Ameliorative effect of cropping Lycium barbarum L. with drip irrigation on soil enzymes activities in takyric solonetz

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    In reclaiming or ameliorating salt-affected soils, it is essential to go in-depth studying soil biological activities so as to evaluate variation of soil environmental quality and sustainability of the amelioration measures. Highly saline-sodic takyric solonetz wastelands are distributed mainly in arid regions in Ningxia Plain, Northwest China. This type of soils is characterized by extremely high content of sodium and high pH, varying in the range of 9~10, and consequent poor soil structure and low saturated hydraulic conductivity (Ks< 0.1 mm d-1). In the 0~40 cm soil layer, the average electrical conductivity of saturated slurry extract (ECe), pH of saturated slurry (pH) and sodium adsorption ratio of saturated slurry extract (SAR) was 10.3 dS m-1, 9.4 and 38.9 (mmol L-1)0.5, respectively. In the past a lot of measures have been tried to reclaim the wastelands, however, most of them failed primarily because of the very low saturated hydraulic conductivity of the soil. In 2009, this type of wastelands was reclaimed by cultivating wolfberry (Lycium barbarum L.) with drip irrigation. Under the drip emitter near the plant, a pit, 0.2 m in diameter and 0.2 m in depth, was prepared and filled with alien sand for planting wolfberry in. The sand-filled pit was to increase the area of contact between soil and water and the area of water infiltration in takyric solonetz under drip irrigation, thus lowering water supply rate down to or approximately to saturated hydraulic conductivity of the native soil. Besides, the sand pit maight also serve as a reservoir to hold surplus water prior to its infiltrating into the soil and extend water infiltration time, thus ensuring water infiltration into the soil and making reclamation of the soil possible. At the end of the wolfberry growing period in 2011 (October 16th, 2011), soil samples were collected intensively from soil profiles, perpendicular to the drip irrigation belt, in fields different in wolfberry cultivation history (1 a, 2 a and 3 a), covering a wide gradient of salinity and alkalinity, for analysis of activities of soil urease, alkaline phosphatase and sucrase, which were the enzymes, respectively, key to N, P and C recycling in soil, and of soil physicochemical properties as well. In order to clarify any potential causal-relationships between soil enzyme activities and physicochemical properties, correlation analysis and path analysis were performed. Results show that all the 3 enzymes were very low in activity in uncultivated soils due to the high saline-alkali stress and low organic matter content. After the soil was reclaimed to cultivate wolfberry with drip irrigation, soil enzyme activities increased gradually with the cultivation going on, displaying high spatial variability within the profile. Enzyme activities were found quite high in the root zone under the drip irrigation belt and declined outwards from root zone. Higher soil enzyme activities in the root zone helped the crop absorb soil nutrients. Both correlation analysis and path analysis show that soil pH is always the dominant factor affecting soil enzyme activities, and activities of all the 3 soil enzymes decreased exponentially with pH in the range from 7.38 to 10.00 (p < 0.01). The exponential relationship between them demonstrates that in soils quite low in pH (< 8.5), any rise in soil pH would induce a sharp drop in soil enzymes activities. In a word, the adoption of such a wolfberry cultivation pattern greatly improves soil biological properties of the highly saline-sodic takyric solonetz wasteland.

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Zhang Tibin, Kang Yaohu, Wan Shuqin, Feng Hao. Ameliorative effect of cropping Lycium barbarum L. with drip irrigation on soil enzymes activities in takyric solonetz[J]. Acta Pedologica Sinica,2015,52(6):1392-1400.

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  • Received:October 23,2014
  • Revised:March 05,2015
  • Adopted:July 09,2015
  • Online: August 31,2015
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