Agronomics of land application of municipal collected shade tree leaves: I. Soil properties

Land application of municipal collected shade tree (MCST)-leaves is a permi tted practice in New Jersey that may be useful in sustainable agriculture. The material helps build soil organic matter, but its overall impact on soi l properties and nutrient levels needs to be determined. This study, conduc ted near Pittstown, NJ on a Quakertown silt loam (fine-loamy-mixed, mesic, Typic hapludult) from 1991 to 1994, examined the effects of MCST-leaves on soil organic matter content, pH, and soil test levels of nutrients and heav y metals, following three years of annual applications at 0, 22.5 and 45 Mg ha(-1) yr(-1) Soil samples were collected four years after the initial app lication of MCST-leaves to evaluate treatment effects. Soil organic carbon levels increased from 13.9 g kg(-1) in the unamended soil to 17.1 g kg(-1) in the 22.5 Mg ha(-1) yr(-1) rate of MCST-leaves and to 18.4 g kg(-1) for t he 45 Mg ha(-1) yr(-1) rate. About 17% of the C that was added to the soil as MCST-leaves remained in the soil one year after the end of the three-yea r period of annual applications. Soil organic nitrogen levels increased fro m 1.0 g kg(-1) for the unamended soil to 2.0 g kg(-1) for the 45 Mg ha(-1) yr(-1) rate. Soil pH levels and Mehlich-3 extractable P, K, Cu, Mn, Zn, Co, Cd, Pb, Ni and Cr were unchanged by the applications of MCST-leaves while levels of Ca and B were increased. Percentage of exchangeable Ca increased in the amended soil while the exchangeable Mg decreased. The practice of la nd applying MCST-leaves is consistent with sustainable agriculture, to rais e soil organic matter and Ca levels without causing an excessive buildup of soil test P.