The Effect Of Nitrogen Forms On Banana Growth And Nitrobacteria In Soil

Ammonium (NH4+) and nitrate (NO3-) are the two major forms of nitrogen sources for the plants, and have different effects on plant physiological metabolism and plant growth. In tropic aera of China, because of using the single urea for long time in Hainan banana plantations, the nitrogen use efficiency is very low and the quality of bananas became poor. Banana is the one of the most important crops, therefore, it’s nessary to get the information about the effect of nitrogen forms on bananas’growth and the transformation of ammonium (NH4+) and nitrate (NO3) in soil of banana plantation. In this study, hydroponic experiment was used to analyze the effect of different ratio of NH4+ and NO3- on the bananas’growth and physiology. The second study was soil pot experiment, and three typical soils in Hainan island were selected to investigate the different nitrogen fertilizers on the bananas growth, physiology and soil indexes. To further understand the transformation of nitrogen in soil after fertilization, soil pot experiment with roots’bag was used to cultivate banana seedlings. Total DNA of rhizosphere and non-rhizosphere soil was extracted to set up the gene library of AOA and AOB and community structure of AOA and AOB was analyzed.The follows were the main results:The hydroponic experiment found that in comparison with the treatments of sole nitrogen resource, the treatment of combinated nitrate and ammonium caused the greatest biomass of banana plants.The results showed that the effect of fertilizers on the plant height and the roots growth were P-K-N(nitrate) & Ca-N(nitrate)> N(urea) in three different types of soils (coastal sandy soil, lateritic red soils developed from granite or basalt), and the contents of nitrate and the activity of nitrate reductase too. The effect of fertilizers on the contents of ammonium and available potassium were N(urea)> P-K-N(nitrate) & Ca-N(nitrate), but the contents of nitrate were contrary. So the sole ammonium nitrogen depressed the potassium absorption by plants.The most of AOB amoA genes clones were uncultured group of classes after comparison with NCBI database, but a part of them had high similarity with Nitrosospira、 Nitrosolobus and Nitrosovibrio, even the Nitrosospira played a dominant role. The size of the order of the microbial diversity on non-rhizosphere and rhizosphere soil:urea> Ca(NO3)2 fertilizer> compound fertilizer> (NH4)2SO4>CK> Ca(NO3)2, (NH4)2SO4> Ca(NO3)2 fertilizer> CK> compound fertilizer>urea> Ca(NO3)2; The size of the order of the abundance of AOB amoA genes on the contrast soil:(NH4)2SO4>compound fertilize>urea> Ca(NO3)2 fertilizer> CK、Ca(NO3)2, and on the non-rhizosphere soil: (NH4)2SO4> compound fertilize>urea> Ca(NO3)2 fertilizer>CK、Ca(NO3)2, and on the rhizosphere soil:urea>(NH4)2SO4>compound fertilize> Ca(NO3)2 fertilizer、CK、 Ca(NO3)2.The most of AOA amoA genes clones were uncultured Crenacheota after comparison with NCBI database, and most of the rest were unclassified Archaea, but we found that a few clones were high similarity with thaumarchaeote; The size of the order of the microbial diversity on contrast soil:Ca(NO3)2> (NH4)2SO4>CK> Ca(NO3)2 fertilizer> compound fertilizer>urea, on the non-rhizosphere soil:Ca(NO3)2 fertilizer>(NH4)2SO4 & urea>Ca(NO3)2> compound fertilizer>CK, on the rhizosphere soil:compound fertilizer、 Ca(NO3)2 fertilizer>(NH4)2SO4、urea>Ca(NO3)2> CK. The size of the order of the abundance of AOA amoA genes on the contrast soil:Ca(NO3)2> CK> Ca(NO3)2 fertilizer>compound fertilize>urea>(NH4)2SO4, on the non-rhizosphere soil: CK>Ca(NO3)2> compound fertilize、(NH4)2SO4>Ca(NO3)2 fertilizer>urea, on the rhizosphere soil:CK、Ca(NO3)2> compound fertilize、Ca(NO3)2 fertilizer & urea> (NH4)2SO4.