Challenges to agriculture - Part iv | Sunday Observer
In the face of climate, health and food security changes:

Challenges to agriculture - Part iv

11 October, 2020

Continued from October 4

d). Paddy lands

Since ancient times, paddy lands have been used for lowland rice farming. It has been one of the oldest land use systems in the country. Paddy cultivation has been confined to Maha and Yala seasons. It is the staple food crop of the nation. The cultivation is practised in the lower portions of the landscape as paddy requires sufficient water for attaining a satisfactory yield. According to a research review conducted in 2006, paddy cultivation is practised under four agro-climatic situations: dry zone, intermediate zone, inland region of the wet zone and coastal region in the wet zone.

Rice in paddy lands in the wet zone

Paddy farming is practised in the districts of Anuradhapura, Polonnaruwa, Batticaloa, Trincomalee, Vavunia, Mulathivu, Mannar, Kilinochchi, Hambantota and some parts of the adjacent districts in the dry zone. Almost all paddy lands have been cultivated during Maha and a greater fraction in Yala depending on the availability of rain or irrigation water. In recent decades, commercial scale upland seasonal crops have been grown to a limited extent during Yalaon lands having well drained soils, especially if rice cultivation is not possible due to water shortage.

Inland salinity, coastal salinity, water stress, flooding and yield stagnation have been the major land related production constraints. Recent climate change has aggravated these production constraints and therefore, this matter must be adequately taken into consideration in designing climate smart systems of farming.

Paddy lands in the intermediate zone mainly lie in districts of Ampara, Badulla, Kandy, Kurunegala, Matale, Moneragala, Puttalam and some parts of the adjacent districts. Paddy has been cultivated in both Maha and Yala seasons depending on the availability of water. Similar to the dry zone, upland seasonal crops have been grown during Yala to a limited extent due to lack of water for paddy cultivation. Inland salinity and water stress have been the major production constraints. Such limitations can be aggravated due to climate change effects.

Paddy lands in the inland region of the wet zone mainly lie in the districts of Kandy, Kegalle and Ratnapura and some parts of the adjacent districts. Paddy has been cultivated both in the Yala and Maha seasons. Water stress, flood and iron toxicity have been the major land related production constraints. These production limitations may aggravate under global warming.

Paddy lands in the coastal regions in the wet zone mainly liein five coastal districts: Colombo, Galle, Gampaha, Kalutara and Matara. Historically, a single crop of long duration paddy, such as Ma wee has been cultivated. However, in recent decades, short duration paddy varieties have been introduced to promote double cropping in the Yala and Maha seasons. The possibility for growing other crops, particularly, leafy vegetable has been limited in extent. Many production constraints, such as water stress, flood, iron toxicity, acid sulfate toxicity, coastal salinity, sea water intrusion have been dominant production limitations.

Conventional paddy land farming systems need inclusion of packages of strategies and practices to develop a climate smart nature. Components to be considered at the land preparation stage include: initiating discussions at the paddy tract level for synchronising farming practices particularly seedling, transplanting or seed sowing, making repairs on field irrigation canals, commencing farming with the onset of seasonal rains to cut down supplementary irrigation water requirement, reconditioning bunds periodically to minimise water losses and to destroy rat breeding sites, introducing organic manure production units to individual farmers to cut down chemical fertiliser use, application of organic manure prior to first ploughing to keep a considerable period for facilitating partial decomposition, considering short duration field crops if water availability is not adequate for paddy according to weather and climate forecast information, quick land preparation within a shortest possible time, introducing lacer levelling techniques for reconditioning irrigation terraces and providing adequate drainage facility for lands having boggy soils.

Strategies and practices to be considered after land preparation include: considering varieties well suited to the earth and climate in the season (short age, salt resistant, flood tolerant varieties), practising self-seed production at farmer or farming tract level, providing seeding trays for practising parachute method in transplanting, row seeding using drum seeder followed by mechanical weeding, application of slow release chemical fertiliser if possible, providing vegetable seeds for promotion of bund cultivation, soil test based chemical fertiliser use if slow release fertiliser application is not feasible, use of leaf colour chart in urea application for saving soil application of nitrogen, foliar application of kieserite and zinc sulfate only when necessary, application of water saving techniques in crop irrigation, such as alternate wetting and drying method, integrated pest and diseases management, use of combine harvesters in crop harvesting, providing paddy dryers, particularly under wet weather, introducing efficient storage systems at small scale for farmers and large scale for community based organisations, selecting an appropriate market channel for selling crop produce, residue management after harvest in an appropriate manne to avoid setting fire on straw and introducing short duration sandwich crop (green gram or cowpea) preferably after the Mahaseason to provide an extra income for the farmer.

Factors to be considered in formulating a package of strategies and practices depend on land characteristics and climate in the season. Similar to home gardens, consultation of a field agriculture extension agent is suggested for finalising a climate smart farming package.

Mitigation of greenhouse gas emission

Mitigation of greenhouse gas emission plays a significant role in addressing issues related to climate change. Tangible impacts can be achieved in areas, such as energy resource use, science based industries, transport services and waste management. Agriculture on the other hand, may have more limited avenues for mitigating greenhouse gas emissions from farming systems. Carbon dioxide, methane and nitrous oxide have been identified major greenhouse gasses emitted from agricultural lands due to farming activities. There are a few strategies and practices available for controlling greenhouse gas emission from farming systems.

a). Carbon dioxide

Measures for the mitigation of carbon dioxide emission from the agriculture sector include: avoiding haphazard clearing of natural forest for farming, introducing conservation tillage practices, such as reduced tillage and minimum tillage, practising agro-forestry, minimising fossil fuel use for operating farm implements, reducing land use intensity and maintaining adequate fallow periods to provide a rest for soil, and crop maintenance options, such as promoting organic manure use and residue management, such as avoiding biomass burning.

