Measurement of water use and pasture growth on Templeton silt loam

Abstract

Soil water contents to a depth of 1.05 m and pasture growth were measured over 3 years on irrigated and dryland perennial ryegrass-white clover pasture on a Templeton silt loam soil near Christchurch, New Zealand. Cumulative dry matter (DM) yield was linearly related to cumulative Penman potential evapotranspiration when soil moisture deficits in the top 1.05 m of soil were less than 90 mm, and averaged 11.3 kg DM/ha per mm potential evapotranspiration. Growth was slower for soil moisture deficits between 90 and 160 mm, and stopped at greater deficits. The maximum soil moisture deficit obtained in a very dry year was 190 mm. Soil moisture extraction occurred mainly from the top 450–600 mm of soil at low water deficits. As the soil dried, progressively more moisture was taken up from lower down the profile. Yields were reduced at smaller soil water deficits than transpiration.

Keywords:

• pasture
• soil moisture
• soil depth
• potential evapotranspiration
• neutron probe