Ecological effects of salinization on soil physico-chemical characteristics and dry matter partitioning in arid region of Northwestern China

Abstract

The research aimed to quantify the change processes of soil physico-chemical characteristics and partitioning of dry matter in alfalfa and barley in farm salinization in saline area of Northwestern China. The experiment was carried out by taking different salinization stage plots under Hordeum vulgare L. and Medicago sativa L. grown fields as the study objects, and by using the method of replacing time with space. Results were as follows: 1) Compared to non- saline plot, soil bulk density was increased by 3.00%, 4.54%, 8.62% and 9.96%, respectively in slightly, moderately, severely and very severely salinized plot in alfalfa grown field, whereas for barley grown field, the change of soil bulk density had no obvious trend in corresponding salinized gradient plots. Soil temperature of different salinized gradient plots in alfalfa grown field showed a low-high-low fluctuation, while that of barley grown field was increased. In the two farmlands, soil organic matter and alkali-hydrolyzable nitrogen were all significantly decreased, and the rate of decrease were faster in soil depth of 0-10 cm than that in soil depth of 10-20 cm, but soil organic matter and alkali-hydrolyzable nitrogen in alfalfa grown field was in the following order: slightly salinized plot (S1)>non-saline plot (CK)>moderately salinized plot (S2)>severely salinized plot (S3)>very severely salinized plot (S4); for barley, it was in the following order: CK>S1>S2>S3>S4, and there had different significant difference between different salinized plots under the two farmlands; 2) In growing seasons, different salinization gradient plots had different soil depths of salt accumulation and appearing the peak of average soil ECP under the two crops farmlands. In the composition of soil soluble salt ions and ratio, the same salinized gradient plots between the two crops farmlands were similar; but in alfalfa grown field, the ratios of Cl- and Na++K+ in CK and S1 were significantly lower than that of CK and S1 in barley grown field, and the change ranges of different ions from CK to S4 were higher than that of barley; 3) In dry matter accumulation and distribution traits, at any given growth stage, along salinization gradient increased, plant total dry matter was more distributed to leaves and roots and center of accumulation and distribution of dry matter in the plant in different salinization gradients was gradually slowly than CK plant. And salt stress made the dry matter partitioning ratio of total shoot of the two crops be gradually reduced and root/shoot ratio increased.