Nutrient warning issued
Researchers have advised graingrowers who have cut crops for hay and silage due to moisture stress and frost to be mindful of the amount of nutrients removed from their paddocks.
Crop nutrition experts supported by Grains Research and Development Corporation said FXWWLQJ KD\ UHPRYHG VLJQL¿FDQWO\ PRUH QLWUR gen, potassium and sulphur than if the crop was left standing for grain production.
The corporation said hay could remove up to two times more nitrogen and up to 10 times more potassium than if a crop was harvested IRU JUDLQ ,Q FDQROD XS WR ¿YH WLPHV PRUH VXO phur could be lost.
Agriculture Victoria research scientist Roger Armstrong said one-off hay cutting of a failed crop could prompt changes in crop nutrition programs and paddock management into the next season.
“With nutrients that would otherwise be recycled in the soil being lost through the removal of crop material in hay and silage, soil tests will become more important ahead of next year’s sowing to inform nutrition programs in 2019,” he said.
More information on nutrient removal from cutting crops is on a GRDC Communities website at http://bit.ly/2qyucre and http://bit. ly/2dbyonz.
Leading agronomist and former International Plant Nutrition Institute regional director for Australia and New Zealand Rob Norton has FRQWULEXWHG D VLJQL¿FDQW DPRXQW RI LQIRUPD tion.
GRDC Communities, for which Dr Armstrong and Dr Norton are among the cropnutrition experts, brings together a range of specialist grains researchers and advisers online to share information, knowledge and technical advice on seasonal issues to improve JURZHU SUR¿WDELOLW\
Dr Armstrong said repeated removal of hay was considered to be one of the most acidifying of agricultural practices, and on acid soils could exacerbate the issue in the long term.
He said the removal of cereal or canola hay required 25 kilograms a hectare of lime for each tonne of biomass removed, or 45kg-ha for each tonne of annual legume hay removed, to neutralise the resulting acidity.
Cutting hay reduced inputs of organic matter into the soil for that season.
The size of the effect when the hay is cut from a failed crop might be roughly similar to organic matter lost from burning stubble residues from a good crop, compared to retained stubble.
Following hay cutting, little residue cover – maybe 0.4 t/ha of residue after hay cutting versus 2.0 t/ha after harvest – remained.
Growers were therefore advised to reduce JUD]LQJ DQG WUDI¿F DFURVV WKHVH SDGGRFNV WR minimise the risk of wind and water erosion, which also contributed to soil-nutrient loss.