There are significant differences in nitrogen absorption and utilization effi- ciency among different maize varieties. So it is very essential to determine nitrogen efficiencies of different maize varieties. The effect of nitrogen application on maize growth can be reflected at the grain filling stage. Many scholars have researched the differences in grain filling characteristics among different maize varieties under the same nitrogen application conditions, but there are reare reports on the differ- ences under different nitrogen application conditions. In this study, the grain filling dynamics of maize were observed so as to determine the differences in nitrogen efficiency and to further compare the differences in grain filling characteristics a- mong different maize varieties. The test was carried out with Tunyu 99, Luyu 19 and Xianyu 335 as the materials during May 1st to October 7th, 2013. Under the nitrogen application levels of NO （0 kg/hm2 of pure nitrogen）, N1 （140 kg/hm2 of pure nitrogen） and N2 （210 kg/hm2 of pure nitrogen）, the filling dynamics of upper- and middle- lower-part grains of spring maize were studied. The results showed that among the three nitrogen application level, the grain fresh weight and dry weight of Tunyu 99 ranked as N2〉NI〉N0; the grain fresh weight and dry weight of Luyu 19 ranked as N1〉N2〉N0; the grain fresh weight and dry weight of Xianyu 335 ranked as （N1, N2）〉N0, and there was no significant difference between N1 and N2. Un- der the nitrogen application level of N1, Luyu 19 showed the best growth; under the nitrogen application level of N2, Tunyu 99 showed the best growth, The growth ad- vantage of Xianyu 335 was unobvious under neither N1 nor N2 nitrogen application levels. The development-promoting effect of nitrogen application was more obvious in upper-part grains than that in middle-lower-part grains.
Photo biodegradable film is an ideal degradable mulch film with synergistic effect of photo-degradability and biodegradability.To examine the covering effects of different films,maize was cultivated in the field with three kinds of degradable films(DF)mulching which had different degradation cycles(DF No.1,No.2 and No.3),with common plastic film mulching and no filming mulching(open ground)as comparison.The degradation rates and degrees of degradable films were examined,and the effects of different films on soil temperature,soil moisture,maize yield and relevant characteristics in each treatment were analyzed.The results indicated that the degradable films had good degradability,and the weight loss rate in 100 d for DF No.1,No.2,and No.3 were 22.31%,19.46%,and 15.63%,which were 4.16,3.63,and 2.92 times of the plastic film,respectively.In the early period of maize growth,the degradable films had good warming effects on soil,which were similar with the plastic film.The effect of DF No.2 on soil water conservation was slightly better than that of DF No.1 or No.3,similar with that of the plastic film.The soil water contents in 0-140 cm depths were significantly higher for DF No.2 than that for the open ground(p<0.05).The degradable films could significantly promote the ear development of maize,improve the ear characteristics,shorten the bald tip,and increase kernel number per plant(KNP)and 1000-kernel weight(TKW).The grain yields(GYs)for DF No.2,No.1,and No.3 were significantly improved,with 35.15%,31.35%,and 30.07%higher than that the open ground respectively(p<0.05).With no significant difference between DF and the plastic film,the GY was increased more for DF No.2 than that for DF No.1 and No.3.The degradable films fulfilled successfully all the functions of the plastic film,thus they were recommended as viable option to the plastic film due to their good degradability.
