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 B0.05) between persistence (measured as basal frequency from year 3 onwards) and percentage decrease in soil water content at both sites (R 2 00.63 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.

Optimum plant density of Digitaria eriantha for herbage accumulation and hydrological performance in a summer dominant rainfall zone

“…Hayes et al. (2010b) also reported little change in SWC below 0.75 m for a range of summer and winter active forage species.…”

“…A density of 1 plant per m 2 was too low to effectively and efficiently use the resources available (e.g., Hayes et al., 2010b; McCaskill & Kearney, ) and was ranked lowest for all parameters measured throughout the experiment (with the exception of root depth during year 3). Digit grass at a plant density of 4 plants per m 2 was ranked low during year 1 and 2, but as the plants developed and crowns increased, this density had similar hydrologic and growth responses to the higher density swards, and over the duration of the experiment showed the highest WUE.…”

“…A grazed perennial pasture requires a sufficient plant population to achieve both production and sustainability goals: high herbage accumulation and persistence (Hayes et al., ,b; McCaskill & Kearney, ) by maximizing soil water usage (rooting depth and extraction); having a dry profile in autumn to store winter rainfall (Hayes et al., 2010b; McCaskill & Kearney, ); and having high ground cover to reduce weeds (Dear, Virgona, Sandral, Swan, & Orchard, ; McCaskill & Kearney, ), minimize runoff (Murphy, Lodge, & Harden, ) and maximize infiltration (Murphy et al., ). There is also a threshold plant density, below which a species is not able to achieve these goals (e.g., Dolling, Lyons, & Latta, ; Hayes et al., ,b; McCaskill & Kearney, ; Virgona, ). Our data indicated that digit grass with density of 1 plant per m 2 was below this threshold, while densities ≥4 plants per m 2 achieved both herbage accumulation and sustainability goals.…”

“…A density of 1 plant per m 2 was too low to effectively and efficiently use the resources available (e.g., Hayes et al, 2010b;McCaskill & Kearney, 2016) and was ranked lowest for all param- A grazed perennial pasture requires a sufficient plant population to achieve both production and sustainability goals: high herbage accumulation and persistence (Hayes et al, 2010a,b;McCaskill & Kearney, 2016) by maximizing soil water usage (rooting depth and extraction); having a dry profile in autumn to store winter rain- high ground cover to reduce weeds (Dear, Virgona, Sandral, Swan, & Orchard, 2007;McCaskill & Kearney, 2016), minimize runoff (Murphy, Lodge, & Harden, 2004) and maximize infiltration (Murphy et al, 2010). There is also a threshold plant density, below which a species is not able to achieve these goals (e.g., Dolling, Lyons, & Latta, 2011;Hayes et al, 2010a,b;McCaskill & Kearney, 2016;Virgona, 2003).…”

Addressing biophysical constraints for Australian farmers applying low rates of composted dairy waste to soil

“…The increase in volumetric water content in the pot experiment in the sandy Binnaway Kandosol soil was as much attributable to the additive blend as to the compost, most likely a result of lime being a key ingredient in the additive blend and fertilizer treatments. Lime is known to impact soil water-holding capacity (Roper, 2005; Hayes et al, 2010b), most likely due to changes in soil physical properties that result in reduced dispersion and slaking where lime is applied (Chan et al, 2007). The effect of compost on soil water-holding capacity may have become evident over a longer period of time.…”