Effects Of Nitrogen Fertilizer Under Simulated Acid Rain Condition On Pakchoi

In this paper, the pakchoi is selected as the experimental material, which is widely planted in our country. Simulated experiment is carried out by outdoor greenhouse. The effects of different p H values of simulated acid rain and different concentration levels of nitrogen fertilizer on growth, physiology, nutrition quality, nutrient content and health quality of pakchoi are studied. This study laid a foundation for further study on the effect of acid rain stress on the growth and development of vegetables, and also provide theoretical basis for reasonable application of nitrogen fertilizer in the cultivation of pakchoi. The main results of the study are as follows:(1):Under the same N application rate condition,the growth indexes of pakchoi decreased with the decrease of p H value of acid rain. Under the same p H value condition, when the sampling time is seventh days and fourteenth days, the growth indexes of pakchoi increased with the increase of N application rate in a certain range of nitrogen fertilizer(0-180 kg/hm2), but when the application rate of nitrogen fertilizer reached a certain level(270kg/hm2), the growth of pakchoi is inhibited. When the sampling time is twenty-first days and twenty-eighth days, the growth indexes of pakchoi increased with the increase of N application rate. Compared with the CK group, the loss rate of the growth indexes of pakchoi decreased with the increase of N application rate under different concentration levels of nitrogen fertilizer. This shows that in the presence of acid rain, appropriately increase nitrogen concentration is helpful to reduce the harm of acid rain on crops(2):The chlorophyll content of pakchoi increased with the increase of the growth time. From the beginning of the seventh day of spaying acid rain, under the same N application rate condition,acid rain with different p H values has an effect on the chlorophyll content of pakchoi, that is p H2.5<p H4.5<CK. Under the same p H value condition, with the increase of N application rate, the chlorophyll content of pakchoi increased. The results showes that the application of nitrogen fertilizer could significantly improve the chlorophyll content of pakchoi. Under the level of CK, the SPAD values of N0 group than N90, N180 and N270 group are respectively low 2.9, 4.33 and 6.8 in harvest term.(3):Under the same N application rate condition,the soluble sugar content of pakchoi decreased with the decrease of p H value of acid rain. Under the same p H value condition, the soluble sugar contents of N90 group are higher than that of N0 group, while N180 and N270 are lower than N0 group. This shows that appropriately increase nitrogen concentration is helpful to improve the soluble sugar content of pakchoi, while excessive fertilization is not only inhibite the growth of pakchoi, but also damage the nutritional quality.(4):The total nitrogen and nitrate content of pakchoi have similar trends, with the increase of growth time are on the decline. Under the same N application rate condition,the total nitrogen and nitrate content of pakchoi decreased with the decrease of p H value of acid rain, and under the same p H value condition, they increased with the increase of N application rate. The high content of total nitrogen is easy to be converted to nitrate. In harvest term, the nitrate content of N0 group reach 2nd standard, the nitrate content of N90 and N180 group under the influence of p H2.5 acid rain reach 3nd standard, other groups are seriously polluted. Therefore, in order to effectively control the content of nitrate in vegetables and to ensure the safety of vegetable consumption, reasonable application of nitrogen fertilizer is the key.