| Due to its inferior characteristics such as high pH value, high salinity, poor structure, and low fertility, coastal solonchak has adverse effect on both plant growth and eco-environment. Therefore, it is important to improve and utilize the soil. This author researched effects of continuous cropping by jute, rotation by paddy and rape, rotation by paddy and wheat on the physico-chemical properties and biological properties for the coastal solonchak, and researched ameliorative effects of different level of jute straw and chicken manure on the soil by way of field experiment. Moreover, pot culture experiments were conducted to document the salt-tolerant mechanisms of beach plum (Prunus maritima) and Japanese mulberry (Morus australis) and to assess the contents and distributions of salinity on mineral elements in rhizosphere microzone of beach plum and white ash (Fraxinus americana) under four salinity levels (0, 3, 6, and 9 g·L-1 NaCl in the irrigation water). The results were shown as follows:⑴The coastal solonchak was ameliorated by each land use. Compared with the control, for three plots by continuous cropping with jute, rotation with paddy and rape, rotation with paddy and wheat for two-year, their soil density at the 0～20 cm soil layer was respectively decreased by 16.11%, 13.42%, and 9.40%, decreased by 5.30% and 5.96% at the 20～40 cm, whereas no significant changes occurred between the plot by rotation with paddy and wheat and the control. Compared with the control, for the plots by continuous cropping with jute, rotation with paddy and rape, their organic content was respectively increased by 26.66 % and 47.93% at the 0～20 cm soil layer, increased by 21.92% and 9.46% at the 20～40 cm, increased by 15.46% and 9.36% at the 40～60 cm, but the organic content was not significantly increased by rotation with paddy and wheat. In addition, soil cation exchange capacity (CEC), total N, hydrolysable N, available K were all promoted, whereas soil salt content and pH value were reduced by way of those land use. For the plots by continuous cropping with jute, rotation with paddy and rape, rotation with paddy and wheat, their soil protease activity at the 0～20 cm soil layer was respectively increased by 2.24, 0.61, and 2.00 times as against the control, microbes by 45.98, 24.66, and 2.27 times. Moreover, the number of bacteria, of actinomycetes, of fungi and activity of urase, of hydrogen peroxidase, of phosphatase were also increased. By using principal component analysis, the plot by rotation with paddy and rape ranked the highest, whereas the lowest by rotation with paddy and wheat in terms of the ameliorative effect.⑵Jute straw (A1, A2, A3) and chicken manure (B1, B2, B3) have 3 application levels (1 200, 2 400, and 3 600 kg·hm-2) respectively. Compared with CK, for A3B1, A3B2, and A3B3, their soil density at the 0～20 cm soil layer was decreased by 4.79%, 6.85%, and 7.53% respectively, whereas the differences in soil density among other treatments were not significant. Compared to CK, the organic content from A1B2 to A3B3 was increased by 7.64%, 8.82%, 8.45%, 16.73%, 13.64%, 25.36%, 36.64%, 54.64% except A1B1. Meanwhile, soil N, P, K, and CEC were also rised with organic fertilizer addition, and pH value, salt content were declined. The soil protease activity from A1B1 to A3B3 was increased by 35.94%, 191.48%, 54.83%, 67.49%, 264.50%, 89.98%, 196.57%, 274.34%, 211.34% compared with CK, so are phosphatase, invertase, hydrogen peroxidase, urease, fungus, and bacterium. According to principal component analysis and cluster analysis, the ameliorative effect of A3B2, A3B3 is good, that of A2B1, A2B2, A3B1, and A2B3 takes second place, and that of CK, A1B1, A1B2, A1B3 is weak.