Template:Chapter 1.2.
1.2 - Low-Cost Grain Moisture Sensor for Drying and Storing Grain
Amanda Poulton, University of Guelph, Canada
Suggested citation for this chapter.
Poulton,A (2022) Low-Cost Grain Moisture Sensor for Drying and Storing Grain. In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org
Introduction to Grain Moisture
On average, farmers living in the tropics experience 1000-2000 mm of rain per year accompanied by intense humidity (FAO, 2001). Having a dry and safe environment is critical in terms of storage to ensure that seeds remain viable for consumption (FAO, 1988). If the drying process is performed incorrectly, it can have a very detrimental impact on the grain. In order to address issues regarding excess moisture, it is critical to look into effective and low-cost solutions that prevent moisture increases during storage. With no solution, there is an inherent risk for increased pests, molds, and pathogens, allowing for the quality of grain to degrade. Seed germination post-harvest will decrease in the presence of excess grain moisture. Within Africa, smallholder farmers experience 20% to 30% post-harvest losses which economically results in an annual loss of $4 billion USD (Armstrong, 2017). Each grain has an exact moisture content that must be achieved to ensure sale, safe transportation and storage. Moving forward, simple technologies are essential for farmers to measure the moisture content level of their grain.
Implications of Wet Seeds
seeds fail to adequately dry, they risk exposure to fungi; this occurs as a result of cool temperatures and high humidity, trapping the moisture within the grain (Danao et al., 2015). When moisture is retained within the grain during storage, respiration increases, ultimately triggering the grain to germinate prematurely (FAO, 1988; Danao et al., 2015). When these seeds are contaminated by fungus/mold, they are no longer viable and cannot be harvested or sold for the upcoming seasons, resulting in an economic loss and increasing the potential for malnourishment (FAO, 1988).
Wet Seeds Attract Insects and Mold
While grain and seeds are in storage, humidity and grain moisture interact. If a seed fails to properly dry and/or experiences temperatures increases, the seed will release moisture into the air, creating an excess amount of humidity (Taruvinga et al., 2104). Seeds consumed by moisture will invite primary and secondary pests to infect the grains (Taruvinga et al., 2014). A primary pest is one in which will attack undamaged grains as well as damaged grains, and a secondary pest will attack previously invaded grains from primary pests (Taruvinga et al., 2014). Examples of primary insects in Africa are the grain weevil, the larger grain borer, the lesser grain borer, the grain moth and the cowpea weevil; and examples of secondary pests that arise in Africa are the red rust flour beetle and the tropical warehouse moth (Taruvinga et al., 2014). Mold has a huge impact on agricultural seeds and grains in storage, causing nutrient degradation, changes in odour and colour, and causes seed inability to germinate (Taruvinga et al., 2014).
Proper Moisture Content for Diverse Seeds
Table 1 shows the ideal grain moisture percentage for different crops present in 27°C environments. If seeds are intended for human consumption, they should be dried an extra 2% to ensure the absence of all fungal growth which may otherwise deposit mycotoxins (FAO, 1988). When examining seeds that have been in storage, a small-holder farmer should conduct a germination test to ensure the viability of the seeds before planting. This consists of planting fewer seeds before planting all seeds to prevent a decrease in food production.
Table 1: Target Equilibrium Moisture Content (EMC) (FAO, 1988)
Introduction to Low Cost Grain Moisture Sensors
The grain moisture sensor assists in measuring levels of moisture in the grain using a probe. The size of the meters varies from relatively small to large units. These meters are quick, simple and efficient and take only 1 minute to produce a moisture reading. In order for moisture to be measured, grain is dropped into the barrel of the meter. The funnel which is attached to the top of the barrel is taken off and all seeds are collected in the chamber. From here, the moisture readings are available to be read.
