Long-Term Effect of Various Agroforestry Systems on Soil Characteristics and Forms of Nitrogen Build up in Acidic Alfisol of Meghalaya

Effect of five Agroforestry Systems (AFS) on soil properties and forms of nitrogen was studied 15 years after their adoption, comparing with natural forest (to serve as control) of same age group in an Acidic Alfisol of Meghalaya. The soil pH was maintained in all the AFS except silvi-horti-pastoral system, but the same system registered maximum organic carbon content (2.19%), while agrisilviculture and agrihorticulture AFS recorded lower organic carbon content compared to control. The base saturation percentage and effective cation exchange capacity (ECEC) were higher by 6.5 to 63.6 and 23.3 to 111.7 per cent, respectively, over control in different AFS. All the systems except multistoreyed AFS had higher values of different forms of acidity as compared to control. Multistoreyed AFS registered maximum values of available N, NH4+-N, NO3-N and mineral N among all the systems, although total N content was quite low (0.18%) as compared to other systems such as control (0.19%), agrihorticulturer and silvihortipastoral AFS (0.20%) indicating, higher rate of N mineralization in this system. Organic carbon, ECEC, exchangeable bases and base saturation had positive correlation with all forms of N and all the forms of N were significantly correlated with each other.