水肥耦合对橡胶树根系垂直分布的影响

Coupling Effects of Water and Fertilizer on Vertical Distribution Characteristics of Fine Roots of Hevea brasiliensis

水分和养分是限制橡胶树生长和产胶量的重要因子。以17 a树龄的热研7-33-97橡胶树为试验材料,通过田间小区试验研究了不同水肥耦合水平对橡胶树根系垂直分布特征的影响,结果表明:橡胶树吸收根系主要分布在0～20 cm土层,随土壤层次的加深,橡胶根系干重在垂直分布上呈递减趋势,可用乘幂函数模型表示。适量增施氮、磷肥均能促进0～20 cm土层根系的生长;氮肥施用量过大,深层根系比重增大;轻度降低土壤水分能够促进根系扎深。水肥耦合对根系生长和分布具有调节作用,本试验条件下,各土层根系干重总量以丰氮丰水和丰磷丰水组合处理最高,分别达0.33和0.31 kg/m3,并且根系在土壤剖面上的分布与养分分布具有一致性。

Nutrients and water are two limiting factors on rubber growth and latex yield. With 17 year-old Hevea brasiliensis of Clone SCATC 7-33-97 as the test materials, the comprehensive coupling effects of application amount of chemical N, P and K fertilizers, and irrigated water on vertical distribution characteristics of fine roots of rubber tree were studied under rubber field condition. The results showed that, the fine roots of rubber tree mainly distributed in 0-20 cm soil layer, with the increase in the depth of soil layer, rubber roots showed a decreasing trend in their vertical distribution, it could be expressed by power function model, increasing N or P fertilizer appropriately could promote the root growth of 0-20 cm soil layer, but the proportion of deep roots increased when the amount of nitrogen fertilizer was too high. Lower soil moisture content was found good for roots elongation that enabled them to penetrate more deeply into the soil for more water uptake at the expense of root number and dry weight. On the whole, positive coupling effects were found existing between soil water and N fertilizer, soil water and P fertilizer on the root dry weight. Among different water and fertilizers combinations, the roots always gave the highest dry weight in each soil layer under the treatment of sufficient fertilizer ＋ sufficient water dosage combination, and they could reach to 0.33 kg/m3 and 0.31g kg/m3, separately. The roots dry weight was significantly correlated with the content of organic matter, NO3--N, NH4＋-N, available P and among the layers of whole soil profile.