施肥深度对生土地玉米根系及根际土壤肥力垂直分布的影响

Effect of fertilization depth on maize root and rhizosphere soil fertility vertical distribution in immature loess subsoil

为探明施肥深度对生土地玉米(Zea mays L.)地上部生产力、根系及根际土壤肥力的影响,连续2年以黄土母质生土为供试土壤,采用根管土柱法,以不施肥为对照,研究不同深度(0~20 cm、60~80 cm、100~120 cm、140~160 cm和180~200 cm)施用生物有机肥对玉米地上部生产力及根重、根际土壤酶活性、根际土壤养分含量垂直分布的影响。结果表明:1)在0~200 cm土层范围内,随施肥深度的加深,玉米地上部生产力、总根重等指标均呈先增加后减少的规律。施肥深度在100~120 cm处的玉米总根重(52.3 g)及地上部生产力(361.0 g)最大。2)所有施肥深度的根重垂直分布均呈"T"型,以0~20 cm耕层根重最大,占总根重的50%左右,随根系下延,根重明显递减(P<0.05)。施肥深度100~120 cm可以获得最大总根重和0~40 cm耕层根重(27.19 g)。根系N、P和K养分积累适中,平均分别为6.60 g·kg^(-1)、2.38 g·kg^(-1)和8.16 g·kg^(-1)。3)施肥明显提高根际土壤酶活性和养分含量。施肥深度为60~80 cm,0~200 cm土层根际土壤脲酶活性较高,介于0.108~0.354 mg(NH3-N)·g^(-1)(soil)·24h~(^(-1));施肥深度为140~160 cm时,0~200 cm土层根际土壤蔗糖酶活性和速效磷含量较高,分别为12.9~19.6 mg(glucose)·g^(-1)(soil)·24h^(-1)和4.31~6.02 mg·kg^(-1);施肥深度180~200 cm,0~200 cm土层根际土壤有机质含量较高,介于5.55~7.14 g·kg^(-1);施肥深度小于100 cm或大于120 cm,0~20 cm土层根际土壤碱性磷酸酶活性和碱解氮含量较高,分别>0.497 mg(phenol)·g^(-1)(soil)·24h^(-1)和>25.4 mg·kg^(-1)。4)相关分析表明,在生土地上,不同施肥深度处理下,玉米根重、根系NPK营养、根际土壤酶活性及根际土壤NPK营养密切相关。5)根据FACTOR过程和CLUSTER聚类分析,优化得出改良黄土母质生土地玉米冠-根-土系统的适合施肥深度范围为60~160 cm。本研究结果为通过施肥加快生土熟化提供了新的思路。

This study was set up to determine the effect of fertilization depth on maize（Zea mays L.） productivity, root growthand rhizosphere soil fertility in immature loess subsoil. To that end, a sample of immature loess subsoil was analyzed for the effect of different fertilization depths（0-20 cm, 60-80 cm, 100-120 cm, 140-160 cm and 180-200 cm） of bio-organic fertilizer on maize productivity and the vertical distribution of root weight, rhizospheric soil enzyme activity and rhizosphere soil nutrients in a 2-year root-tube soil column culture. The control treatment（CK） was not treated with fertilizer. The results showed that： 1） indicators such as maize productivity, total root weight, etc., increased at the start and then decreased with increasing fertilization depth from 0 cm to 200 cm. The largest root weight（52.3 g） and productivity（361.0 g） of maize were obtained under the 100-120 cm fertilization depth. 2） In all the treatments, the vertical distribution of maize root weight followed a T-shape and the largest maize root weight was noted in the 0-20 cm soil layer, which accounted for up about 50% of the total root weight. Root weight significantly declined with increasing soil depth（P 〈 0.05）. Under 100-120 cm fertilization depth treatment, both total root weight and root weight of 0-40 cm soil layer（27.19 g） reached the highest level, furthermore, N, P and K accumulation in the root were moderate with 6.60 g·kg-1, 2.38 g·kg-1 and 8.16 g·kg-1, respectively. 3） Fertilization significantly increased enzymes activities and nutrients contents in rhizospheric soil. Urease activity in 0- 200 cm rhizospheric soil increased [0.108-0.354 mg（NH3-N）·g-1（soil）·24h-1] in the 60-80 cm fertilization depth treatment. In the 140-160 cm fertilization depth treatment, sucrase activity and available phosphorus content of 0-200 cm rhizospheric soil increased to 12.9-19.6 mg（glucose）·g-1（soil）·24h-1 and 4.31-6.02 mg·kg-1, respectively. Maize rhizosphere soil organic matter content was higher（5.55-7.14 g·kg-1） in the 180-200 cm fertilization depth treatment. When fertilization depth was less than 100 cm or deeper than 120 cm, maize rhizospheric soil alkline phosphatase activity and available nitrogen content kept higher level, which were more than 0.497 mg（phenol）·g-1（soil）·24h-1 and 25.4 mg·kg-1, respectively. 4） Significant correlations among root weight, root NPK nutrient, three rhizospheric soil enzyme activities and three rhizospheric soil nutrients under different fertilization depth treatments were observed in the immature loess subsoil. 5） The optimized fertilization depth was 60-160 cm for improving maize shoot-root-soil systems in the immature loess subsoil based on FACTOR and CLUSTER analyses. This study provided a new idea for speeding up the raw soil maturation process through changing fertilizers application depth.