Vetch has been grown on commercial cotton farms in most cotton growing regions for several years, and as a legume it takes nitrogen from the air and “fixes” it in the soil to allow plants to use it as an organic nitrogen fertiliser.

To evaluate the benefits of growing vetch Dr Ian Rochester and his team at CSIRO Plant Industry, Narrabri, have conducted extensive field trials to identify just what vetch has to offer cotton farmers.

The Cotton Catchment Communities CRC and CSIRO Plant Industry research scientist, Dr Ian Rochester, Narrabri, NSW, assessed a variety of legumes commonly grown in rotation with cotton including faba beans, field peas, clovers and medics.

Vetch’s ability to fix nitrogen far exceeded all the other legumes, commonly fixing up to 200 kilograms of nitrogen an hectare.

Dr Rochester said with nitrogen fertiliser prices on the rise, incorporating vetch rotations into farming systems allows growers to reduce nitrogen fertiliser inputs.

In 2008 trials, cotton, following a vetch rotation, yielded between 13.6 and 14.8 bales an hectare (5.5 and six bales an 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 140kg/ha to achieve maximum yields,” Dr Rochester said.

“Coupled with increased yield, the gross margin per hectare for a rotation system including vetch can be increased by $540/ha.

“Although vetch is not an income-producing crop itself, the $110/ha cost of growing it is substantially outweighed by the financial benefits accrued for the following cotton crop.”

Incorporating vetch stubble added organic matter to the soil and over the past eight years of the CSIRO Plant Industry trials, the organic matter levels in cotton/vetch rotations increased by 14 per cent.

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