Perennial pastures for recharge control in temperate drought-prone environments. Part 2: soil drying capacity of key species

Abstract

Perennial-based pasture swards potentially offer land managers the capacity for recharge control in temperate cropping zone environments to satisfy the dual role of fostering increased agricultural productivity and reduced deep drainage. This study used a neutron moisture meter to monitor levels of stored soil water to 1.70 m under pastures sown to lucerne (Medicago sativa L.), phalaris (Phalaris aquatica L.), chicory (Cichorium intybus L.), perennial veldt grass (Ehrhata calcycina Sm.), grazing brome (Bromus stamineus E. Desv.), plantain (Plantago lanceolata L.), Rhodes grass (Chloris gayana Kunth), tall fescue (Festuca arundinacea syn. Lolium arundinaceum Schreb. syn. Schedonorus phoenix (Scop.) Holub.) and cocksfoot (Dactylis glomerata L.) in two contrasting environments in the cropping zone of southern New South Wales (NSW), Australia. Performance of two cultivars with contrasting levels of summer activity of each of the latter two species was also assessed. Differences in soil water between the various treatments were small but significant throughout the 5-year study due to successive below average rainfall years. However, the study demonstrated that lucerne remains the perennial pasture species with the greatest capacity to dry the soil profile for recharge control. Lucerne was the most persistent species under drought of all species evaluated, creating the largest total dry soil deficit at both sites (214 and 138 mm at Cootamundra and Wagga Wagga, respectively). There was a significant positive correlation (P<0.05) between persistence (measured as basal frequency from year 3 onwards) and percentage decrease in soil water content at both sites (R 2=0.63 and 0.68, respectively). Kasbah cocksfoot, Fraydo tall fescue, phalaris, chicory and perennial veldt grass all persisted moderately well and created dry soil buffers that were not significantly lower than lucerne at both sites (mean 200 and 133 mm, respectively). In contrast to previous findings, summer-active cultivars of cocksfoot and tall fescue did not show any advantage in drying soils in low-rainfall environments compared with more summer-dormant cultivars. The summer-dormant cultivars of each species were shown to be more persistent, enabling them to dry the soil profile incrementally over a longer period of time. This study has demonstrated the importance of increased plant persistence on reducing the water content of the soil profile in drought-prone environments.