Agricultural Practices and Sustainable Management in South Asia
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Allelopathy is an ecological phenomenon by which plants and/or microorganisms release organic chemicals (allelochemicals) into the environment influencing the growth and survival of other organisms (Cheema et al. 2013).
Conservation agriculture involves the maintenance of soil cover (permanent), minimum soil disturbance, planned crop rotations, and weed management (Kassam 2020).
Precision agriculture involves the use of temporal, spatial, and individual data in management decisions for efficient use of input resources, and profitability and sustainability of agricultural production systems.
Zero-till wheat corresponds to wheat crop directly sown in the residues of previous crops, without seedbed preparation (Nawaz et al. 2017). Direct seeded aerobic rice is rice direct seeding and water application as per crop requirement without maintaining of flooded conditions throughout the crop season (Farooq et al. 2011).
Total population, labor force engaged in agriculture, share of agriculture in GDP, and land use in South Asian countries
Labor force in agriculture (%)
Share of agriculture in GDP (%)
Area (Million hectares)
Forest and woodland
Irrigated crop land
By 2050, the world population is predicted to exceed 2 billion by 2050 of which 30% increase will be in South and Southeast Asia (UN 2019). The impacts of climate change, as erratic rains, heatwaves and extreme flooding, will also be more severe in this region (Thornton et al. 2014). According to the International Maize and Wheat Improvement Center (CIMMYT 2018), rice (Oryza sativa L.), maize (Zea mays L.), and wheat (Triticum aestivum L.) yields may decrease by 30% over next century if farmers will not adopt sustainable innovations to mitigate the impact of changing climate.
Benefits of sustainable agricultural practices over traditional practices in South Asia
Traditional farming practices
Sustainable farming practices
Benefits of sustainable practices over traditional farming practices
Puddling and flooding in transplanted rice
Direct seeded aerobic rice
Reduction in methane emission
Saving in production cost
Post rice crops perform better after direct seeded rice than transplanted rice
Plough tillage in wheat
Zero tillage in wheat
Saving of production cost
Timely planation of wheat in rice-wheat system
Reduction in soil erosion
Improvement in soil properties
Manual land leveling
Laser land leveling
Improvement in water use efficiency and grain yield
Drip and sprinkler irrigation
Increase in water use efficiency
Flat sowing of crops
Bed and ridge sowing
Plough tillage in rainfed areas
Saving of production cost
Reduction in soil erosion on sloppy lands
Improvement in soil properties
Use of synthetic fertilizers
Combine use of organic and inorganic sources of fertilizers, use of green manures
Improvement in soil water holding capacity
Improvement in soil biological health
Better nutrient recycling
Improvement in water use efficiency of crops
Unwise use of synthetic fertilizers
Use of nanotechnology
Very useful for applying the exact amount of nutrient to the crops
Improvement in nutrient use efficiency
Crop diversification with legumes and other crops
Suppress the pest outbreaks
Reduces the pathogen transmission
Buffer the crop production from the negative consequences of climatic variations
Improved soil fertility
Use of synthetic pesticides to control insect-pests and weeds
Use of allelopathic water extracts and powders
Organic and eco-friendly management of agricultural pests
Total arable area (39%, 2.03 million square kilometers) of South Asia comprises of three topographical regions viz., (i) the Hindu Kush, the Himalayas, and the Karakorum mountain ranges and their southern slopes, (ii) Indus and Indo-Gangetic Plains (IGP), and (iii) Deccan Plateau and other uplands. Land degradation has become a serious threat to the sustainability of current crop production practices in all arable areas. The main drivers to land/soil degradation include intensive cropping and nutrient mining (north India, mid-altitude of Nepal), water erosion (riverbank erosion in major flood plains of rivers, Himalaya foothills), wind erosion [western Rajasthan, coastal regions of India, dry regions (Thal and Thar) of Pakistan], waterlogging (India, Pakistan, Bangladesh), soil salinization (IGP plains, Indus river basin, southern coastal lines of Sri Lanka), agrochemical pollution (especially Pakistan), overgrazing, removal of vegetative cover, sedimentation, and poor soil management practices (e.g., puddling and flooding in rice in India, Pakistan, Bangladesh, and Nepal) (Cook et al. 2016; Dahal 2017).
