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Ecology & Environment
Mahesh

05/08/24 06:56 AM IST

Weed control in Rice & wheat fields

In News
  • A push for direct-seeded rice and zero-tillage wheat, using a new non-GM herbicide-tolerance technology, has the potential to reduce the environmental footprint of India’s two major cereal crops.
Weed control 
  • Farmers flood their paddy fields and do 3-4 ploughings for wheat mainly to control weeds.
  • Normal rice cultivation involves preparing nurseries, where the paddy seeds are raised into young plants that are uprooted and re-planted around 30 days later in the main field.
  • The field in which the seedlings are transplanted is first “puddled” or tilled in standing water to break up the clods and churn the soil to make it soft.
  • For the first 2-3 weeks after transplanting, the field has to be irrigated every 1-2 days to maintain a water depth of 4-5 cm.
  • This is necessary to prevent weed growth during the crop’s early stage.
  • Water acts like a natural herbicide, preventing the weed seeds from germinating and killing the already emerged seedlings.
  • Farmers continue giving water once a week in the remaining 105-110 days – out of the crop’s total 155-160 days duration from seed to grain.
  • In all, the traditional puddling-cum-transplantation route requires up to 30 irrigations, each consuming over 200,000 litres of water per acre.
  • Puddling alone consumes water equivalent to three irrigations. Besides, there is the labour cost of transplanting, at Rs 4,000-5,000/acre.
  • In wheat, farmers not only burn the stubble from the previously-harvested paddy crop.
  • They also plough the field – initially twice using a harrow or cultivator, followed by an irrigation and either one more ploughing with a rotavator or two with harrow/cultivator.
  • All this, before sowing the wheat seeds, is primarily for weed management.
Herbicide-tolerant solutions
  • DSR and ZT wheat basically replace water and repeated field ploughings with a chemical herbicide (Imazethapyr) to take care of weeds.
  • DSR dispenses with the need for any paddy nursery, puddling, transplanting and flooding of fields.
  • The paddy seeds can be sown directly, just like wheat.
  • Only laser leveling of the land, once before sowing and costing Rs 1,200/acre or so, is recommended to ensure uniform placement of seeds and fertiliser as well as distribution of water.
  • Overall, there is roughly 30% saving of water, apart from labour in transplanting and weed management, and fuel used for puddling.
  • Mahyco claims that ‘FreeHit’ ZT technology makes it possible to sow wheat directly – without any paddy stubble burning or even land preparation.
  • Farmers can use a tractor-mounted Super Seeder machine with rotavator that cuts the standing stubble and mixes it in the soil.
  • Alternatively, they can use a Happy Seeder without rotavator that only cuts and leaves the crop residue on the field.
  • Either way, sowing is done with no tillage, saving both cost and time.
  • Imazethapyr is to be sprayed along with Metribuzin, a selective herbicide already used in wheat, when the crop is about 25 days old.
Source- Indian Express

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