Without an iota of doubt , residue incorporated into the soil unvariably far effective than residues left on soil surface....

soil incorporated residues can undoubtedly improve soil quality and crop yield.

Residue incorporated into soil

Strengthens soil organic matter

Residue incorporation on or into the soil depends on the purpose of use. For example, it is applied on the surface to cover the inter-rows so as to reduce evaporative loss of water, thus serving the purpose of (organic) mulch. While, into the soil to increase organic matter, porosity, and so on. But, be careful about termites, so better if it is applied after decomposition of the residues.

Residue on the surface will provide mulching benefits such as conserving soil moisture, reducing weed density, protection against soil erosion. While incorporation will improve soil soil organic matter level once decomposed. Decomposition being a function of temperature, water and soil porosity (determine by texture). Hence, which is better in entirely dependent on purpose as answered by @ Pradeep Kumar. Thank you

This will depend on your farm practice: if you practice tillage, the best will be to incorporate the plant residues to improve organic matter and nutrient content in the soil as a result of degradation by soil microbia, earthworms, ants or termites. By contrast, if you practice no-till, plant residues will obviously remain on the soil surface for the main purpose of reducing erosion and soil dehydration.

The best is residue in the soil, because in the ecosystem, organisms that break down organic matter hold important role because the organic residues that have died are decomposed into elements returned to the soil (N, P, K, Ca, Mg, etc.) and atmosphere (CH4 or CO2) as nutrients that can be reused by plants, so that the nutrient cycle runs as it should and the process life on earth can take place, the existence of the activity of organisms decompose organic matter such as microbes and mesofauna (animals, invertebrates) mutually support the continuity of the nutrient cycling process in land.

dear doctor

This is introduction of a valuable study done by Kumar et al. (2023) hoping shed a light on the subject of interest.

"Crop residues are rich source of plant nutrients, hence have the potential to improve the resource use efficiency along with sustainability of the agro-ecosystem. The unsystematic use and disposal of crop residues is of major concern as it promotes the imprudent practice of on-field residue burning, causing irreversible loss of nutrients, soil fertility and environment. India generates an enormous amount of crop residues, which have agricultural, industrial and energy applications. According to Hiloidhari et al. (2014), India produces more than 686 million tonnes (Mt) of crop residue every year, of which 368 Mt comes from cereal crops. Among cereal crops, rice and wheat are the dominating crops, contributing about 154 and 131 Mt, respectively, in the total crop residue production. In India, crop residue is mainly used as cattle feed and cooking fuel, whereas in countries like China, Indonesia, Thailand, Bangladesh and Sri Lanka, it is utilized as feedstock in bioenergy generation, organic fertilizers and paper industry . The management of rice residue particularly in the Indo-Gangetic Plains of India is challenging, where the rice-wheat cropping system is intensively followed and the farmers are more anxious about timely seeding of wheat in combine harvested paddy fields (Sidhu et al., 2007, Singh et al., 2020). Farmers of this region burn rice residue due to the narrow window period between rice harvesting and wheat sowing, timely unavailability of suitable residue handling machines and labour intensive operation of manual residue removal (Kumar et al., 2021). The annual surplus crop residue production in India is estimated to be 178 Mt of which 87 Mt is burnt . Rice residue holds the major share in total crop residue burnt and associated increase in CH4, N2O and CO2 equivalent (CO2-eq) emissions, thereby elevates the global warming potential every year . About 65 thousand Mg of CH4, 1.7 thousand Mg of N2O and 1897 thousand Mg of CO2-eq emissions were generated from rice residue burning in India during 2019, which adversely affected the environmental quality . Researchers and the farming community need to make comparative assessment of different crops not only based on the yield and net-profit but also their net-return to the environment. For instance, the production of 1 kg of rice returns 2.6 times more CO2-eq emission to the environment than other cereals (Source: FAOSTAT 2022). In fact, agriculture is the second-largest sector having 19.9% share after energy sector holding 68.1% share in total CO2-eq emission (Source: FAOSTAT 2022).

The burning of crop residue is not only degrading the environment but also making a loss of precious nutrients imbedded in the straw. Carbon, nitrogen, phosphorus, potassium, and other nutrients retained in various proportions in different crop residues (Table 2) are lost by 20–100% upon burning (Singh et al., 2008). Considering the severity of residue burning problem, the Government of India has made several policy interventions such as subsidy on purchasing of residue handling machines, subsidy on farm implements, setting up the custom hiring centres for farm implements, ban on crop residue burning, etc. Despite these interventions and possible alternatives, residue burning is still practiced every year, leading to deterioration of the air quality to an alarming level in many cities of India. Researchers, policymakers and stakeholders need to understand the quote of Smil (1999) “Crop residues should be seen not as wastes but as providers of essential environmental services, assuring the perpetuation of productive agro ecosystems”. Local resources based integrated systematic approaches are required to be implemented for effective management of crop residues, and to alleviate the interlinked issues of residue burning and environmental degradation."