‘Take good care of precious assets’

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Windhoek

Liesl Wiese, a consultant of United Nations Food and Agricultural Organisation (FAO) is acknowledging that Namibian producers are challenged with sandy soils and shared insights into just how sandy soils can be productive if they are managed well.

The Namibian Agronomic Board (NAB) invited the FAO to address local producers on the International Year of Soils theme. Wiese explained how on a micro level, healthy soils lock in nutrients and minerals that are needed for high yielding and nutritious crop outputs. To improve soils and promote nutrient availability for plant uptake, building up organic matter in soils is crucial. Organic matter gives soil a sponge-like structure and fluffy texture because of the humate coating that is introduced to it that binds soil particles together. The humate coating of the soil particles gives soil a negative charge, enabling it to hold onto the positively charged soil nutrients. The gridlock structure that results from this binding of soil and nutrients also holds onto water for longer and slows down the movement of water through the soil profile. This means that nutrients are not lost to leaching, but locked into place in magnet-like fashion by the negatively charged soil particles and the positively charged nutrients. These nutrients are then bio-available to plants and taken up through its root hairs and root system, ensuring a healthy, nutrient rich plant and crop.

Adding organic compost to soils is a sure way of maintaining the health of soils and continuing to produce healthy crops. Eliminating chemical and artificial inputs when fertilising soils ensures the “living system” definition of the FAO, a system where microorganisms coexist and live in symbioses with nutrients and essential gases in soils. Chemical inputs destroy that natural balance of living soil systems and interrupts, for example, a soil’s natural ability to absorb much needed carbon from the atmosphere. This simple action from a healthy soil system helps to mitigate climate change, a crucial by-product of sustainable food production.

Managing the effects of sun exposure to crops ensures the longevity of healthy soils. This is achieved by mulching, an easy process that minimises the evaporation of water in the topsoil and also minimises the disturbance of soils. Wiese introduced many ways of mulching; using newspaper, cardboard, wood chips and leaves. The exposed soil surface is merely covered with these which allows water to remain in the soil and more available for uptake by the plants.

Effective irrigation systems in crop production were also introduced as an element of healthy soils. The aspect is particularly relevant for drought-prone countries like Namibia. Drip irrigation delivers water to exactly where it is needed at a rate that is determined by the producer who will judge how much water is required. Implementing the practice of mulching, along with increasing the water holding capacity of soils, is important for Namibian producers because of the uncertainty of reliable rainfall and the longevity of water sources for irrigated crops in our country.

Wiese told producers, “If you take care of your soils and implement these processes, even the sandy soils that you have to work with, can be extremely productive.”

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