The influence of alternative tillage systems on the distribution of nutrients and organic-carbon in some common Western Australian wheatbelt soils

Abstract

The effect of reduced cultivation on the chemical fertility of three agricultural soils important in Western Australia was investigated.The experiment compared the effect of different tillage systems for continuously cropping wheat on the distribution of extractable P, extractable K, total N, organic C and pH for soils ranging from a sand to a sandy clay loam. Three tillage systems were applied (conventional cultivation, direct drilled with a combine, direct drilled with a triple disc drill) and the distribution of nutrients was measured to a depth of 25 cm. Developments were monitored for a period of 9 years.Clear differences between treatments were evident within the first 3 years of the experiment. Relative differences between treatments remained constant after this time. The concentrations of extractable P, extractable K, total N and organic C in the soil were all higher with direct drilling than with conventional cultivation, regardless of soil type or environment. The concentration of these elements declined in all treatments throughout the duration of the experiment. Major differences between treatments occurred in the surface 5-10 cm of the soil, although trends differed slightly depending on the element measured. Ammonium nitrate application substantially reduced the pH of the sandy soil, regardless of tillage treatment, but had no effect on the other soil types. Conventionally cultivated sandy and sandy clay loam soils also had a slightly higher pH than the direct drilled soils. The yield of plants was not directly related to the concentration in the soil of any elements measured.Accumulation of nutrients near the surface indicated that, if the surface soil is dry, then nutrients may be less available to plants established with direct drilling than with conventional cultivation. Further research is needed to establish whether present 'soil testing-P recommendation' relationships, based on conventional cultivation systems, are appropriate under direct drilling systems in Western Australia. Changes in pH with different tillage systems may have a bearing on fertilizer application strategies. Finally, the decline in organic C with conventional cropping indicates that the structure of soils in this experiment remains fragile even with direct drilling.

Effect of tillage system and nitrogen fertilization on the pH, extractable phosphorus and exchangeable potassium of Nitisols in Western Ethiopia

“…This phenomenon could be attributed to the nitrification of NH 4 + released from either the fertilizer or residues at or near the soil surface (Blevins et al, 1983;Ismail et al, 1994) since the process produces acidifying hydrogen ions (Fox and Bandel, 1986). Similar changes in pH on account of tillage systems were reported by other researchers (Shear and Moschler, 1969;Blevins et al, 1983;White, 1990;Du Preez et al, 2001;Kotzé and Du Preez, 2008).…”

“…The pH in the upper few centimeters of a soil usually decreases rapidly under minimum tillage compared to conventional tillage, especially when high rates of N fertilizer are used (Moschler et al, 1973;Blevins et al, 1983;White, 1990;Yadvinder-Singh et al, 2005). This drop in pH is attributed mainly to the H + released through the nitrification of NH 4 + .…”

Soil carbon change and its responses to agricultural practices in Australian agro-ecosystems: A review and synthesis

“…8), which made the absolute amount of soil C accumulation comparable with Sodosol and Chromosol. The difference in the relative change of soil C between soil types may attribute to many factors, which may be either climate related ones affecting productivity, or soil related ones affecting C decomposition (White, 1990;Mason, 1992;Robertson and Thorburn, 2007).…”

Carbon balance in maize fields under cattle manure application and no-tillage cultivation in Northeast Thailand

“…In a study in central Thailand, sugarcane yield was lower with notillage treatment than with tillage during the planting year and the first ratooning year (Grange et al 2002). In Australia, lower crop yields under no-tillage treatment than under comparative tillage treatments have been reported (Hamblin et al 1982;White 1990). However, reports of no difference in crop yield between no-tillage and tillage treatments have come from Thailand on clay loam and sandy loam soils (e.g.…”

“…Min et al 2003;Smith et al 1997) and no-tillage cultivation (e.g. McConkey et al 2003;West and Post 2002;White 1990). However, there have not been many studies of carbon sequestration in agricultural fields in tropical areas.…”