Seed care: why it matters and how to do it for a better harvest

In late autumn, courtyards across rural Bangladesh fill with paddy spread out on mats to dry in the sun. Most of it goes to the granary. A share is set aside as seed for the next season, and on those handfuls depends how green the fields will be a year later and how full the store. Seed is rightly called the life of farming. Cared for properly, it germinates better, stands up to disease, delivers the harvest it promises and brings down the cost of growing it.

Yet seed gets less attention in our fields than it deserves. Many farmers spend far more money and effort on fertiliser, irrigation and pesticide than on sorting or treating seed. Agricultural experts have argued for years that, with every other input held the same, the use of quality seed alone can raise crop yields by 15 to 20 per cent. The figure recurs in discussions on seed published by The Daily Star and The Financial Express.

Field experience points the same way. In a participatory study with farmers in Bangladesh, replacing farmer-saved seed with cleaned and sorted seed gave about 10 per cent more paddy in the Boro season and about 11 per cent more in transplanted Aman. No new fertiliser, no new machine: just a little more attention to the seed.

Seed care is not a one-day job. It begins at harvest, runs through the months of storage and ends just before sowing. Five steps matter most along the way: choosing good seed, treating it, storing it properly, testing germination and preparing it for sowing.

Selection is the first step in growing a crop, and a mistake here cannot be fully made good by any later care. Good seed means seed that is free of disease, well filled, roughly uniform in size, and free of other varieties, weed seed, clods of soil and chaff.

Uniform seed has a real advantage. It sprouts at about the same time, the seedlings grow at the same pace, and flowering and fruiting come close together. That makes fertilising, weeding and timing the harvest far more manageable. Shrivelled, empty or broken grains either fail to sprout or give weak seedlings, the first victims of pests and disease.

Where possible, use certified or tested seed. In Bangladesh, the Seed Certification Agency is the government body responsible for checking and certifying seed quality. The Bangladesh Agricultural Development Corporation (BADC) supplies rice, wheat, pulse, oilseed and vegetable seed across the country through its sales centres and registered dealers, and there are reliable private seed companies too. Before buying, check that the packet shows the variety, date of production, germination rate and expiry.

Farmers who keep their own seed need to sort it just as carefully. It is best to harvest seed separately from the healthiest, disease-free part of the field. For paddy, a long-standing village technique is to pour the grain into water: plump, heavy grains sink while empty and light ones float. Skim off the floaters, rinse the grains that sank in clean water and dry them, and a large share of poor seed is removed.

Seed treatment means removing the disease organisms and pests carried on or inside the seed. Many diseases travel with the seed from one season to the next and become active the moment it sprouts, when the young seedling is at its most vulnerable. Fungi and insects in the soil strike at the same stage.

The commonest treatment uses a fungicide or insecticide. A standard guide is 2 to 3 grams of fungicide per kilogram of seed. Which product, and at what dose, for which crop should be decided from the label and the advice of the upazila agriculture office. Too little and the organisms survive; too much and the seed itself may lose its ability to germinate.

For those who want to avoid chemicals, there is organic treatment. Seed can be treated with natural materials such as neem leaf extract. The bitter compounds in neem act against many insects and some microbes, which is why villages have used it for generations.

A familiar example of disease that comes home with the seed is bakanae in rice. Seedlings infected with this fungal disease grow abnormally tall and pale, and many eventually die. It spreads mainly through seed, which is why the Bangladesh Rice Research Institute (BRRI) stresses treating seed before it goes into the seedbed as the remedy. The organisms behind brown spot and blast can also be carried on the seed. Untreated seed, in other words, often invites disease into the new season.

With pulses, seed treatment has another side that is about feeding the crop rather than protecting it. Coating lentil, chickpea, mung bean or groundnut seed with an inoculant of the beneficial bacterium Rhizobium before sowing leads to small nodules on the roots. The bacteria inside capture nitrogen from the air and pass it to the plant, reducing the need for urea. The Bangladesh Institute of Nuclear Agriculture (BINA) has worked on producing and spreading such bio-fertilisers. Mixing a chemical treatment and the inoculant together can kill the useful bacteria, however, so follow the label and apply them separately.

