Evaluation of Different Conservation Tillage Practices for Soil Erosion Control and Their Effect on Crop Yield on the Severely Eroded Soils of Southern Guam.

Severely eroded lands of southern Guam are referred to as badlands.  These are actively eroding areas of very deep, well–drained saprolite derived from tuff and tuff breccia.  These badlands are exposed to overland flow, wind and rain causing sever erosion as the result of rapid runoff from the pitted, sloping sites that are void of vegetation.  The challenge facing soil and agricultural scientists is to develop conservation and restoration strategies that address crop production needs within a framework of increasing environmental and financial constraints.  Toward this end, we will emphasize crop residue management and green manure as means of restoration and conservation of badly eroded soils of southern Guam.  In this investigation, an integrated approach is designed to evaluate a variety of options, including the effect of conservation tillage, crop rotation with leguminous plants as green manure for organic matter build up, and residue management for soil conservation.  An annual legume cover crop (sunnhemp) is planted in rotation to corn as green manure to provide a baseline nitrogen source and increase the organic content of the eroded soils.  The objectives of this project are:  1) to evaluate cropping rotation and tillage management for increasing the organic matter content of these severely eroded soils.  2) To assess the effects of conservation practices and restoration techniques on water runoff and infiltration. Twelve field plots (33ft X 28ft⁾ are set up at the Ija experiment station in Southern Guam for this project.  Plots were initially planted with sunnhemp seeds to provide a nitrogen source and cover before corn was planted.  Control plots, however, are left fallow and without cover before corn planting.  In this presentation, the methodology as well as up-to-date data will be presented to illustrate the effect of conservation practices on the severely eroded soils of southern Guam.Key Words:  Conservation practices, No-till, Soil erosion, Guam, Sunnhemp, green manure.