Fallow management, soil water, plant-available soil nitrogen and grain sorghum production in south west Queensland

Abstract

The effects of tillage frequency (conventional, reduced and zero), primary tillage implement (disc, blade and chisel plough), stubble management (retention and removal), gypsum application, and paraplowing were examined with respect to soil water storage, soil nitrate accumulation, crop establishment, crop growth, grain yield and grain nitrogen content for 4 successive sorghum crops on a sodic, texture-contrast soil in south west Queensland. Retention of sorghum stubble (v. removal) produced an increase in mean yield of sorghum grain of 393 kg/ha, due to increased soil water extraction and increased water use efficiency by the following crop. The highest mean yield occurred after reduced blade tillage with stubble retained. Zero tillage with stubble removed gave the lowest mean grain yield. Zero tillage always had the lowest quantity of soil nitrate-nitrogen at sowing. In one fallow, increased aggressiveness of primary tillage (disc v. blade plough) increased the quantity of nitrate-nitrogen in the top 60 cm of soil at sowing. These effects on available soil nitrogen did not result in corresponding differences in grain nitrogen content. Results indicate that for optimum fallow management on this texture-contrast soil in south west Queensland, sorghum residues should be retained, tillage frequency should be reduced, but not to zero, blade ploughing should be preferred to discing, and gypsum application should not be practised.

Effect of Soybean Plant Populations in a Soybean and Maize Rotation

“…Even though the fallow plots had no addition of N, greater N accumulation occurred in maize grown in a fallow–maize system than in a soybean–maize or maize–maize system. Soil water availability as a result of water storage during the fallow period has been attributed to better performance of crops on fallow (Gibson et al, 1992; Schillinger and Bolton, 1993). But greater N uptake and higher chlorophyll in our study indicated that more N was available.…”

Managing Soils to Achieve Greater Water Use Efficiency

“…In Australia, Gibson et al (1992) found that retaining sorghum stubble on the soil increased the sorghum yield by 393 kg ha −1 due to increased WUE because of a greater amount of water stored in and extracted from the soil profile compared with conventional tillage. They also found that decreasing tillage frequency increased soil water extraction; however, no tillage did not result in the optimum yield or WUE.…”

Soil Management for Increasing Water Use Efficiency in Field Crops under Changing Climates

“…An opposite result was found in Australia, where Gibson et al (1992) observed that keeping sorghum stubble on the soil surface increased sorghum yield by 393 kg ha −1 because of increased WUE from the greater amount of water stored in and available to be used by the crop when extracted from the soil profi le compared to conventional tillage. In this study, they found that decreasing tillage frequency increased soil water extraction, but no-tillage did not result in the optimum yield or WUE (Gibson et al, 1992).…”

“…An opposite result was found in Australia, where Gibson et al (1992) observed that keeping sorghum stubble on the soil surface increased sorghum yield by 393 kg ha −1 because of increased WUE from the greater amount of water stored in and available to be used by the crop when extracted from the soil profi le compared to conventional tillage. In this study, they found that decreasing tillage frequency increased soil water extraction, but no-tillage did not result in the optimum yield or WUE (Gibson et al, 1992). Water use effi ciency can be enhanced by additional availability of soil water, and in the southern High Plains, the addition of soil water through irrigation increased WUE for wheat to 8 kg ha −1 mm −1 compared to 4 kg ha −1 mm −1 under dryland conditions (Musick et al, 1994).…”