Agronomy

Agronomy is a branch of agricultural science which deals with principles and practices of soil, water and crop management.

Main objective of Agronomy Department

The main objective is to develop suitable agronomic practices that increase input use efficiency, increase productivity, reduce cost of production, addresses issues of climate change and reduce green house gas emission and promoting sustainable rice production.

Functions of Agronomy Department

  • To conduct experimentation and other evaluations that results in technology development that will accompany the new varieties at the time of release in the form of a package of practices that will manage the variety in farmers’ fields.
  • To provide remedies to short term problems or situations such as salinity, drought, nutrient deficiencies etc. as the need arise.
  • To train and conduct demonstrations for stake holders (new researchers, extension officers and farmers) about newly developed rice production technologies.

Current activities of the Agronomy Department

  • Optimizing seeding rates, nitrogen and potassium levels and timing of application for the newly developed rice varieties or potential varieties.
  • Optimizing dates of sowing for increase yield, reduce incidence of pest and diseases.
  • Evaluation of pre and post emergent herbicides for their time and rate of application.
  • Integrated weed management.
  • Integrated nutrient management
  • Water management with respect to increase its use efficiency and productivity, its management during drought.
  • Evaluation of newly created breeding line for their tolerance to salinity.
  • Development of an integrated approach to managing weedy or red rice.
  • Development of improved management practices for higher yield in rice.
  • Evaluation of various products that help in seedling vigour, growth, yield and quality of the grain.
  • Development of suitable rice based cropping system (crop rotation).
  • Crop establishment methods.
  • Soil sampling, analysis, mapping and making recommendations.
  • Conducting training and field demonstrations.

 

Rice grown in Guyana occupies approximately 225,000 acres and has been double cropped per year. Several varieties (10) are presently under cultivation however, GRDB 9, GRDB 10, G98-22-4, G98-196 and G98-135 are the dominant varieties.  Average grain yields obtain by farmers is 30 bags/ acre. The following management practices are recommended to follow for obtaining high grain yields.

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Land preparation—   Land preparation aids in weeds reduction, to incorporate fertilizers and produce a fine tilt that enhances seedling emergence and establishment. Land preparation normally consists of: 

Primary tillage—1st and 2nd cut (Rome or disc)  – 4 to 6″ (10 to 15 cm) and harrowing (Rome). The primary tillage operations may be carried out at intervals, which allow for the emergence (by rainfall or irrigation) and successive destruction of volunteers.

Secondary Tillage—If rainfall is inadequate, fields are irrigated to allow for the secondary tillage operations.  Harrowing (disc) also referred to as puddling. Raking and levelling. Back blade and henga (one operation).

Suspended sediments should be allowed to settle for 2 to 3 days before sowing.

Seed Preparation and Sowing

First, choice of variety, source of seed material and how much seed should be used must be determined.  Seeds purchased from GRDB or RPA (clean seeds) should be used at a rate of 100 to 120 lbs/ac.  Seeds produced by the farmer or purchased from another farmer (unclean seeds) should be used at 140 lbs/ac.

Seed increases in volume by around 25% during the soaking exercise.  It is therefore recommended that each bag of seed is divided into 2 equal parts and tied slack to accommodate the increase in volume during soaking.  Avoid using muddy or stagnant water when soaking seed.  Water in the irrigation channels is usually suitable for soaking.  Soak seeds for 24 to 30 hours.  Remove at the end of the soaking period and wash-off mud if necessary.  Allow water trapped in bags to drain off.

Seed incubation can now be achieved by covering the soaked lots of seed with moist bags or straw for 36 to 48 hours.  All of the important requirements for germination (adequate moisture, oxygen and suitable temperature) would have been satisfied by the above procedure.

If sowing is to be carried out by aircraft, 24 hours of incubation is normally adequate.  Light wetting (watering) may be necessary during incubation to maintain a Relative Humidity close to 100% in the germinating environment.

Seed treatment: Seeds can be treated with Regent, Crusier or Prunto which will prevent the infestation of water weevil and to some extent leaf miner.

Drainage after Sowing-The field is drained 2-5 days after sowing to encourage uniform establishment.  After gravitational flow, manual digging of internal drains are required to drain water from deep areas of the field. In some instances, drainage may not be done, this is practiced to retard growth of grass weeds and weedy/red rice.

