Net water benefit of cover crops in Northern grains production. Farming water with ground cover

Abstract

Low groundcover increases risk of soil erosion and reduces fallow efficiency. To remedy this cover crops
can be grown to increase groundcover, but does the increased ground cover improve fallow water
accumulation enough to recover the water used to grow the cover crop? To answer this, cover crops were
planted into a long fallow following skip row sorghum, and sprayed out prior to growing wheat. The main
cover crop was White French millet, which had different termination timings imposed. Other crops included
sorghum, lablab and a mixed species (millet, lablab and tillage radish), which were all sprayed out at the
same time as the mid-terminated millet. By planting of the subsequent wheat crop, all cover crop treatments,
except the lablab, had recovered the water they used prior to termination, with some accumulating more
plant available water (PAW) than the control. Increased ground-cover improved establishment of the wheat
and all cover crop treatments had higher grain yield than the bare control in a drier than average season.
These results confirm a crop can be grown and sprayed out to improve ground cover in a long fallow,
without having a net negative effect on PAW, with yield benefits in the following crop in excess of what can
be explained by increased soil water.