Study On Sensitivity Of Spring Maize To Nicosulfuron

Nicosulfuron, as selective foliar-applied herbicide in corn field and for its controlling perennial and annual weed effectively, low dosage, high safety to the corn, decreasing the dosage with adjuvant addition, high stability of control efficacy, easy mixture, has been the important herbicide in corn field. However, spray injury in some of spring maize varieties to nicosulfuron in some areare results in massive yield reduction in these years. Corn is one of the primary crops in China. For its richness in variety resources and species, high sensitivity varieties to herbicide are probably existed. So it is very important for industry and agriculture to study the sensitivity of different corn variety to Nicosulfuron. Main Spring Maize Varieties were choosen to determine the sensitivity of different spring maize varieties to Nicosulfuron. The physiological biochemical characteristics of corn, different application conditions, adjuvants addition and mixture base were studied to definite different sensitivity mechanism of spring maize. All the results were as follows:1. The different sensitivities of maize varieties to nicosulfuron were measured by pot test. The results showed that with the normal dosage 60 g/hm~2, the sensitivities of maize varieties to nicosulfuron was significance. Eight varieties including Denghai 9, DFS-4, Kenyu 7, Xianyu 335 were sensitive varieties whose inhibiting rate of the plant height and weight were over 41.8% and 35.09%. And it is obviously observed that plant growing was inhibited, the leaves etiolated and newleaves were too twist to grow normally. Thirty-two varieties of corn including Jidan 522, Zhengdan 958, Dongnong 48, Longdan 38 whose inhibiting rate of the plant height was 20.8%~37.9% and inhibiting rate of the plant weight was 17.63%~27.64% was examined that the first leave of plant was etiolated, leaves were chlorosis in small-scale, and the effect of plant growing was so little that it might recover by itself. The inhibiting rate of the plant height and weight of ten varieties including Fenghe 10, Fenghe 1, Jidan 530, Jidan 419, Jidong 26, Jindan 1021 and Shenyu 30 were below 19.0% and 15.31%, the resistance to nicosulfuron are higher than other varieties. No clearly spray injury was observed.2. The inhibiting rate of ChloropHll content of sensitivity spring maize varieties keeped increasing, as well as the photosynthesis decreased for inhibiting strongly after nicosulfuron applied 4 days. In the same conditions, firstly the inhibiting rate of ChloropHll content of mid-tolerance spring maize varieties increased then reduced to the zero after 8 days that was observed that the varieties could recover by itself after inhibition. No significance change in tolerance spring maize varieties was examined so that it had no significance effects of tolerance maize to nicosulfuron, the photosynthesis of tolerance corn was still good. It had the same direction between change of ChloropHll and spray injury in physiology morphology of different spring maize varieties after application.3. ALS is target enzyme of nicosulfuron action. ALS activity of sensitivity maize varieties was inhibited significantly that the inhibiting rate of ALS activity was 19.2% after nicosulfuron application 1 day, keeping inhibited during 12 days. It was important for enhancing tolerance to nicosulfuron to keep high target enzyme activity after appling to tolerance spring maize varieties. ALS activity of tolerance and mid-tolerance varieties were high which were to maxmum in third day duing to no inhibiting by nicosulfuron. The key in increasing tolerance to nicosulfuron was ALS activity of tolerance varieties increasing, compared with the sensitive varieties.4. GSTs is the important way to detoxicate of biology. GSTs activity of Denghai1 that was sensitivity variety was increasing to the maxmum then decreasing during 3 days, reducing from 51.8 U/min·mg to 24.7 U/min·mg during 12 days, and the range was 52.32%. The results showed that nicosulfuron could not be metabolited with the GSTs activity of sensitivity variety increasing, and it was hard to control inhitition of sensitivity variety to nicosulfuron. GSTs activities of Fenghe 1 which was tolerance variety and Zhengdan 958 which was mid-tolerance variety were higher than control treatment after 3 days, then reducing to the same to untreated after 6 days. Nicosulfuron was uptaked rapidly to metabolite by tolerance varieties because of conjugation increasing with GSTs activity increasing. It was the important reason for recovering rapidly of tolerance variety and keeping growing after application.5. Optimization of application conditions of nicosulfuron in spring maize field were show as follows: spraying time were three leaves to five leaves; temperatures were 20~30℃, atmospheric humidity were over 70%, soil water content were higher 20%.6. The results of combination were showed as follows: nicosulfuron combinating with atrazine and 2,4-D were multiplier actions. They had synergistic effects, as well as increasing tolerance of maize varieties to nicosulfuron.7. The results of adding adjuvant were showed as follows: control efficacy enhanced with adding adjuvant, under nicosulfuron dosage decreasing, and spray injury of spring maize reduced at the same time. It wins in both ecological benefit and economic benefit.8. The inhibiting rate of the plant height was the same between the field trial and the pot experiment, as well as the inhibiting rate of the plant weight. The inhibiting rate of the plant height and weight in the field trial were lower those in the pot experiment, especially sensitive spring maize varieties. No yield reduction was detected in Xinyu 335 that was determined to sensitive varietiy during seedling, so the seedling symptom and yield were the factors to determine it was tolerance varietiy or not.