Pest Management-Water weevil (Helodytes foveolatus) – Control is most effective 7-14 days after a permanent flood and weevil numbers are at or above economic threshold level. Control of larvae can be done by draining field and allowing it to dry until it cracks. Good field sanitation will get rid of alternative weed hosts and apply insecticide (Fastac, Pestac, Karate or Pronto).

Leaf miner (Hydrellia sp.) – Plant early and high tillering varieties.  Drain fields after sowing to provide a poor habitat for leaf miner reproduction, not in excess of 3 days.  Employ chemical control with a systemic insecticide if infestation is high e.g. Pronto, Actara, Regent

Caterpillar (Spodoptera frugiperda) – Deep     ploughing to expose pupae to predators. Flood infested fields for 24-48 hrs in order to drown caterpillars.  Spraying contact insecticides e.g. Fastac or Pestac during high infestation, that is, a threshold of 30 damage leaves/square metre.

Snails (Pomacea sp.) – Place a wire or woven bamboo screen on the main irrigation water inlet and outlet to prevent the entry.  Snails are active in standing water and thus, good land leveling and field drainage can help reduce damage.  After the final land preparation small canals can be constructed, this will serve as focal points for snails making manual collection or killing easier.  Handpick snails and crush egg masses. This is best done in the morning and afternoon when snails are most active. Place bamboo stakes to attract adults for egg laying.

Stem borer (Rupela albinella) – Good field sanitation.  Avoid using high nitrogen rates.  Synchronize planting. Apply contact and systemic insecticides.

Paddy bug (Oebalus poecilus) – Practice block planting, good land preparation or soil tillage,     field sanitation is an important and highly effective farm practice to keep most pests under control. It involves keeping weeds under control at all times from in and around the field as these will serve as alternate hosts for pests.  Hand picking or rouging – where plants that are heavily infested, especially with egg masses of paddy bug or snails, are pulled out and properly disposed of. Rouging of volunteer plants and red rice, which also serve as alternative hosts to the paddy bug, within the rice fields.

Monitoring by the sweep net method should be done in the fields for paddy bug incidence during the cool periods (early morning and late afternoon) from late tillering to harvesting.  Should the number of bugs exceed 1 bug/2 sweeps, then chemical control is needed with:

  • Fastac/Pestac –  60-100 ml/ac
  • Actara –  39g/ac
  • Pronto –  10-15 g/ac
  • Relevo –  100-140 ml/ac
  • Admire  –  40 ml/ac
  • Pilarking –  40 ml/ac
  • Admister –  10-30 ml/ac

Note:  These insecticides should be applied early morning or late afternoon when the rice is flowering. Failure to do so will cause interference with pollination and hence “wind paddy will result”.

Weed Control-Early post emergent weed control should be undertaken to prevent crop weed competition which will further result in yield and quality losses.  Herbicide application around 15 to21 DAS is best recommended so that it can facilitate fertilizer application and subsequentirrigation.  Some herbicide recommendations are Nomeny 40 to 60 ml, Rice Weed Killer

Fertilizer Application-Half bag of TSP and MOP to be incorporated dry or broadcast at 18-21 DAS.  Urea is required at 1.5 to 2 bags/ac. It must be split in three application timings (18-21, 42 and 60 DAS) in proportions of 25, 50 and 25 % respectively.  Urea must be applied in field with reduce or low water content.

Water Management-Field can be drained 24-48 hours after sowing to enhance a uniform establishment of the crop.  In some cases where the fields have history of weed and red rice, the crop is allowed to emerge through water.  After weed control and fertilization irrigation is provided and depth of water is adjusted as plants grows taller.  During this time and afterwards, the field should not be allowed to be drained or dry out until after grain filling.  Final drainage will be effected after grain filling to facilitate mechanical harvesting.

Rouging-This will commence before fertilizer application and ends before harvesting.  All old roots, volunteer, red rice, other variety and weed plants are to be removed manually otherwise this will deteriorate the quality of produce at harvest, hence lower market value.  In addition, these plants will serve at host for diseases and pests.

Harvesting-This will commence when the crop is physiologically mature.  To obtain best headrice recovery, the grain should be harvested at around 18-21 % moisture.  For seed purpose, grain moisture can be reduced before harvesting.