Studies On The Factors Affecting Shaanxi Apple Safety And The Relative Control Techniques

Food and agricultural product safety is one of the key problems paid more attention by foreign and domestic people nowadays. Studies on the factors affecting agricultural product safety and their control techniques have also caught wide attention. Apple is one of the most important fruits in the world. Few researches on fruit safety are conducted even though China ranks first in the world for apple production and exportation. Shaanxi, as one of the good quality apple production regions in the world, ranks first in China for its apple production. The objective in this research was to supply with technical basis for apple safety production through studies on the factors affecting apple safety and their control techniques. From 2003 to 2005, the main technical indexes of fruit safety and environmental quality in the apple production bases distributed in more than 15 counties in Shaanxi were monitored and analyzed. The agricultural material (pesticide, fertilizer, etc.) market and reality utilization by family hold were traced and investigated in some of the key counties. The effects of the production links including pesticide and foliage fertilizer application, bagging, etc. and the tail gas of the car, etc. on fruit safety were studied crucially. At the mean time, the regulating and controlling effect of orchard grass on soil nutrition and water were researched and the circulating effect of the ecological orchard production mode linked by marsh gas was also investigated in this paper. The main results were as follows:1. Even though the contents of nitrate and nitrite in apple fruit were far less than the limited standard provided by the national government in Shaanxi, the rate of pesticide residual found in the test and the content of heavy mental in fruit were relatively high, which were main factors affecting apple safety in which dimethoate, a kind of organic phosphorus pesticides, and carbendazim, a kind of fungicides, were key objects for controlling pesticide residual nowadays. Lead, fluorin, arsenic and cadmium, etc. were key objects for controlling pollution caused by the elements of heavy metals.2. The main indexes of environmental quality in Shaanxi apple production base tally with the standard required by the state no harmful food and green food production, in which the content level of SO2 and NOx in air, the contents of mercury, cadmium, copper and lead in soil and the contents of lead, chromium, fluorin, mercury in irrigation water were far less than the limited standard of environmental quality for green food - apple production in Shaanxi apple production base. According to the standard of environmental quality for green food production in the production base, even though the contents of suspending polluters (TSP) and fluoride in atmosphere as well as arsenic and chromium in soil did not exceed the standard, the pollution indexes were relatively high, which were key factors for controlling environmental quality in the production base.3. Different kinds of pesticides and application methods produced great effect on the content of pesticide residual in fruit. The decomposing rules of the organic phosphorus (chlorpyrifos and parathion) and pyrethroid (fenpropathrin and cyhalothrin) pesticide residuals were different. The residual level in fruit increased significantly as the pesticide application concentration and the spray time increased. The contents of fungicide residuals in fruit varied greatly when the fungicide was sprayed in different intervals between spray time and fruit harvest time before fruit harvest. There was no residual found in the test when the interval was 30 days, but the residuals were found in the test respectively when the intervals were 20 and 10 days respectively. The amount of pesticide residual increased and the interval of the days between spray time and fruit harvest time when pesticide residual was found in the test prolonged as the pesticide application concentration increased.4. The arsenic contents in soil and all organs of the fruit tree showed an increased trend after asomate was sprayed in the orchard. In which arsenic contents in trunk barks, bough barks, and taproots accumulated more compared with the other organs. The arsenic contents in whole fruit, fruit flesh and fruit core were higher than control, which showed that the arsenical pesticide took part in the metabolism in tree, arsenic pollution manifested permanently and extensively in apple orchards.5. Fruit bagging reduced the lead contents of fruits. Spraying fertilizer on the fruit tree leaves and the bus tail gas beside the roads were main approaches to contaminate apple trees by heavy metal. The leaf fertilizers generally had heavy metal elements, such as chromium and lead, etc. which increased the level of chromium and lead contents in apple fruit and leaves to different extent. The phenomenon of fruit contamination showed that the residual was in the pericarp. The phenomenon of leaf contamination showed that the heavy metals were absorbed on the surface and in the tissue, i.e. double pollution. Fruits, leaves and orchard soil were contaminated by bus tail gas which contained lead particles to different extent within 200 meter scope beside the national roads. Especially, the most contaminated area was within 100 meter away from national roads. In this range, the contents of lead in apple fruit were beyond the national standard of non-harmful fruit quality.6. The pericarp of apple fruit was the main residual part of pesticide and heavy metal. The flesh and core parts had less residual.7. To grow forage grass in the apple orchard in dry land of Weibei, Shaanxi had important effect on soil nutrient and water change in 0-40cm soil layer. The organic matter contents in soil of apple orchard growing grass could increase 0.1 percent to 0.15 percent every year. The contents of whole nitrogen, whole phosphorous and whole potassium in soil showed the changes of"S"curve in the seasons of a year. The contents of hydrolyzed nitrogen, quick-acting phosphorous and potassium increased. The total water storage capacity in the orchard was reduced due to the water competition between the forage grass and fruit trees. The ecological orchards based on growing forage grass and linked by marsh gas pool, formed"five sets together"including forage grass, livestock, marsh gas, cellar and fruit, which increased organic fertilizer source and reduced the amount of chemical fertilizer and pesticide. The efficiency of production was improved.8. To develop green food is the main effort direction and objective in future. Area layouts are optimized on the basis of investigation and study. Monitoring Agricultural material market, utilizing pesticide safely and using fertilizer properly are the key links for controlling quality safety. The integrative pest and disease prevention and control technical system characterized mainly by biological and physical control should be built and completed step by step. The fertilizer application system mainly using organic fertilizer and soil manage system based on growing forage grass are established. The fruit culture through fruit bagging is the key measure for apple safety production in Shannxi. Developing ecological orchards based on growing forage grass in orchard and linked by the marsh gas pool is a leading production mode to ensure fruit quality safety.