Effects of frequency of peanut (Arachis hypogaea L.) cropping on some properties of krasnozem and euchrozem soils in the South Burnett area, Queensland

Abstract

We examined relationships between peanut (Arachis hypogae L.) cropping frequency and some properties of the tilled layer of krasnozem and euchrozem soils of the South Burnett area of southeastern Queensland. The average period of cultivation for the sites studied was 22 years. Organic carbon (OC) was not significantly correlated (P<0.05) with the period under cultivation, indicating that OC had reached equilibrium with the cropping pattern imposed. Frequency of peanut cropping in the 10 years before sampling was correlated negatively with OC (r = 0.49 1, P < 0.001), percentage of dry aggregates 0.5-5 mm (r= -0.385, P<0.01) and water stability of dry aggregates 2-5 mm (r = - 0.499, P< 0.001), and positively with percentage dry aggregates < 0.5 mm (r=0.313, P<0.05). Both OC and mean-weight-diameter of water-stable aggregates were approximately halved as frequency of peanut cropping increased from 0 to 10 crops in the 10 years before sampling. Estimated return of dry matter to the soil is consistent with differences in OC, as peanuts produce approximately half the dry matter of alternative crops. However, apparent rates of loss of OC due to peanut cropping are high for soils that are not newly cultivated, and intensive tillage associated with peanut cropping may increase rates of loss of OC due to increased disruption of aggregates.