There are two relatively small low-cost solutions that can easily be accessed. The first product is a “Digital Grain Moisture Meter” (Fuzhu, 2011). This meter costs $10.80 USD and can measure moisture content in up to 14 different crops. This meter can measure moisture ranging from 7.5% to 50%, by utilizing robust moisture probes. This probe does require 4 AAA batteries, but it is reported to have a slightly longer battery life than other models. Another low-cost option is the “LGS-1G Cup Grain Moisture Meter”; however it costs $58.00 USD, and can measure the moisture content in the ranges of 3-35% (Haosen, 2016). The advantage of this more expensive option is that it can be applied to 24 different kinds of grain and comes with manual instructions inside a briefcase to keep everything organized and protected. This meter provides readings for moisture, the capacity as well as the weight of the grains/seeds, however a downfall is its battery requirement in addition to an electric outlet. This meter can also be purchased on the website “Alibaba”.
Additionally, a project directed by Kansas State University focused on giving a particular grain moisture meter to several small-holder famers to measure the benefits (Armstrong, 2107). This meter is called the PHL, which stands for “Post-Harvest Loss” (Armstrong, 2107). This meter was used to measure the moisture content in seeds of maize and other crops specifically focusing on the temperature and the humidity. The probe was able to read moisture from bags and bulk seeds (Armstrong, 2107). PHL meters cost $28 USD and were effective for small-holder farmers: the feedback suggested to add a newer sensor model which would reduce the price to $3 USD, manufactured by Sensirion (Armstrong, 2017).
Durability and Ease of Use These products were said to have strong durable probes (Fuzhu, 2011), along with lasting batteries that therefore do not have to be changed as frequently. Nevertheless, a common problem would consist of having to purchase new batteries which might be costly and inaccessible in remote regions; to prevent this problem, the meters should be turned off at all times when inactive and only be used when necessary. The more expensive meter comes with a briefcase, as already noted, in order to ensure the durability and safe keeping of the meter (Haosen, 2016). Small-holder farmers can share the probes which can reduce the costs. These meters come with instructions on how to use them and how to read the moisture content. Language translation may be helpful, along with picture-based instructions for low literacy populations.
More expensive moisture sensor probes
In addition to the low cost grain moisture sensor, there are a variety of more expensive options. A more elaborate grain moisture probe consists of 4 chambers and includes a total of 6 probes (Danao et al., 2015). These probes are highly priced at $1500 USD each; the breakdown of the cost is $1000 per sensor, $100 for hardware and $400 for required power and electrical components, which would be out of reach of small-holder farmers (Danao et al., 2015).
Free, Alternative Methods to Determine if Seeds are Dry
Some moisture meters can be shared between small-holder farmers and may be available at public grain storage facilities (Taruvinga et al., 2014). However, public storage facilities may be remote or inconvenient as specific times; therefore other solutions may be needed to measure grain moisture content. These methods include using one’s teeth to bite the hard seeds; pinching the seeds; or shaking the seeds (Taruvinga et al., 2014). When determining the moisture within the seeds, the seed is dry enough if the seed is hard to the touch, makes sharp sounds or cracks (Taruvinga et al., 2014). Another free and relatively efficient method consists of placing grains in a jar with dry salt for a few minutes. After a few minutes, if the salt is detected on the sides of the jar, then the moisture content is too high; however if the salt is absent from the glass, it has an acceptable moisture content for storage (Taruvinga et al., 2014).
Other grain storage issues
When focusing on the viability of the seeds, one should make certain each seed is dry before being placed in storage (Taruvinga et al., 2014). Aside from proper grain drying, temperature and other issues must also be considered for storing grain. The most effective conditions for storing seeds are at low temperature with little to no moisture: the maximum being 27˚C and 70% relative humidity (FAO, 1988). It is important to note grains being stored in stacks can accommodate temperatures 1-2% higher (FAO, 1988). If temperatures exceed 25°C or fall below 35°C, insects achieve an optimal temperature to destroy the grains, and if the temperature ranges from 15°C and 30°C mold will thrive; however a temperature below 15˚C prevents insect and mold growth (Taruvinga et al., 2014). Grain can easily become affected by insects, mold, and rodents. To ensure the best insect resistant grain, all dust and contaminants should be removed before storing; this can be achieved through threshing (e.g. beating grain heads on the ground) to ensure the removal of insects and pests (FAO, 1988).
