种植密度和施氮量互作对盐碱地紫花苜蓿生长性能和生理特性的影响

以紫花苜蓿(Medicago sativa)WL919品种为材料,设置15.0 kg·hm?2(D1)、30.0 kg·hm?2(D2)、45.0 kg·hm?2(D3)3个播种量,150.0 kg·hm?2(N1)、225.0 kg·hm?2(N2)、300.0 kg·hm?2(N3)3个施肥量,研究了种植密度和施肥...

Interaction effects of plant density and nitrogen rate on the growth and physiological traits of alfalfa in saline alkali soils

Field experiments were conducted to study the effect of nitrogen rate and planting density on the growth and physiological traits of alfalfa WL919 grown in saline soil. The effects of three planting densities (D1 = 15.0 kg·ha?1, D2 = 30.0 kg·ha?1, and D3 = 45.0 kg·ha?1) and three nitrogen rates (N1 = 150.0 kg·ha?1, N2 = 225.0 kg·ha?1, and N3 = 300.0 kg·ha?1) were investigated in this study to provide technical support for high-yield cultivation of alfalfa in saline-alkali soils. The results showed that 1) the plant height and dry biomass yield of alfalfa increased at first and then decreased with the increase in planting density. They reached their highest at medium density (D2) and then decreased, but they always increased with the increase in nitrogen application rate. 2) The results for the interactions between planting density and nitrogen application rate showed that alfalfa plant height and hay yield were both optimal under the medium-density and medium-nitrogen (D2N2) treatment. 3) Alfalfa is at the budding stage and the initial flowering stage at 120 days after sowing. At this time, the forage quality of alfalfa is optimal and the hay yield is 11 057.2 kg·ha?1, which means that it is the most suitable harvest time. 4) The malondialdehyde content was the lowest at 60 d after sowing. At this time, the nitrogen application rate had no significant effect on the malondialdehyde content (P > 0.05). At 120 d after sowing, the D3N2 combination had the lowest malondialdehyde content. 5) The proline content first increased and then decreased as the planting density and nitrogen application rate increased. In general, superoxide dismutase activity increased as the planting density and nitrogen application rate rose, and the maximum value was showed under D2N2 treatment. Peroxidase activity was higher under the medium density (D2) treatment and under the D2N2 treatment. Oxidase activity was optimal, whereas catalase activity increased at first and then decreased with the increase in nitrogen application at the D2 and D3 densities. Catalase reached its optimal activity under medium nitrogen (N2). The results for the interaction between planting density and nitrogen application rate showed that the growth and physiological characteristics of alfalfa in saline soil under the medium density and medium nitrogen (D2N2) treatment were optimal.