Cultivated Land Resources And Grain Security

Faced with the general tendency of "four unchanged-abilities" in supply-demand relationship of grain in our country in the future, namely, unchangeable tendency of population growth, unchangeable tendency of the reduction of total amount of cultivated land resources, particularly, amount of cultivated land per capita, unchangeable tendency of the increasing demand for total amount of grain, unchangeable principle for solving grain problem mainly based on domestic means, and "four hard nuts" situation in grain production, namely, farmers growing grain hard to become rich, scattered cultivated land hard to be scaled, compensation hard to be made for forcibly occupied cultivated land, improved varieties and good methods hard to be popularized, problems concerning grain and grain security become increasingly crucial in our country. The fundamental way to solve the problem of grain security in our country is to increase grain production. And of the ways to increase grain production, the first is to increase the grain-growing areas, the second is to increase unit output. The former must be based on certain amount of cultivated land and the latter must have good quality of cultivated land as safeguard. Meanwhile, attention must be paid on the ecological security in application of cultivated land.By adopting the combination of model prediction and mathematic analysis and aims to ensure the grain security, the thesis studied the dynamic changing tendency of cultivated land resources quantity security, quality security and ecological security, and the relations with grain production after the People's Republic of China was founded. The productive capability and consumption demand of grain in 2030, as well as the situation of grain security were scientifically predicted. Suggestions for protecting and increasing security of cultivated land resources based on grain security were also proposed. The results are of great valuable for protecting the security of cultivated land resources, increasing the ability of grain production, and ensuring grain security in our country.1. A new concept of "cultivated land resources security" was proposed based on synthesizing the past research. Innovatively, it was studied as an overall entity, in which cultivated land resources security includes quantity security, quality security, and ecological security. Moreover, grain security system was studied by being brought into cultivated land resources security, which exploits a new idea for the study of cultivated land resources security in our country.2. In accordance with the features of cultivated land resources security and the actual situation in our country, the system for assessing security of cultivated land resources was established. It adopted "barrel principle", analytic hierarchy process method and index number sum method in combination to conduct scientific assessment and comparative study on the situation of cultivated land resources in 31 provinces (autonomous regions and cities directly under central jurisdiction) in our country and pointed out that the overall situation of cultivated land resources security in our country was worrisome.3. Since the People's Republic of China was founded, annual increase rate of total grain output, affected by the descending reward law, has showed off a feature of gradual decrease with time. The annual decrease rate of cultivated land resources was conformed basically by the annual increase rate oftotal grain output, in a tendency of changing with time. In general, the years when cultivated land resources increase were sure to be followed by the years when total grain output increases, while the years when cultivated land resources substantially decrease were followed by decrease of total grain output, but these two factors were not necessarily synchronous.4. The study showed that in recent years the major process in which cultivated land resources decreased includes four factors. The first is farmland occupied by constructions, the second is farmland returned to Nature for ecological purpose, the third is farmland destroyed by calamity, the fourth is farmland adjusted in agricultural structure. Of these, farmland returned to nature for ecological purpose is the major factor, while farmland adjusted in agricultural structure is the second factor, the percentages of them to the total decreasing of cultivated land were 62.54% and 16.77% respectively. The major factors that lead to disordered non-agricultural occupation of farmland include four factors. The fundamental factor is unclear ownership of property right of land, the direct factor is blind urbanization, the inherent factor is that legal system construction for land is lagging behind, less effort is spent on monitoring and surveillance and on strictly reinforcing laws, the major motive is driven by interest and power.5. Quality of cultivated land in our country appears to be declining, including not only degrading quality of soil and pollution of cultivated land, which lead to static degrade of quality of land, caused by decreasing proportion of organic fertilizer invested, constantly increasing proportion of chemical fertilizer used in improper ratio, and soil erosion, but also policy for dynamic balance of cultivated land, which unilaterally emphasizes balance in quantity of cultivated land, and which leads to dynamic decline of quality of cultivated land. Besides, social economic factors such as population pressure, malfunction in market and errors in policies, are also factors for declining quality of cultivated land in our country.Deposit of soil organic carbon is the medium-sensitive index showing quality of cultivated land. Compared with sensitive indexes of contents of N, P, and K in soil, its description of quality of cultivated land, fertility in particular, is more stable, and it can describe fertility of soil to some extent, and can approximately describe comprehensive indexes of quality of cultivated land. The result of simulation using DNDC model shows that deposit of soil organic carbon in ecological system of cultivated land in our country is "income falling short of expenditure" for a long period of time, and the way to use cultivated land urgently needs improvement, and the overall situation of cultivated land security in our country is not optimistic.6. The major factors that lead to declining situation of ecological security of cultivated land resources in our country include over-abundance and irrational use of chemical fertilizer in cultivated land, pollution caused by pesticide, pollution caused by plastic film, pollution caused by heavy metals, pollution caused by industrial sewage, exhaust and waste, pollution caused by manure of poultry and livestock, pollution caused by municipal waste and stalks of agricultural plants, and soil erosion, etc.7. In a view of grain production and grain consumption as a system, by prediction, this thesis deems that by 2030, this system has an input (productive capability of grain) and an output (grain...