Wise management of soil resources supported by government policies can interpose soil degradation. For example, the contour plowing, terracing, strip cropping, mulching, and agro-forestry may be useful to control water erosion in hilly areas. Construction of small dams in hilly areas (e.g., potohar regions in Pakistan) may help to harvest water and reduce soil erosion. Afforestation may help to reduce the soil losses by wind erosion. Retention of previous crop residues also provides soil cover, which helps to not only reduce soil losses associated with wind erosion but also improve the soil organic matter and the soil water holding capacity.
Waterlogging is severe on heavy soils and can be mitigated by the lining of water canals and regulating the water flow in canals. Waterlogging at field levels can be managed by re-scheduling the irrigation, namely using higher efficient irrigation systems. An efficient surface and/or subsurface drainage system may also help (Bhattacharyya et al. 2015).
Soil salinization can be controlled by ponding freshwater that is highly useful to remove excess salts toward the deep soil layers; water ponds can also be used for fish farming. Sodic soils can be reclaimed by application of some chemical amendments, such as calcium chloride, gypsum, and other acid-forming compounds, for example, iron/aluminum sulfate, sulfuric acid, calcium and pyrite salt, lime sulfur (Shahid et al. 2018). Salt tolerant crops (e.g., Chenopodium quinoa W.), have been successfully introduced in saline areas (Iqbal et al. 2019); farmers need guidance and training on reclamation of saline and sodic soils. The promotion and marketing of these crops will contribute to use of saline soils for profitable crop production.
South Asia is surrounded by three main water bodies viz. the Arabian Sea, the Bay of Bengal, and the Indian Ocean, and spans through two major river basins, that is, Ganges River Basin and Indus River Basin. There are three distinct rainfall systems in the region, namely, (i) southwestern monsoon system in summer (which contributes 80% annual rainfall in whole South Asia), (ii) northeastern monsoon system during winter (in Bangladesh and adjoining areas), and (iii) western weather system (in Pakistan and other parts of the region) in winter. The summer monsoon rains are intensive and cause a flood in rivers and the areas adjoining to rivers. The winter rainfalls are less intensive but effective and are a major source of water for winter crops in rainfed areas (Hanif 2003).
The Indus Basin irrigation systems of Pakistan and India are considered as one of the best irrigation systems in the world. However, most of the irrigation canals and field channels are not lined, which results in water losses as seepage, percolation, and evaporation. The lining of irrigation canals and field water channels may help reduce these losses to a greater extent. Flood irrigation is the most common method of irrigation, which results in great loss of water through gravity in deep soil layers. For sustainable management of water, the century-old system of flood irrigation should be replaced with high-efficiency irrigation systems, for example, drip and sprinkler irrigation. Drip irrigation has been widely adopted for irrigating the fruit and some vegetable crops. The sprinkler method of irrigation is getting momentum in the water-limited areas, for example, thal and Potowar region in Pakistan. However, institutional support and credit facility are required for the promotion of high-efficiency irrigation system to economize water use. Most of the agronomic crops grown on flat land are irrigated by flooding. Adoption of raised bed sowing and ridges in wheat, rice, maize, and cotton may save a surplus quantity of water for our future generation.