Chemically treated seed has to be handled with care. Wear gloves and a mask while working, wash hands thoroughly afterwards, and never use treated seed as food or animal feed. Keep sacks of treated seed out of reach of children and livestock.

Between harvest and the next sowing, seed may spend several months, sometimes close to a year, in the house. This is when most seed is lost. Seed is alive: it breathes and it absorbs moisture. In damp, warm conditions its stored food runs down quickly, fungi move in and insects get in.

So seed must be kept in a dry, cool place where humidity is low and air circulates, away from direct sunlight and the heat of the stove. The best results come from airtight containers or packets: a sealed tin, a plastic drum with a tight lid, or a heavy polythene bag well sealed. If outside air cannot get in, neither can moisture or insects.

Above all, dry the seed completely before it goes into the container. Half-dry seed sealed in an airtight container does more harm than good: the moisture is trapped and the seed rots. The advice of research bodies including the International Rice Research Institute is to bring paddy seed down to 12 per cent moisture or below for longer storage. In villages, many farmers bite a grain: if it snaps with a crack, the seed is dry enough.

Paddy shows why. Boro seed harvested in April and May goes back into the seedbed in November and December, with the whole monsoon in between. Aman seed harvested in November and December is sown the following June and July. Either way the seed must sit in the house for six or seven months or more, much of it in hot, humid weather. That long wait is what makes storage so important.

It is a good habit to label every container or sack with the variety, the field it came from and the date it was collected. With several kinds of seed in store, labels reduce the risk of mixing, and they make it easier to keep track of which seed performed how in the next season.

Stand containers on a platform or wooden boards rather than directly on the floor so that damp from the ground does not rise into them. During the monsoon, open them now and then to check for mould or insects. Neem leaves or neem oil can be used to keep storage pests away.

After months in storage, it is wise to find out before sowing whether the seed will actually sprout. Sow blind, and half the seedbed may come up empty. Buying fresh seed and sowing again then costs time, money and the season all at once.

The test can be done at home without any equipment:

• Count out 100 seeds, taken from different parts of the sack or container.
• Spread them on a damp cloth and roll it up, making sure the cloth does not dry out.
• After a few days, unroll the cloth and count how many seeds have sprouted.
• If 80 or more of the 100 have sprouted, a germination rate of 80 per cent or above, the seed is fit for sowing.

If the result is below 80 per cent, there are two options. If it is only a little short, sow slightly more seed. If it is well short, set that seed aside and obtain fresh, good seed. This small test saves a lot of trouble at the start of the season. A plate of damp sand or soil works just as well as a cloth. It is worth testing bought seed too, since quality can also fall during transport and while it sits in the shop.

A little preparation just before sowing helps seed sprout quickly and evenly. The commonest step is soaking. Soaking seed in water for 12 to 24 hours before sowing lets the dry seed take up water, wakes the dormant embryo and speeds germination. Soaking paddy seed and then keeping it covered and warm until the tips of the sprouts appear, before it goes into the seedbed, is a long-standing habit among our farmers.

The second factor is temperature. The seed of each crop needs a certain warmth to sprout, and that has to be ensured before sowing. It is the reason extension workers advise covering Boro seedbeds with polythene on bitterly cold nights: in the cold, seed does not sprout properly, and the seedlings that do come up are weak.

Sowing depth also affects germination. Too deep, and the young shoot cannot push through the soil; too shallow, and the seed is eaten by birds and ants or dried out by the sun. Follow the depth recommended for each crop.

