施磷对滴灌苜蓿干草产量及磷素含量的影响

为探讨不同施磷量对滴灌苜蓿干草产量、吸磷量及苜蓿磷素利用效率的影响,明确不同磷素水平下土壤全磷和速效磷的含量分布特征。试验设4种施磷梯度,分别为施P₂O₅ 0 kg·hm^-2(CK)、50 kg·hm^-2(P₁)、100 kg·hm^-2(P₂)、150 kg·hm^-2(P₃),采用滴灌水肥一体化施肥方式,平均分4次分别在返青后的分枝期、第1茬、第2茬、第3茬刈割后3~5 d施入。结果表明,各茬次苜蓿植株叶片、茎秆磷含量在P₂处理下达到最大值,其中叶片磷含量数值分别为0.223%,0.275%,0.292%和0.218%;茎秆磷含量数值分别为0.202%,0.223%,0.201%和0.146%。苜蓿叶片磷含量大于茎秆磷含量。滴灌苜蓿植株的干草产量、吸磷量随着施磷量的增加呈先增加后降低的趋势,在第1茬P₂处理达到最大值,数值分别为6.54 t·hm^-2和13.78 kg·hm^-2。土壤全磷含量、速效磷含量随着施磷量的增加呈逐渐增大的趋势,且各施磷处理显著大于未施磷处理(P<0.05),滴灌苜蓿总干草产量在P₂处理条件下达到最大,达21.24 t·hm^-2。苜蓿的磷素利用效率为随施磷量的增加呈逐渐降低的趋势,P₁处理苜蓿的磷素利用效率在第1茬达到最大值为28.37%。滴灌苜蓿植株吸磷量与干草产量呈极显著正相关(P<0.01)。当施P₂O₅为100 kg·hm^-2(P₂)时,能够有效促进苜蓿根系对土壤速效磷的吸收,提高苜蓿磷素利用效率,进而提高滴灌苜蓿干草产量。

Effects of phosphorus application on hay yield and phosphorus contents of alfalfa under drip irrigation

This research aimed to explore the effect of different phosphorus (P) fertilizer application rates on the yield and P use efficiency of alfalfa, and to determine the soil total P and available P levels and plant tissue P levels under the different P fertilizer regimes. P fertilizer rates applied in the experiment were (as P₂O₅ equivalent) 0 kg·ha^-1 (CK), 50 kg·ha^-1 (P₁), 100 kg·ha^-1 (P₂) and 150 kg·ha^-1 (P₃). The P fertilizer was applied together with irrigation water under drip irrigation, beginning at the branching stage of spring growth following winter dormancy, and subsequently 3-5 d after the first, second and third cuts. The maximum P concentration of leaves and stems was attained under the P₂ treatment. The P concentration of leaves was 0.223%, 0.275%, 0.292% and 0.218%, under CK, P₁, P₂, and P₃ treatments, respectively; and the corresponding P concentration of stems was 0.202%, 0.223%, 0.201% and 0.146%. Hence, the P concentration of alfalfa leaves was higher than the P concentration of stems. The hay dry matter yield and elemental P yield were also maximized under the P₂ treatment (6.54 t·ha^-1 and 13.78 kg·ha^-1, respectively). Soil total P concentration and available P concentration increased with increased P fertilizer. The P fertilizer treatments had significantly greater soil P than the CK treatment (P<0.05). The P use efficiency decreased with increased P application, and was highest (28.37%) in the P₁ treatment at the first cutting. The phosphorus uptake of drip-irrigated alfalfa was significantly positively correlated with the hay yield of alfalfa (P<0.01). In conclusion, for the P₂ treatment (100 kg·ha^-1 P₂O₅), and this treatment promoted absorption of soil available P by the alfalfa roots, improved the P use efficiency of alfalfa, and improved the hay yield.