根际注射施肥对黄土高原苹果氮素吸收利用及产量和品质的影响

【目的】在西北黄土高原地区,春季干旱少雨和肥料利用率低限制着生产优质苹果。国外通常应用水肥一体化技术来克服水肥利用率低的问题,但由于其硬件设施要求高,投资大,短期内在我国难以推广。近年来我国采用的根际注射施肥可利用施肥枪将肥料溶液直接注入根际土壤中,施肥成本低且技术简单。本研究利用同位素15N示踪技术,研究根际注射施肥对苹果氮素吸收利用及产量品质的影响,可为黄土高原果园水肥高效利用提供依据。【方法】以9年生富士/M26/新疆野苹果为试验材料,利用15N尿素标记肥料去向,最后通过MAT-251质谱计测15N丰度,得出果树各器官和土壤的肥料利用率。同时利用叶绿素仪(SPAD-502)测定标记叶片的SPAD值,用浸以磷酸甘油溶液的海绵进行田间原位测定,得到土壤氨挥发的量,用静态箱—气相色谱法测定土壤的N2O逸失量。综合对比分析黄土高原传统环状开沟撒施肥与根际注射施肥对苹果吸收利用氮素、肥料氮在土壤中残留及果实产量和品质的影响。【结果】黄土高原苹果园根际注射施肥的优越性体现在:1)施肥后一个月内,果园土壤的气态氮素损失发生变化,根际注射施肥比传统环状开沟施肥的氨挥发总量低54.9%,同时N2O的排放通量低5.0%。2)根际注射施肥后,促进了肥料在土壤中的扩散范围,扩大了根系肥水吸收容积,叶片和果实吸收的肥料氮比例(Ndff%)在整个生长季始终处于较高水平。生长季末期,根际注射施肥的整株氮素当季吸收率为53.04%,比环状开沟施肥提高12.25个百分点,表明根际注射施肥有利于氮素更快地被吸收利用,显著提高苹果树的氮素当季利用率。3)生长季末,在0—60 cm土层内,根际注射施肥的土壤氮素残留率为36.55%,而环状开沟施肥为43.13%,前者显著低于后者。4)在整个生长季内,根际注射施肥处理下的树体新梢叶片内叶绿素含量(SPAD)值一直高于环状开沟施肥。根际注射施肥能提高苹果单株产量和单果重,其单果重和单株产量分别比环状开沟施肥处理提高了3.8%和19.7%。【结论】黄土高原地区推广的果树根际注射施肥技术可以有效提高苹果树体氮素的利用率,降低了土壤中的氮素残留。此外注射施肥的深度、注射量、密度和时间均可根据不同时期的养分需要随时调整,使水肥在土壤中均匀分布,达到节水节肥的目的。同时可避免传统施肥时挖坑作业对浅土层吸收根的损伤,降低劳动力成本。综合来看,根际注射施肥是提高黄土高原区旱地苹果树肥水利用率、产量和品质的有效方式之一。

Effects of fertilization with injection to the rhizosphere on nitrogen absorption and utilization,fruit yield and quality of apple in the Loess Plateau

【Objectives】 The drought in spring and low fertilizer utilization efficiency limit the high quality apple production in the Loess Plateau in northwest region of China. Fertigation is usually used in abroad to overcome the problem of low fertilizer utilization efficiency. But this technology is difficult to spread in China for its strict requirements of irrigation system and investment at the level of farmer household in the short run. In recent years, fertilization with injection to the rhizosphere is used broadly in many places of China. This technology needs low cost and is simple.¹⁵N urea was used in this experiment as tracer to study the effects of fertilization with injection to the rhizosphere on nitrogen absorption and utilization, fruit yield and quality of apple in the Loess Plateau.【Methods】 The 9-year-old Fuji treesMalus pumila Mill cv.Red Fuji/M26/Malus Sieversii (Ledeb) Roem] and¹⁵N tracer element which was measured by MAT-251 mass spectrometer were used to calculate the fertilizer utilization efficiency of various tree organs and soil. SPAD-502 was used to determine the SPAD value of marked leaves. Sponge soaked in a solution of glycerol phosphate was used to measure the amount of field soil ammonia volatilization. Static chambers-gas chromatography was used to determine the soil N₂O fluxes. These methods were used to explore the effect of fertilization either with injection or traditional ring ditch on nitrogen absorption, distribution and utilization, fruit yield and quality of apple in the Loess Plateau.【Results】 The results show that the advantages of apple orchard fertilization with injection to the rhizosphere in the Loess Plateau are as follows: 1)Within one month after fertilization, the gaseous nitrogen loss in apple orchard changed. The amount of soil ammonia volatilization of fertilization with injection to the rhizosphere was significantly less than the traditional ring ditch fertilization by 54.9%, and the N₂O flux was 5.0%. 2)After fertilization with injection to the rhizosphere, the distribution range of water and fertilizer increased at the same time, the volume of fertilizer absorbed by apple tree roots was expanded eventually, the percentage nitrogen derived from fertilizer (Ndff%) of new shoot leaves and fruits was always at a high level throughout the whole growing season. After the fruits were harvested, the absorption rate of the whole tree was 53.04%, and 12.25 percentage points higher than the control. This result indicated nitrogen was absorbed more quickly following fertilization with injection to the rhizosphere, and nitrogen utilization efficiency was significantly improved. 3)In the end of growth season, the 0-60 cm soil nitrogen residual rates of treatment of fertilization with injection and the control were 36.55% and 43.13%, respectively. And the former was significantly lower than the latter. 4)The chlorophyll content (SPAD value) of new shoot leaves was maintained in higher level than the treatment of traditional ring ditch fertilization in the whole growing season. Compared with traditional ring ditch fertilization, fruit weight and yield of per tree in treatment of fertilization with injection were higher than the control by 3.8% and 19.7%, respectively.【Conclusions】 The technology of fertilization with injection in the Loess Plateau region can increase tree nitrogen absorption, utilization and decrease soil nitrogen residual significantly. So the water and fertilizer distributed evenly in soil and the purpose to save water and fertilizer can be achieved eventually. Fertilization with injection also avoided the root damage caused by traditional digging and reduced labor costs at the same time. On the whole, fertilization with injection is an effective way to improve the fertilizer and water use efficiency in dryland apple production in the Loess Plateau.