Burning of rice straw is a common practice for residue management and weed control in Manipur. Rice residue has to be burned, removed or incorporated into the soil in order to prepare fields for the next crop. The need to prepare fields for the succeeding crop, especially rapeseed-mustard crop, results in hasty burning of rice residue.
The main reasons for burning rice straw rather than incorporation for enriching the soils are low cost, labour scarcity and absence of any suitable residue management practice.
Open-field straw burning has increased dramatically over the last decade. Improved rice straw management and technologies that can help reduce the environmental footprint and increase revenues from rice production and processing are therefore important for sustainable rice production systems.
Crop residues are also a principal source of carbon, which constitutes about 40 per cent of the total biomass on a dry weight basis.
The ratio of straw to paddy ranges from 0.7-1.4 depending on the variety and growth. These were considered as a precious commodity because it can be used as a feed for the fodder and mulching for various crops and must never be considered as waste.
Sustainable rice straw management is currently practised with the following scalable options:
Rice Straw for improved soil fertility:
Incorporation of rice straw into the soil can maintain and enhance soil fertility with proper management.
The in-situ incorporation of rice straw in the soil has been shown to contribute to recycling of nutrients and increasing soil organic carbon (C) and yields of subsequent crops.
On the other hand, straw burning releases particulate matter into the atmosphere, which is associated with air pollution and human respiratory ailments.
Large amounts of rice straw left in the field have posed challenges in rice-growing areas because of the need for mechanization and multiple tillage operations to enable effective incorporation of the straw into the soil.
Similarly, the adoption of no-till in rice-cropping systems has been limited by the presence of the large amounts of straw on the soil surface.
Straw incorporation benefits the next crop and ecosystem services, in general, depending on management practices and the cropping system employed.
Incorporating straw in rice fields serves as a source of food for an array of fauna that use rice fields as a habitat. For example, rice straw provides substrate to promote biodiversity through flourishing of invertebrates that decompose the straw, which in turn enhances nutrient cycling in rice soils.
Rice Straw for Mushroom Production:
In Manipur most popular and easily grown mushroom is Oyster mushroom as rice straw being a key substrate for mushroom cultivation, which is available in abundance and at a very low cost.
The adoption of this mushroom cultivation will bring the well needed diversification and will provide nutritional food at a cheaper rate than many other foods of similar nature. Primarily our diet is based on cereals (rice wheat and maize), which is deficient in protein.
Supplementation of mushroom recipes in our diet will bridge protein gaps and improve the general health of socio-economically backward communities. Earlier mushrooms were considered as an expensive vegetable and were preferred by affluent peoples for culinary purposes.
Currently the common populace also considers mushroom as a quality food due to its health benefits. Oyster mushrooms are quite popular in Manipur because of the faster growth rate. It can be cultivated very easily using raw straw and can be harvested in 45-60 days.
Most of the oyster mushroom species grow well in a temperature range of 20-32°C, and this mushroom also has species suitable for temperate regions.
Rice Straw silage for Cattle Feed:
Ruminants depend on year-round grazing on natural pastures or the animals are fed with cut grass and crop residues. Most of the areas face seasonal dry periods in which the availability of pasture decreases and also its quality by a reduction in the content of digestible energy and nitrogen.
Due to the fact that rice straw is abundantly available from cultivating paddy, farmers offer rice straw as the main roughage source to their animals. In general, the use of rice straw as an animal feed as well as its treatment is always an economic decision.
Rice straw has few nutrients to be used as the only source of food for cattle but is a good feed additive and can also be treated to increase the supply of energy and protein. In general, the daily recommended maximum intake of rice straw by ruminants is 1.0 to 1.5 kg per 100 kg live-weight per day.
Urea-treated straw (rice straw is enlarged with 2-3 % urea) can increase intake and digestibility of this rice straw-based feed.
The utilization of rice straw by ruminants is possibly the most efficient means of rice straw management.
Rice straw for production of Biochar:
Agricultural wastes represent a major environmental problem and re-using these wastes by turning them into valuable materials is an increasing challenge. Transforming agricultural wastes to biochar may be a good solution.
Biochar is a carbon-rich product prepared by combusting biomass (such as agricultural wastes), at temperatures between 350oC and700 oC in a closed chamber with insufficient air or no air.
Biochar has several proven applications including its application for soil remediation. Biochar as soil amendment is of appealing global interest owing to its many benefits, including sequestration of carbon, decrease of greenhouse gases, enhancement of soil fertility and crop growth.
The application of biochar to agriculture soils has many positive effects such as decreasing phytotoxicity of heavy metals, increasing cation exchange capacity, water-use efficiency and holding plant nutrients, along with enhancing the nutrient uptake and growth of plants.
So “Need of the hour” is to think about proper management of rice straw instead of burning it in the field. The impact of air pollution associated with the burning of rice residue is to rethink the practice of it. And the long term benefits of residue incorporation in the soil and proper practice and management of rice straw has to be encouraged.
Farmers should adopt rice straw management techniques to increase their income and to keep the environment clean.