ARS | Publication request: EFFECTS OF UNDER-STORY MANAGEMENT AND FORAGE SPECIES ON SOIL MOISTURE IN A PECAN ALLEY CROPPING PRACTICE

Submitted to: Northern Nut Growers Annual Report
Publication Type: Proceedings
Publication Acceptance Date: January 15, 2005
Publication Date: September 1, 2006
Citation: Brauer, D.K., Horton, T.Y., Burner, D.M. 2006. Effects of under-story management and forage species on soil moisture in a pecan alley cropping practice. Northern Nut Growers Annual Report. 95:27-37.

Interpretive Summary: Bermudagrass and tall fescue are common warm- and cool-season forage species that are recommended for use in pecan agroforestry practices. Productivity of such agroforestry practices, especially in upland situations, is usually determined by the optimum use of soil moisture by the pecan trees, but there is little information comparing the effects of bermudagrass to tall fescue on soil moisture in agroforestry practices. Changes in soil moisture, tree growth and forage production were determined in hay alley cropping practice with either tall fescue or common bermudagrass as the under-story species and 15-year old pecan trees. Tree growth was not affected by the forage species despite the fact that soil moisture during the summer months tended to be less when the forage was bermudagrass. These results are of interest to landowners and natural resource professionals advising landowners on the design and management of pecan agroforesty practices.

Technical Abstract: Bermudagrass (Cynodon dactylon L.) and tall fescue (Fesctua arundinacea Schreb.) are common warm- and cool-season forage species in the transition zone and are recommended for use in pecan (Carya illinoinensis (Wangenh.) K. Koch) agroforestry practices. Productivity of such agroforestry practices, especially in upland situations, is usually determined by the optimum use of soil moisture by the pecan trees. Changes in soil moisture, tree growth parameters and forage production on an upland site near Booneville AR were determined over two growing season (2002-2003) in a pecan hay alley cropping practice with either tall fescue or common bermudagrass as the under-story species. The pecan trees were approximately 15 years old when the study was started. Under-story vegetation was kept to a minimum within 6 feet of the tree trunk by frequent herbicide applications. Changes in tree growth (DBH and height) were not significantly affected by under-story forage species. Tall fescue was harvested in April and September each year, while bermudagrass was harvested in June and July. Annual production of fescue forage was significantly greater than that of bermudagrass. Soil moisture content was monitored weekly throughout the growing season and was very low in August and September regardless of sward type. Soil moisture content was significantly less when bermudagrass was the under-story forage, especially during the summer months of July, August and September. Changes in soil moisture were determined daily for 4 to 14 days after significant rain event (> 1 inch) in May through August. When averaged across seven events in 2002-2003, there was no significant effect of under-story forage species on the rate of soil moisture decrease, although the rate of soil drying was slightly greater when bermudagrass was the under-story forage. These results indicate that soil moisture tended to be less when bermudagrass was the under-story forage but this decrease in soil moisture did not affect tree growth. Severe moisture stress under both forage species may explain a lack of tree growth response to differences in soil moisture.