Seed priming: a simple but successful solution

Every year, mankind relies on the miraculous transformation of seeds into plants and back into seeds again. Yet few people realise the fragility of this transition from seed to seedling. To fulfil their genetic potential, seeds must germinate and seedlings emerge, quickly and uniformly throughout the field so that light, water and soil nutrients may be used for maximum efficiency. Unfortunately, this seldom occurs in the marginal environments of the semi-arid tropics. Unpredictable and erratic rainfall, poor soils, low/inferior quality seed and limited access to reliable draft power all contribute to a situation where good crop establishment is often the exception rather than the rule. Sparse crops need to be re-sown, which is expensive and can lead poor farmers into crippling debt. If farmers are to improve their livelihoods, solutions must be found, however simple, for better germination and establishment of crops. Fortunately, such solutions are available.

Credit: Dr D Harris - DFID plant sciences research programme

Once sown, seeds spend significant amounts of time just absorbing water from the soil. By reducing this time to a minimum seeds can be made to germinate, and seedlings emerge, more quickly. The easiest way to do this is to soak seeds in water before sowing. This is not a new idea, of course. When asked, farmers in India, Nepal, Pakistan, Botswana, Malawi and Zimbabwe all reported that they, or their fathers, had soaked seed before. Remarkably, however, soaking was only ever done when conditions were poor - to "catch up" on time lost to drought. Soaking was never done on a regular basis and the duration of soaking was highly variable. Thus results had been mixed.

Researchers from the Centre for Arid Zone Studies (CAZS), funded by the Plant Sciences Research Programme of the Department for International Development (DFID), have taken a fresh look at this "on-farm" seed soaking or "priming". In collaboration with resource-poor farmers, they calculated "safe limits" - the maximum length of time for which seeds can be soaked and which, if exceeded could lead to seed or seedling damage - for maize, upland rice, wheat, chickpea and sorghum. Farmers modified these limits to "overnight" for all crops and implemented simple on-farm trials in which the performance of primed seed was compared with that of non-primed seed. The results were remarkable. Farmers reported that primed crops emerged faster and grew more vigorously. They also flowered earlier (very important in drought-prone areas), matured earlier and gave higher yields. Priming has therefore become very popular with collaborating farmers and their friends and neighbours because it is simple and cheap yet extremely effective.

On-farm seed priming seems to be a robust, widely applicable technology and its effects are generally independent of the crop variety used. This is important, because priming can be used to "add value" to the benefits achieved by using improved, modern varieties. For example, large areas of India and Bangladesh are left fallow after the rainfed rice crop has been harvested because, although there is still plenty of water stored deep in the soil, the surface dries out too quickly to allow another crop to germinate and establish. The International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) has been promoting the use of chickpea in such an area in Bangladesh called the Barind. Scientists have found that even with modern, high yielding varieties yields are low, around 1.1 tonnes per hectare. However, in a recent set of 30 on-farm trials priming of seed by soaking raised average yields by almost 50%. Consequently, with yields over 1.5 tonnes per hectare, chickpea has become a much more attractive crop for Barind farmers to grow on their 140,000 hectares of fallow land.

This just goes to prove that high-tech results can be obtained from low-tech solutions.

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