Rice

Land preparation

• While waiting the seedlings in the nursery, rice growers prepare the plots to be planted: soil erosion on the watersheds around the marshland, repairing water drainage infrastructures, ploughing and leveling and puddling the plot.

Planting

• Nursery establishment

• Preparing seed beds for a 500 m² field
• 3 seed beds of 1 m wide and 6 m long (Figure 1).

Figure 1: Seed beds

• Spacing between beds= 40-50 cm to enable the farmer to pass while caring for the seedlings. (Figure 2).

Figure 2: Seed bed preparation and spacing

Leveling the seed beds using a wood stick (Figure 3)

Figure 3: Leveling the seed beds

• Fertilizer application (12.5 gr of NPK in every m² or two caps of a water bottle since one cap weights 6 gr ( Figure 5). The fertilizer is immediately mixed with the soil using own fingers. You can also use well decomposed manure ( Figure 6).

   

• Preparing rice seeds and fertilizers

• Seed selection and disinfection

• Seeds are selected through water soaking. Sunken seeds remain in the bottom while unfilled ones float to water level. These ones are removed ( Figure 7,8)
•  Sunken seeds are, then soaked in Kitazine solution for 24 hours. Kitazine is diluted as follows:  (Figure 9)

– I liter of water + 10 ml of Kitazine or 5 gr of Beam (5 caps of lemonade bottle)

– Needed seeds we need 25-30 per Hectare or 1.25 – 1.5 kg per 500m² (Standard plot).

• After soaking the seeds in the solution, they must be air-dried so that the solution can be removed from them ( this operation lasts for half a day) (Figure 10).
• Soaking the seeds in water for 48-72 hours. Soaking water must be changed daily (Figure 11).

                                                                                 

              

• Covering the seeds from soaking for 24 hour in a cool place so that they can sprout (Figure 12 and 13).

     

  Figure 12                                                           Figure 13                       

Note:

Seed disinfection plays a role to control occurrence of seed-born disease such as Bakanae disease, blast disease, brown spot, and grain rot.

• Planting seeds in the nursery

• Seed quantity and distribution

• Use 0.15 Kg – 0.2 Kg per are following the seed variety.

•  Sow the seeds evenly in the seed beds (Figure 14)

Figure 14: sowing the seeds in the nursery seedbeds

• Caring for the nursery after sowing the seeds in the seedbeds

• Covering the seedbeds with dry grass or banana leaves so that the soil can remain moist and preventing birds from eating the seeds (Figure 15).

Figure 15

Remove the mulch 4-5 days after sowing when the seeds are sprouting. Water between the seed beds must be at the same

• level as the seedbeds because it controls weeds and allows the seedbeds to maintain the moisture (Figure 16).

Figure 16

                                                                                                      

Transplantation

• Apply basal fertilizer: 70/m²
• Rice is transplanted 3 weeks after the nursery establishment
• Transplantation is done on parallel lines with 25cm of spacing between lines and hole

• Plant 2-3 seedlings in the hole.

RICE PLANTATION MANAGEMENT

Fertilisation

. Needed fertilizers, their importance and application time

No	Fertilizer importance	Fertilizer Type	Quantity	Comments
1	Basal fertilizer	NPK (17-17-17)	10kg/ 500 m2 or 200 Kg/Ha	– It is applied before planting. – It helps rice seedlings to grow well at the beginning of tillering. – All amounts of Phosphorus and Potash minerals are applied as basal fertilizer.
2	Top dressing fertilizer: first application at the beginning of panicle initiation	Urea (46%)	2.5kg/ 500 m2 or 50Kg/Ha	– Top dressing urea is applied 30 days after transplanting – Increasing rice tillering ability to increases the number of panicle per m2
3	Top dressing fertilizer: second application at panicle formation	Urea (46%)	2.5kg/ 500 m2 or 50Kg/Ha	– Urea application at boosting stage – Mitigation of degradation of glumaceous  flowers – Increasing the number of grains per panicle and reducing unfilled grains.

