عنوان مقاله [English]
In the foreseeable future, plants are still the most important source of human food supply, and given the rapid rise in demand for food in developing countries, the demand for food will increase sharply over the next 20 years. Compression is the most important factor in increasing agricultural production. One of the useful indicators in determining the compression rate is the use of agronomic index. In Nepal, an applied definition has been used to compress agriculture, which includes increasing the number of crops per unit area in a crop season, along with the trend of chemical changes to improve plant performance. One of the important indicators used by many researchers is made by Boserup (1966). In this definition, agricultural compression means increasing the cultivation of crops in a given period in an agricultural system., The idea of increasing the frequency of planting important crops originated in agriculture prior to industrialization and was the only way to increase crop production in one year. This concept later became more comprehensive by other researchers by adding the differences in the length of sowing and planting of crops. In a number of studies, the frequency of products indicating the amount of land use has been used as a compression index.
In order to study the trend of changes in crop density, agronomy and stability in agricultural production, statistical data of 15 agricultural variables including crop area and rainfall in different provinces of the country for the period of 50 years from 1961 to 2011 have been obtained from the Statistical Yearbook, databases The Ministry of Agriculture, the Center for Statistics of Iran and the FAO Database.
Agronomic index was used to study the land use status of arable land and an aspect of compression including land cover with one-year cultivars.
Result and Discussion
Based on the average, total agricultural density in 1971, 2004 and 2011were 9.26, 8.48 and 8.80, respectively, and the mean of three years was 8.94 months. The lowest index of agricultural density index in 1350 belonged to southern coastal provinces (Hormozgan and Bushehr) and Mazandaran with average of 6.98 and 7.33 months, respectively. In 2004 Guilan and Mazandaran provinces had the least index of 4 and 62.5 months, and in 2011 the lowest rate of this indicator was in Gilan and southern coastal provinces, with a period of coverage of 63.6 and 5.3 months, respectively. Considering that in most regions of the country more than half of the cultivated area is allocated to wheat, and also wheat remains on the ground longer than the other crops, therefore, wheat cultivation owns the most important share in the determination of the index of agronomic agglomeration (or crop cover). On the other hand, in the northwestern regions due to climatic conditions and colder periods of time, cereals especially wheat remail on the ground longer ,so the main reason for the higher index of agronomy in these areas is that wheat is present at the surface of earth. The study of agronomy in the country's arable crops showed that, contrary to expectation, in areas with higher rainfall the duration of land cover is less and soil remains without cultivation a long time in the year, due to the cultivation of crops such as rice. Therefore, changing the pattern of planting is essential in these areas .
The results of this study showed that due to the dominance of cereal cultivation in cropping pattern, crop density was affected by the cropping area of these plants. Food security is one of the basic needs and increasing the production per unit area isone of the important ways to achieve it. So, changing the pattern or planting system is necessary in areas where compression is low.