Economics are forcing farmers to produce more with less. This especially applies to fertiliser, a major agronomic input. A recent combined symposium by the Fertiliser Society of South Africa and the International Zinc Association of Southern Africa in Pretoria addressed the hows, whats, whys, whens and how muchs of efficient fertiliser use. Chris Nel was there.
Precision farming ideal for lime application
Yield potential is limited in South Africa’s summer rainfall region due to soil variations and uncertain, relatively low rainfall in the growing season. Land suitable for crop production must be properly and sustainably managed, says Kobus van Zyl of Omnia Fertiliser.
“Global food production is just keeping up with consumption,” he explains. “Precision farming will let farmers produce higher yields of healthier crops. It provides detailed field information on soil, chemical and physical properties, which farmers can apply to improve production. They can focus on high-potential fields and withdraw low-potential areas from production.” Precision application is eminently suitable for applying lime to counter soil acidification.
Lime is spread according to chemical maps, indicating each fields’ site-specific requirements. “Subsoil acidity is very difficult to manage but can be rectified with lime, although it may take several years to reach full effect,” advises Kobus. “The right type of lime – calcitic or dolomitic – must be selected to address specific deficiencies.”
Kobus stressed properly liming acid soils dramatically improves fertiliser efficiency. “Liming maize land can increase yields by 0,5t/ha to 3,5t/ha but only if the right type of lime, at the right application rate and time of the year, is spread and incorporated into the soil according to its chemical needs.”
Cultivating and fertilising land to produce more food, especially with nitrogenous fertilisers, accelerates soil acidification, Kobus explains. As the soil pH drops, aluminium dissolves and interferes with root growth and nutrient uptake in sensitive crops and cultivars. Acid conditions may also cause calcium or magnesium deficiencies.
Crop tolerance for acidic soil conditions varies. Sunflower and wheat are very susceptible to aluminium toxicity, while maize is more tolerant of acidic soil as long as enough calcium and magnesium is available for uptake. Cultivar tolerances also vary.
Contact Omnia Fertiliser on (011) 709 8888. |fw
Tips for fertilising efficiently
Variable climatic conditions and rising input costs make farming in South Africa risky for financial institutions, farmers and input suppliers, but the risk can be reduced by increasing fertiliser use efficiency (FUE). So says Dr Johan van Biljon of Omnia Nutriology in a joint paper with Thinus Louw, presented at the symposium. Several practices influence FUE, he explained. “The new technology of precision farming ensures the entire field is fertilised according to site-specific soil analysis and expected yield, without over- or underfertilisation in places,” Dr Van Biljon explains.
“Differential application can save a lot of money, increase yield and reduce risk. The higher the target yield, the higher the fertiliser application rate. The interpretation of the analysis must be specific to the site’s climate, soil and crop.
General tips
“Experience shows farmers often cut back on liming when finances are under pressure – often with catastrophic consequences,” he warns. “High acidity will inhibit uptake and use of both water and fertiliser, and it can also hamper herbicide efficiency and the microorganisms in the soil.”
A wide fertiliser product range, from mineral to organic products, is available. “More concentrated products reduce transportation cost, while less concentrated products may contain other essential nutrients necessary for sustainable production,” explains Dr Van Biljon.
The method of application definitely affects efficiency. In general, band placement is far more efficient than broadcast application. Timing and water availability are also key. “Land without enough initial water available should be considered risky to plant. Rather plant less to reduce the total risk and financial exposure,” recommends Dr Van Biljon.
Effective weed control and proper soil cultivation can also help optimise FUE, and tissue and plant sap analysis have become a vital part of nutrition management.
Dr Van Biljon says improved FUE makes production more environmentally friendly, reduces risk and increases profitability across the production chain.
Contact Dr Johan van Biljon on (012) 654 7246
or e-mail [email protected]. |fw
Beating world’s biggest nutrient deficiency
Zinc deficiency is a global problem affecting crop production and human health. Zinc has many cellular functions, and deficiencies cause severe physiological disorders in plant and mammalian systems. So says Prof Ismail Cakmak, of the Faculty of Engineering and Natural Sciences at Sabanci University, Istanbul, Turkey. He presented the symposium’s keynote address. “Nearly half the soil on which the world’s grain is grown contains very low levels of available zinc, and nearly a third of the world’s population suffers from a zinc deficiency,” he explains.
“It’s the most widespread micronutrient deficiency in crops worldwide, decreasing both yield and quality. Zinc and vitamin A deficiency are responsible for nearly 11% of mortality in children under five years worldwide.” However, zinc-enriched fertiliser can be applied to crop plants. “A Turkish study on the impact of zinc on wheat in the mid-1990s demonstrated spectacular yield increases when zinc was added, and Turkey started producing zinc-containing fertiliser in 1995,” Prof Cakmak explains.
“This year a record 400 000t of zinc-containing NPK fertiliser was applied in Turkey. The Ministry of Agriculture estimates an economic benefit of at least US0 million (over R1 trillion) annually.
“The Turkish experience shows adding zinc to fertiliser is an excellent investment,” he concludes. Zinc is crucial for the structure and function of biological membranes, and detoxifying free radicals. It’s the cation proteins also need the most to function and for stability. Proteins that need to bind zinc to function make up nearly 10% of the proteomes in eukaryotic cells. E-mail Prof Ismail Cakmak at [email protected]. |fw
Growth media fatten up soil organisms
To determine if there’s a healthy balance of microorganisms in your soil, have it analysed and managed, says Vanessa Moodley, head of microbiology at Omnia Fertiliser. “Soil can be supplemented with growth media formulated especially to increase fungi or bacteria,” she recommends. “Healthy microbial life ensures a healthy crop.“ The microbial biomass consists mainly of bacteria and fungi, and also of nematodes. The interactions of bacteria and fungi are vital in maintaining a healthy biological system in the soil.
“Bacteria and fungi in the rhizosphere can alter the movement of carbon compounds from roots to shoots,” she says. “Some bacteria, fungi such as Trichoderma spp. and some nematodes are natural biological control agents, killing off pathogens. Microbes are also involved in mineralisation, which increases plants’ fertiliser uptake.” Bacteria and fungi are also important decomposers in the soil food web. Fungi can’t synthesise their own food and depend on complex organic substances for carbon. They perform important services in water dynamics, nutrient cycling and disease suppression. Bacteria live in water-filled pore spaces within and between soil aggregates. Their functions include degrading organic matter, disease suppression, improving soil structure and transforming nutrients inside roots.
Microbial life and soil organic animals are one of the three main components of organic matter, alongside decaying matter such as dead plants and living parts, mostly the roots. “Organic matter is anything containing carbon compounds created by plants and organisms,” Vanessa explains. Overall soil organic matter increases plant nutrient availability and water retention, improves soil structure and influences the type and number of organisms present. Its management is crucial in creating a sustainable, profitable system, says Vanessa. Contact Omnia Fertiliser on (011) 709 8888. |fw