Helpful Links To Get Started
https://www.youtube.com/watch?v=NqnNfTqOkhk&ab_channel=Bry-Air%28Asia%29Pvt.Ltd.
YouTube video explaining seed retardation and giving other viable seed drying options.
https://www.youtube.com/watch?v=WztV5c5Hlxk&ab_channel=ThomasTKtungnung
A video describing the vital importance of having dry seeds in storage.
https://www.fao.org/3/AD230E/AD230E04.htm
A text providing useful tips for seed storage and seed handling.
https://www.fao.org/3/i1816e/i1816e00.pdf
A textbook providing the attributes of seeds, and whether or not they are healthy, also allows for information in seed testing and seed sampling.
https://www.fao.org/3/CA1495EN/ca1495en.pdf
A textbook chapter on proper and effective seed storage.
https://www.youtube.com/watch?v=dLwDQZmALvQ&ab_channel=PARISATECHNOLOGY.
This video included shows how to put together and how to utilize the “Digital Grain Moisture Meter”.
A website (Alibaba) where you can purchase a “Digital Grain Moisture Meter” for $10.80 USD.
A website (Alibaba) where you can purchaser a “LGS-1G Cup Grain Moisture Meter” for $58.00 USD.
https://www.youtube.com/watch?v=wTgZzF-MiK0&ab_channel=SKZINDUSTRIAL
A video giving descriptions on how to use the “LGS-1G Cup Grain Moisture Meter”.
References
1. Armstrong, P. R. (2017). Development and Evaluation of a Low-Cost Probe-Type Instrument to Measure the Equilibrium Moisture Content of Grain Applied Engineering in Agriculture, 33(5), 619–627. https://doi.org/10.13031/aea.12266
2. Haosen (Shenzhen) Electronics Technology (2016). Cup Grain Moisture Meter. Alibaba.com. Retrieved November 11, 2021 from https://www.alibaba.com/product-detail/Grain-Moisture-Factory-Wholesale-LGS-1G_1600227103518.html?spm=a2700.galleryofferlist.normal_offer.d_title.79c23bb0P73T0S&s=p
3. Fuzhu Heado Thade (2011). Digital Grain Moisture Meter Hygrometer use for Corn Wheat Rice Bean Peanut Grain Measurement Moisture Humidity Tester AR991. Alibaba.com. Retrieved November 11, 2021 https://www.alibaba.com/product-detail/Grain-Moisture-Digital-Grain-Moisture Meter_1600093027696.html?spm=a2700.galleryofferlist.normal_offer.d_title.79c23bb0asKvXw&s=p
4. Danao, M.-G. C. (2015). Development of a Grain Monitoring Probe to Measure Temperature, Relative Humidity, Carbon Dioxide Levels and Logistical Information During Handling and Transportation of Soybeans. Computers and Electronics in Agriculture, 119, 74–82. https://doi.org/10.1016/j.compag.2015.10.008
5. FAO (1988). Farm Structures in Tropical Climates: Chapter Grain Crop Drying, Handling and Storage. Food and Agriculture Organization, Rome. Retrieved November 2, 2021, from https://www.fao.org/3/i2433e/i2433e10.pdf.
6. FAO (2001). Global Ecological Zoning for the Global Forest Resources Assessment 2000 Final Report. Food and Agriculture Organization, Rome. Retrieved November 2, 2021, from https://www.fao.org/3/ad652e/ad652e00.htm7. Kandala, C. V. K. (2012). Non-destructive Measurement of Moisture Content of Different Varieties of Wheat Using a Single Calibration with a Parallel-Plate Capacitance Sensor. Transactions of the ASABE, 55(4), 1583–1587.
8. Taruvinga C., Mejia D., & Alvarez S.J. (2014). Appropriate Seed and Grain Storage Systems for Small-scale Farmers: Key practices for DRR Implements. FAO, Rome.E-ISBN 978-92-5-108335-2. https://www.fao.org/3/i3769e/i3769e.pdf