By EMILIE ABRAHAM*
Manure refers to the aggregation of livestock waste that accumulates on the floor of the kraal.
Similar to all living organisms, crops need food to grow. This food is obtained from the soil in the form of nutrients. Manure contains several nutrients (NPK) and organic matter, which are important for maintaining soil structure and fertility.
Applying manure to your crop field replenishes the soil nutrients mined by previously grown crops. Through its use, crop yield is increased while the risk of soil degradation is reduced. It is believed that many households in rural areas have a livestock kraal and thus farmers should take advantage of this cheaper and readily available resource.
Despite some kraal manure limitations such as weeds that can grow in large numbers, manure can reconstruct the soil by adding organic matter to the soil to support plant growth. Thus, this article discusses the benefits of manure to the soil and crops as well as its application:
Crops require a balanced diet to grow well. NPK is a common element on the periodic table that is considered as the macronutrient for crops. Crops need around 30+ different elements, but nitrogen (N), phosphorus (P) and potassium (K) are considered the main three.
Different crops have varying nourishment needs. Some vegetables such as carrots do not necessarily need manure as it can cause carrots to split thereby reducing their quality.
It is worth noting, that with each passing harvest, crop soils become more deficient in essential elements that plants require for growth. Thus adequate soil replenishment through the use of manure or fertilizers is required to avoid the depletion of soil nutrients.
Starved crops grow slowly, with thin stems, small leaves, pale green or yellowish leaves and give poor yield.
Thus manure makes plant leaves green and healthy. Green leaves allow photosynthesis and translocation processes to take place effectively and eventually improve crop growth and yield.
Kraal manure consists of NPK in the following composition 2.1.4 (3) on average, however it should be noted that high soil mass can dilute the concentration of nutrients in manure.
Thus, manure with high soil mass is 2.1.4 (2) and manure with little soil mass is 2.1.4 (7), therefore the more the soil in one’s manure, the lesser the concentration of nutrients.
IMPROVE SOIL STRUCTURE:
Compacted soils are anaerobic and unable to retain water. Non-compacted soils allow plant root system to dig deeper more quickly. This makes it easy for the roots to spread, allowing them to access nutrients, water and air.
Thus, animal manure is required to improve the structure, aeration and moisture holding capacity of the soil. When manure is applied to compacted clay soil, it loosens and separates the dense particles in the clay soil and improves the drainage and aeration of the soil.
Whereas in sandy soil, it tightens large particles making it hold water and reduces the leaching of nutrients thus making it fit for crop growth. Increase soil bioactivity: Soil without microorganisms is dead and unproductive.
Manure supplies energy to soil microorganisms such as earthworms that help to further break down its components in the soil. Different soil organisms feed on different organic substrates. Their biological activity depends on the organic matter supply.
The higher the organic content of the soil, the more active they become. More biological activity facilitates nutrient availability and recycling in the soil resulting in better plant productivity and yield.
Manure can be applied dry (before and at planting) or as a liquid (after planting as top dressing). Manure that is applied as liquid is known as kraal manure tea; this is prepared by soaking partially dried sheep, goat and cow manure in water for one to two weeks. This method is very useful for treating trace element deficiencies.
However, the nutrients that are present in manure tea are not immediately available to plants as compared to dry manure. Thus, manure should be spread evenly over the crop field and worked into the soil several months before planting. It is advisable to apply manure at least one month in advance before planting.
This allows manure to decompose and make nutrients available at planting or preferably, manure should be composted and aged before use. It is advisable to age manure for at least three months – the longer you age it the better.
Such time-line for aging can kill about 60 percent of the weed seeds present in the manure and speed up the release of nutrients. Farmers are advised to apply manure correctly as per unit area of the crop field/plot for good results.
The recommended application rate for kraal manure is 250 wheelbarrow loads of manure per hectare (one hectare is roughly the size of a soccer field/10 000m2 ) or one (1) wheelbarrow load for every 40m2.
Thus in order to determine the number of wheel barrow loads of kraal manure that need to be applied to the crop field/plot, divide the area of the field expressed in m 2 by 40. Conclusively, in order for farmers to boost yield through manure application, it should be done correctly.
Livestock manure can contain a large amount of weeds depending on what the livestock digested and the efficiency of their digestive systems.
Thus, it is worthwhile to compost and age manure before use, to minimize weed infestation and simultaneously prepare the manure for plant use.
For synthetic fertilizers farmers are advised to confirm soil nutrient levels through proper soil analysis to help determine deficient elements.
*Emilie Abraham is the technical officer within Agribank’s Agri Advisory Services Division.