Seasonal differences in the soil water balance under perennial and annual pastures on an acid Sodosol in southeastern Australia

Abstract

Summary Replacement of native deep‐rooted grasses by shallow‐rooted ones has resulted in greater losses of water and nitrogen by drainage. To counter this effect we have tested the hypothesis that liming, and the conversion of annual grass pastures to perennial grass pastures, could improve the sustainability of grazing systems in the high rainfall zone (> 600 mm per annum) in southeastern Australia, through better use of water and nitrogen. A field experiment consisting of sixteen 0.135 ha (30 m × 45 m) grazed paddocks representing four pasture combinations (annual pasture (mainly Lolium rigidum) without lime (AP–); annual pasture with lime (AP+); perennial pasture (mainly Phalaris aquatica) without lime (PP–), and perennial pasture with lime (PP+)) was carried out from 1994 to 1997 on an acid Sodosol (Aquic Hapludalf) in southern New South Wales, Australia. Measurements were made of surface runoff, subsurface flow (on top of the B horizon) and soil water content. The results showed that perennial grass pastures, especially PP+, extracted approximately 40 mm more soil water each year than the annual grass pastures. As a result, surface runoff, subsurface flow and deep drainage were at least 40 mm less from the perennial pastures. These measurements were further supported by a simulation of soil water deficit and deep drainage for AP– and PP+ paddocks, using 10 years' past meteorological records. Overall, the results suggested that well‐grown, phalaris‐based pastures could reduce recharge to groundwater and make pastoral systems more sustainable in the high rainfall zone.

Perennial pastures for recharge control in temperate drought-prone environments. Part 1: productivity, persistence and herbage quality of key species

“…There is little doubt that perennial pasture species have demonstrated a greater capacity to create a larger 'dry soil buffer' than annual crop and pasture species in a range of seasons and environments (Ridley et al 1997;Lolicato 2000;Angus et al 2001;Heng et al 2001;Latta et al 2001;Brown et al 2005;Bell et al 2006;Sandral et al 2006;Ward et al 2006).…”

Lixiviação de cátions favorecida pela presença de ânions inorgânicos e ácidos orgânicos de baixa massa molecular em solos adubados com camas de aviário

“…Isso se deve às grandes e frequentes doses de KCl aplicadas nesta cultura e de N, que, com o tempo, é nitrificado, e ao expressivo arraste do Cl -e NO 3 -mesmo nos solos mais argilosos (6) . Em outros estudos, também tem sido observada maior mobilidade do Cl -em relação ao NO 3 -e ao SO 4 2-e que há boa correlação entre concentração de cátions lixiviados do solo com os mols de carga de ânions inorgânicos (Heng et al, 2001). Wong et al (1992) também constataram que as perdas de Ca e Mg em solo estavam intimamente relacionadas com aquelas de NO 3 -.…”

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

“…6 where there is a gradual splaying of deep soil water data at both experiments, with volumetric water content becoming less at depth under the more persistent perennial species. There have been many studies in the past decade examining soil water under crops and pastures, particularly in Australia, due to an emphasis on research related to managing dryland salinity (Lolicato 2000;Angus et al 2001;Heng et al 2001;Latta et al 2001;Ridley et al 2001a;Brown et al 2005;Bell et al 2006;Sandral et al 2006;Ward et al 2006). Implicit in the findings of previous studies is the need for perennial plant persistence because, in the absence of plant survival, none of the other agronomic characteristics important in maximising water extraction such as rooting depth, ground cover, length of growing season and herbage yield can be expressed.…”

“…Australian agricultural production systems are located in environments that typically have low natural soil fertility and dry climates. Therefore the loss of water and nutrients due to deep drainage (Heng et al 2001) has the potential to reduce agricultural yields and increase input costs. Incorporating perennial pastures into farming systems within the cropping zone has been suggested as an option for reducing soil degradation attributable to deep drainage (Cransberg & McFarlane 1994;Cocks 2001;Dear et al 2003;Singh et al 2003).…”