Nematodes play an important role in agricultural soil in terms of their pest status and their contribution to soil quality, where they may serve as a valuable indicator of soil health. The aim of the study was to assess changes occurring in nematode community structure, as affected by soil tillage applied to high N-input and irrigated pastures in South Africa. Such practices were investigated by means of analysing diversity and ecosystem function indices, as well as the faunal profile, to enable analysis of their effect on soil quality. The pre-treatment soil analyses showed a low overall mean nematode density. No clear and predictable pattern was present in the nematode community structure in relation to tillage. The lack of indicative information leading from the nematode community structure to the tillage disturbance types might be linked to the fact that such systems were able to recover from soil disturbance within the relatively short period of less than a year.
Bougainvillea plants, native of Brazil, are cultivated in home gardens in South Africa. Vittacus bougainvilleae (Keifer) (Eriophyidae), Brevipalpus californicus s.l. (Banks) and Brevipalpus yothersi Baker (Tenuipalpidae) are recorded for the first time in this country infesting bougainvillea plants. The bougainvillea rust mite, V. bougainvilleae, was detected in the Western Cape Province during the summer season. Infested plants showed symptoms of leaf rolling, as well as leaf and flower drop. Brevipalpus californicus and B. yothersi were detected in Mpumalanga Province during winter and late autumn causing no obvious damage.
Vermicomposts (VCs) are the solid excreta of earthworms known to contain plant available nutrients, large amounts of microbial life and diversity, and plant growth regulating hormones. VCs may play an integral role in the nitrogen nutrition of Lupinus angustifolius and function to reduce the reliance of legume crops on chemical fertilizers. The aim of the present study was to determine the role of varying concentrations of chicken manure VC on the biomass production and N nutrition of the legume, L. angustifolius. The effect of increasing concentrations of VCs has been investigated, in conjunction with commercial rhizobia inoculum additions on the biomass yield of L. angustifolius. Plants were germinated and allowed to establish for 10 days in various mixtures of VC, rhizobia inoculum, and quartz sand under glasshouse conditions. After cultivation of a further 30 days, the plants were harvested and analyzed for tissue nutrient concentrations. The VCcontaining substrates were assessed for wide-spectrum soil analyses and microbial diversity via Biolog EcoPlates. The combined treatments of 5% VC and rhizobia inoculation yielded the greatest biomass response. Furthermore, the addition of VC allowed for bacterial nitrogen fixation within non-rhizobia treatments. Nematode numbers and diversity grew with increases in VC concentrations, likely driven by similar increases in abundance of their microbial prey. However, changes in VC concentration had no effect on bacterial guild structure. In conclusion VC concentrations should be an important consideration for substrate nutrient availability, microbial abundance, and bacterial nitrogen fixation.
Soil is a non-renewable resource and supports all land-based forms of life. The sustainable production of crops is becoming progressively more critical as human populations increase and viable agricultural land decreases. Soil health plays an indispensable part in the sustainability of soil as a resource for future generations. For this very reason it is important to have suitable tools to measure the improvement or deterioration of soil health in vineyards and orchards. In this review, the use of different bio-indicators to indicate soil health will be discussed, with special emphasis on the use of nematode population structure and function as indicators of soil health. The use of nematodes as a bio-indicator of soil health can play a crucial role in the establishment of future sustainable production of grapes and fruit in the Western Cape. This paper provides a comprehensive review of soil health, the use of different biological indicators, and the potential of nematodes as suitable indicators thereof, aimed at vineyards and deciduous fruit orchards.
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