‘Night soil’ can help boost soil fertility in arid areas

Water is not the major constraint in crop production in the drylands; soil fertility is. Studies have demonstrated that there is enough moisture in the first season in the drylands to support crop production and in particular, short duration maize production.

However, there is no enough fertility to be utilised by this limited moisture of an average of 400mm in the March to May season.

Increased application of nitrogen and phosphorus tremendously improves crop yields. Therefore, what farmers need to know is which fertilisers to utilise and conserve the available moisture.

Farmers can adopt two approaches. The first is to use inorganic fertiliser for immediate release of nutrients during the cropping cycle while the second approach is to use organic fertilisers and agroforestry for the conservation and improvement of soil properties.

Organic fertilisers, which are sourced from both plants and animals, should be applied a month before planting and incorporated into the soil to allow the microbe community to work on them to accelerate the decaying process.

This will ensure that there will be nutrients for the plants’ early in the season. Furthermore, incorporation will guard against volatilisation of nutrients such as nitrogen.

Often, many farmers in the drylands do not apply fertilisers, practice crop rotation or exploit agroforestry for improvement of soil fertility. The good news is that most own livestock and use animal manure to increase crop yields and improve soil fertility.

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Crop rotation systems using drought-tolerant and adaptable crops such as legumes, cereals and root crops improves soil fertility. Application of fertilisers to maize is better in seasons with reliable rainfall and to high value crops grown under irrigation.

Though organic fertilisers are increasingly popular, they are unavailable in drylands as some of these communities are pastoralists while the alternative commercial fertilisers are expensive for the resource-constrained farmers. Now, we must think outside the box and what comes to mind is the use of night soil (faecal matter) as a source of organic fertiliser.

Night soil, which has been successfully utilised in Asia, is a nutrient-rich fertiliser that sustains soil fertility and crop yields.

By applying night soil over large areas of cropland, nutrients are recycled within the farm without risking pollution of surface water with nitrogen and phosphorus-rich wastes.

The recycling of phosphorus in human waste is especially important since human beings are the top consumer in agro ecosystems. However, there are risks associated with night soil. One of them is the total avoidance of some of the foods by consumers as has been the case in China, and diseases.

But these risks have been reduced by contemporary awareness of the spread of germs in human wastes, with farmers being asked to avoid contact with night soil. Night soil is also allowed to ferment longer in the tank before application.

Once diseases and pests are curbed by fermenting the wastes for longer periods, I think the possibilities of night soil are endless.

The use of this manure can help our country make drylands productive as we adopt short and long-term strategies to provide food for the increasing population in a more sustainable way.

Muriuki Ruth Wangari, Department of Crops, Horticulture and Soils, Egerton University.