Unused, non-traditional organic resources grow on or near smallholder farms. Some have relatively high nutrient concentrations, but little is known about their potential as a nutrient source to improve soil fertility and crop yields. One such organic resource is the green biomass of Mexican sunflower. It is undoubtedly a potential source of nitrogen (3.50%), phosphorus (0.37%) and potassium (4.10%) contents. It, therefore, has great potential for use as soil amendment.
Mexican sunflower produces high biomass and is as effective biomass for mulching and increasing yield of crops. The abundance and adaptation of this shrub to various environment couples with its rapid growth rate and very high vegetative matter turn over makes it a candidate species for soil rejuvenation.
Addition of foliage of Mexican sunflower to the cropping area leads to double the yield of the crops and that it is more effective than urea when applied at the same nitrogen rate.
To apply Mexican sunflower, cut leaves and soft twigs from the hedges, chop them into small pieces, and either place them in each planting hole or spread them evenly over the surface and then incorporate them into the soil.
You can continue applying Mexican sunflower green manure throughout the active growing period of the crop either by placing it along the rows of plants or by incorporating it into the soil.
After you apply the leaves, they must be mixed well with the soil or left to decompose for at least one week before you plant.
Leaves and young shoots of Mexican sunflower can be composted with cow manure, ash and other materials to produce high quality manure for crop production.
The quantities of green biomass available from Mexican sunflower growing near to smallholder agricultural fields, however, will typically not be sufficient to supply all the nutrients required to eliminate nutrient deficiencies over large areas of the fields. The integration of Mexican sunflower biomass with mineral fertilisers is consequently essential to supply sufficient nutrients.
The integration of Mexican sunflower and mineral fertilisers would have added advantages, as compared to sole use of mineral fertilisers, if Mexican sunflower enhanced the use efficiency of mineral fertilisers or provided non-nutritional benefits to crops.
The potential for Mexican sunflower to improve soil fertility improvement is greatest on small landholdings with nearby production of Mexican sunflower biomass and with ample, low-cost labour for cutting and carrying the biomass.
The availability of labour and its cost relative to the value of crops are important considerations because the cutting and carrying of Mexican sunflower biomass are labour intensive.
The importance of labour is further amplified by the bulkiness of green Mexican sunflower biomass due to its high-water content and the need to cut and carry it during a period of peak labour demand for land preparation and planting.
The use of Mexican sunflower biomass is economically more attractive with high- than low-valued crops such as vegetables (high-valued crop).
Written by Dr Jolly Kabirizi, a livestock nutrition consultant and zero-grazing farmer