Effect Of Different Irrigation Amount On Growth Of Alfalfa (Medicago Sativa L.) Before Winter Under Drip Irrigation Sowing In Autumn In Beijing

Alfalfa (Medicago sativa L.) as a high protein forage, play a vital role in the dairy industry. And drip irrigation (DI) as the most water-saving irrigation methods in the world are widely used in the production of a variety of crops, but has not application in the alfalfa production widespread. DI has obvious advantages in water saving and yield of alfalfa. However, in the north of China due to seasonal reasons, at the same time, we need to consider sowing time and winter survival of alfalfa. Considered high germination rate at next year, and low weed infestation degree, autumn as a warm and suitable season, is thought to be a better time to sow. This study was conducted in Beijing, autumn sown alfalfa under different DI treatments, explore alfalfa in different irrigation treatments and the changes of alfalfa in the biomass and the varieties of nodule numbers with moisture in soil. Test using randomized complete block design, respectively the irrigation frequency (10D,20D,30D) and irrigation quantity (irrigation limits 80%FC, irrigation limits 60%FC) two factor experiment. Growth characteristic, including growth rate, plant height, stem diameter(SD), branch number(BN),intermodal number(IN) and internode length(IL), leaf area index(LAI), etc. and biomass index, including biomass per plant, fresh weight(FW) and dry matter weight (DW), etc. and nodule numbers, including total number of root nodules(TNN), effective number of nodules (ENN), roots nodule number (RNN) and lateral root nodule number (LNN), underground biomass, including root diameter, root weight, total root length(TRL), root surf area(RSA), root average diameter(RAD), root length per volume(RLV), root volume(RV), root forks(RF) and root tips(RT). Research results show that:1. In the irrigation time interval 10d, irrigation limits of 80% FC, that is irrigation treatments W1 (65.35mm), alfalfa LAI was the highest reached 3.07, plant biomass was 0.9g, FW was 645kg/hm2, DW reached 131kg/hm2 at significant index (P<0.05).2. Different irrigation treatments had significant effects on alfalfa nodule numbers (P<0.05). The autumn sowing TNN, ENN and LNN in irrigation treatments W6 (31.39mm) performance was the best, respectively,24,23,20; overall performance for with the irrigation quantity decreased (except for treatments W1), alfalfa nodule numbers had been an increasing trend with the increase of different irrigation intervals (10D,20D,30D).3. Different irrigation treatments had significant effect on alfalfa root weight, TRL, RLV, RV, RSA and RV (P<0.05), alfalfa root weight, root diameter, RDW, RSA, RAD, RLV and RV under the condition of treatments W6 (31.39mm) were best, and these indicators were the best performance in the irrigation cycle 30D.4. Overall, the autumn sowing alfalfa’s main purpose is to improve the rate of reviving at the next year, and also increase the root biomass. If the autumn sowing alfalfa harvest, more biomass and LAI in irrigation treatment W1 performance was the best. When autumn sowing alfalfa not play as a forage, but prepared for the coming year reviving their own, while considering the nodule number and root biomass, then choose irrigation W6 (31.39mm).