An on-farm evaluation of the capability of saline land for livestock production in southern Australia

Abstract

Grazing livestock on revegetated saline land is one of few profitable options to continue using this class of agricultural land. However, there has been little research conducted to assess the capability of saline land to support livestock production based on the soil and water characteristics at a particular site. In this study, data from 11 grazing studies collected from eight commercial farms across southern Australia were used to estimate metabolisable energy (ME) utilised/ha, as well as total ME produced/ha. All data were from the autumn (March–May) period, when feed is normally in short supply and of limited quality. Site characteristics indicative of the severity of salinisation varied across the sites. Topsoil electrical conductivity (ECe) ranged from 1 to 33 dS/m and groundwater EC from 14 to 60 dS/m (equivalent to sea water). Feed on offer before grazing varied from 700 kg dry matter/ha to 9000 kg dry matter/ha between sites. Thinopyrum ponticum and Puccinellia ciliata featured prominently in the less saline revegetated sites, with Atriplex spp. present on the more saline sites and some lucerne and rhodes grass on the less saline, well drained sites. Grazing days per ha for sheep (ME-adjusted dry sheep equivalent) on autumn pastures across the sites ranged from 41 to 3600, and liveweight gains ranged from –95 to 314 g/sheep.day. The grazing value of the highest producing saltland was at least as high as that expected on adjacent areas that were not salt affected. The major advantage of establishing saltland pastures included an out-of-season feed supply high in crude protein and micronutrients that possessed the ability to capture summer and autumn rain. This should represent a substantial reduction in supplementary feed costs and increases the flexibility of methods for feeding livestock through periods of low annual pasture availability. The value of the ME produced on the highest yielding saltland pasture was estimated to be $360/ha based on substituting the best alternative strategy of purchasing lupin grain as a supplement. A quadratic relationship (R2 = 0.62, P = 0.024) was found between soil ECe and ME produced across the sites. Significant relationships were not found between other saline site characteristics and ME production, which partly reflects the complexity of these systems as well as limitations with site characterisation.

Livestock preference and feeding value as key determinants for forage improvement – why not ask the consumers?

“…Despite these limitations, saltbush is a valuable source of CP, sulfur, vitamin E and some essential minerals (Ben Salem et al 2010;Pearce et al 2010;Fancote et al 2013;Norman et al 2019). A collaborative research project, involving farmers, agronomists, livestock scientists and system modellers, identified low FV, particularly ME content, as the key constraint that limited profitability of saltbush systems (Thomas et al 2009). Pre-experimental modelling indicated that improving shrub organic-matter digestibility by 10% would increase profits by three times the increment associated with increasing biomass production by 10%, or reducing the cost of establishment by 10% (O'Connell et al 2006).…”

The value of stubbles and chaff from grain crops as a source of summer feed for sheep

“…The daily ME intake (MEI) of the ewes was calculated using the method of Thomas et al (2009), where liveweight gain or loss, in combination with the animal's current liveweight, are used to predict the MEI of the animal.…”

“…A multiple linear-regression analysis was conducted to examine the relationships between estimated MEI (dependent variable) and the number of sheep grazing days on stubble, and initial sheep liveweight and body condition score (independent variables). Both sheep grazing days (ewe days/ha, not adjusted for liveweight) and dry sheep equivalent (DSE) grazing days (DSE days/ha, 1 DSE = 8.9 MJ ME/day; Thomas et al 2009) variates were used in analyses. For linear-regression analyses for variates predicting MEI, sheep grazing days (unadjusted for ME requirements) was included as a fixed effect because initial sheep liveweight was included in the statistical model.…”

Simulation of water-limited growth of the forage shrub saltbush (Atriplex nummularia Lindl.) in a low-rainfall environment of southern Australia

“…Saltbush plantations on mixed farms may also foster biodiversity in the landscape (Seddon et al 2009;Collard and Fisher 2010) via the provision of habitat for animals. Recent research (Norman et al 2008(Norman et al , 2010Thomas et al 2009;Llewellyn et al 2013), and the recognition of increased productivity of otherwise marginal land, has highlighted the important role of perennial shrubs in the low to medium rainfall zones of Australia (Revell et al 2013).…”