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Crop Production and Management - Harvesting and Storage of Food Grains

Grade 8CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Harvesting is the process of cutting the crop after it is mature. For cereal crops, it usually takes 33 to 44 months to mature.

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Harvesting can be done manually using a sickle or by a machine called a harvester. In the combined process, a machine called a 'Combine' acts as both a harvester and a thresher.

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Threshing is the process of separating the grain seeds from the chaff. For small-scale farmers, winnowing is used to separate grain and chaff using the wind.

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Storage is the final step where grains are protected from moisture, insects, rats, and microorganisms. Freshly harvested grains have higher moisture content (usually above 18−20%18-20\%).

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To prevent spoilage and germination loss, grains must be sun-dried until their moisture content is reduced to approximately 14%14\% or less.

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Large-scale storage of grains is done in silos and granaries (godowns) to protect them from pests like rats and insects.

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For home storage, dried neem leaves are used. For large godowns, specific chemical treatments (fumigation) are used to protect grains from pests and microorganisms.

📐Formulae

Moisture Content (%)=(Weight of fresh grain−Weight of dried grainWeight of fresh grain)×100\text{Moisture Content (\%)} = \left( \frac{\text{Weight of fresh grain} - \text{Weight of dried grain}}{\text{Weight of fresh grain}} \right) \times 100

Crop Yield=Total mass of harvested grainTotal area of land used\text{Crop Yield} = \frac{\text{Total mass of harvested grain}}{\text{Total area of land used}}

💡Examples

Problem 1:

A farmer harvests 500 kg500\text{ kg} of wheat which contains 20%20\% moisture. After sun-drying, the moisture content drops to 12%12\%. Calculate the approximate mass of the wheat after drying.

Solution:

Let the initial mass be Mi=500 kgM_i = 500\text{ kg} and initial moisture be 20%20\%. The dry matter content is 80%80\% of 500 kg=400 kg500\text{ kg} = 400\text{ kg}. After drying, this 400 kg400\text{ kg} represents 100%−12%=88%100\% - 12\% = 88\% of the final mass MfM_f. Therefore, 0.88×Mf=400  ⟹  Mf≈454.55 kg0.88 \times M_f = 400 \implies M_f \approx 454.55\text{ kg}.

Explanation:

Since only water evaporates during drying, the mass of the 'dry matter' remains constant. We calculate the dry matter first and then find the new total weight based on the target moisture percentage.

Problem 2:

Explain the dual function of a 'Combine' machine in modern agriculture.

Solution:

A 'Combine' machine performs two distinct operations: 1. Harvesting (cutting the mature crop) and 2. Threshing (separating the graingrain from the chaffchaff).

Explanation:

The machine automates the labor-intensive process of manual cutting and subsequent beating of the crop to release seeds, increasing efficiency and reducing time.