Soil water measurements on four alluvial soils in Canterbury 1. Soil water extraction patterns under spring-sown peas and barley, and pasture

Abstract

Changes in water content of four soil types from alluvium were monitored under spring-sown barley during 1978/79, spring-sown peas during 1979/80 and under pasture during September 1981 - August 1984. The soil types varied in texture and depth to sandy gravels and are representative of a large area of the Canterbury and North Otago Plains. Patterns of soil water depletion over time are depicted graphically for representative soils in each season. All crops extracted similar amounts of water from the upper 30 cm, but spring-sown crops extracted less water below 30 cm. In stone-free soils, pea and barley crops obtained more than 80% of their total soil water from above 60 cm depth, and pasture obtained less than 60% of total soil water from the same depth. Pasture grown in moderately deep and shallow soils extracted 70–80% of total soil water from above 60 cm. Spring-sown crops extracted water to 90–100 cm depth in stone-free horizons, but pasture extracted water to at least 120 cm in soils underlain by sandy gravels, and to 180 cm in deep stone-free soils. High amounts of soil water extracted by pasture from subsoil horizons were considered to be related to perching of water in sandy layers.

Keywords:

• available water
• soil depth
• water deficit
• peas
• barley
• pasture
• Canterbury
• water extraction
• soil types
• water storage