OPERATING a dryland cropping operation in a variable rainfall environment has put the focus of southern Queensland farmer Neville Boland squarely on soil health to convert every available drop of moisture into crop yield.
Mr Boland says the key to success in his climate is fallow efficiency of moisture infiltration and ensuring crops then have the ability to draw that moisture back out.
"Because of our climate and rainfall pattern, the moisture we've got in the soil is 80 or 90 per cent of our crop a lot of the time; we can't rely on in-crop rain like they do in the south or further east," he said.
"We have to make sure we're infiltrating as much rainfall as we can and we're extracting as much rainfall as we can - the two sides of that mean we have to have soil cover for infiltration, and for extraction we can't have compaction or subsoil problems so the crops can draw out the water easily."
Mr Boland and his wife Penny cultivate about 4000 hectares a year out of
the 5000ha they own and |lease across three blocks between Goondiwindi and Moonie.
Despite an annual rainfall of just 450 millimetres, they grow cotton, wheat, barley, sorghum, mungbeans and the niche crop sesame, in a complex rotation based on matching crops to soil types, as well as grabbing the opportunity to tap into any available moisture.
To improve their soil health, they were early adopters of controlled traffic, switching to 2-metre wheel spacings in 1992 and then to 3m spacings in 2003, and have undertaken a long-term program of mapping and levelling melon-hole country to convert grazing lands into cropping country.
The Bolands have also had their soils EM38 mapped to support the adoption of variable rate technology, and have hosted a series of trials supported by the Grains Research and Development Corporation (GRDC) and the Queensland Department of Agriculture Fisheries and Forestry (DAFF), including the use of gypsum on sodic soils and strategic tillage in controlling resistant weeds.
Most of their soils are soft-cracking clay vertisols, but there are also areas of hard-setting spodosol soils. Soil testing has revealed deficiencies in phosphorus, zinc and nitrogen.
"And we have sodicity and salinity at depth, so that can restrict our root zone on some of the soils," Mr Boland said.
"This means that not all of the soils are suitable for sensitive crops; for example, mungbeans, chickpeas and the sesame.
"I try to manage my way around that by trying to use more tolerant crops in those areas that we've identified with subsoil constraints, so that includes barley, cot-
ton, wheat and sorghum, which are fairly tolerant.
"As a result, the rotation is fairly complex and it can vary on a paddock-to-paddock basis."
Mr Boland applies fertiliser accordingly to address the nutrient deficiencies, as well as gypsum to improve sodicity.
"Most of the farm will get a response out of phosphorous and most areas also zinc, and then with the nitrogen - because it's been farmed probably 40 years now - we're getting a response out of applications of urea or nitrogen in the rotation.
"We have also achieved good results out of our surface-applied gypsum for those areas of the farm that have fairly high sodicity at the surface. Most of the response was quite immediate in the first crop and carried on for a few years after that.
"The main thing with the gypsum is to identify those areas that will respond to it because it is quite expensive.
"We did an EM38 survey and that showed up those sodic areas quite well, and we applied gypsum just on those areas to minimise the expense."
