Studies On The Yields And Qualities Of Maize In Middle And High Elevation Areas Of Guizhou Province

Maize is one of major food crops in Guizhou province. Both the yields and growing area are just less than rice but largest in drought crop. There are now 73.5 million hectare land for growing maize in Guizhou, accounting for more than 30% of till land and 25% of whole crop output. The improvement of cultivar distribution and cultivation techniques could be beneficial to the increment of the yield and quality of maize.Series of field experiments were carried out to study the characters of two maize cultivars, Zunyu No.3 and Qianxing-2302, which were widely grown in Guizhaou. Then three site experiments at different height (high, middle and low) above the sea were established in the central and west of Guizhou to study the impact of climate, slowing date and density on the yields and qualities of maize. The investigations were also conducted on the fertilization with typical and representative yellow soil derived from lime stone of Triassic Period. The main objective was to provide scientific guidance for high yields and qualities of maize in Guizhou province. Following are the main results:1. Two maize cultivars varied greatly in the yields and qualities due to different genetic backgrounds. The plant height, yield, ear grain number, weight per grain or per 100 grains were much higher for Zunyu No.3 than Qianxing-2302. The growth period of the former was longer than the later, which led to more photoproducts accumulated and high yields. There were no significant differences in the content of starches and fatty acids in the grains of the two cultivars, but higher in protein content in Qianxing-2302 than Zunyu No.3. Therefore, Zunyu No. was higher in the yield and poorer in quality than Qianxing-2302.2. The growth and yield of maize were influenced significantly by the climate factors, such as light, temperature and rainfall during maize growth period. Both plant height and yield of Zunyu No.3 were higher in three field site experiments at high, middle and low elevations than Qianxing-2302. The plant height was decreased as the elevation increased. The growth period was prolonged in experimental site at high elevation with low temperature and less rainfall, while it behaved otherwise in low elevation site. Higher yield of maize was found at the site with large temperature difference during the day and night compared to that with less. The yield of maize could thus be controlled not only by genes, but also influenced by climate. There was no significant difference in the contents of proteins, starches, and fatty acids in maize grains at three experiment sites at variable heights above the sea. It seems thus reasonable to suggest the strict control of the grain qualities by genes but no significant influence of climate on it. The breeding could be the main measurement for the improvement of grain qualities.3. Sowing date was different at variable places. Zunyu No.3 was suitable to sow approximately on 25 Aprill in Anshun (the low elevation site) and Shuicheng (the high elevation site) but on 15 Aprill in Panxian (the middle elevation site). However, Qianxing-2302 was suitable to sow approximately on 25 Aprill in Anshun and but on 15 Aprill in Shuicheng and Panxian. The density also varied in different places and the optimal intensities were from 52500 seedlings per hectare to 60000 seedlings per hectare in Ashun and Shuicheng, and 60000 seedlings per hectare in Panxian. Greater influence of climate on the yields of maize was observed than qualities.4. N fertilization increased grain yield from 9.59% to 23.14% compared with blank control (without N fertilizer), and also enhanced the contents of proteins, amino acids, starches and fatty acids in grains, but did not change the ratio of amylase to amylopetine. In maize grains, the contents of MET, PHE, LYS, ASP, SER, GLU, GLY, HIS and flax acid were rather consistent and mainly controlled by genes instead of fertilization. However, the other nutrient components, such as albumin, globulin, prolomine, glutamine, THR, VAL, ILE, LUE, ALA, TYR, PRO, amylase, amylopetine, oleic acid, sub-oleic acid, palm acid and stearic acid was varied, which could be influenced both genes and nitrogen fertilization. 150 kg N·ha^-1 could be optimal for higher yield with better qualities.P fertilization increased grain yield from 6.98% to 26.87% compared with blank control (without P fertilizer), and also improve the contents of proteins, amino acids, fatty acids and starch in grains. Albumin, globulin, THR, MET, PHE,LYS, SER, HIS, ARG,PRO and the ratio of amylase to amylopetine were relatively stable, indicating the strict control by genes but not by P fertilization. The contents of VAL, ILE, LUE, GLU, GLY, TYR, ASP and ALA were increased by P fertilization, suggesting that they were influenced by both genes and P fertilization. Optimal amount of P fertilizer was from 75 kg P₂O₅·ha^-1 to 105 P₂O₅ kg/ha for higher yield with better qualities of maize.The yield of maize varied greatly under different K fertilization as compared to the quality. K fertilization increased the yield of maize but had little impact on the quality, if any. K fertilization not only increased the content of proteins, but also improve their qualities, since high contents of THR, ILE, LUE, VAL , PHE and LYS, and 16.88% of increment in total essential amino acids were detected in maize grains, K fertilization also increased total content of starch but decreased the ratio of amylase to amylopetine, indicating the improvement of the test of food made from maize grains. Total content of fatty acids, including oleic acid and sub-oleic acid, was increased by K fertilization at same times. Approximately, 60 Kg K·ha^-1 was optimal for higher yield with better qualities.Among no fertilizer, NP, NK, PK, NPK treatment, The yield of maize changed in the sequence: NPK > NP > NK >PK> CK (without fertilization) indicating the most importance of N, less of P and least of K for the maize yield. NPK fertilization increased the contents of proteins, essential amino acids, starches and fatty acids content, but decreased the ratio of amylase to amylopetine in maize grains. It seems thus reasonable to suggest the improvement of NPK fertilization kernel nutrient quality and the food test. It was worthy to point out the obvious changes in the yield as compared to the quality, such as the contents of proteins, starches and fatty acids and so forth, in combination fertilization treatments. Therefore, the yields and qualities of maize yield could be controlled by both genes and environment. The yields were greatly influenced by environments in contrast to the qualities which could be controlled mainly by genes.