Organic matter mattersThe indigenous knowledge of Nepali farmers about compost quality is worth emulating.
Food begins with soil, and the nutritional quality of our food is directly related to its quality and health. Plants acquire 18 essential elements for their growth and development from two different environments, soil and air. Fifteen elements are provided by the soil, whereas the other three—carbon, hydrogen and oxygen—are taken by plants from the air during photosynthesis. Even nutrients in animal foods come from plants or plant-based foods, which obtain their nutrients from the soil.
Soil combines water, air, minerals and organic matter. It contains 45 percent mineral, 20-30 percent water, 20-30 percent air and 5 percent organic matter. The organic matter in soil is primarily composed of carbon (58 percent), with the remaining mass consisting of water and other minerals and nutrients such as nitrogen, phosphorus and potassium. Microorganisms convert minerals in plant-available nutrients as part of the soil organic matter, which provides the crop production base, without which there would be no crops.
Organic soil in Nepal
According to the Nepal Agricultural Sector Strategy Study conducted by the Asian Development Bank, the yields of cereal crops, especially rice, in Nepal during 1966 were among the highest in South Asia but dropped to the lowest by the 1980s. Today, we have become one of the main food importer countries. Several studies also suggest declining agricultural yields in Nepal are the result of the low soil organic matter content, limited access and scarcity of fertilisers, and changing climate. The soil organic matter content of cropland sharply declined near to 1 percent. This raises the question of whether we are producing healthy foods from our soil.
Most of our productive agricultural soil contains between 3-5 percent organic matter. It is necessary to monitor the changes in soil organic matter, which can take a few years to a decade. However, adding good quality organic matter into the soil is one of the viable options for building organic matter in the soil. One may think that added organic matter would fill the existing pores in the soil and make it more solid. Nonetheless, soil rich in organic matter is more like a sponge than a solid material. It will be more porous and hold more water since soil tends to expand in volume. Every 1 percent increase in organic matter results in as much as 2.34 lakh litres of available soil water per hectare.
In the Pandora Neural Network of the movie Avatar 2, all flora and fauna of Pandora communicate. There’re billions of microbes in a single gram of soil, including microscopic thread-like organisms called “mycorrhizal fungi”, much like the Pandora Neural Network that form the world wide web of soil. Fungi are important in producing healthy soil and healthy and nutritious food. Life in the soil includes all the bacteria, protozoa, nematodes, and fungi as well as the food they obtain, nutrients from plant root exudates, excretions they produce, and the root systems they sustain. All these things eventually provide sustained and healthy production.
Supportive farming practices
Our farming practices support plant nutrient flow and balance the soil system. Forest is also considered an integral part of our cropping system. For centuries, our traditional form of agriculture used organic fertiliser, i.e. compost, as the primary means of soil fertility replenishment. Compost is a rotted organic material, mainly made from livestock/animal manure and is more common in areas where there are large numbers of livestock or a trans-humane system (goth). Animals grazed in forests and fields allow converting plant biomass into organic materials composed of nutrients from new plants after building up organic matter in the soils. In addition, forest litter is mixed up with animal excreta to make compost; hence, the cycling and balance of nutrient flow occur in our existing cropping system.
Farmers have indigenous knowledge about the selection of land and quality of compost, based on the quality of vegetative materials and nutrient status of livestock manure. They use the best quality compost, containing manure, fine and friable, to produce vigorous seedlings. The quality of compost/manure used by farmers in upland and lowland fields shows their consciousness towards nutrient balance. For example, moderate-quality compost in upland (bari), like maize crops, demands high levels of nutrients because soil nutrients need replacing as they are leached annually. Besides this, there are naturally fertile soils, also called black soils or kalo mato, in some parts of Nepal, including Bhaktapur, Kalimati, and Balkhu areas in Kathmandu valley. Black soil is formed after the deposition of fine sediments into a lake from rivers and streams with higher organic matter levels. Soil that is high in organic matter has higher workability which helps to extend crop roots and uptake available plant nutrients.
However, the indigenous system of livestock rearing and access to forest resources has been broken down due to enormous pressure on the land. Compost preparation and handling are time-consuming and labour-intensive works that necessitate rearing enough numbers of livestock and regularly collecting fodder and vegetation from the forest. With the introduction of chemical fertilisers, pesticides and mechanisation, we are entering commercial and competitive farming. External sources of plant nutrients, especially chemical fertilisers, gained popularity, accounting for their less bulky nature, transportability, ease of application and, most importantly, the dramatic increase in yield. Traditionally used organic fertilisers are getting less attention, and balanced nutrient cycling in the farming system is broken.
When the soil has nutrient(s) deficiency resulting from low organic matter, it cannot be restored by increased chemical fertiliser, especially in the Terai region. The readily available nutrients from chemical fertilisers applied to the soil will instantly be leached. This is one of the main reasons for decreasing productivity of major food crops for the last few decades. The government of Nepal has set an ambitious target to increase soil organic matter from the current level to 4 percent by 2035.
We have failed to realise the importance of the organic matter in soil, educate farmers about the value of organic resources, and integrate organic fertiliser in subsidy programmes and chemical fertiliser. We rarely consider the value of organic crop residues/manure they make to agricultural production. Failure of development projects to account for the value of organic resources may inhibit technology take-up.
There is a growing concern about the circular economy, an idea close to the life cycle of a product which involves utilising the by-products and waste where industrial, biological, household waste, or sewage sludge as sources of organic manure. A pilot project, conducted in 2011, produced 15 tons of high-quality compost using 140 tons of fresh organic waste collected from local markets in Kathmandu, which can be considered an alternative source of organic fertiliser production. However, the nutrient value and presence of contaminants with associated risks to humans or the food chain must be evaluated before use in soil.
Soil organic matter is responsible for maintaining healthy, productive soil by providing food and habitat for microbes. We need to change our way of thinking and working behaviour. A soil managed with organic matter will be strong, healthy, and resilient to our farming systems in the long run and this should matter.