 

Water management

Water is a precious and scarce resource input in rice

• production, so it is very important that irrigation water is used wisely and efficiently.
• The farmer must insure that needed water is available at the different growth stages of rice:

–  Transplanting to Tillering stage: the plant is vulnerable to water shortage. lack of sufficient water causes growth delay or even failure to the crop recover.

– Tillering- panicle initiation: in this stage, plants resist to low water content. Water level can be kept as low as possible to accelerate tillering.

– Panicle initiation- flowering: prevent water shortage

– Flowering- maturity: transpiration is high from heading/flowering period onwards. Water shortage will increase imperfect grains and affect ripening negatively. Drainage is done 15-20 days after heading to hasten maturity and to prevent excessive nitrogen intake.

Weeding 

• Preventive method: Use of paddy seeds without contamination of weed seeds, and keep soil bund and canals free of weeds.
• Push rotary weeder in between rows as seen in picture. This weeder has the function to incorporate juvenile weeds/weed seed into soil to suppress weed infestation (Figure 17)

Figure 17: Weed control with a rotary weeder

Canals and bunds

• Rice growing involves infrastructures such as canals and bunds. The farmer must take care of them and use them efficiently since water is a determining factor to rice production.
• Cultural method: good land preparation, flooding.

1. Bacterial Blight

Bacterial blight is caused by Xanthomonas oryzae pv. oryzae (Xoo) and affects the rice plant at the seedling stage where infected leaves turn grayish green and roll up. As the disease  progresses, leaves turn yellow to straw-colored and wilt, leading whole seedlings to dry up and die. The disease occurs in both tropical and temperate environments, particularly in irrigated and rainfed lowland areas. It is commonly observed when strong winds and continuous heavy rains occur. The disease is severe in susceptible rice varieties that are treated with high nitrogen fertilizer.

Prevention and control measures: use resistant varieties, avoid all host materials, use appropriate Nitrogen fertilizer and avoid flooding.

2.The rice blast

This disease is transmitted by a fungus called Pyricularia oryzae, which attacks the whole plant: leaves, stem, flowers and even seeds. Symptoms: They are visible especially during rainy season or in wet conditions. The disease is seen through greyish spots on stems and ears. In seedbeds, the seedlings dry out.

Period of serious outbreak of the disease: The disease is particularly severe in nursery, and at flowering stage. Chemical fertilizers with high concentration of nitrogen worsen the situation.

Prevention and control measures:

As prevention measures, plant on time and use healthy seedlings from resistant varieties; apply chemical fertilizers in moderate quantity. It is also necessary to keep the surrounding area clean, mobilize sufficient water towards the field; treat the seeds with Thiran and benomyl, (1gr of Thiran and 1gr. of benomyl per kg of seeds; soak the seeds in the solution for 24 hours before sowing in the seedbed

• Treat the disease once it is identified, using propiconazole or tebuconazole on attacked fields, and benomyl in nursery seedbeds.

Photo: Symptoms of Rice blast on leaves.

3. Rice Yellow Mottle Virus (RYMV)

Rice Yellow Mottle Virus (RYMV) is endemic and largely restricted to the African continent, where it has been found in most of the rice-growing countries. The virus has also been reported in Turkey.

Virus attacked rice plants.

Rice Yellow Mottle Virus (RYMV) is transmitted by several species of insects, cows, rats, and donkeys. Insect vectors that feed on infected wild rice usually invade and infect newly established crops or seedlings in a nursery. Rice plants, alternate hosts, ratoon or stubbles that grow between cropping seasons, allow the continuous survival of the pathogen. RYMV can also be mechanically transmitted through inter-plant movement of sap (irrigation water, guttation water, and contact between infected and healthy plant tissues and crop residues).

The virus can also been found on roots of infected plants and can infect plants through injured roots.

