Agricultural Inputs

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From the viewpoint of stability, all agricultural ecosystems (agroecosystems) may be divided into two groups. First are natural pastures and hayfields, which can preserve their stability without anthropogenic inputs. Second are arable lands, permanent crops, and artificial pastures and hayfields, which can only preserve their stability at the expense of anthropogenic inputs (management practices). Without them, these agroecosystems will be destroyed and replaced by different natural ecosystems.

'Energy' is a necessary resource for modern agriculture. Direct energy inputs (oil, electricity, etc.) ensure the work of tractors, harvesters, and other equipment, the initial processing of products, etc. World agriculture (2001) consumes 189 636 000 toe of direct energy (toe - metric tons of oil equivalent - measures the energy contained in a metric ton of crude oil; 1 toe is equal to 10 kcal, 41 868GJ, or 11 628 GWh). But it is only 2.5% of the total energy consumption in the world (to compare, industry uses 32% and transport, 25.2%). In different parts of the world, energy consumption in agriculture is different. The 'energy

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Figure 1 Dynamics of agricultural and arable lands in the world (1961-2003).

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1980 1985 Year

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Figure 1 Dynamics of agricultural and arable lands in the world (1961-2003).

140.0 130.0 120.0

110.0

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90.0

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1960 1965 1970 1975 1980 1985

Year

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1995 2000

2005

♦ Africa M Asia--Europe--North America South America

Figure 2 The dynamics of agricultural lands in different parts of the world.

Oceania pressure' (toeha-1) is maximum in Europe and Asia and minimum in Africa and Oceania (Table 4).

Indirect energy consumption in agriculture is associated with energy spent for the manufacturing of tractors, equipment and fertilizers; with labor force, etc. The calculation of energy expenses makes it possible to compare different types of inputs in uniform (energy) units. In modern farms (Table 5), the input of direct energy averages about 40%; the input of indirect energy with fertilizers, about 32%; and with equipment and chemical weed-killers, 11-12%. The input of labor force is very small, but in traditional farms in developing countries it may reach 50% and more.

'Fertilizers' are necessary for restoring soil fertility. Organic fertilizers (manure, dung, peat) have been actively used throughout the history of agriculture. Now, their input reaches 10-40 tha-1. The application of mineral fertilizers began at the end of the nineteenth century. In 2005, their consumption reached 157 million tons annually. There are three main types of mineral fertilizers: nitrogen (93 million tons), phosphorus (39 million tons), and

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40.0

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30.0

m

25.0

œ

<

20.0

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5.0

47.5

32.3

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17.0

14.1

Forests

Savannas

Deserts

Tundras Steppes Highlands

Figure 3 Changes in the areas of major biomes (percent of the Earth area) as a result of human activity.

Table 4 Consumption of direct energy in agriculture

Africa Asia Europe N. America S. America Oceania World

Energy consumption (1000toe) 12725 63086 50185 22721 13095 1995 189636

Energy consumption (toe ha~1) 0.046 0.132 0.164 0.085 0.113 0.036 0.127

Table 5 The consumption of energy in a modern farm (corn production, the USA)

Inputs

MJha-1 yr-1

% of total

Gasoline and gas

1395

21.0

Electricity

6436

18.3

Labor force

29

0.08

Tractors and other equipment

4158

11.8

Fertilizers

1 1355

32.2

Seeds

1 869

5.3

Herbicides and insecticides

3162

10.1

Transport

214

0.6

Total

35 218

100

potassium (25 million tons); thus, they are applied in the following average ratios: N(55%):P(25%):K(20%). The world average input of mineral fertilizers is 91.1 kg ha- : from 32 kg ha- in Africa to 144 kg ha- in Asia (Table 6). In some countries, their application may be much higher (Ireland: 600 kg ha-1) or smaller (Congo: 0.1 kg ha-1). In many developing countries, the NPK input is less then the output of these nutrients with agricultural products, which leads to a decrease in soil fertility.

