Template:Chapter 1.3

2.3 – Soaking seeds before planting (seed priming)

Samantha Martin, University of Guelph, Canada

Introduction

There are many problems that subsistence farmers face all over the world. One major problem that affects both yield and income equally is low germination rates for several important crops. “In the semi-arid tropics, … unpredictable and erratic rainfall, poor soils, [and] low quality seeds” contribute to low germination rates; so as a result, many farmers are forced to plant 2-3 seeds per hole while only expecting one of these seeds to properly establish itself in the soil (DFID, 2000). Poor crop establishment also occurs because these seedlings are unable to outcompete weeds for nutrients in the soil as well as for water and sunlight. The transition from seed to seedling is a very fragile one. If a seed is to grow properly, seeds must germinate and emerge, both fast and consistently in the field so that the seedlings can maximize the growing benefits from water, light and nutrients from the soil (CAZS, 2007). A very simple intervention that farmers can use to improve germination as well as strengthen their seedlings is to soak their seeds in water before planting them. This chapter will describe seed soaking and its benefits, provide a breakdown of methods including correct usage, discuss the issues with seed soaking, as well as provide alternatives to using water to soak seeds.

Description of seed soaking

Seed soaking is a very simple intervention to both understand and to put into practice. This practice includes soaking seeds in water for a prescribed amount of time, drying them, and then planting. “Seeds that are pre-hydrated and then surface-dried have a better chance of absorbing water from the soil because they germinate more quickly and the roots they produce grow faster, seeking moisture deep in the ground” (DFID, 2007). Once seeds are soaked and dried, they can either be immediately sown into a field, or they can be kept in storage for several days if weather conditions delay planting (DFID, 2007).

Benefits to seed soaking

There are many benefits to soaking seeds before planting. First, soaking seeds mainly increases germination rates among many different crops. Studies and farmers have reported, “that primed crops emerge faster, grow more vigorously, and in some cases use less fertilizer” (DFID, 2000). These effects allow seedlings to outcompete weeds for water, light and nutrients from the soil, which in turn suppresses weeds and makes crops less susceptible to disease (CAZS, 2007; Anwar et al., 2012). Next, because uniform germination is much higher when seeds are soaked, farmers can increase their overall yield because, rather than planting 2-3 seeds per hole, they can plant 1 seed per hole, thus giving farmers more seeds to plant, and more yield (reported yield increases have ranged from 20% to >200%) (CAZS, 2007). After soaking chickpea seeds for 16 hours and then drying them to approximately 30% moisture content, there was a reported 40% yield improvement than when seeds were not primed (Ghassemi-Golezani, 2008). Furthermore, soaked seeds are reported to emerge faster (approximately 1-3 days sooner), flower and mature earlier (up to 10 days sooner), which means that if there is a second crop being planted, it can also be planted sooner (CAZS, 2007; Ibrahim, et al., 2013). In a study conducted regarding soaking wheat seeds, seeds that were not soaked reached 50% emergence in approximately 5.5 days, whereas seeds that were soaked for 8 hours reached the same stage at approximately 3.5 days (Murungu, 2011). Upland rice also had similar results – when seeds were not soaked there was a 59% germination rate of seeds planted. However, when seeds were soaked for 12 hours and dried for 2 hours, there was a 78% germination rate among planted seeds (Ibrahim, et al., 2013). Moreover, this practice allows farmers to sort their seeds at the same time and remove those seeds that float to the top because they are deficient or diseased from those that sink to the bottom and should be planted (IRRI, 2016). Finally, there is essentially no cost and low-risk associated with seed soaking, so “it should be very attractive for farmers to prime their seed as a form of insurance” (Rajbhandari et al., 2014).

How to: Seed soaking

Submerge seeds to be planted in a bucket of water.

Once placed in water, remove the seeds that float to the top as they are diseased or defective and will not grow properly if planted.

Consult a ‘safe-limit’ table to determine the proper amount of time to soak seeds. Do not soak for less or more time than is recommended.

Dry seeds after the soaking period, either by laying them in the sun or by using a cloth. Sow seeds immediately, or store them in a dry location if sowing is delayed (IRRI, 2016).

Correct usage

The most important aspect of seed soaking has to do with the amount of time that the seeds are soaked for. In order for seed soaking to have a positive effect on germination, the seeds cannot be under or over soaked. If seeds are under soaked, they will not realize all the benefits of seed soaking and if seeds are over soaked, they have the potential to germinate before being planted. This causes new problems for subsistence farmers because they are no longer sowing seeds, but rather transplanting seedlings. The Centre for Arid Zone Studies at Bangor University researched the prime soaking time for many different tropical crops. Table 1 shows these recommended soaking times.

Table 1. Recommended soaking times for tropical crops (reproduced from CAZS, 2007)

Tropical Crop	Soaking Time (in hours)
Bambara groundnut	8
Chickpea	8
Finger millet	8
Lentil	12
Maize	12 - 18
Mungbean	8
Pearl millet	10
Sorghum	10
Upland rice	12 - 18
Wheat	12
Barley	12
Cowpea	8
Groundnut	8
Horsegram	8
Linseed	8
Pigeonpea	8

The majority of crops require 8 hours of soaking before it will make a viable difference to their germination and growth. For most farmers, this would entail soaking the seeds overnight and then using the next day to dry them.

Helpful Links To Get Started

Here are websites to find more information about how to obtain gloves:

Alibaba

Indiamart

Store Nzfarmsource

Adenna

Farmcity

Crazystore

Usefull Images

References

Espasandín-Arias, M., & Goossens, A. (2014). Natural rubber gloves might not protect against skin penetration of methylisothiazolinone. Contact Dermatitis, 70(4), 249-251. doi:10.1111/cod.12221

European Commission For The Control Of Foot-And-Mouth Disease. Suggested FMD PPE guidelines - Food and Agriculture, (2016) Food and Agriculture Organization. Rural women in household production: Increasing contributions and persisting drudgery. (2016).

Furlong, M., Tanner, C. M., Goldman, S. M., Bhudhikanok, G. S., Blair, A., Chade, A., . . . Kamel, F. (2015). Protective glove use and hygiene habits modify the associations of specific pesticides with Parkinson's disease. Environment International, 75, 144-150. doi:10.1016/j.envint.2014.11.002

Keeble, V. B., Correll, L., & Ehrich, M. (1996). Effect of Laundering on Ability of Glove Fabrics to Decrease the Penetration of Organophosphate Insecticides Through in vitro Epidermal Systems. J. Appl. Toxicol. Journal of Applied Toxicology, 16(5), 401-406. doi:10.1002/(sici)1099-1263(199609)16:53.3.co;2-6

Kim, J., Kim, J., Cha, E., Ko, Y., Kim, D., & Lee, W. (2013). Work-Related Risk Factors by Severity for Acute Pesticide Poisoning Among Male Farmers in South Korea. International Journal of Environmental Research and Public Health, 10(3), 1100-1112. doi:10.3390/ijerph10031100

Melco, M. (2016). Gardening Gloves. Retrieved from Garden Lovetoknow

Schaffner, A. D. (2013). Minimizing Surgical Skin Incision Scars with a Latex Surgical Glove. Aesthetic Plastic Surgery, 37(2), 463-463. doi:10.1007/s00266-013-0071-y

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