Symptoms:

• RYMV symptoms initially appear as yellow-green oblong to linear spots on the base of the youngest leaves. These spots later expand parallel to the leaf veins and appear as yellow or orange streaks.
• Leaves formed after infection are mottled and often twisted.
• The disease also causes brown to dark-brown discoloration and poor panicle exsertion.
• Severely infected plants are stunted, have reduced tillers, sterile spikelets, and eventually die.
• Plants infected 20 to 50 days after transplanting may show yellow stripes and spots, produce flowers and seeds, but have stunted growth.

How to manage

The use of resistant varieties appears to be the most convenient control measure against RYMV.

Other management options include:

• employ the use of large-scale synchronous planting combined with fallow period to prevent the buildup of the virus and vectors,
• plow under-infected crop residues, volunteer rice, infected ratoons, alternate hosts of the virus, and the vector immediately after harvest to reduce the primary inoculum in the field and prevent continuous survival of the virus and the vector,
• establish the crop before the increase in the vector population,
• roguing and burning infected plants, especially when infection is still low,
• regular weeding during the cropping season and even after harvest to reduce sources of primary inoculum.

4. Bacterial Leaf Streak

Symptoms begin with fine translucent streak between veins. As the disease progresses, the streaks becomes yellowish-gray, the lesion coalesce, then eventually turn to brown to grayish white causing the leaves to die.

Prevention and control measures:

• As prevention measures, plant on time and use healthy seedlings from resistant varieties; apply chemical fertilizers in moderate quantity. It is also necessary to keep the surrounding area clean, mobilize sufficient water towards the field; treat the seeds with Thiran and Benomyl, (1gr of Thiran and 1gr. of Benomyl per kg of seeds; soak the seeds in the solution for 24 hours before sowing in the seedbed.
• Treat the disease once it is identified, using Propiconazole or Tebuconazole on attacked fields, and Benomyl in nursery seedbeds.

Pests, rodents and weeds

`1. Stem borer

Larvae of the stem borer enter into the stem, feed on its heart and dig holes in the tillers. When young rice is attached by stem borers, its growth is stunting, the leaves turn yellowish and dry When rice is infected during tillering or flowering stage, grains are not well filled and become whitish. At harvesting stage, larvae start to pupate in the lower part of the stem. When the season immediately follows the harvest, stem borers increase.

Photo: Rice stem borer

Control measures:

• After harvesting, ploughing rice stubble into the soil to kill larvae and pupae and avoid leaving unwanted rations.
• Apply appropriate insecticides when deemed necessary.

2. Stalk eyed-fly

• This kind of fly with black head, called “Diopsis Thoracica’’ lays eggs which give larvae later on. These larvae attack the seedlings. This takes place mainly during dry season.

Photo: stalk-eyed fly

• Control measures: The field must be always clean. In addition, increase the quantity of water in the field once the first symptoms of attack by the larvae are confirmed. Finally, use specific product to fight against the fly, preferably a product containing pyrethrin.

3. Rats: rats damage rice plants in the field and can reduce the yield up to 20%.

Prevention and treatment measures:

• It is necessary to keep the surrounding area clean,
• Use rat traps and predators.

4. Birds: various birds feed in rice grains in the field and reduce the yield by 25-30%.

• Plant on time and use healthy seedlings from resistant varieties (NERICA) with sharp leaves on which birds cannot stand;
• No specific way to fight against birds other than chasing them away is used so far.

Weeds

Rice weeds which are available in Rwanda include: Echnochloa crusgali, Echnochloa Colonum, Cyperus diformis, cyperus rutondus.

Prevention and treatment measures:

• Apply chemical fertilizers in moderate quantity;
• is also necessary to keep the surrounding area clean,
• Mobilize sufficient water towards the field;
• Treat the seeds with Thiran and benomyl, (1gr of Thiran and 1gr. of benomyl per kg of seeds. Soak the seeds in the solution for 24 hours before sowing in the seedbed;
• Treat the disease once it is identified, using propiconazole or tebuconazole on attacked fields, and benomyl in nursery seedbeds.

