Validating no-till in KZN

Early experimentation with no-till in KZN was done by farmers themselves. Now soil scientists from the University of Tennessee visit to learn from their experience. Lloyd Phillips reports.

According to Guy Thibaud, a specialist scientist in the fields of soil fertility and plant nutrition with the KwaZulu-Natal Department of Agriculture and Environmental Affairs, research into and implementation of no-till practices in the province have in the past been driven more by farmers than scientists.
The farmers’ aim was to improve their cropping productivity off the declining quality of their soils. “This increased production off weakening soils can only be achieved through soil and moisture conservation, increased soil organic matter and enhanced soil biodiversity, all of which can also contribute to reduced production costs,” Guy says. “However, questions frequently asked by no-till farmers have been on issues such as reducing soil compaction, effectively dealing with soilborne pests and diseases, combating soil acidity through liming, fertilisation requirements, and most commonly, how much organic matter is required in the soil. Scientists are currently working on these questions.”

No equipment for early no-till farmers
Ant Muirhead of Winterton, KZN has been a successful no-till farmer for almost 20 years, but he still faces a variety of challenges relating to his farming philosophy, which others have only begun to take seriously in the past 10 years or so. “The driver for my change from conventional to no-till agriculture was purely economic,” says Ant. “Using conventional tillage I used to struggle with wasted irrigation run-off, and I used more diesel and fertiliser during planting than I do now. Unfortunately, the process of changing to no-till was very slow for me because of the lack of specially designed no-till equipment at the time. I often had to modify existing conventional tillage equipment, some of which worked and some of which didn’t. Fortunately, with no-till now internationally recognised, there is a wide range of specially designed dedicated no-till equipment available.” Guy and Ant have for years worked closely on research into no-till for KZN. With Ant providing the equipment, land and crops, Guy has conducted intensive studies on the former’s farm, trying to answer the many questions that no-till still poses to scientists and farmers alike. One of Ant’s early no-till experiments that validated his decision to move away from conventional tillage involved soil moisture retention. After the first 10 years of using no-till, Ant’s croplands had a dramatically improved ability to retain valuable irrigation and rainwater. If he applied 20mm of irrigation using conventional tillage, much of this water would run off the fields and be wasted, taking valuable topsoil with it. However, after his initial 10 years of no-tilling, a trial conducted by scientists from the Cedara Agricultural Research facility of the KZN DAEA found that the retained organic matter on Ant’s croplands could absorb as much as 100mm of water without any excessive run-off. In addition, any irrigation water that left the fields through groundwater flow came out clean, unlike the soil- and nutrient-laden water from a nearby conventionally tilled test field. “Thanks to the high organic matter content and ground covering of my no-till fields, my crops can stand for 10 to 14 days longer in drought conditions than crops grown in conventionally tilled soils,” Ant points out. “This is a valuable safety margin for no-till farmers – we can wait for rain up to an extra two weeks, while conventionally tilled crops are already dead. This simple fact can mean the difference between making or losing lots of money.”

Another KZN disciple of no-till, Tony Matchett, also places great value on retaining organic crop residue on his no-till soils. He is passionate about encouraging soil biodiversity in terms of microbial and earthworm activity. Soil studies conducted on his Karkloof farm after he began implementing no-till nearly 10 years ago revealed that the fields’ earthworm populations had substantially increased to approximately 500/m2 in the top 30cm of his now organically rich soils. This equates to 50 million earthworms per hectare.

The importance of biodiversity
“The network of channels left by these creatures improves water infiltration, with the water also taking surface-applied lime and other nutrients down to deeper soil levels more efficiently than any disc or plough,” says Tony. “In addition to the earthworms, a good crop residue cover encourages populations of moulds, fungi, insects and nematodes in the soil, improving its health.”
Unfortunately, KZN’s no-till farmers have found that with the beneficial soil life come unwanted crop pests and diseases. Fungal and viral diseases of common crops like maize, soya and winter wheat are often harboured in the plant residues until they emerge to plague the following crop. Animal pests also challenge no-till crops. Last year, Ant had such a massive problem with slugs damaging his soya that he eventually took the drastic measure of burning 130ha of wheat stover that preceded his soya crop.“This is a common problem for no-till farmers world-wide, “ he says. “British no-till farmers now clear fields totally for up to two months to force the slugs to die off. Dealing with pests and diseases in no-till is an ongoing challenge, but we hope that scientific research will come up with ideas for us to use.” Crop rotation is currently one of the most important methods used by KZN’s no-till farmers to limit pest and disease problems. This practice can also improve soil health, for example legumes improve soil nitrogen levels while generating valuable grazing or cash for no-till farmers. ”Brassica cover crops, such as oil radish, can act as biological drills to alleviate soil compaction and improve moisture penetration,” Guy says. “Ideally, cover crops should also have large root mass and root length density, supply large amounts of organic carbon, support dense microbial populations and markedly improve soil aggregate stability.”

Beating soil acidity is a common challenge facing no-till farming in KZN, and the experts agree that soil acidity should be under control before any farmer changes from conventional tillage to no-till. Soil acidity problems almost always start at the soil surface and then work their way down the soil profile over time unless they are controlled by practices such as adequate liming. While yields under no-till conditions compare well with those of most conventionally tilled crops, the latter will always outperform the former if soil acidity is not controlled in no-till. Ant and Guy’s trials have also found that no-till needs more nitrogen than conventional tillage, and that potassium and phosphorous from no-till’s organic matter tend to accumulate near the soil surface. “If there is a decent mulch, roots will come to the surface to collect these surface nutrients,” concludes Guy. – Lloyd Phillips Contact Guy Thibaud on (033) 355 9447, fax (033) 355 9454 or e-mail [email protected]. Contact Ant Muirhead on 083 378 6751 and Tony Matchett on tel/fax (033) 330 2057. |fw