Cultivation Support – PFT, Polypit, Biopesticides

Photo: Jitendra Raj Bajracharya/ICIMOD.

Polythene film technology (PFT)

Polythene (plastic) film technology (PFT) is a method for increasing production of field crops by covering the soil between the plants with a sheet of polythene film 0.003 to 0.014 mm thick. Covering the surface of the soil increases the temperature, helps retain moisture, promotes seed germination and emergence, accelerates the growth and development of the roots and the whole plant, and leads to improved quality and higher yields of crops. The method is demonstrated with appropriate crops on selected terraces within the site.

Polypit and hotbeds

One of the problems that mountain farmers face is raising of forest or horticultural plants in nurseries and growing high value vegetables during the off-season, especially in regions with high annual variation in temperature and relatively severe winters. Low temperatures and frost delay germination and subsequent growth, and lead to high plant mortality, poor plant quality, lack of uniformity in plant size, and overall low plant productivity. These constraints can be overcome to a great extent using ‘polypit’ technology. A polypit is a rectangular pit, usually about 1m deep, dug in the ground and covered with semi transparent polythene sheet, preferably UV stabilised, supported by a bamboo frame. A mud wall about 30 cm high is built on one side so that the cover slopes. The polythene sheet is sealed on the (higher) side, leaving three sides unsealed. These are normally held in place with stones, but can be lifted to access the pit. The base and sides of the pit are left rough without any plastering (even with mud). In general, the polythene cover is opened from 11 o’clock in the morning to 4 o’clock in the afternoon, except on rainy and very cold days. The size of the pit can vary according to availability of space and the kind of crops or plants to be raised. A hotbed can be constructed inside the pit using different layers of dry straw or biomass, animal manure, and good top soil. The bed generates heat slowly and can support plant growth in winter. The polypit technique has several advantages: 1) it is a simple, inexpensive, practical, and effective technique for raising plants and protecting them from severe winter temperatures; 2) CO₂ enrichment inside the polypit leads to a gain in plant biomass and growth; 3) plants raised inside a polypit are better acclimatised to the outside environment as the polythene cover is removed everyday; and 4) the frequency of irrigation is reduced.

Bio-pesticides and plant tonics

Biopesticides are plant proteins with broad biocidal properties against insects, pests, and fungal and bacterial pathogens; they offer a good alternative to chemical pesticides in controlling crop diseases and pests. Application of chemical pesticides is increasingly associated with negative impacts to human health and the environment, whereas biopesticides are safer and environmentally friendly. Insect repellent plant species such as titopati (Artemia vulgaris), bojho (Acorus calamus) and neem (Azadirachta indica) can be used as a base. Around 30 kg of the insect repellent plant species is chopped into small pieces and mixed with 30 kg fresh cow dung and 100 litres fresh cow urine in a 200 litre plastic drum. Approximately 10 gm yeast and a little salt is added to speed fermentation. The mixture is stirred for five minutes every day for a week and then once a week for 4-5 weeks. It is then filtered through a plain cloth to give concentrated bio-pesticide solution. The concentrated solution is diluted 1:10 with water before applying to plants. The procedure used to prepare biopesticides can also be used to prepare a plant tonic (liquid fertiliser) by substituting an appropriate plant species. Any kind of grass that is not edible by livestock can be used (e.g. banmara or Eupatorium adhenophorum). The bio-pesticides and plant tonics should be used within six months of preparation.