Harvesting

• Water should be drained 7-10 days prior to harvesting, and do not dry more than 10 days before.  Early draining of water more than 10 days before increase cracked rains.
• Paddy field is ready for harvesting 120-160 days after planting and the yield is 3 to 9 tonsof paddy per 1Ha.

• Cut the stems with a sickle about 10 cm above the ground to reduce stem borer in the field.

Post-harvest management

Amaranth is a perishable leafy vegetable which must be carefully handled so as to preserve its nutritional properties.

Postharvest loss of quality and deterioration can be seen through:

• Yellowing as a result of loss of chlorophyll;
• Wilting and loss of textural properties;
• Decay from pathological breakdown.

After harvesting, the leaves are kept in a bag and usually sold on the day of harvest to avoid quality loss. However, where there is cooling storage the leaves can be kept in such containers.

Once you have harvested the grain  amaranth, it needs to be completely dried before you store it; otherwise, it will mold. Leave it on trays to dry in the sun or inside near an indoor heating source. Stir the seed around on occasion until they are completely dry. Store them in an air tight container in a cool, dry area for up to 6 months.

Threshing

Thresh immediately after reaping rice to avoid quantity losses and deterioration of grain quality and do not keep reaped rice on wet paddy field several days.Use foot pedal thresher or traditional method to beat rice against the tarpaulin spread over the ground to avoid contamination with sand and other foreign matter.

   

Manual Rice threshing                              Rice threshing using a foot pedal threshing machine

Drying paddy by Sun drying method 

Grain moisture content (GMC) of the harvested paddy roughly ranges from 20 to 30 % depending on weather condition.Adjusting grain moisture content to 14 % is necessary for dehusking/milling operation to minimize cracked grain and for long storage and 13 % for seeds makes long storagewithout deterioration.

Dry paddy properly to a safe GMC of 14 % by spreading in a thin layer (5 cm) on  concrete drying yard or tarpaulins and turning over periodically (every 30 to 60 min)   for even drying

•  

Sun-dry slowly for 2-3 days (6-8 hours perday) depending on weather condition to reduce breakage during milling and avoid rapid dryness (1 or 2 cm thickness ofpaddy layer) of paddy within short period such as one day.

Checking the moisture contents by biting the de-husked rice:

-Be crushed by biting (about 20%)

-Be cracked by biting without a sound (about 18%)

-Be cracked with a click sound (about 15%).

Milling

Milling is a crucial step in post-production of rice. The basic objective of a rice milling system is to remove the husk and the bran layers, and produce an edible, white rice kernel that is sufficiently milled and free of impurities.

Depending on the requirements of the customer, the rice should have a minimum number of broken kernels.

Photo: Mini Rice milling machine

Winnowing Paddy by machine or traditional winnower (Urutaro)

Winnow to separate chaff and empty grains from the well filled matured grains by using winnowing machine or a traditional winnower (Urutaro).

Photo: Traditionally winnowing rice                                              Using a winnowing machine

Bagging and storing paddy for long time:

• Grains under 13 – 14 % of grain moisture content (GMC) can be stored for long time without quality deterioration.
• Store grain bags indoors on pallets or logs to protect paddy from moisture migration under good air ventilation.
• Paddy is stored in bag or lofts. Husked rice is disinfected with actelic (100 gr. for 100 kg of rice) or 50 gr of Super Grain Dust in 90 Kgs of rice. Cocoons are also used by people who can afford them.
• Factor affecting quality and quantity consists of as follow:

1) Physical factors: temperature, humidity

2) Chemical factor: moisture, enzyme action, oxidation

3) Physiological factor: respiration, heat generation

4) Biological factor: pest, microorganism, rat.