LONG-TERM research across Victoria’s Mallee region is highlighting the impacts different crop managements on soil carbon and nitrogen.

Agriculture Victoria (AgVic) has been conducting a research trial, dubbed MC14, at Walpeup since 1985 to determine how crop management can affect soil carbon and nitrogen stocks.

AgVic senior researcher scientist Roger Armstrong said three crop rotation treatments have been tested. 

Professor Armstrong said the three were; legume and wheat; legume, fallow and wheat; and fallow and wheat. 

“The standout treatment was the legume/fallow/wheat in terms of the significant productivity benefits of additional moisture and nitrogen added to the subsequent crop,” he said. 

“However, this needs to be balanced with the finding of nitrate leaching, as well as a reduction in the accumulation of soil carbon compared to the other continuous rotations.”

Prof Armstrong said the initial stages of the trial had medic as the legume in rotation, but it had been swapped out for vetch to keep with modern farming practices.

“Cropping farmers know that adding a legume into the rotation increases nitrogen in the soil,” he said. 

“When an annual legume phase is included in the rotation, we have recorded not only good grain yield responses but also large amounts of soil nitrate, a valuable commodity in low rainfall Mallee cropping zone. 

“Most notably the amount of soil nitrate is greater in the crop rotations that exclude a fallow period.”

He said the results also found fallowing reduced the amount of organic carbon in the soil.

For more information, visit the AgVic website.