In order to increase the total agricultural production, the energy input in agriculture mSst be increased.

Otherwise, the attainment of self-sufficiency in food will be confined to slogan only and will never be a reality.

Though modem agricultural sciences have developed technologies to food the fast-growing population of the world, challenge of the 21st century are different. Some people claim that we have won the Malthusian food-population race. But a recent study by the Johns Hopkins University predicts that there won’t be enough food by 2025 for the world's projected 8 billion hungry mouth unless the population growth slows or agricultural production Increases dramatically. Both these challenges are not easy to solve.

For food production, lot of energy is required. Major energy is spent in fertilizer production. farm machinery, irrigation and pesticides. Agriculture sector produces lots of energy like crops, fuel, wood and crop residues. Both men and animals get energy for their day to day work from food. Wood and crop residues are sources of energy. Thus agriculture sector is l»tn producer and consumer of energy.

In the 21st century, govern-

ment and people will be even more concern on environmental problem. Therefore, energy input to agriculture cannot be increased without taking proper account the environmental issues. All the development activities including agricultural production must be environment-friendly. Food production needs to be increased in a sustainable way.

What is the relationship between food production and energy requirement? Food production and energy requirement intersect at nearly every step of the food system. For crop production, two different kind of energy is required. One is natural energy. 1. e.. the energy from the sum. The other energy is external energy — energy from human, animal, traditional fuel and commercial energy.

During the ancient time, agriculture was dependent fully on the energy of sun and humans. Lana preparation by humans was the main energy input. To produce their own food, plants utilize the energy

from the sun. In the process, plants grow and ultimately render food for human and animal. In the ancient agriculture, one man could produce food for only a few people. Average man cap produce only 75 watts of energy for 8 hours, which is very insufficient to achieve a reasonable standard of living. Later more and more energy has been applied to agriculture and food production has increased accordingly. When people learned the technique of domesticating animals and could use them for agricultural operations. that was a milestone in agriculture. This happened about 6000 years ago.

Draught animals can continuously produce only 500 watts. Human and animal energy together can produce only a bare subsistence standard of living. When more land with the aid of animals. Next energy investment in agriculture occurred when internal combustion engine was used for land preparation as well as for other agricultural operations.

In the USA. 80 per cent of the population were farmers in 1855. In 1916 and 1973. this figure was reused to 33 and 9 pier cent, respectively. Today only 2 Sier cent people of the US are armers.

Within a certain limit, agricultural production increases with the increase of energy input to agriculture. Farmers of the developing countries cannot afford to pay the price of the energy required for optimum crop production and depend mainly on human and animal energy. Therefore, the yield is low. thereby energy used to produce unit quantity of food is high. For example, in India. 5000 kilocalorie (Kcal) of energy is used to produce 1 kg of rice or 3460 kcal of food energy. For each kcal of energy input for rice production. 0.69 kcal of food energy output is obtained. In the US and Japan. 2000 kcal of energy is required to produce 1 kg olrich which means that for each kcal of energy invested for rice production, 1.73 kcal of food energy output obtained.

Agricultural production increases with the use of better inputs like seed, fertilizer, water and piesticides. Modern varieties of crops require lot of fertilizers. The growing population of the past 5 years could never have been fed without an increasing reliance on chemical fertilizers. Al Ihe world level, chemical fertilizer is the largest consumer (58 per cent) of commercial energy in agriculture. In the far east, its share is about 85 per cent. It is use is increasing rapidly in the developing countries and is ahead of farm machinery is respect of its share in commercial energy in agriculture. In the developed countries, farm machinery manufacture and operation is the largest user of commercial energy in agriculture and ac-I count for more than 50 per cent of energy in agriculture.

Nitrogen fertilizer production is very energy intensive.

One kilogram of nutrient requires about two kilograms of fossil fuel for its manufacturing. packaging, transport, distribution and application. Phosphate fertilizer is much less energy intensive than nitrogen. The energy required to mine, concentrate, process, package, transport and distribute one kilogram of nutrient is estimated at 0.33 kilograms of fossil fuel. Similarly for potash. 0.21 kilograms of fossil fuel is required for one kilogram of nutrient.

Irrigation has been used for crop production for a few thousand years. Many traditional varieties can sustain water stress to some extent. But the modern varieties, yielding two to three times more than the traditional varieties, cannot endure water stress. Also, their physiological characteristics are such that they need lot of water. Irrigation is very important for agriculture in the developing countries because it enables to produce 2-3 crop a year. At the world level. 65 per cent of the total commercial energy required for the manufacture and operation of irrigation equipment is used in the developing countries. However, only about 2 per cent of the total commercial energy in agricul-ture are used in irrigation at the global level.

Modern varieties- of most crops are susceptible to insect pests and diseases. Therefore, pesticides are essential for production of modern varieties. Raw materials for pesticides come mostly from the petrochemical industries. Manufacturing. packaging, transport, distribution and application require further enerj^ inputs. The total energy required to supply one kilogram of pesticide has been estimated at about 2.4 kilograms of petroleum equivalent, which means that pesticides are the most energy-intensive agriculture input.

Introduction of modern varieties made is possible to increase yield, hence the total production. For every input use, farm machinery is required. It has made it possible to increase the productivity of land as well as labour. For example, in the USA. in 1855 one person could produce food for only 5-6 persons. In 1955. this figure rose to 18. In 1963 and 1974. the figures were 30 and 55 respectively.

It can be inferred that agricultural production depends on energy input. In Bangladesh, the energy use in agriculture is very low. and so is the yield. Agricultural sector contributes 35 per cent to the gross domestic product (GDP), but the energy input to this sector is only 2 per cent. In order to increase the total agricultural production, the energy input in agriculture must be increased. Otherwise, the attainment of self-sufficiency in food will be confined to slogan only and will never be a reality.

The writer is the Principal Scientific Officer of BARI, Joy debpur.