Effects Of Subsurface Drip Irrigation On Alfalfa Seed Production

The focus of the experiment is to increase the output and profitability of seeds of alfalfa, during which, it introduces subsurface drip irrigation (SDI) experimental production into the seeds of alfalfa. Through the study of salt distribution of SDI in the soil and the characteristics of growth of alfalfa, it explores the possibility of effectiveness of alfalfa production, thus establishing the system of SDI for alfalfa seeds.The mode of 60 cm and 40×80 row space is adopted in the experiment. The drip irrigation belt is designed by 60 cm every row (T1) or 60 cm every other row (T2) and 40×80 cm (T3) every narrow row. It sets up three irrigation quotas: W1, W2, and W3. After the irrigation, the soil moisture can reach 65~80% (W1),50~65% (W2),35~50% (W3) respectively. The main findings are as follows:1. The conditions of SDI and distribution characteristics of the three irrigation quota: the moist radius is 40 cm in the surface layer and the forth layer and 50 cm in the secondary and the third layer under W1. In the vertical direction, the moist peak can move upward to the surface and downward to 40 cm place. The moist radius of surface layer was 30 cm, the secondary layer was 50 cm, and the secondary layer was 20 cm under W2. In this direction, the moist peak can reach upwards the surface of the soil and downwards to 40 cm; Under W3, the moist radius can not reach more than 10 cm in the surface and the fourth layer and 20 cm in the secondary and the third layer. The vertical moist peak can move upwards to the surface and downwards to 30 cm.2. The SDI condition, the formation and the shape and size of the moist figure are similar to the ellipsoid of the desalinated area. Under W1, the level radius of the desalinated area is 50 cm and the vertial raius is 15 cm. Under W2, the level radius is 30 cm and vertical radius 15 cm. Under W3, the level radius is 20 cm and vertical one is 15 cm.3. The highest seed amount of T3W1 was 909.62 kg/hm2, which is distinctly higher than CK(611.39 kg/hm2) (P<0.01). This indicates that the application of SDI in alfalfa seed production could increase the yield.4. Under SDI condition, alfalfa root quantity shows an obvious increase with the increase of moisture content. Under flood irrigation (sufficient irrigation), too much moisture content is not in favour of the growth fo alfalfa roots.5. Racemes/shoots (x2), pods/ raceme(x3), seeds/pod(x4) and seed yield(y)of each plang shows significant positive correlationship. Its regress equation is y=-2.677+0.025x2+0.136x3+1.712x46. The preliminary estimated results of alfalfa seed production in SDI system is: the irrigated quantum of water was 81.67 mm in the shoot separating period, 88.42 mm in flowing period and 104.67 mm in scabbing-mature period. The date of dripping must be adjusted according to the climate condition during the growth period.