Why spend the extra time and labour on seed? The answer lies in the field. The benefits of treated seed are, broadly:

• The sprouting seed and young seedling are protected from soil-borne and seed-borne disease and pests.
• The germination rate goes up.
• Seedlings grow quickly and uniformly.
• Pulses come into pod earlier.
• Attending to the seed is far more convenient, and cheaper, than treating the soil or the foliage.
• Output stays more even even in bad conditions, when moisture is too high or too low.

The fifth point is worth dwelling on. Mixing 2 to 3 grams of chemical into a kilogram of seed costs a fraction of spraying a whole field once the seedlings are diseased, and by then part of the loss cannot be recovered. Seed is the cheapest place to stop disease.

Seed treatment is a term that covers both the product and the process: what is applied to the seed, and the act of applying it. In practice it is done in three main ways.

The first is seed dressing, the most widely used method. The seed is mixed with a dry powder, a liquid, or a thick slurry. For the farmer it is the most practical option. A cheap clay pot will do for mixing insecticide into seed. Seed can be spread on a polythene sheet, sprinkled with the right amount of chemical and turned over to mix. A metal seed dresser, a clay pot or a polythene bag can all be used for dressing, and on a larger scale farmers can do it mechanically. Seed dressing is carried out both on the farm and in industry.

Dressing in a polythene bag is popular in villages. Put the seed and a measured dose of chemical in the bag, tie the mouth tightly and shake it for a few minutes: every grain gets an even coat, and there is less risk of dust reaching hands and face.

The second method is seed coating. A special material is applied to form a thin layer around the seed to improve its performance; the layer may carry a fungicide, an insecticide or nutrients. Coating needs advanced seed treatment technology, so it is generally done industrially, in seed company plants. The coloured seed seen in shops is made this way.

The third is seed pelleting, considered the most advanced method. A thick layer of material is built up around the seed until it becomes a small round pellet. This changes the seed's shape and size and makes even very small seed convenient to sow, by machine or by hand. It requires modern equipment and technology, however, and it is a very expensive method.

Taken together, the benefits of seed care fall into four broad groups.

First, a higher germination rate: treated seed sprouts faster and leaves fewer gaps in the field. Second, better resistance to disease: treatment protects against disease and insect pests, especially in the first few weeks of life when the seedling is most fragile.

Third, a better yield: care keeps the seed's quality intact, and healthy, even, vigorous seedlings end up giving more grain. Fourth, lower cost: sound seed management cuts the overall cost of farming, with no extra seed to buy, no resowing, and less medicine needed later to fight disease.

There is also a gain that never appears in the accounts. When even seedlings come up on time, the whole season's work runs to schedule. If a seedbed fails and has to be sown again, transplanting is delayed, and a late crop often meets drought, hail or flood at the end of its season.

A few pieces of advice drawn from field experience make seed care more effective:

• Dry seed completely before storing it.
• Use neem oil or an organic insecticide against storage pests.
• Use fresh, good seed each season rather than old seed.
• Use a mix of high-yielding and local varieties.

There is a reason behind the advice on fresh seed. When the same seed is kept at home and sown year after year, mixtures of other varieties, disease organisms and weakness gradually build up in it. Replacing it from a reliable source from time to time is a good habit.

The advice to mix high-yielding and local varieties is a way of spreading risk. High-yielding varieties give more grain, while local varieties are often better suited to the area's weather and soil. With both, a single bad year is less likely to wipe out the whole crop.

On questions of which variety, which treatment and at what dose for which crop, the nearest help is the upazila agriculture office and the sub-assistant agriculture officer at union level. These staff of the Department of Agricultural Extension can advise with an understanding of local soil and season.

Seed treated the right way produces more and resists disease better. The work is within every farmer's reach and costs little, but it matters a great deal. Selection, treatment, storage, the germination test and preparation before sowing: follow these five steps season after season and the results will show in the field.

The handfuls of grain drying in the courtyard at the start of this report are the first capital of the coming season. Looking after that capital protects the work of the whole season.

Photo: Germinated paddy seed on trays, Prajna Prabhu / Wikimedia Commons (CC BY-SA 4.0)