Ground Cover Supplement : GC Supplement - Soil Biology 2005
GROUND COVER SOIL BIOLOGY 10 CHEMICAL FERTILITY THE CURRENT INTEREST in soil health in Australian agricultural systems has tended to focus solidly on soil biota and the interactions between biota and manage- ment practices (for example tillage and crop rotation). However it is important not to overlook the fact that soil chemical fertility (both the rate at which chemi- cal properties change and the management practices employed to counter these changes) is just as important to long-term soil health. Nutrient balances, fertiliser application strategies, rates of acidification and subsequent amelioration and soil organic matter management are key components of soil chemical fertility. Development and implementation of management practices to address chemical fertility issues will have long-term implications for sustainable land management. The northern grains region is dominated by alkaline heavy clay (Vertosol) soils, although there are smaller but important areas of Kandosols in the west and Red Ferrosols in the east and far north. The high seasonal rainfall variability in the region (while countered somewhat by good water-holding capacity in some deeper Vertosols), combined with often (originally) high starting soil fertility, has present- ed particular problems for the economically sustainable maintenance of chemical fertility in these systems. The following are examples for rainfed cropping systems on the Darling Downs and the inland Burnett regions of southern Queensland. NUTRIENT BALANCE The inland Burnett and nearby Darling Downs provide interesting contrasts in cropping systems and subsequent challenges to maintaining sustainable nutrient balances. The neutral-alkaline pH, high background fertility and cereal grain-dominated cropping systems of the Darling Downs have resulted in an overwhelming focus on nitrogen fertility, although in more recent years responses to phosphorus and zinc inputs have become important in some areas. Farm records of fertiliser inputs and grain removal over the past 40 to 45 years have allowed tentative nutri- ent budgets to be undertaken for this system, with the example of sorghum shown in Figure 1. Sorghum yields have increased dramatically from an average of one tonne per hectare in the decade of the 1960s to more than 6.5 tonnes a hectare since 2000. During this period nitrogen inputs have risen from nil to more than 130kg/ha, phosphorus inputs have risen from nil to about 7kg/ha but have stalled over the past 15 years and zinc is now a common component of phos- phorus fertiliser blends. However, despite these large increases in inputs, the Mike Bell The inland Burnett and nearby Darling Downs provide interesting contrasts in cropping systems and subsequent challenges ... Chemical fertility and soil health in northern systems MIKE BELL AND PHIL MOODY LOOK AT THE IMPORTANCE OF SOIL'S CHEMICAL FERTILITY TO ITS LONG-TERM HEALTH Queensland Department of Primary Industries and Fisheries principal agronomist and project leader Mike Bell.
GC Supplement - Value Chain
GC Supplement - Grain Storage 2005