Study Of Salt Resistance And Coupling Effects Of Salt And Fertilizer On Amaranth

The sand culture in the green house and field experiments in the coast of Jiangsu province were carried out to study the salt stress and combined effects of seawater irrigation with nitrogen fertilizer (N, urea) application on the growth, yield, physiological characteristics, chlorophyll contents, ion distribution and total nitrogen contents of grain amaranth. The results were as follows:1) Compared with the control, the germination rate of grain amaranth seedlings was not significantly changed over a range of NaCl concentrations from12.5mmol·L-1to100mmol·L-1NaCl. Along with NaCl stress strength upward, the germination rate decreased significantly.12.5mmol·L-1to50mmol·L-1NaCl treatment and5%seawater significantly increased the growth of grain amaranth seedlings, but significantly decreased when the NaCl and seawater stress strength upward. With the NaCl concentration increased, K+concentration in the root reduced while K+concentration in the leaf increased, the root, stem and leaf accumulated more Na+and Cl-when the NaCl concentrations increased, and Na+content in the root increased the largest, Na+content in root and stem always larger than leaf. Na+content in leaves was no significant difference with the control, More of the Na+retention in the roots. In all treatments, the vablue of K+/Na+sequence was always showed:the leaf>the stem>the root.2) The chlorophyll content was not significant difference compared to the control over a range of5%to15%, while significantly decreased when the seawater stress strength upward.5%seawater significantly increased the net photosynthetic rate of grain amaranth seedlings, but significantly decreased when the seawater concentration increasing, it was only16.4%of the control under the40%seawater treatment. These indicated that low NaCl and seawater concentration could improve the photosynthesis of the grain amaranth. 3)-0.096,-0.198MPa NaCl, and Na-salt all did not influenced the dry weight of grain amaranth seedlings. Nevertheless,-0.096,-0.198MPa Cl-salt all increased the dry weight of grain amaranth seedlings compared with the control.-0.437NaCl, Na-salt and Cl-salt decreased plant dry weight significantly, and the dry weight of NaCl and Na-salt was decreased more than that of Cl-salt.-0.096MPa NaCl and Na-salt did not affect the growth rate, at the same time, the growth rate under-0.096MPa Cl-salt treatment was increased markedly. Along with all stress strength upward, the growth rate all decreased remarkably. The order of growth inhibition under different treatments with high pressure condition (-0.437MPa) was as follows:Na-salt> NaCl>Cl-salt. Salt stress all decreased leaf chlorophyll content, however, there were no significant difference between-0.096,-0.198MPa Na-salt treatment and control. SK,Na in roots, stems and leaves were all increased under-0.096,-0.198,-0.437MPa NaCl and Na-salt treatments. In general, growth inhibition of grain amaranth seedlings from Na-salt stress was much more than that from Cl-salt stress. Salt adaptation at a certain degree to Na+of grain amaranth seedlings was due to high K+selective absorption and transport.4) Under20%seawater irrigation and N application120kg N·hm-2treatment, the fresh grass and grain yields increased significantly compared to N application60kg N·hm-2, while the yields had no significant difference with N application180kg N·hm-2. Under40%seawater irrigation, the grain yield was the highest at N application of120kg N·hm-2, while still significantly lower than these under20%seawater irrigation and N application120kg N·hm-2treatment. The grass yield was the highest at freshwater irrigation and N application of60kg N·hm-2, the grain yield was the highest at freshwater irrigation and N application of180kg N·hm-2. While with20%seawater irrigation, N application of120kg N·hm-2, grain and grass yields were not very significantly different from the highest values. The K+contents in the stem and leaf were increased with N application increasing. The Na+contents, the same as the changes of Cl-contents in root, stem and leaf, were all first decreased and then increased. Appropriate N application within120kg·hm-2could increase K+/Na+ratio in stem, while decreased when N application increasing to180kg N·hm-2Under20%seawater irrigation, the total nitrogen content in the leaf was the highest at N application of120kg N·hm-2. Nitrogen fertilizer application had little effect on the total nitrogen content in the leaf under40%seawater irrigation. In general, nitrogen application of120kg·hm-2improved salt tolerance and the yield of grain amaranth significantly under 20%seawater irrigation in coastal beach of north Jiangsu and this combination was feasible.