Growth of field pea on red-brown earth soils in a year with high rainfall

Abstract

A study of 4 commercial crops of peas was conducted in the Lower North of South Australia during 1992 to assess the importance of waterlogging on growth and yield. The area chosen for the survey has a high proportion of red-brown earth soils that slake and seal, have poor internal drainage, and are prone to transient waterlogging. Rainfall in the year of the survey was above average, particularly during September and October, and waterlogging and disease were common in pea crops throughout the region. Based on air-filled porosity and soil water tension, waterlogging occurred in each of the survey paddocks. Differences in vegetative growth and grain yields within and between paddocks could be related to the severity of waterlogging. There were differences between the 4 survey paddocks for concentrations of potassium, sodium, iron, and manganese in pea shoots, and these differences appeared to correspond to differences in the severity of waterlogging. Nutrient concentrations were, however, confounded by differences in soil pH and soil fertility. Despite adequate to high levels of available phosphorus (P) in each of the 4 paddocks, concentrations of P in shoots were generally low and, in 2 cases, indicated P deficiency. Phosphorus concentrations were not related to the concentration in the soil or to the severity of waterlogging. In field experiments conducted over 2 seasons (1991, 1992), peas were grown in raised hill plots to promote drainage around the upper root system. The method significantly increased plant establishment in both years, and in 1992, a year of record high rainfall, grain yields from the drained plots were 5-64 times greater than those from undrained plots. In 1991, a year with lower rainfall, drainage improved pod yield by 13%. Observations during the survey suggested that disease was worse in the paddocks that were severely affected by excess water.