Effects Of Cutting, Lodging And Fertilizers On The Alfalfa (Medicago Sativa L.) Seed Yield And Quality

The studies were carried out in Jiuquan, Gansu Province, to evaluate the effects of cutting, loging, foliar application boron and KH2PO4 on alfalfa seed yield, yield components and quality parameters, and the effects of potassium and phosphorous application on alfalfa seed quality parameters and quality parameters changing after four years storage. The results indicated that:1. Cutting times effected alfalfa reproductive rates. After the cutting of brunch-stem formed stage, alfalfa reproduction lasted 9d on bloom stage and 41d on pod-set and seed-fill stage, the growth rate was higher, and then slowed down. After the cutting of bud stage, alfalfa growth lasted 15d on bloom stage and 33d on pod-set and seed-fill stage, the reproduction rate was initially slow and then quickened. The cutting heights delayed reproductive growth stage and harvesting time with stubble height decreasing, but not change the reproductive rate. Shoots/m~2 and pods/raceme increased with the delay of cutting time. The highest seed yield (1118.08kg/hm~2) was obtained at the cutting of brunch-stem formed stage with 25cm stubble height. Bud stage cutting decreased seed yield significantly. The cutting of brunch-stem formed stage did not influence seed germination, first count, hard seed, and death seed percentage, but the cutting of bud stage decreased seed germination and first count significantly, and increased hard seed percentage.2. The lodging during bud stage decreased seed yield significantly ( P<0.05), seed yield decreasing rate reached 23.4% on average. The lodging in full florets stage, early pod stage and later pod stage also decreased the seed yield, the decreasing rate were 11.2%, 8.6% and 11.6% respectively. The reason of seed yield decreased by lodging was that lodging reduced racemes per stem and pods per raceme significantly (P<0.05). Lodging did not affect alfalfa seed quality significantly.3. Foliar application boron significally increased seed yield, the prime application concentration was 0.4%. Foliar application KH2PO4 increased seed yield as well, the prime application concentration was 0.3%. The application of boron decreased death seed percentage significantly, but not changed the germination percentage, hard seed and fist count. The application of KH2PO4 did not affect the first count and germination percentage, but death seed percentage decreased significantly and hard seed percentage increased significantly with application concentration increasing.4. In the harvest year, combined application of potassium and phosphorous significantly improved seed germination and first count, and decreased hard seed percentage. Potassium application also increased seed germination and first count, and decreased hard seed percentage, but there was no statistical significant difference compared with control. After four years storage, potassium application slowed down the decreasing rate of seed germination and delayed seed aging. Alfalfa seed vigor index increased with the increase of application rate, but the difference was not significant.