P (2.62-20.47) and K (69.95-86.51). The result also shows that net soil nutrient balance of N, P and K for both pure maize and hedgerow intercropping system is similar. This is due to the high nutrient contribution of rainfall to the nutrient budget of pure maize that is drastically reduced by canopy interception in the hedgerow intercropping system.