The role of land use planning in semi-arid areas
Worldwide, the semi-arid grazing and cropping regions are being subjected to severe overuse. Australian semi-arid regions have been cleared on a vast scale for marginal cropping. Grazing land has been overused and shows widespread signs of vegetation and soil degradation. Ecological realism on land capability based on objective condition monitoring, is essential to land management if sustainable production is to be achieved. The Land Care Movement can markedly influence this achievement. The margins of semi-arid cropland and the application of ecologically-based animal stocking rates require attention in several States. Drought assistance policy requires amendment to safeguard natural pastures. Lease covenants have a potentially central role to play in land administration.
Problems Of Adaptation Of Pastoral Businesses In The Arid Zone
With emphasis upon Central Australia, an assessment is made of the economic problems of pastoral firms in meeting the climatic conditions of the arid zone. Analysis ranges over the responsibility for conservation and drought planning, the inadequacy of a purely physical approach to conservation, the difficulties of station organization and management in the arid zone, the array of possible managerial strategies for meeting these difficulties, and the effect of social institutions on the choices avail. able to management.
Effect of Soybean Cyst Nematode (Heterodera glycines) on Yield of Resistant and Susceptible Soybean Cultivars Grown in Ohio.
Soybean (Glycine max) producers in Ohio rarely use soybean cyst nematode (Heterodera glycines, SCN)-resistant cultivars because of concerns over limited yield potential and lack of resistance to Phytophthora sojae. A two-year study was initiated to determine grain yield and nematode population increase on soybean cyst nematode-resistant cultivars in maturity groups II and III in production fields. Sites differed in soil texture, nematode densities, and P. sojae infestation at a number of locations in Ohio. Soil was assayed for nematode densities before planting and at harvest. Yields of resistant cultivars averaged 0% to 18% higher than those of susceptible cultivars in fine-textured soils with average preplant populations ranging from 463 to 14,330 SCN eggs/100 cm(3) soil. In coarse-textured soils, yields of susceptible cultivars were 21% to 56% less than the resistant cultivars with average preplant densities ranging from 1,661 to 15,558 SCN eggs/100 cm(3) soil. The reproductive index ranged from 0.1 to 5.5 for resistant cultivars and 0.4 to 112 for susceptible cultivars. In 1993, yield of P. sojae-susceptible, nematode-resistant 'Asgrow A 3431' was as high as yield of the P. sojae-resistant, nematode-susceptible cultivar 'Resnik' in a Phytophthora-infested field. The nematode-resistant cultivars Madison Experimental 131527 and Asgrow A3431 had higher yields than AgVenture AV1341 and susceptible cultivars Resnik and Kenwood when compared over five nematode-infested sites. Nematode-resistant cultivars were found to be excellent alternatives to currently grown susceptible cultivars for managing SCN where group III cultivars are used. However, better cultivar alternatives may be needed for sites with combined Phytophthora root rot and cyst nematode problems.