South Asia is the second-largest fertilizer user region of the world (FAO 2015), with nitrogen (N), phosphorus (P), and potassium (K) fertilizer consumption of 24.5%, 31.3%, and 19.3%, respectively. The synthetic fertilization varies among the South Asia regions. For example, the average in fertilizer consumption is ~12 kg ha−1 in Afghanistan and ~ 200 kg ha−1 in Bangladesh compared with the world average of 120 kg ha−1 (Mujeri et al. 2013). Although intensive use of synthetic fertilizers after the green revolution contributed to several folds increase in yield, the productivity of many crops (including rice and wheat) has become stagnant for the last few years (Cook et al. 2016). Intensive cropping has caused higher removal of macro- (N, P, K, sulfur) and micronutrients (zinc, boron) from the soil, as they did not return to soil in the same proportions (Dahal 2017). The ideal ratio for NPK application is 4:3:1; it is 6.5:2.4:1.1. Imbalanced fertilizer application reduces the nutrient use efficiencies with high cost of production and environmental (Rehman et al. 2019) and human health risks (Ahmed et al. 2017).
Precision agriculture can be effectively used for site-specific nutrient management (Dahal 2017). The use of nanotechnology may also be useful in decreasing the field losses of fertilizers and improve use efficiencies (Usman et al. 2020). Both precision agriculture and nanotechnology require institutional support.
Crop Pests and Disease Management
Insect-pests and diseases are the main potential threats to global food security in terms of qualitative and quantitative losses in agriculture (Tenzin 2013). Climate change has detrimental effects on crop health, and a range of insect pests and diseases have been expanding toward higher latitude with increasing temperature every year (Rosenzweig et al. 2001). The increase of 1 °C may cause up to 10–20% loss in major staple crops – rice, wheat, and maize (Deutsch et al. 2018).
Farmers typically combat insect-pests with chemical insecticides. However, many insect biotypes have developed resistance against the chemical insecticides owing to continuous and excessive use of these insecticides all over the world (Praneetvatakul et al. 2013) including South Asia. This situation has forced farmers to adopt alternative control measures of pest management safer to ecosystems and human-animal health. Governments are also encouraged on integrated pest management (IPM) measures to tackle the increase of disease and insect-pests in agriculture (Gautam et al. 2017). The term IPM is applied in the pest management system using all possible control measures, with minimum reliance on synthetic pesticides, to maintain the pest population below the economic threshold level (ETL). Several microbial pesticides have been registered and widely used against several insect pests, namely, Bacillus thuringiensis, entomopathogenic fungi (EPFs), entomopathogenic nematodes (EPNs), and Trichoderma (Sinha and Biswas 2009). Biopesticides are available commercially in Pakistan (Iqbal 2013), but less accessible in Sri Lanka and Afghanistan; Nepal has registered 54 microbial products of 10 pathogens to control important agricultural insect pests.
Genetically modified crops (GMOs) have also been contributing to the extension in controlling insect-pests. Although South Asians are in strong opposition of GMOs, maize, cotton, and eggplant (Solanum trongum Poir.), GMO are flourishing in India and some areas of Pakistan.
Biological control has been used for decades. In 1968, biological control was initiated in Pakistan; since then, about ~750 natural enemies were used to control insect pests, among predators, parasites, parasitoids, and pathogens. Several success stories of biological control have been reported from India, Bangladesh, Sri Lanka, Nepal, Bhutan, and Maldives with biological control (Irshad and Stephen 2014; Alam et al. 2018). It is further needed to explore and deploy indigenous biocontrol agents (insects and pathogens) in IPM programs to reduce reliance on chemical insecticides.
Locust swarms have emerged as a serious threat to future food production in South Asia, especially in Pakistan and India. Vast crop losses have been reported in different pockets of both countries. Measures being undertaken to address ongoing locust outbreak merit every support irrespective of jurisdictional boundaries. Particular attention should be paid to the affected areas for a thorough treatment. Governments should also maintain the necessary funds to compensate for the affected rural populations. Cross-country cooperation is crucial to control the severe pests.
Wheat rust has also emerged as a severe disease in the year during the last few years in the region. This disease caused significant yield losses in the year 2019–20. Conducing environment, light rains, cloud cover, high humidity, and mild temperature, during the reproductive stage of wheat crop, triggered the spread of this disease. Rust-susceptible wheat varieties should be banned for general cultivation. Farmers should be advised to treat wheat seeds with board-spectrum fungicides before planting. Breeding programs to develop rust-resistant wheat genotypes should be strengthened.
