Addressing soil fertility

Focus
As part of the EUCCR project, the National Agricultural Research Institute (Nari) is integrating sustainable local farming practices with recently developed climate-smart agricultural methods to enhance the resilience of vulnerable communities, TAI KUI writes

SOIL organic matter is the nutrient rich material accumulated from decomposed plant or animal wastes.
It makes up to 10 per cent of the soil mass and is critical for retaining essential nutrients and maintaining good soil structure.
However, soil fertility levels have deteriorated over the years due to impacts of rising populations and increased use of intensive farming methods on limited plots of land.
Ongoing changes in climatic patterns have increased this issue through impacts of extreme events such as droughts.
Initial surveys under the European Union Climate Change Resilience (EUCCR) project have identified targeted communities around the country which have very low soil fertility levels.
This situation threatens food and socio-economic security for vulnerable, rural communities.
As part of the EUCCR project, the National Agricultural Research Institute (Nari) is integrating sustainable local farming practices with recently developed climate-smart agricultural methods to enhance the resilience of vulnerable communities.
The project is undertaken in nine most drought prone provinces.
In Morobe, five local practices have been adopted different parts of the province.
These include kekai terracing and large compost-mound methods from Kabwum; a plot ridging method from Teptep; peanut crop rotation method from Menyamya; and, the widely practiced natural fallow method.
These practices are useful for building up soil organic matter; retaining optimum levels of nutrients – such as nitrogen, phosphorous and potassium – and ultimately improving the growth and yield of crops.

Teptep ridging system showing new ridges constructed on the piled up compost.

In Kabum, kekai is made as a series of levelled plot beds (terraces) cut across a slope. These beds measure between three to six meters in width.
Farmers usually spread leaves and stems of old hedge rows along the edges of these terraces to create new hedge rows.
This helps to prevent the loss
of rich top soils and retain moisture.
In addition, Kabums make large sweet potato mounds that are buried with fresh composts.
The decomposing leaves, stems and weeds inside the compost-mounds feed new crops of sweet potato.
The mounds measure about two metres across and 80 centimetres in height.
The Teptep ridging system comprises of rows of raised piles made from crop remains after harvest and weeds.
These wastes piles serve as compost beds across the slope of a hill.
They stretch to about a metre in width and spaced at 50-70 centimetres apart.
Farmers do mixed cropping between the ridges with early maturing crops like beans and corns.
Soils from compost ridges are used to establish plots of new crops.
Rotation of peanut with crops like sweet potato is a common practice in Kome.
This is very sustainable as peanut is a legume crop.
Its leaves and stocks add or fix organic matter such as nitrogen in the soil. Long fallow period is practiced widely by communities in all the districts, including Bulolo.
The period of time for vegetation re-growth is determined by factors such as size of land, population and the type of vegetation.
Long fallowing system is a sustainable practice because it allows ample time for the regeneration of natural vegetation as well as contributes to the conservation of local forests, wildlife and fresh water systems.
Nari takes these local sustainable practices and introduces them to areas together recently developed climate-smart agricultural methods.
For example, improved crop rotations are encouraged among farmers to complement the Kome peanut rotation practice.
This adds the knowledge of using nutrient accumulating plants like tithonia and pigeon pea.
Such plants are very important as they can store up and release high amounts of essential nutrients into the soil between three to six months.
This created less need for dependence on long fallow which could take years to build up similar levels of soil organic matter volumes.

Soil profile in Menyamya showing shallow top soil as a result of unsustainable farming.

Nutrient accumulating plants also provide an extra advantage as they have natural pest repellent properties.
Furthermore, improved composting methods are also introduced to complete local composting methods such as the Kabwum large sweet potato mounds.
Farmers are also shown how
to prepare and use coffee pulp, leaves and stems of nutrient accumulating plants and livestock manure.
Part of this exercise involves the distribution of legume beans to farmers, to use as cover crops.
An additional benefit of using organic matter to build soil nutrients levels is that it helps to prevent the use of factory made or chemical fertiliser options.
Factory made fertilisers may pose risk of environmental destruction if not used properly.
In light of stresses posed by
rising populations and prevailing effects of climate change, we will continue to integrate sustainable local farming methods with recently developed climate-smart practices in order to enhance the reliance of our vulnerable communities.

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