Cultivation versus direct drilling?

Press, 3 February 1984, Page 23

Cultivation versus direct drilling?

Conventional cultivation or direct drilling? The choice is one between thousands of years of farming practice and a system which has only been around for 30 years. Dr Garth Janson of the Ministry of Agriculture and Fisheries’ Winchmore Irrigation Research Station has been working on a programme of long term comparision between the two methods. “Direct drilling has been around for about 30 years, but it was not until recently that we had all the tools to operate the system effectively,” he says. “In 1978 I decided to look at the long term effects of direct drilling because work overseas had indicated that the benefits may only show up after some time.” Dr Janson decided to deal with arable crops because Canterbury was the ideal locality for this. Trials were set up with a rotation which included no pasture phase. Although a pasture phase maintains the soil structure, it is generally the least profitable part of a cropping rotation. The system was based on maximising profit and minimising disease. Field operations have also been conducted on a scale which is relevant to the on-farm situation, so allowing accurate costing. From 1979 to 1981 the rotation was started each year on new areas, to cover a variety of conditions for each crop. In 1980 similar trials

were begun on heavy clay soils near Ashburton to provide a contrast with the light, stony soils of Winchmore. All the trial work is being done under irrigation, with surface irrigation on the light soils and sprinkler irrigation on the heavy soils. Treatments with 50 and 100 units of nitrogen are run on both areas. The rotation on the light soils at Winchmore is from old grass to linseed in the first year, to wheat in the second, then white clover, with a winter crop of turnips. The fourth year is wheat again with a winter brassica, followed by peas in the fifth year and barley in the sixth. After white clover in the seventh year, the rotation returns to the first crop of wheat. On the heavy soils the rotation is shorter, peas to winter wheat to barley and back to peas, with a winter forage crop following the wheat and the barley. Dr Janson says that although the studies are comparative, operations on the direct drilled and cultivated treatments are not tied. “We want to exploit the advantages of each system, so there is no point in keeping to a rigid timetable for both,” he says. Measurements are taken of the crop yields, physical and chemical soil characteristics and the comparative economics of the systems. In both study areas at this stage, the total crop yield from direct drilling and conventional cultivation shows no difference. This is after five years on the light soils at Winchmore and three years on the heavy soils at Wakanui. However, the pattern of crop yield has been very different on the two soils. On Winchmore’s light soils the direct drilled crops have yielded equally as well as the cultivated crops — no better and no worse — from year one. On the heavy soil at Wakanui, however, a very different picture is emerging. Direct drilled spring barley has two tonnes per ha poorer than the cultivated crop in the first year, one tonne per ha poorer in the second year, but had achieved a comparable yield by the third year. Direct drilled winter wheat was 0.5 tonne per ha poorer than the cultivated crop in the first year, one tonne better in the second year, and 1.5 tonne per ha better in the third year. Peas have been a disaster under both establishment systems on the heavy soil because of flooding and hungry ducks. The differences between the two soils illustrate an important point. It is easier to achieve reliability in crop yield under direct drilling on the light soils. On the heavier soils, the problems are greater, but the potential benefits may also be greater. “The difference between the two rates of nitrogen application is disappearing after two to three years,” Dr Janson-says. “With direct drilling there isn’t a high rate of mineralisation because the soil is not disturbed, but there is a build up in soil organic matter which means an increased nitrogen release eventually. Soil effects take time, which is why a long term approach to the research is appropriate.” Other soil measurements include numbers of earthworms and rate of water infiltration. “

The earthworm population doubled within 16 months of ceasing cultivation before levelling off. Dr Janson says that initially it looks as though water infiltrates the soil more slowly under direct drilling, although the picture is starting to change. Root and worm channels are not disrupted as they are under cultivation and provide natural drainage. This is creating an increasingly attractive environment for plant growth. “As far as disease goes, there have been no problems with the transfer of disease materials, even though gut reaction would say there should be,” says Dr Janson. Generally, he believes that people have not given themselves long enough to try out direct drilling. "Early in a rotation, direct drilling is usually at a disadvantage because of the higher rates of expensive herbicide needed, and a lack of expertise. “As experience increases, so does profitability. Instead of having a go for one year and then giving up, farmers should consider sticking with it on the same ground to pick up the accumulating benefits.” Dr Janson says the trials can only show certain things, such as establishing likely crop yields, direct costs and what is happening to the soil. However, the trials cannot define what direct drilling means for the farmer’s total system. Most of the people taking it up have been intensive cropping farmers with 70 to 80 per cent of the farm in crops. “This means they usually have an enormous labour requirement peak in the spring. Direct drilling is very valuable for them because of the great saving of time in crop establishment. This can be up to 80 per cent,” says Dr Janson. He says each farmer needs to work out whether time saving in this way is an important factor for consideration when looking at direct drilling. “I think this system is made for someone who wants to expand their cropping area without increasing their labour force.”