Weeds are a serious threat to profitable crop production in South Asia. However, weed management component of crop husbandry practices is often ignored in minor crops. Weed infestation varies across cropping systems and agroecological zones. While switching from the conventional crop production systems to the conservation crop production systems, weed infestation often increases during initial years of adaptation. There are three major groups of weeds, namely, grasses, sedges (grass-like), and broad-leaved weeds. Grassy weeds are difficult to control in most of the cropping systems. The most important grassy weeds in South Asian cropping systems include wild oat (Avena fatua L.), littleseed canarygrass (Phalaris minor Retz.), jungle rice (Echinochloa colona (L.) Link), barnyard grass (Echinochloa crus-galli (L.) P. Beauv), and crowfoot grass (Dactyloctenium aegyptium (L.) Willd.). The major sedges reported in South Asia include purplenut sedge (Cyperus rotundus L.), rice flatsedge (Cyperus iria L.), and small flower umbrella-sedge (Cyperus difformis L.). The important broad-leaved weeds found in field crops of South Asia are horse purslane (Trianthema portulacastrum L.), field bindweed (Convolvulus arvensis L.), wild onion (Asphodelus tenuifolius CAV.), Digera species (Digera muricata (L.) Mart. and Digera arvensis Forssk.), wild safflower (Carthamus oxyacantha [M.] Bieb.), common lambsquarter (Chenopodium album L.), swine cress (Cronopus didymus (L.) Sm.), sweet clover (Melilotus indica (L.) Pall.), and redroot pigweed (Amaranthus retroflexus L.).
Most of these weeds can be effectively controlled by the use of chemical herbicides. However, excessive and continuous use of chemical herbicides is polluting the soil and aerial environment and may cause health issues. Moreover, many weed biotypes (e.g., littleseed canarygrass) have developed resistance against many herbicides due to repetitive and indiscriminate (Heap 2014). Although cultural and physical weed controls had been popular for weed control in the region, their use is limited due to labor requirement and increasing labor cost. In this scenario, the phenomenon of allelopathy may be an attractive option for eco-friendly weed management. The use of allelopathic water extracts alone, in combination, or with lower doses of herbicides can provide effective weed control in a range of field crops (Cheema et al. 2013). Likewise, the incorporation of allelopathic crops [especially sorghum (Sorghum bicolor [L.] Moench) and brassica species], use of mulch of allelopathic crops, intercropping with allelopathic crops, and incorporation of residues of allelopathic crops are pragmatic options to reduce weed pressure in a range of field crops.
Another concern is the recent Parthenium weed that invaded many fields in Pakistan (Bajwa et al. 2019) and additional regions in South Asia. Centre for Agriculture and Bioscience International (CABI) in Pakistan (REF) is working on a pilot project for biological control of parthenium through Mexican beetle (Zygogramma bicolorata). This type of biological control methods should be optimized for complex weed flora to lessen the reliance on chemical herbicides.
Crop Diversification for Optimizing the Soil and Water Management
Diversification of cropping systems increases the resilience of the agricultural systems by (i) suppressing the pest outbreaks, (ii) damping the pathogen transmission, and (iii) buffering the crop production from climate adverse effects (Lin 2011; Paul et al. 2016). Unfortunately, farmers in the South Asia region are using monocultures of the same crops for decades, namely, the rice-wheat and cotton-wheat cropping systems in India and Pakistan, respectively. The continuous rotation of rice and wheat with century-old production practices has caused the deterioration of soil as well as the emergence of new weed biotypes, herbicide-resistant weeds, and aerial contamination via greenhouse gases. In these scenarios, new diversification of rice-wheat systems are recommended, namely through the inclusion of legumes, for example, Sesbania spp., chickpea (Cicer arietinum L.), Phaseolus spp., lentil (Lens cularis L.), and soybean (Glycine max (L.) Merr.), green gram (Vigna radiata (L.) R. Wilczek), and pigeon pea (Cajanus cajan (L.) Millsp.), to promote productivity and health of the ecosystems (Choudhary et al. 2018; Nawaz et al. 2019). The legumes can be included within existing cropping systems and be used as a green manure crop (Nawaz et al. 2019) or as an intercrop. A recent study in India, conducted over 13 years by Hazra et al. (2019), showed that diversification of the maize-wheat system with legumes contributed to increasing the carbon sequestration and the soil macro-aggregates. The same study concluded carbon indices were higher for pigeon pea-wheat and maize-wheat-mungbean rotations. In another long-term study, Nath et al. (2019) found that the inclusion of legumes in rice-wheat crop rotation increased water-stable macroaggregates in surface and subsurface.