⑶Beach plum came to no harm at low salinity (3 g·L-1), whereas at high salinity (9 g·L-1) it was observed that the addition of the degradable substance in the cell, organelle degradation, the nucleus chromatin reduction, and part invagination of plama membranes, but the plasmolysis did not occur. Meanwhile, NaCl treatments stimulated an increase in these parameters, i.e., water content in the root of beach plum, Ca2+ content in the root, Mg2+ content in the leaf, Cl- content in the leaf and Na+ content in the leaf or the root. In addition, salt treatments led to an increase in water content in the root of Japanese mulberry, proline content, activity of superoxide dismutase (SOD) and peroxidase (POD), the content of Ca2+, Mg2+ in the root, the content of Mg2+ in the leaf, Cl- content in the root or the leaf, and Na+ content in the leaf or the root.⑷K, Mg, and Ca were aggregated in the stele of the root of beach plum under the treatment of 9 g·L-1 NaCl. Meanwhile, contents of Na, Mg in the root were increased with the addition of NaCl concentration. Cl content was relatively low in the rhizosphere of beach plum. NaCl treatments made Cl transform its accumulation into a deficit at 1～100μm in the rhizosphere of beach plum, and the content of Cl in the root was higher under the NaCl treatments compared to the control. The content of Fe was high in rhizosphere of beach plum. Contents of Cl, Ca, and Na in the root of white ash were low under the control. Contents of Na, Cl, Ca, and Mg in the root of white ash were higher at low salinity (3 g·L-1) compared to the control. At high salinity (9 g·L-1), contents of Na, Ca, Mg, and Cl in the root of white ash were declined, and increased for K, Fe, Zn. Meanwhile, the content of Na was relatively high in the rhizosphere, K, Ca, and Mg were accumulated in the stele of white ash under the NaCl treatments. The accumulation for Fe occurred at 1~100μm in the rhizosphere of white ash under the control, but the deficit for Fe under the NaCl treatments. Moreover, the content of Fe in the root was higher compared with the treatment of 3 g·L-1 NaCl.Those results indicated that:①Each land use can increase the organic content, improve soil perviousness and water retention ability, raise soil nutrients, enhance biological activity, promote nutrient cycle, and the ameliorative effect at the 0～20 cm soil layer was better than that in 20～40 cm or 40～60 cm. Those land use was put in order with ameliorative effect: rotation with paddy and rape>continuous cropping with jute>rotation with paddy and wheat>barren coastal solonchak.②The application of jute straw and chicken manure increased the organic content, reduced soil density, enhanced soil perviousness, accelerated desalting, reduced pH value, raised soil N, P, K content. Moreover, the activity of soil urease, invertase, hydrogen peroxidase, phosphatase was increased with the addition of jute straw and chicken manure, and the change of the microbial number is similar to that of those enzymes activity. The classification of the coastal solonchak according to ameliorative effect of different levels of jute straw and chicken manure was obtained, namely CK, A1B1, A1B2, A1B3 belonging to the first kind, their weak amelioration; A2B1, A2B2, A3B1, A2B3 belonging to the second kind, their medium amelioration; A3B2, A3B3 belonging to the third kind, their strong amelioration.③Beach plum has evolved its mechanisms to adapt to salt stress by the following way: an increase in water content in the root, an accumulation in the content of Ca2+ in the root, of Mg2+ in the leaf of beach plum, but the salt-tolerance of beach plum was weakened by a simultaneous increase in the content of Cl- in the leaf, the content of Na+ in the root or the leaf. It was an excess of the content of Na+ in the root or the leaf of Japanese mulberry, the content of Cl- in the root or the leaf that caused the salt injury. However, Japanese mulberry's positive response to salinity depends on the following way: an increase in water content in the root, an accumulation of proline, an ascent in activity of SOD and POD, an increase in the content of Ca2+, Mg2+ in the root, in the content of Mg2+ in the leaf.④The root absorption of Cl, Fe didn't correlate closely with salt injury of beach plum, whereas over-accumulation of Na might be main mechanism of generating salt injury. Over-accumulation of Na, Cl in the root resulted in salt injury of white ash, but it is not known for Fe.
|
PDF Full Text Request