Influence Of Farming Practices Research Articles

Influence of farming practices on the population genetics of the maize pathogen Cercospora zeina in South Africa

Gray leaf spot (GLS) is an important foliar disease of maize. This disease, caused by Cercospora zeina, is prevalent in both smallholder and commercial maize farms in South Africa. Notably, smallholder practices are geared towards conservation agriculture, planting diverse maize genotypes within a field and avoiding chemical control. This study examined the population genetic structure of 129 C. zeina isolates from three smallholder farm sites in KwaZulu-Natal in South Africa using 13 microsatellite markers. These were analysed, together with 239 isolates previously analysed from four commercial farms in the same province, to determine whether farming systems influence the genetic diversity of C.zeina. In addition, we wanted to determine whether the smallholder farming system harboured a greater diversity of C.zeina haplotypes due to lack of chemical spraying of these crops. Overall, farming systems exhibited partial, but significant, population differentiation, contributing 10% of the genetic variation observed. A 16% genetic variation conferred between KwaNxamalala (smallholder) and Cedara (commercial) areas that are in close proximity, confirmed this. Private alleles accounted for 29% of the 52 alleles observed in smallholder farms. Smallholder farms harboured a higher gene and genotypic diversity, with a clonal fraction of only 13% compared to 32% in commercial farms. Mating type ratios indicative of sexual recombination and lower linkage disequilibrium in most smallholder populations were consistent with higher levels of diversity. This study suggests that commercial farming practices, such as fungicides and monoculture crop planting, may result in a narrower genetic diversity of the pathogen that is then propagated by asexual reproduction. In contrast, management of GLS disease in smallholder farms should consider the greater diversity of pathogen genotypes, especially if future research shows that this equates to a greater diversity of pathogenicity alleles.

Influence of Farming Practices on Weight-Length Relationship of the Loach (Misgurnus anguillicaudatus) Population in Rice Paddy Fields

Influence of Farming Practices on Weight-Length Relationship of the Loach (Misgurnus anguillicaudatus) Population in Rice Paddy Fields

Distribution of applied cadmium in different size fractions of soils after incubation

The size fraction of soils is one of the important factors that influence the retention of heavy metals. The sorptive properties of soils for heavy metals are principally associated with clay and silt-size fractions. Phosphate fertilizers that are applied to highly weathered tropical soils contain a wide concentration range of cadmium (Cd) as an impurity. Tropical soils contain kaolinite and oxides of Al, Fe, and Mn, which have the ability to sorb Cd. However, the distribution of Cd in different size fractions and the chemical speciation of particulate-bound Cd in the clay size fractions when introduced to soil and allowed to incubate at field moisture capacity merits attention. Cadmium was, therefore, applied to selected surface Kenyan soils varying widely in physicochemical properties to investigate its distribution in different soil particle size fractions and the speciation of particulate-bound species in clay size fractions after incubation. The Cd content in different particle fractions was analyzed by graphite furnace atomic absorption technique after HF-HClO4 digestion. The particulate-bound Cd species were investigated using chemical sequential extraction method. The study showed that clay size fraction of the natural and the Idaho monoammonium phosphate (MAP)-fertilizer or the Cd perchlorate-added MAP chemical reagent-treated soils contained the highest amount of the total Cd. However, silt and sand fractions of the treated soils also retained appreciable amounts of Cd. Speciation studies revealed that metal-organic complex-bound Cd was the most predominant compared to other particulate-bound Cd species in the clay size fractions of the soils treated with Idaho MAP fertilizer or the Cd perchlorate-added MAP chemical reagent. The distribution of total Cd in the different soil particle size fractions and the speciation of particulate-bound Cd in the clay size fractions varied with the soil type. The results indicate that clay size fractions can retain Cd making it less available; however, the influence of farming practices, which affect Cd mobility, should not be overlooked.

Belowground effects of organic and conventional farming on aboveground plant–herbivore and plant–pathogen interactions

Soil organisms may significantly affect the aboveground system. However, the influence of farming practices in modifying the effects of soil organisms on aboveground systems is poorly understood. The aim of our study was to investigate: (1) How important are soil organisms for plant growth and the development of herbivores and pathogens above the ground? (2) How do agricultural management practices affect interactions between soil organisms, plants and their aboveground herbivores and pathogens? To answer these questions we investigated the effect of experimental defaunation of soils from organic versus conventional farms on growth of wheat, abundance of aphids and infection of wheat by Septoria fungi. Plant biomass in soil from conventional farms exceeded that of soils from organic farms, presumably due to the higher nutrient input in the conventional farming system. Soil defaunation likely mobilized nutrients that increased plant growth. Aphid abundance and Septoria infection was reduced by defaunation but only in organic soils. This suggests that soil organisms in organic farming systems are more important for aphid performance and the infection rate by Septoria than in conventional systems. Hence, changes in the soil animal food web caused by farming practice feed back on aboveground organisms, and this appears to be more pronounced in organic farming systems. Further, the results indicate that soil organisms may modify higher trophic levels (aphid and pathogen infection) without significantly affecting lower trophic levels (plant growth).

Environmental consequences of land degradation in coastal drainage basins of north Queensland, Australia: Influence of farming practices

AbstractViews expressed by sugar cane farmers in the Johnstone Rivers system, north Queensland, are consistent with the broader community concern about the potentially adverse ecological effects of point source discharges to the Great Barrier Reef lagoon. the main link between agricultural land use and the deterioration of surface and groundwater quality in the region is perceived by the farmers to be a consequence of the influence exerted by new farm management strategies and economic constraints on local environmental variables, particularly soils. the effectiveness of the land use practices in relation to land capability and productivity thresholds is considered by farmers to be essential for developing new farm management strategies and for improving water quality in the north Queensland coastal regions. as a result of increasing inhomogeneity of land use practices involving the application of chemicals, catchment based investigation, including systematic interviews with the land users, is needed for the development of reliable databases on problems related to the discharge of agricultural chemicals to coastal waters.