Research On Effect Of Irrigation Amount, Sand/Clay Ratio And Fertilizer Treatment On ¹⁵N Absorption, Utilization And Loss Of Apple

The experiment using potted one-year-old Malus hupehensis and two-year-old apple grafted seedlings as main materials was carried out in the research institute of horticulture of Shandong Agricultural University from 2009 to 2010.It mainly studied the effects of different irrigation and different sand/clay ratio and different organic matter fertilizered on ¹⁵N absorption, utilization, and loss of apple by using tracer technique of ¹⁵N. Meanwhile, we used device of nitrogen leaching underground to study nitrogen leaching loss under different fertilizer treatment and distribution features of NO₃^--N in the different soil layer in Laishan of Yantai. The main results are as follows:1 Results showed that high-irrigation treatments (70%FC⁹0%FC) could more significantly promote plant growth, absorption and utilization of ¹⁵N among the five irrigation treatments. The value of height, stem diameter and fresh weight were highest (31.02 cm,0.364 cm and 29.707 g)under 90%FC irrigation treatment while those were lowest(19.05 cm,0.267 cm and 16.887 g)under 50%FC irrigation treatment. The irrigation effects were significantly differential among high and low treatments. ¹⁵N absorption and utilization reduced along with the irrigation decrease. The ¹⁵N distribution of aerial part was more than that of underground under different irrigation treatments while the ¹⁵N ratio of aerial part and underground was more under high irrigation treatment. Irrigation amount was negatively correlated with the residue level of ¹⁵N in soil. High-irrigations could promote plant vegetative growth as well as the absorption and utilization of ¹⁵N, yet the loss of ¹⁵N was also aggravated to some degree.2 Results showed that there were different values of plant growth, ¹⁵N absorption and utilization under different sand/clay ratio treatments. The value of plant growth(height, stem diameter and dry weight)was highest (37.54cm, 3.457mm and 16.20g) under 1/4 treatment , while the total nitrogen and ¹⁵N uptake amount were greatest(189.31mg and 32.39mg) under 3/2 treatment , the value of plant growth and ¹⁵N absorption and utilization under 1/4³/2 treatments were higher than that of ck and high sand/clay ratio treatments. The ¹⁵N Ndff and distribution of aerial part was higher than that of underground portion among different treatments. The Ndff of each part of plant becomes higher with the increases of Sand/clay ratio under 1/4⁴/1 treatments. The residue level of ¹⁵N in soil was negatively correlated with sand/clay ratio, the loss of ¹⁵N showed a rising trend along with the increase of sand/clay ratio. The plant growth and nutrient uptake and utilization were closely related to soil texture. The appropriate sand/clay ratio was beneficial to the growth and nitrogen absorption and utilization, while higher ratio aggravated the nitrogen loss in soil.3 Results showed that the application of organic manure could promote absorption and utilization of ¹⁵N and could improve utilization rate of nitrogen fertilizer. Absorption and utilization of ¹⁵N showed a rising trend along with the increase of Soil Organic Matter. There were highest (60.66mg and 5.055%)under 56.75 g.kg^-1 treatment, while those were lowest(19.48mg and 1.623%)under ck(10.13 g.kg^-1) treatment. Difference becomes more significantly with the increased of organic matter content. The residue level of ¹⁵N in soil was positively correlated with amount of soil organic matter, the loss of ¹⁵N showed a decreasing trend along with the increase of soil organic matter. The capacity of water retention and fertilizer retention of soil increasesed with organic matter, therefore, it has low leaching loss of nitrogen.4 Results showed that NO₃^--N was main form of nitrogen of leaching loss, NO₃^--N amount account for 90%( mass fraction) of nitrogen leaching loss in the soil. Nitrogen leaching loss of controlled release fertilizer treatment was lower than that of custom fertilizer treatment. The leaching loss amount of NO₃^--N was positively correlated with nitrogen rate among controlled release fertilizer treatments. The NO₃^--N has different Cumulant in the 0²00cm soil layer, it has a lager number in the 40-100cm soil layer and has a Maximum number in the 80-100cm soil layer. The accumulation of nitrate nitrogen was still higher in the 200cm soil layer.