Study On Root Characteristics And Regulation Of Water-Absorption Among Alfalfa Cultivars With Different Fall Dormancy

In order to research root system characteristics among alfalfa cultivars with different fall dormancy sowed in spring, we used combinative method which connected diagnostic-sampling of the up-ground part and delaminated-analysing of the root system together.Fall dormancy is the most important index for introducing alfalfa. This study showed that it had close relation between fall dormancy and characteristics of fighting-cold, but there was not evident consistency between fall dormancy and its root system characteristics, fresh grass biomasses.Crown characteristics were evidently different among different alfalfa cultivars. Crown depth in soil, crown diameter, crown branching numbers and branches diameter increased evidently in the first year. Secondary crown did not appear until second cutting in the second year. Crown depth in soil decreased with fall dormancy increasing.Study on root syetem characteristics of 15 introduced alfalfa cultivars in the first year. The results showed that the deepest taproot was underground 162.3 cm. Secondary root of Alfalfa cultivars grew mainly from the taproot which underground 0~30 cm, there was not secondary root below 40 cm. Root system biomasses and root diameter were decreased from surface layer to deep layer.Study on the root system characteristics of 8 introduced alfalfa cultivars in the second and third year, whose fall dormancy are 2, 3, 4, and 6. The results showed that the deepest taproot was 305 cm in the end of second year. Root system mainly grew underground 60 cm. The proportion of root system biomasses below 60 cm was 84%~94% of the total root system biomasses, and the proportion was increasing with the vegetal year extending. In the end of third year, secondary root of Alfalfa cultivars grew mainly from the taproot underground 0~40 cm; there was not secondary root below 60 cm. And the secondary root position was descending with vegetal year extending.In order to research the regulation of water-absorption of 8 alfalfa cultivars with different fall dormancy, we studied the relationship of root system, up ground biomasses and soil moisture. The results showed that dormancy and semi-dormancy cultivars had the same spatio-temporal characteristics in water-absorption. Water moisture had decreasing trend with the year extending. When harvested three times in one year, up-ground biomasses were closely related with water consumption. During the generational time, the most water consumption and the longest growing time was in branching stage, flowering stage had the fastest water consumption speed. Root system mainly depended on the secondary root to absorb water from top layer to 120 cm layer in the soil.