Integrated Straw Management

Summary

Pilot projects implemented in China and Vietnam by the Centre for Sustainable Agricultural Mechanization (CSAM) are testing the use of straw as fertilizer, fodder, base material and a clean energy source. By encouraging circular food systems, the projects can reduce in-field straw-burning and greenhouse gas emissions, increase the efficiency of crop straw use, return nutrients from straw to the soil and help lead to sustainable agriculture in developing countries.

Challenge/Problem

In many developing countries, the most common way for farmers to deal with straw in their fields post-harvest is to burn it. However, burning straw causes serious environmental and health problems. Apart from accelerating the release of greenhouse gases and particulate matter into the atmosphere, straw-burning leads to loss of soil carbon and micronutrients while harming soil’s temperature, pH levels, moisture content and organic matter. Burning straw also hurts human health. Crop straw contains nitrogen, phosphorus, potassium, hydrocarbons and organic sulfur. Incomplete combustion, which often occurs if the straw is not completely dry, generates a large amount of harmful substances. Farmers choose to burn straw in their fields mainly because of the lack of low-cost, effective and technically feasible alternatives for using straw.

Solution

Building upon a strong understanding of the status and available practices of straw management in the region, CSAM identified and tested a circular model of using straw as fertilizer, fodder, base material and a clean energy source. The pilot projects in China and Vietnam have adopted different approaches in response to specific local conditions.

In Laixi, Shandong Province in China, the project encouraged ensiling maize and returning both straw and cow manure to crop fields. It was implemented by CSAM in collaboration with China Agricultural University, local government agencies and a farmers’ cooperative. Subsidies encourage farmers to buy key machines and tools that enabled them to return straw to the fields or store it for the off season. The straw is processed and then used as fertilizer, fodder, fuel for generating electricity, a base material for growing mushrooms and an industrial raw material. The demonstration areas for returning straw and manure to the field were both 7 hectares, and the area for returning cow manure to the field was 40 hectares. A total of 400 cows were involved in the demonstration.

The Vietnam pilot used straw to support indoor mushroom-growing and earthworm-farming. It was implemented in Can Tho City, Mekong Delta Region through the collaboration of CSAM and the Sub-Institute of Agricultural Engineering & Post-Harvest Technology. To better control temperatures for mushroom growth, two metal-roofed houses were built before 3,500 kilograms of rice straw were collected, sterilized, inoculated with spawn and brought in. The rice straw substrate was enriched, stacked into piles covered with plastic sheets to maintain the temperature for composing and mixed evenly every 10-15 days. The rice straw substrate was also used as natural fertilizer to cover about 50 mature fruit trees and 2,000 square meters of farmland for vegetables and ornamental plants, reducing chemical fertilizer use.

Results

Between July 2019 and July 2020 at the pilot site in Laixi, China, 48.5 tons of winter wheat straw and 61.6 tons of summer maize straw were repurposed (through returning straw to the field, feeding cows whose manure was returned to the field and ensiling maize). Compared to burning the same amount of straw, over one year, the project reduced carbon dioxide emissions by 134,123.5 kilograms in just the seven-hectare demonstration site.

Furthermore, the improved technical modes of returning straw to the field and returning cow manure to the field increased net incomes per hectare by US$157 and US$386, respectively. For ensilage, new fodder improved milk production per cow by 1 liter per day (up from 20 liters per day before the project), resulting in an increase of US$53 per day across 100 cows.

The Vietnam pilot also experienced positive outcomes. It produced 385 kilograms of mushrooms, or 26 kilograms of mushroom per 100 kilograms of rice straw. This growing efficiency of 26 per cent is almost double that of traditional mushroom growing methods, at 13-15 per cent.

Lessons Learned/Potential for replication

- If managed properly, crop straw could turn from a source of pollution into an important resource for improving yields and increasing farmers’ incomes.

- Projects for dealing with crop straw should be adaptable, technically feasible, and environmentally, economically and socially sustainable. They should build upon a strong understanding of the status and available practices of straw management in the target region.

- Partnerships among local governments, international organizations, research institutes, the private sector and local farmers’ organizations should be built to leverage resources to support the scaling up of pilot programs.

Next Steps

Building upon its achievements so far, the integrated straw management approach is now being expanded to Cambodia, Indonesia and Nepal with funding from the China-ESCAP (United Nations Economic and Social Commission for Asia and the Pacific) Cooperation Programme. Over the next two or three years, the project will continue to test the integrated and circular model of straw residue management in new agro-ecological contexts, enabling adaptation and dissemination of appropriate mechanization solutions based on a participatory and needs-based approach.