Water-Use Efficiency and Infiltration under Different Rangeland Conditions and Cultivation in a Semi-Arid Climate of South Africa

The objective of this study was to determine the impact of rangeland in different botanical composition classes (good, moderate and poor), on water-use efficiency (WUE: crude protein produced per unit of evapotranspiration) and soilwater content. The same measurements were also made on an undisturbed bare soil surface and soil cultivated twice per annum. Evapotranspiration was determined by quantifying the soil-water balance equation with the aid of runoff plots and soil-water content measurements done by a neutron hydroprobe. Water-use efficiency declined significantly (P ≤ 0.01) with rangeland degradation. Rangeland in good condition averaged a WUE of 0.28 kg crude protein ha-1 mm-1. Higher surface runoff occurring in rangeland in poor condition due to less vegetation cover, caused soil-water content to be much lower than that of grassland in good condition. Soil-water storage increased by 31% due to cultivation. The study shows it is important to keep rangeland in optimal condition to utilise limited soil water for sustainable plant and therefore animal production

Influence of Water Stress on Root/Cladode Ratio and Water-Use Efficiency of Opuntia \u3cem\u3eFicus-Indica\u3c/em\u3e and \u3cem\u3eO. Robusta\u3c/em\u3e

Due to the regular occurrence of drought in southern Africa, there is a need for more research on drought tolerant fodder plants such as Opuntia (cactus pear) species. In contrast with the cladode system, the roots of cactus pear have received little attention, however, they certainly differ from other plants, as they develop xeromorphic characteristics, enabling the plant to survive prolonged periods of drought (Nobel, 1988). The influence of different water applications was evaluated in terms of root and cladode mass, water-use efficiency (WUE) and root length for one-year-old plants of Opuntia ficus-indica (cultivar Morado) and O. robusta (cultivar Monterey)

Defoliation Impact on the Above and Belowground Productivity of \u3cem\u3eFestuca arundinaceae\u3c/em\u3e Schreb

The main objective of pasture management is to maximize plant productivity and ensure sustainable animal performance, without inducing pasture deterioration. Many researchers indicated that plant survival and sustainable production is a function of seedbed preparation, irrigation and defoliation, with defoliation having the largest impact on plant persistence (Fulkerson and Donaghy, 2001). The net effect of defoliation (degree of intensity and frequency) can therefore either be beneficial or detrimental to survival and productivity of a pasture. The aim of this study was to quantify the impact of different intensities and frequencies of defoliation on above- and belowground phytomass production of the cultivated pasture Festuca arundinaceae Schreb. under irrigation

Influence of Water Stress on Protein Concentration in \u3ci\u3eThemeda triandra\u3c/i\u3e Forsk. in a Semi-Arid Climate of South Africa

The objective of this study was to determine the influence of four water treatments (T1 = 75-100%, T2 = 50-75%, T3 = 25-50% and T4 = 0-25% of Field Water Capacity) on the concentration of water-soluble protein as growth reserve during three growth stages (vegetative, pipe and reproductive) in three plant parts (roots, stubble and leafs). The water-soluble protein concentration (WSPC) in the plants under the four water treatments differed (P≤0.01) among the plant parts as well as among growth stages (P≤0.05). WSPC in leafs increased (P≤0.01) with increased water stress from T1 to T4 for the pipe growth stage. For the vegetative and reproductive growth stages the WSPC increased (P≤0.01) from T1 to T2, decreased from T2 to T3 and increased again to T4 with concentration higher (P≤0.01) in T4 than T1, for the vegetative and reproductive growth stages. The WSPC in the roots differed (P≤0.01) across growth stages and water treatments. The results confirm that water-soluble protein growth reserve is influenced by the intensity of water stress and accumulation occurs with increased water stress, with the largest accumulation in the stubble

Influence of Fertilization on Botanical Composition and Productivity of Rangeland in a Semi-Arid Climate of South Africa

The objective of this study was to determine the short-term response of rangeland to fertilization rangeland (all combinations of 0; 10; 30 and 50 kg ha-1 nitrogen, with 0 and 10 kg ha-1 of phosphorus) in terms of dry matter production and botanical composition. After three years of fertilization, the botanical composition of the high-N fertilized plots changed completely from a climax to sub-climax vegetation. Wire grass (Elionurus muticus) showed the greatest decrease in frequency (62%) due to N fertilization. Phosphorus fertilization had an insignificant influence on species composition over the three years. The increase (P\u3c 0.01) in production with increased N fertilizer, peaked in the second season, declining afterwards. With N and P fertilizer applied together, the production increased constantly and peaked in the last season. After three years the production increased (P≤ 0.01) with the application of N together with P, compared to the applying of only N. The higher the amount of fertilizer, the more sensitive to drought the climax grasses became. The results confirm the vulnerability of native grasses in dry areas, due to change in soil fertility

Soil Organic Matter Along a Degradation Gradient in a Semi-Arid Rangeland of South Africa

In a semi-arid South Africa rangeland on a sandy loam soil, artificial manipulations to create various rangeland conditions typical of different levels of livestock impact were shown to result in considerable losses of organic matter after 15 years (Du Preez & Snyman, 1993). In this follow-up study on a similar soil, we regularly measured the organic matter content following the conversion of rangeland in a good to a poor ecological condition, an undisturbed bare soil and a cultivated soil respectively. The changes in soil organic matter content after five years are reported