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Vetch improves soil health, profits and reduces greenhouse gas emissions
6th May 2008

A decade of research by Cotton Catchment Communities CRC and CSIRO Plant Industry research scientist Dr Ian Rochester concludes that rotating cotton production with vetch, a winter legume which takes nitrogen from the air and ‘fixes’ it in the soil allowing plants to use it as an organic nitrogen fertiliser.

Vetch has been grown on commercial cotton farms for several years in most cotton growing regions. To evaluate the benefits of growing vetch Dr Ian Rochester and his team at CSIRO Plant Industry in Narrabri have conducted extensive field trials to identify just what vetch has to offer cotton farmers.

Dr Ian Rochester’s research assessed a variety of legumes commonly grown in rotation with cotton included faba beans, field peas, clovers and medics, yet vetch’s ability to fix nitrogen far exceeded all the other legumes, commonly fixing up to 200 kg of nitrogen per hectare

Dr Rochester said that Nitrogen fertiliser prices are constantly on the rise, as the cost of nitrogen fertiliser manufacture is closely linked to oil prices. Manufacturing Nitrogen fertiliser requires a large input of energy; often natural gas is used. Therefore, by incorporating vetch rotations into their farming systems, growers are able to reduce nitrogen fertiliser inputs by utilising this organic form of nitrogen from the legume crop. Importantly, greenhouse gas emissions are dramatically reduced as well. In our 2008 trials, cotton following vetch yielded between 5.5 and 6 bales/acre.

“Within a continuous cotton system where cotton was planted year after year, growing vetch reduced the amount of nitrogen fertiliser required for cotton by 140 kg per hectare to achieve maximum yields. Coupled with increased yield, the gross margin per hectare for a rotation system including vetch can be increased by $540”.

Although vetch is not an income producing crop itself, the $110 per hectare cost of growing it is substantially outweighed by the financial benefits accrued for the following cotton crop.

In addition to the increased levels of soil nitrogen vetch produces, it can also assist in increasing soil organic matter which is becoming an issue in cropping soils. Incorporating vetch stubble adds organic matter to the soil and over the last eight years of the CSIRO Plant Industry trials the organic matter levels in cotton fields in rotation with vetch increased by 14 per cent.

“Another advantage of vetch is the ability of the following cotton crops to absorb greater amounts of nutrients, such as nitrogen, phosphorus, potassium, zinc and copper, while sodium uptake is reduced to the crop’s benefit.

Soil structure improves after vetch, making cultivation easier, as well as root penetration and growth. This, coupled with increased water holding capacity of the soil, aids the cotton crop to access more water.

“Vetch is also an excellent break crop that reduces the incidence of Black Root Rot in those areas where this fungal disease occurs”

There are two varieties of vetch, Namoi Woolly Pod Vetch and Capello generally performed better than other varieties in the CSIRO Plant Industry trials concluded Dr Rochester.

For more information please contact Dr Ian Rochester on (02) 6799-1520.