Case study 3: Derrick Davis use of field peas and lupins as break crops.
Farming at Lake Cargelligo
Property size: 10,000 ha.
pH: 7 red loam/clay
Average rainfall: 400mm
The Davis’s annually grow approximately 6000 hectares of wheat, 2000 hectares of lupins and field peas and leave 1000 hectares long fallow.
They like to use Sturt field peas in their rotations as they can be sown earlier and provide rapid growth to provide thick biomass for brown manure, spraying in July/August while retaining about 20% for grain. In the past green manured crops were offset ploughed but they have modified their system to now brown manuring.
They tend to grow lupins more for grain as it tends to be higher yielding than peas and are simpler to bring to harvest.
Sowing of peas begins in in April. The sowing rate depends on whether or not they are to be retained for seed or brown manured. Pea biomass is generally not a problem as its sprayed early enough before jointing becomes an issue.
If being sown for purely brown manuring, i.e., not for seed retention the peas are sown at a rate of 50-55 kg/ha with fertilizer (MAP) at a rate of 20 kg/ha. Lupins are also sown in April at a rate of 65 kg/ha with a fertilizer (MAP) rate of 40kg/ha. All seed is inoculated pre-sowing.
One of the two main reasons the Davis’s use peas and lupins for break crops is weed control. After continuous cropping for many years they had noticed an increase in the population of wild oats, rye grass and barley grass and since using these break crops control of these weed populations has improved greatly.
Nitrogen: Costs of applying urea are greatly reduced with enough nitrogen in the soil after a pea or lupins break crop for two subsequent cereal crops, assuring high levels of protein.
The Davis’s experience very little disease in their cereals since growing pulse break crops with crown rot and take-all virtually non-existent.
The Davis’s have no issues with stubble management at harvest as they have found inter-row sowing with a disc seeder eliminates any stubble issues, whether with break crops or cereal stubble.
Soil health, profitability and sustainability:
The major negative aspect of growing peas and to lesser extent lupins as break crops for the Davis’s is the cost of the operation. Although it would be cheaper to just leave the paddocks out of operation and still gain weed control, the obvious benefits to soil health in microbial activity and the higher yields with higher protein (both approximately 20% higher) not only compensate the costs but are leaving the country in better condition into the future.
There is also more certainty in growing a higher yielding crop the following year regardless of the season, with the break crops improving weed and disease control and better yield and protein, with the retained stubble providing better moisture retention in the soils. The decisions are certainly based on long term planning.
Project Number: CWF00018