Banded Wetting Agent and Compaction Improve Barley Production on a Water‐Repellent Sand

Abstract

Large areas of cropland in Western Australia exhibit severe annual water repellency. Crop establishment is frustrated by the staggered emergence of plants, despite significant amounts ofrain falling prior to the desired time of seeding. Three techniques were used to investigate improvements in barley (Hordeum vulgare L.) establishment on a water-repellent sand: (i) spraying various rates of banded (2 em wide) wetting agent while furrow seeding with press wheels, (ii) seed placement either in a furrow or in the side of a ridge, and (iii) compaction with press wheels or a Flexi-Coil land packer. The application of wetting agent increased seedling emergence from 110 to 170 plants m-2 , dry matter production from 4.2 to 6.0 t ha-1 and grain yield from 1.96 to 2.60 t ha-1 , despite more weeds occurring with increasing rate of banded wetting agent. Use of press wheels, which also resulted in a furrow sowing condition, increased seedling emergence from 72 to 101 plants m-2 and grain yield from 1.70 to 2.13 t ha-1 • In the absence of heavy press wheel compaction, furrow sowing at 18-cm row spacings with full soil disturbance had no effect on seedling emergence or grain yield. The application of wetting agent increased topsoil wetting. Increased soil wetting may have increased plant nutrient availability (from fertilizer and soil), reduced soil water evaporation, and possibly reduced water loss to subsoil on this duplex soil. The optimum degree of compaction required on water-repellent soils is not known and needs further research.

Claying and deep ripping can increase crop yields and profits on water repellent sands with marginal fertility in southern Western Australia

“…Management options for water repellent soils include lowering of surface water tension using soil-applied wetting agents (Crabtree and Gilkes 1999), masking hydrophobic sites through the addition of clay-rich subsoils (Roberts 1966;Carter and Hetherington 1994;Obst 1994;Cann 2003), furrow sowing with press wheels to 'harvest' rainfall (Blackwell et al 1994;Crabtree and Henderson 1999), and utilising microorganisms to break down the organic causal agents (Franco et al 2000;Roper and Gupta 2005). The application of clay-rich subsoil, commonly referred to as 'claying', is the only treatment that provides both an immediate and long-term solution to the problem.…”

Improved Pasture Establishment and Production on Water‐Repellent Soils

“…The topsoil had a pH of 5.0 (1:5 0.01 M CaC1 2 ), with a gravel content of 220 g kg-1, a clay content of 40 g kg-\ organic C of 12 g kg-1 , a sand content of 920 g kg-1, and a water repellency value of 3.9 MED. This site had been sown to barley 2 years earlier (in 1987) (Crabtree and Gilkes, 1999) with various rates of a wetting agent (0-75 L ha-1 ) applied at the time of sowing. The site receives an average 440 mm annual rainfall, but received 600 mm in 1988, which probably leached some of the 1987 applied wetting agent to below the surface soil.…”

“…), and perennial ryegrass (Lolium perenne L.) were sown at 18-cm row spacings either in the furrow with wetting agent applied (at 0, 0.5, 1, and 4 L ha-l) or into level soil without wetting agent (control). Heavy (33 kg) press wheels were trailed behind the seeder in all but the control treatments, and this improved furrow definition (Crabtree and Gilkes, 1999). Each treatment was replicated three times in a randomized complete block design.…”

“…The residual effects of Aquasoil wetting agent were determined by measuring effects on volunteer pasture growth and composition. This was 2 years after barley had been sown in the furrow with a planter having press wheels and with wetting agent applied at six rates (from 0 to 75 L ha~1 ) in June 1987 (see Crabtree and Gilkes, 1999). The subterranean clover-rich annual pasture had regenerated the previous year, providing an adequate seedbank for regeneration in 1989.…”

“…Surface soil compaction can improve plant emergence under these circumstances (Stout et al, 1961;Pathak et al, 1976;Crabtree and Gilkes, 1999). Earlier work has shown that using a combination of a wetting agent, furrow sowing, and press wheels increased soil water content around seeds, which increased emergence and grain yield of barley (Hordeum vulgare L.) (Crabtree and Gilkes, 1999). These treatments are likely to have similar beneficial effects for pasture species, which is the principal hypothesis examined in this research.…”