Summer cropping trial during astonishingly dry season shows crops can be grown on soil moisture alone

A South Coast cropping trial run during an unexpectedly bone dry summer has given good indication farmers can grow grazing fodder with solid biomass using soil moisture alone. The driest summer Green Range farmer Jeremy Walker had ever experienced coincided with his decision to host a spring and summer cropping trial funded by Grains Research Development Corporation and led by Stirlings to Coast Farmers. The project was announced in January after excessive waterlogging occurred in the Great Southern, South Coast and parts of the Central Wheatbelt last year, impacting crop yields. It aimed to improve growers’ knowledge and confidence of sowing a spring or summer crop on paddocks where winter crops or pastures had failed due to waterlogging. While the wet winter was followed by a bone-dry summer, Mr Walker said he regarded it a success because the results showed how summer crops would perform in the “worst case”. Mr Walker said he wanted to take part in the trial because he was trying to transition to “shifting the sheep feed curve” and be able to finish lambs on summer crops. He has been experimenting with summer cropping for about five years, holding his own trials by planting winter varieties that could be carried through to harvest or traditional summer varieties to “strip moisture” in paddocks prone to waterlogging. “Our biggest risk is waterlogging, by a long way,” Mr Walker said. “We have a small bucket – about 350mm of soil until we hit clay - and we are always trying to chew that up before it affects the winter crop.” The project included three multi-species spring and summer sown field trials at Jerramungup, Boyup Brook and Green Range – including at least one cereal, brassica and legume. Four single species grain crop demonstrations are also being carried out at South Stirlings, Mobrup, Wickepin and Lake Cairlocup, between Jerramungup and Pingrup. In addition to the farm-scale demonstrations, Nutrien Ag Solutions is also conducting a summer grains small plot trial with crops including sunflower, hemp and safflower. The trials are being held after one of the “longest, wettest winters” Mr Walker had ever experienced, with 900mm of rain last year causing severe waterlogging and failed crops. He said summer rain had been scarce, with 12mm in January, 7.5mm in February and 20mm in March – well down on the 120mm-plus that would normally fall in that time. “Our canola program averaged 300kg/t due to waterlogging and spraying it out,” Mr Walker said. “That was followed by the worst summer I’ve seen in my 10 years home on the farm.” Stirlings to Coast project manager Dan Flay said he had been amazed at how much biomass grew almost exclusively using moisture stored in the soil after the wet winter. The paddock-scale trial at Jeremy’s included 10ha of millet, 10ha of a millet and lablab legume mix, 61ha of sorghum, and a 3ha fallow strip to measure soil moisture. The area was grazed by 1800 ewes for 3.5 weeks, with the sheep favouring the millet crop. “The trial has shown that a viable summer crop can be grown using existing soil moisture,” Mr Flay said. “It is valuable to know you can seed summer crops in September or October with a fair amount of confidence you can get one solid graze, without it having to rain again.” Mr Walker said he was not surprised the crops were able to sustain reasonable biomass on subsoil moisture alone, saying the “hardiness” of some of the plants had been impressive. Mr Flay said the main focus of the Stirlings to Coast trial was to determine how summer crops could help fill the feed gap in mixed farming operations, and whether there was potential to bring grazed summer crops through to harvest. Mr Flay said a second aspect was to determine how summer cropping would impact winter crops by reducing the soil moisture profile and reducing the risk of waterlogging in winter. Stirlings to Coast chief executive Nathan Dovey said summer crops had been trialled in the Albany Port Zone before, but he believed it was an area that needed “revisited”. “It is a combination of new agronomic knowledge, taking advantage of the season you have, and then a little bit of luck – no one knows how much summer rain there will be,” he said. “We wouldn’t have needed much summer rain (this year) for an excellent result.” Mr Walker said he was particularly interested in sorghum as a summer sheep feed, after finding it to be “particularly hardy” and able to withstand the dry conditions. Mr Dovey said both the Stirlings to Coast and Nutrien Ag Solutions trial crop types were chosen according to localised growing conditions and with advice from farmers’ agronomists. The broadacre trials will be sprayed out in April and sown over, with Stirlings to Coast tracking the performance of the primary crop and “running the economics”. Mr Flay said results would be released after the 2022-23 harvest, calculating grazing value, the feed value of the summer crop, the biomass produced, and the effect on the winter crop. “So far the biggest outcome has been that you can produce a viable summer crop from a full soil moisture profile, and still get a full graze,” he said. “Farmers on the coastal fringe can put in summer crops with a fair bit of confidence.”