Ground Cover Supplement : GC Supplement - Growers sharing knowledge
GROUND COVER GROWERS SHARING KNOWLEDGE 12 ENVIRONMENTAL BENEFITS Soil health check A TRIAL AIMED AT IMPROVING LONG-TERM YIELD INCREASES THROUGH IMPROVED WATER STORAGE AND SOIL BIOLOGY IS SHOWING PROMISE -- AND THROWING UP SOME SURPRISES FOR THE WA-BASED LIEBE GROUP RETAINING STUBBLE IS a contentious issue. Ecologically, farmers know it is the logical way to go. But when a trial plot with burnt stubble yields 25 per cent (560 kilograms per hectare) more than full stubble retention, it is hard to justify the economic value of stubble retention. That was in 2005, yet in 2004 a 22 per cent (600kg/ha) improvement in wheat yield was recorded for a crop sown after brown-manured lupins. These results illustrate that soil health is a dynamic and complex issue and that short-term results can be misleading. So the Liebe Group is taking a long-term approach to studying soil health with a trial members hope to continue for at least 10 years at the same site. Soil health work started in 2003 at the Long-Term Research Site (LTRS). The LTRS – located on Stuart McAlpine’s property, 30 kilometres west of Buntine on yellow sandplain country – was selected because of the absence of significant chemical or physical soil barriers. The LTRS site was established together with eight satellite sites located throughout the Liebe region which evaluate the effect of different biological, physical and chemical applications to soil health. The LTRS has a number of long- term trials growing on the site. One particular trial – the soil biology trial, run collaboratively by the University of Western Australia (UWA) and the Liebe Group – was the driver for the establishment of the LTRS. However, it was deep-ripped to 450 millimetres to ensure there was no residual traffic compaction before being sown to lupins. In 2004, 14 treatments were applied (Table 1) ranging from full stubble retention and brown manuring (with and without the addition of humates), zeolites and microbes to a cocktail of all of them. Other treatments included incorporating stubble with offset discs prior to seeding, the use of decomposition agents and the addition of 20kg/ha of organic matter in the form of barley straw. All plots were sown to WyalkatchemA wheat in 2004 and 2005. In 2005, the wheat grain yields across the treatments achieved 78 to 105 per cent of their water-limited yield potential, 2.76t/ha based on the growing season rainfall of 182mm. In 2004, the brown manure treatments resulted in significantly improved wheat yields, with an additional 600kg/ha. However, in 2005 a 20 per cent increase in biomass was measured at anthesis, but this was not reflected in the grain yield of the brown manure plus 2004 retained stubble treatment. This suggests that the value of a brown manure crop on sandplain soils, depending on seasonal conditions, may be relatively short-lived. Although too early for a full understanding, the research team considers that the lower yields obtained in the initial phases of converting to full stubble retention systems may be associated with the initial microbial immobilisation of nitrogen associated with stubble decomposition. Where TABLE 1 TREATMENTS -- SOIL BIOLOGY TRIAL, LIEBE GROUP LONG-TERM RESEARCH SITE, BUNTINE, WA Brown manure The 2003 lupin crop was desiccated at 70% anthesis and left standing High organic matter The 2003 lupin crop was left standing and an equivalent of 20t/ha hay applied to all plots Tilled soil Most treatments were sown by no-till methods but a set of offset discs was used to quantify the effects of tillage Zeolite Zeolites are robust, insoluble and chemically stable aluminium silicate minerals. They have a unique atomic structure with a well-defined internal porosity of cavities and channels that host cations, water and other molecules. They provide a refuge for soil microbes. (Zeolite treatments have ceased for 2006 as the treatment was found to have no significant effects over the three years the trials have been running). Microbes Nutri-Life 4/20 microbes include effective cellulose digesters, general decomposers, mineral solubilisers, co-factor species, effective free-living nitrogen fixers (Azotobacter species), phosphorus solubilisers (Bacillus megaterium) and predatory fungi. These species are hardy and flourish in a wide range of soil types. Humates Humates are 85% soluble and comprise 70% humic acid and 10% potassium. The humic acid component includes a minimum of 16% fulvic and ulmic acid. The rapid solubility of these granules allows them to fuse well with soluble fertilisers that are particularly important for reducing the lock-up rate of soluble phosphate sources, stabilising urea, chelating and complexing elements and buffering high sodium and heavy metals. Left: Ben Parkin (CSBP, left), Peter Bryant (Liebe Group grower, centre) and Chris Gazey (DAFWA, Northam, right) with Mohammed Hamza's (DAFWA, Merredin) shallow leading tyne deep ripper on Peter Bryant's Latham property. Right: the ripper in action -- a rubber tyre roller is attached to assist with seed depth control.
GC Supplement - No-till
GC Supplement - Pastures