Effects Of Different Fertilization Placements On Growth And The Nitrogen Uptake In Apple

The experiments were carried out to study the effects of different fertilizer placements on the characteristics of nitrogen absorption, distribution and utilization of fifteen year old apple trees(Gala/Malus hupehensis) and five kinds of apple stocks using 15 N urea tracer technique. The main results were as follows:1. The absorbed 15 N by roots transfers to new vegetative organs prior at the new shoot growing stage and fruit rapid-swelling stage under the different horizontal fertilization placements. The Ndff values of fruits are the highest among the organs at the fruit maturity stage under the three fertilization treatments. The Ndff values of the same organ are different under different fertilization treatments, and the Ndff values of the organs under the inner treatment are significant higher than those under the outer and middle fertilization treatments, especially for roots and fruits. The Ndff values of roots under the three treatments show different variation tendency as the phonological phase changing, and these of the inner fertilization are greater than those of the other treatments. The Ndff values of roots under the M and O treatments present a trend of upward after a fall first. But in the treatment I, The Ndff value of root is increasing until reaches the highest level at the fruit maturity stage. The Ndff values of fruits under the three treatments all present an increasing tendency as the phonological phase changing and reach the maxima at the fruit maturity stage, and the Ndff values of fruits in M and I are respectively 1.43 and 1.42 times of that under the treatment O. The result of the Ndff values of fruit at the new shoot growing stage and fruit rapid-swelling stage is I>O>M. The 15 N distributions in the organs at different phonological phases are significantly different and are not significantly different among different treatments. At the fruit maturity stage, the trend of the nitrogen distribution in different organs under different fertilization treatments is consistent, vegetative organs﹥storage organs﹥reproductive organs, and the values of NUE under different treatments are I﹥M﹥O. The NUE of trees under the I treatment is 29.25%, which is significantly higher than those under the other two treatments(19.33% and 19.04%). Fertilization placement significantly affects plant organs’ ability of absorbing fertilizer, especially roots. Different fertilizer placements show little effects on the nitrogen allocation rate but obviously affect the nitrogen utilization efficiency. Combining previous research results and the results of this experiment, it suggests that for ridging planted orchard, fertilizing at 1/3 of the canopy projection could improve the utilization rate of nitrogen fertilizer.2. The five kinds of apple stock showed different reaction under root layer fertilization measures. Each index of M. hupehensis Rehd relatively balanced. Its biomass, root-shoot ratio, utilization rate of nitrogen is in the middle level but its root-shoot ratio is a larger one among the five kinds of apple stock. The biomass and the utilization rate of nitrogen of M. micromalus Makin is large but its root-shoot ratio is small. The biomass of M.baccata Borkh is in the medium level and its root-shoot ratio and the utilization rate of nitrogen is small. The biomass and the utilization rate of nitrogen of M.micromalus( Willd) Borkh is in the medium level but its root-shoot ratio is the minimum one among the five. The biomass of M.micromalus( Ledeb) Roemer is large,only smaller than M. micromalus Makin. Its root-shoot ratio is lightly smaller than that of M.micromalus( Willd) Borkh and its utilization rate of nitrogen is larger one among the five. The change of root surface area and total root length of M. hupehensis Rehd is smallest among the five and that of M.micromalus( Ledeb) is the largest. The other three are in the middle level. Under the different fertilization measures, the root activity of M. hupehensis Rehd and M.micromalus( Ledeb) Roemer little changed. The change of root activity the other three apple rootstock seedling is more abvious. Under the root pruning five apple rootstock seedling root activity significantly changed. Different from the results on mature apple trees, root activity of the some kinds of apple rootstock seedling did not improve but the utilization rate of nitrogen degreed. This may be because the rootstock seedling aboveground growth cannot make up for the part of the root system and bring nutrient deficiency in time, not like the mature trees’ "compensate for growth". The root of nutrient absorption ability is reduced. About the regulation on the growth and development of plant root and the influence of aboveground growth mechanism still needs further research.