In this thesis, the hypothesis was tested that AMF (<i>Glomus mosseae, Scutellospora calospora</i> and <i>Gigaspora margarita</i>), thought to differ functionally, will produce different effects on water relations when inoculated onto sorghum. To overcome inherent differences between nonmycorrhizal (NM) and mycorrhizal (M) plants, a split-root system (SRS) was devised.  In this approach, the plant root system was equally divided between two compartments one of which was subsequently inoculated with AMF, allowing NM and M roots on the same plant to be compared. Initially, water loss from NM and M (inoculated with <i>G. mosseae</i>) compartments of the SRS was measured.  Roots in the M compartment had 73% of root length colonized (RLC) by <i>G. mosseae.</i>  The water holding capacity (WHC) of the substrate was enhanced in the M compartment, and this was maintained through the drought period.  <i>G. mosseae</i> increased root length (RL), number of root tips, root surface area and root volume.  However, there was no difference in the rate of water loss between the M and NM sides of the SRS. The next experiment examined the possibility that different species of AMF might alter water loss in sorghum plants differently.  Above ground, inoculation with <i>S. calospora</i> produced bigger plants than the other two isolates. Below ground, %RLC also differed between isolates.  There was no significant difference in total RL (adding both sides) between plants, but there were differences in the number of root tips, root surface area, root volume and root branching degree.  When NM and M compartments of the SRS for each AMF isolate were contrasted, roots colonized by <i>S. calospora</i> and <i>G. margarita</i> had greater RL, number of root tips and root surface area, whereas roots colonized by <i>G. mosseae</i> had more root tips and a different degree of branching.  Once again, <i>G. mosseae</i> increased the WHC of the substrate, but<i> G. margarita</i> did so only at the last harvest. There was no effect of <i>S. calospora </i>on WHC.   However, there were no significant differences in water loss either per LA (with one exception) or per RL between the NM and M sides of the SRS with any AMF isolate.  This leads to the conclusion that while AMF affected the WHC of the substrate used in these experiments, they did not affect rates of transpirational water loss from that substrate.

Thesis (M.Sc. (Agriculture)) --University of Limpopo, 2008 / Maize is a dominant crop in smallholder farming systems in the Limpopo province of South Africa, generally cultivated as intercrop with grain legumes. The major constraint in this cropping system is inadequate soil moisture during the growing season, which also limits nutrient availability to the component crops. The minimum tillage system has been reported to improve soil moisture availability on farmers’ fields but this has not yet been verified in an intercropping system in the province. The objective of this study was to quantify grain yield and chlorophyll production of intercropped maize, and to assess seasonal moisture availability under minimum tillage (MT) and conventional tillage (CT) systems. Dryland field experiments were conducted at two locations in the province namely, farmer’s field at Dalmada in 2002/2003 and 2003/2004 growing seasons and at the University of Limpopo Experimental farm at Syferkuil during the 2003/2004. The experimental design was a randomized complete block in split plot arrangement at all locations and seasons. Tillage systems consisting of conventional tillage and minimum tillage were the main plot treatments, whereas five different cropping systems namely, sole maize, and maize intercrop with cowpea (variety, Bechuana White), cowpea (variety, Agripers), Lablab bean (variety, Rongai) and Velvet bean were assigned as sub-plot treatments. Maize grain yield in 2002/2003 at Dalmada was significantly lower (357 kg/ha) under CT relative to 755kg/ha under MT. In 2003/2004 at Dalmada, grain yields under the two systems were similar, where as at Syferkuil, 15% higher grain yield results was obtained under MT. Minimum tillage systems resulted in higher number of maize cobs per plant at Dalmada in both growing seasons and weight per cob was higher under MT at both locations and seasons. At Dalmada, significantly higher soil moisture was recorded under the MT relative to the CT depending on depth and sampling dates. Chlorophyll content of the youngest fully expanded leaves of maize was generally higher under MT than CT, but this was observed only at the later stages of plant growth. The results also showed that the rate of senescence (reduced chlorophyll content in older leaves) was higher in maize plants grown under CT relative to those under MT. The minimum tillage system has shown the potential of being a superior system for dryland maize production, but further research involving additional locations is required to ascertain this fact.