Soil water competition in a temperate hedgerow agroforestry system in South Africa

Abstract

An on-farm trial was conducted to determine dry matter production of four fodder tree species and their effect on soil water and maize production. The trees were planted in rows intercropped with maize. The four tree species selected were Acacia karroo Hayne (indigenous fodder tree), Leucaena leucocephala (Lam.) De Wit (nitrogen fixing), Morus alba L. (fodder and fruit), and Gleditsia triacanthos L. (fodder and fuel). Volumetric soil water was measured in the upper 0.3 m of soil in each row of the trial using the time domain reflectometry technique. The neutron probe technique was used for monitoring the water content deeper in the soil. Geostatistical methods were used to analyse treatment differences in the upper 0.3 m of soil. The soil water content did not differ significantly between the maize and tree rows indicating that competition for water in the upper horizon was not the reason for lower maize yields. However, at greater soil depths (75-125 cm) trees in the wide spacing used less water than those in the narrow spacing. Light interception was an important factor in reducing maize yields in the row nearest to the trees. High soil water values recorded during summer indicated that in the current cycle of good rainfall the plants in the agroforestry trial were not stressed. Thus the trees do not compete with the crops for soil moisture in good rainfall seasons. However, this study would need further evaluation for the competition for water for the low rainfall years. Since the trees have access to water at greater depths, they are likely to be more productive into the dry season than shallow rooted crops.

Determinants of agroforestry technology adoption in Eastern Cape Province, South Africa

“…Note that this is not an exhaustive list of AF tree species useful to South Africa. Everson et al (2009) conducted an on-farm study in the Upper Thukela region of KwaZuluNatal to determine dry matter production for fodder tree species and their effect on soil water and maize production.…”

Trees in agricultural landscapes enhance provision of ecosystem services in Sub-Saharan Africa

“…The former was notable for green manure trees and fallowing, which is often associated with loss of a growing season and this will have especially large impact where there is only one short growing season (Bünemann et al 2004). Yields can also be reduced if trees compete with the crops for nutrients, water and light; a phenomenon common when the density of trees is high (Everson et al 2009), and in close proximity to crops (Jama et al 1995(Jama et al , 2000Boffa et al 2000). Certain tree species are considered competitive and provide too much shading when grown together with crops, and this may reduce yields (Mathuva et al 1998;Bayala et al 2002;Gaafar et al 2006).…”

“…crops, such as cocoa (Isaac et al 2007), chilli pepper, millet (Kho et al 2001) and coffee. In studies where microclimatic conditions were reporting negative effects in tree-crop systems, it was mainly due to reduced photosynthetically active radiation in semi-arid zones (McIntyre et al 1997;Ong et al 2000;Bayala et al 2002;Everson et al 2009), higher relative humidity and lower air temperature compared to monoculture in sub-humid zones (Koech & Whitbread 2006;Schroth, Balle, et al 1995). This resulted in reduced crop yields (McIntyre et al 1997;Everson et al 2009) and increased pest infestation (Koech & Whitbread 2006;Schroth, Balle, et al 1995).…”

Switchgrass growth and pine–switchgrass interactions in established intercropping systems

“…Belowground interaction is affected by several biotic and abiotic factors such as soil resources availability, root characteristics, climatic conditions, and phenology (Ong et al, 1991;Jose et al, 2004) and could result in various outcomes in terms of understory growth. Some studies have observed favorable soil water conditions for understory growth in agroforestry because of hydraulic lift by trees (Emerman & Dawson, 1996;Hirota et al, 2004), while many others have reported crop yield reduction due to competition for water (Gillespie et al, 2000;Jose et al, 2000a;Miller & Pallardy, 2001;Livesley et al, 2004;Everson et al, 2009;Sudmeyer & Hall, 2015). Roots of pine trees and switchgrass could share some soil space despite the presence of 1.5-m-wide buffer between the switchgrass alley and tree row.…”