Agriculture Reference
In-Depth Information
maximization. As a result, the cropping systems changed dramatically from a cereal
cropping for sustaining the family to the economically profitable cotton cultivation.
Compared to 1999, the per capita GDP increased to 6842 Yuan, an increase of
54% ( Table 8.4 ). From the survey in 2006, the average area of farmland per house-
hold was 0.96 ha, with seven persons per household and 6.33 plots per household.
This means that each household was faced with a choice of which cropping system
would be most profitable given the limited farm area.
Unlike the first period, the survey showed that family farms made decisions on
the basis of economics—98% believed that cotton was economically advantageous
compared with other crops. Yet, the demand for wheat was still high. For exam-
ple, 98% of the farms planned to grow wheat for family consumption. These trends
indicate that maximizing crop production was no longer the main goal, but rather
profit maximization was the principal driver (Kong et al. 2004a). With the change in
household's land use objective, the way forward was changing the cropping system
and increasing the rate of fertilizer application.
The second factor is the availability of biomass-C in the form of crop residues,
animal dung, poultry litter, and manure used in an attempt to increase the SOC con-
centration and improve soil quality. The survey showed that it is more difficult for
family farms to return cotton stalks to soil than to retain the straw of wheat or maize.
Thus, only 15% of the cotton residues were returned to the land ( Table 8.5 ). Because
of the high cost, only 43% of the farm households applied poultry litter to the land.
The third issue is that the availability of water resources affected the change in
the cropping system and application rate of fertilizers. The limited availability of
freshwater resources and the high salt content led to an increase in the cultivation
of cotton. Soils of the region are highly prone to salinization (Li et al. 2005), which
increased demand for irrigation water (Kong et al. 2004a,b, 2006). In particular, cul-
tivation of the monoculture of wheat and maize depleted the groundwater reserves
and reduced the amount of water supply. The data of survey showed that 65% of
farm households believed that lack of adequate water supply was the major chal-
lenge to agricultural intensification, followed by soil quality (13%), and the capital
availability (10%).
8.4 CONCLUSIONS
The data presented support the following conclusions:
Economic development led to the availability of biomass-C (crop residues, ani-
mal dung, poultry manure), which could be used as soil amendments, and increased
SOC concentration. Increasing yields of grain crops was necessitated by the growing
demand for food and was achieved by high input of nitrogenous fertilizers.
Conversion of wheat-maize to the cotton-based system was driven by the high
profit margin. However, low input of biomass residues in a cotton-based system
decreased the SOC concentration.
Factors such as the transition of family farms, economic development, limited
availability of water resources, and high salt contents affected the change in rate of
fertilizer application and conversion of the cropping system. More crop residues had
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