At the same time, big 'fertilizer pressure' results in contamination of food and environmental pollution. A large portion of fertilizers is washed away from croplands into rivers and lakes, which is the cause of their eutrophi-cation (e.g., in Europe, Asia, and North America). Moreover, on the global scale, the use of fertilizers results in deep changes in the character of nitrogen, phosphorus, and potassium cycles in the biosphere. This is especially true with respect to nitrogen. The anthropogenic fixation of nitrogen via the production of nitrogen fertilizers (80 million tons per year) is only a little less than the biological fixation ofnitrogen by all terrestrial ecosystems (100-130 million tons).

'Herbicides' and 'insecticides' are necessary to control weeds and pests. Their active use began in the second part of the twentieth century. Now, the average world rate of their application is 300 gha-1 (fro m 0 in Laos to 2-3 kg ha-1 in the USA and Western Europe and 51 kg ha-1 in Costa Rica). Specialists say that these chemicals help save about one-third of the world agricultural produce. At the same time, their application results in the contamination of not only food products but also natural ecosystems on a global scale (hydrosphere, soils, etc.). Herbicide DDT was found even in Antarctica.

Without 'machineries' and 'equipment', modern intensive agriculture is impossible, because it involves many manipulations with agricultural lands, primary processing, cattle, etc. The average world number of tractors per 1000 ha is 17.6 - from 7 tractors/ha in Africa to 36 tractors/ha in Europe (Table 6). Note that their use results in soil compaction on croplands and additional CO2 emission because of the utilization of fossil fuels. Therefore, agricultural lands, first of all arable lands, play the role of ecosystems with a negative carbon balance on the global scale.

Table 6 Different types of agricultural inputs to croplands

Africa Asia Europe N. America S. America Oceania World

Labor force (men/100 ha) 80 210 10 10 20 5 90

Tractors per 1000 ha 6.9 12.4 35.9 21.7 11.1 7.2 17.6

Fertilizers (kg ha"1) 31.9 144 72.5 89.2 88.4 57.4 91.1

Table 7 Irrigated lands and water input for irrigation

Asia (excl.

Middle

East)

Europe

Middle East Sub-and North Saharan

Africa Africa N. America S. America Oceania World

Irrigated lands (% of total cropland) Irrigation water use

(million m3) Irrigation water (% of the total water consumption)

1 739480 132088 279196 81 33 86

99758 199601 111 812 88 38 68

18 855 2 661 624 72 70

In modern agriculture, 'labor force' is, foremost, the 'management block' of agricultural systems, and only in backward farming, it is the 'energy source'. At present, the average world 'labor force pressure' is 90 men/100ha (from 5-10 men/100 ha in Oceania, Europe, and North America to 210 men/100ha in Asia) (Table 6).

'Irrigation' is one of the biggest inputs to agriculture in arid zones. The world area of irrigated lands is not very large - only 277 098 thousandha, or 18.1% of the total cropland (from 5-8% in Oceania and Europe to 35.3% in Asia) (Table 7). But irrigated lands are the largest consumer of water resources: 2661.2 km3 or 70% of the total world water consumption is spent for irrigation (industry - 20%, domestic use - 10%). In some countries, the portion of irrigation water in the total water use may reach 95-99% (Mali, Cambodia, Thailand, etc.). In the case of normal irrigation, almost 50% of water is lost for evaporation; overhead (sprinkling) irrigation gives 30% losses; and only very capital expensive drip irrigation, 1-2%. Thus, irrigation is the crucial factor altering the water circulation, first of all in arid regions. For example, the disappearance of the Aral Sea is the result of irrigation of large areas in Central Asia. Moreover, intensive irrigation may result in soil sali-nization. Because of salinization, 0.2-0.3 million ha of irrigated land is being abandoned in the world every year.

'Drainage' is one of the types of agricultural inputs in humid zones. The world area of artificially drained lands is about 157 million ha, including 56 million ha in North and Central America, 40 million ha in Europe, and 15 million ha in the former USSR. In Finland, more than 90% of cropland is drained area; in Hungary, 74%; in the UK, 61%. This method of soil reclamation provides possibility to increase crop yields in overmoistened areas, but is also associated with the destruction of peat layers and with a decrease in soil fertility in 15-20 years. Moreover, drainage worsens the water regime of landscapes on a regional scale.

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