Forage and Tree Production on Marginal Soils in Tennessee

Abstract

Few data are available to compare perennial forage and tree crops grown on marginal soils not adapted to row and annual crops in land capability classes III to VI. A long-term project was initiated in 1983 to study the productivity of loblolly pine (Pinus taeda L.), American sycamore (Platanus occidentalis L.), tall fescue (Festuca arundinacea Schreb.) and bermudagrass (Cynodon dactylon L.) on 10 marginal soils. Interim results are presented because the advent of the Conservation Reserve Program (CRP) brought attention to the scarcity of management information needed for such lands. Tree growth and biomass were measured 4 yr after planting. Grass production was measured with several cuts each year. Soil and weather characteristics which affected trees and grasses were identified by regression analysis. Tall fescue yields ranged from 1000 to over 8000 lb/acre with a mean of 3560. Bermudagrass yields averaged 2580 lb/acre with a range of 680 to almost 8000. Both grasses were affected by growing degree days and drought days associated with each soil each year. Exchangeable Al, percent silt, available water, and coarse fragment content also affected grass yield. Mean survival of loblolly pine at 5 yr was 89% with a predicted site index (25-yr base) between 50 and 70. Predicted loblolly productivity was related to variations in extractable K, exchangeable Al, percent silt, total acidity, and available water. Fresh biomass of sycamore averaged 10 000 lb/acre, with a range of 625 to 28 000 lb/acre. Mean survival at age 5 was 96%. Predicted sycamore biomass production depended on soil available water, extractable P, and exchangeable Al in the top 6 in. of soil. The wide adaptation of loblolly pine and the genetic potential of sycamore to respond to better conditions were associated with the greater variation in sycamore production than in loblolly growth. Early sycamore biomass production has more closely followed grass yields than loblolly pine growth. The direct biological comparison of some tree vs. grass species on marginal soils will enhance the predictability of many potential land uses between competitive agriculture and forestry alternatives.