In addition to reducing emissions, carbon sequestration can reduce atmospheric carbon dioxide by depositing it in more secured reservoirs in the environment. For example, the home gardens as an agro-forestry system can play a significant role in accelerating this sequestration process as it captures and deposits carbon in plants, particularly in trees for many decades. At maturity, trees can be harvested for timber and used for making long lasting wooden products, such as building materials and furniture, which helps store carbon in a secured form for many more decades. Hence, strengthening the perennial tree component in home gardens does provide a method for accelerating the carbon sequestration albeit in limited form.

A tree component can also be introduced to other farming systems. Steps should betaken to reintroduce alley cropping technology for upland farming systems in the dry and semi-dry areas and expand gliricidia tree hedgerow based technology for sloping agricultural lands in the wet and semi-wet areas of the country.

Home gardens as an agro-forestry system for enhancing carbon sequestration

b). Methane

Methane gas emission occurs in natural land systems as well as man-made farming lands. The natural land systems associated with farming areas include wetlands and termite colonies. Some of the agricultural induced methane emissions are related to animal production systems. Methane emission occurs in dung heaps and other farm wastes exposed to open environment and microbial digestion in livestock. Flood irrigation for paddies on bog soils, fossil fuel use for operating farm implements and landfills are other sources of agricultural methane.

Some mitigation measures include restricting irrigation and promoting dry farming techniques, such as Kekulan and Manawari methods in paddies, drainage improvement in bog soils, immediate use of animal dung and other farm wastes for bio gas production to minimise duration of heaping in open environment and the use of alternative energy sources for operating farm implements.

c). Nitrous oxide

Nitrogen applied to soil in excess of crop requirements is subject to losses, including volatilisation from the soil surface and leaching down to deeper soils for biological decomposition in the form of nitrate. This lost fraction of nitrate serves as an input for the denitrification process particularly under anaerobic condition. As an intermittent product of denitrification, nitrous oxide is produced and emitted out to the atmosphere. Most farmers, particularly in commercial scale farming systems in Nuwara Eliya, Boragas, Keppetipola, Bogahakumbura, Welimade, Boralanda, Bandarawela, Kalpitiya peninsula (Norochcholai, Etalai, Talawila, Narakkalliya), Dambulla, Kimbissa, Sigiriya, kilinochchi and Jaffna peninsula (Kondari, Urumpirai, Chunnakam, Mylankadu, Achchelu, Palai) use more than recommended quantities of nitrogen fertiliser and organic manure. The major nitrogen containing chemical fertilisers are urea and ammonium sulfate and organic manures include green manure, cattle dung, goat dung, discarded poultry litter and compost.

Measures for reducing nitrous oxide emission to atmosphere include use of slow release or controlled release nitrogen fertilisers (granular urea, prilled urea, sulphur coated urea and mud coated urea), use of nitrification inhibitors, such as dicyandiamide and 3, 4-dimethypyrazole phosphate, application of commonly available nitrogen fertilisers based on leaf colour information, safe storage of organic manure in open areas until required for soil application, application of organic manure in place of chemical fertiliser as much as possible and promotion of inter-cropping practices with leguminous crops.

The available nitrification inhibitors are expensive in the market and therefore, immediate local research is needed to develop methodologies for local manufacture of such inhibitors at affordable costs for farmers. The high price is the major reason for restricted use of slow release fertiliser in local farming.

Support services for climate smart agriculture

An appropriate way to build resilience to climate change by local agriculture is to develop and adopt packages of adaptation strategies and practices targeted to each specific agriculture production system. According to available literature, building resilience can be briefly described as the creation of an ability of a system to bounce back or return to normal functioning after climatic adversity. For example, management strategies, such as quick land preparation immediate after the onset of seasonal rains play a significant role for adaptation to climate change.

For this purpose, at present in most of farming communities, family labour is not adequately available and hired labour is not affordable due to high cost involved. As a result, there is a need to consider the use of mechanised farm implements as an adaptation strategy. However, in this country, most farmers have not been equipped with required set of farm implements under their own custody.

Farm implements are intensively used for only a short time during land preparation and crop harvesting. Hence, particularly smallholder farmers are reluctant to maintain their own collection of farm implements. Hiring implements from private owners is also expensive and availability is not assured at the required time in most cases. Therefore, establishing farm implement rental centres at the community level serves as a support service to facilitate farm mechanisation and ensure quick land preparation.

Some support services, such as management packages to promote the buildup of resilience in the affected farming systems include: a). Providing a facility for hiring farm implements, b). Re-promoting the Aththam method in labor use particularly in hill agriculture, c). Practicing the bethma method in seasons having water shortages, d). Installing electrified fences to protect crops from major wild animal pests, e). Introducing crop insurance schemes particularly for commercial scale farming, f). Introducing value-added land races for different climatic regions, g). Producing byproducts from adapted crops and h). Establishing effective market chains.

To Be Continued...