A severe attack of insect-pests in the cotton-wheat system has lowered the profits margins of many Pakistani farmers. Cotton is a summer crop and can be easily replaced by other crops like peanut (Arachis hypogea L.) or sesame (Sesamum indicum L.), with the perspective of improving farmers livelihood and sustainability in soil processes. The introduction of safflower (Carthamus tinctorius L.) and other oilseeds and food legume crops may be also highly successful in marginal areas where water is scarce, since these crops require less water than cereals. The intercropping of legume crops, for example, mungbean, sesame, in cotton is another option to diversify the cotton-wheat cropping system. Some cucurbits, like watermelon (Citrullus lanatus (Thunberg) Matsumura & Nakai) and musk melon (Cucumis melo L.), intercropped in the cotton system act as cover crops and thus an efficient profitable product that conserves soil moisture. The availability of certified quality seed of cotton may help improve its production. Sugarcane (Saccharum officinarum L.) is also an important cash crop of the South Asia region. The intercropping of lentil and chickpea in sugarcane improves net income and water productivity (Kanchannainwal 2014); soybean can also be a good option for the rainfed areas.
Looming water crisis, deteriorating soil health owing to unwise cultivation practices, an outbreak of pests and diseases, the emergence of new weed biotypes, development of herbicide resistant weeds, increasing post-harvest losses, and monocultures are threatening the long-term sustainability of crop production systems in South Asian countries. As a management scheme, the soil losses from soil degradation can be lessened through adopting the resource conservation technologies (rice direct seeding, zero-till wheat, and laser land leveling), construction of mini dams in sloppy areas, use of straw mulching, contour farming, and afforestation. From a nutrient perspective, soil nutrient cycling can be improved by adding organic/green manures, retention of crop residues, use of fertilizer at right time with the right dose and right method, site-specific nutrient management, and use of nano-fertilizers. For the management of insect pests, weeds, and diseases in an eco-friendly manner, the phenomenon of allelopathy may be quite effective. For the management of water, adopting bed/ridge sowing in field crops and high-efficiency irrigation system in water scare and rainfed areas should be advocated. Crop diversification through the inclusion of legumes crops is a viable option to suppress the pest outbreaks, reduce the pathogen transmission, and buffer the crop production from the negative consequences of climatic variations with improved soil fertility. For the management of locust swarms, cross-border cooperation is crucial. Measures being undertaken to address ongoing locust outbreak merit every support irrespective of jurisdictional boundaries. For the management of wheat rust, rust-susceptible wheat varieties should be banned for general cultivation. Breeding programs to develop rust-resistant wheat genotypes should be strengthened. The availability of certified quality seeds is central for profitable crop production and requires institutional support. From a policy perspective, immediate steps are needed to review, reform, and develop policies (related to taxes, price incentives, subsidies, laws, and provision of technical services), which support sustainable soil, water, and post-harvest management. Policies are needed to ensure easy access to soil and fertilizer testing facilities for site-specific fertilizer application. Switching to sustainable intensification of agriculture requires an effective agricultural extension, research, education, and capacity building. More investment is also needed to improve rural infrastructures, road connectivity, and market access.
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