Improvement in Crop Yields: Quick Revision

A brief note on Improvement in Crop Yields. Read it before a test. Try each question at the end before you open its answer.

Better varieties

• Farmland is limited, so the yield from each hectare must rise.
• Kharif crops are sown in June with the rains. Rabi crops grow in winter, from November to April.
• Hybridisation crosses two parents: intervarietal (two varieties), interspecific (two species of one genus) or intergeneric (two genera). Genetic modification adds a gene.
• Aims: higher yield, better quality, resistance to biotic and abiotic stress, a shorter time to ripen, wider adaptability and a useful plant shape.

Managing the crop

• A plant needs 16 nutrients: 13 from the soil, 6 of them macronutrients and 7 micronutrients.
• Manure adds organic matter. It includes compost, vermi-compost and green manure. Fertilisers give nitrogen, phosphorus and potassium.
• Irrigation: wells, canals, river lift systems and tanks.
• Cropping patterns: mixed cropping, inter-cropping and crop rotation.

Protecting and storing

• Weeds, insect pests and diseases lower the yield. Pesticides work but are poisonous.
• Use good field preparation, timely sowing, inter-cropping, crop rotation, resistant varieties and summer ploughing to need less chemical.
• Stored grain is lost to biotic causes (insects, rodents, fungi, mites) and abiotic causes (moisture, temperature).
• Prevent the loss: clean, dry and fumigate.

A worked example

A farm has $8$ hectares of wheat. Each hectare gives $2500$ kg. A fifth of the harvest is spoilt in an untreated store, but only $2\%$ in a treated store. How much grain does the treatment save?

1. The harvest. $8 \times 2500 = 20\,000$ kg.
2. Untreated. $20\,000 \times 0.8 = 16\,000$ kg are kept.
3. Treated. $20\,000 \times 0.98 = 19\,600$ kg are kept.
4. Saved. $19\,600 - 16\,000 = 3600$ kg.

Practice with new numbers

A program to try

The program follows the grain in the worked example.

Mistakes to avoid

• Mixing up the hybrid kinds. Intervarietal is two varieties, interspecific is two species and intergeneric is two genera.
• Calling manure and fertiliser the same. Manure is rotted waste with organic matter. Fertiliser is factory-made nutrient.
• Mixing up mixed cropping and inter-cropping. Inter-cropping has a definite pattern of rows.
• Thinking a herbicide kills insects. Herbicides kill weeds, and insecticides kill insects.

Check yourself

1. Why must the yield from each hectare be raised?

2. What kind of hybridisation crosses two species of the same genus?

3. What is green manure?

4. Name the three steps that protect stored grain.

5. Why is too much pesticide harmful?