The optimum harvest time of Caragana microphylla for forage in Shanxi

To find out the optimum harvest time of Caragana microphylla for forage, and to provide a theoretical basis for their scientific management and reasonable utilization, our study evaluated the changes in the nutrient contents in different periods of its life cycle and phenological periods of the yearly growth cycle. Growth and phenological stages of C. microphylla plants were recorded continuously over three years. The branches of 1~8 a and 3 a in different phenological stages, containing the leaves, flowers, and fruits, were collected to measure the nutrient contents, such as crude protein, crude fat, crude fiber, crude ash, nitrogen-free extract, calcium, phosphorus, and so on, and then to compare whether there exists significant differences between the branches. The optimum harvest time for forage was determined by the analytic hierarchy process (AHP) method to calculate the grey correlation degree of each branch age, phenological stages, and reference vector. Our study shows: 1) Based on nutritional value of branches in different growth ages, the equal relational grade sequence is 3 a>2 a>4 a>5 a>1 a>6 a>7 a>8 a, while the weighted grade is 3 a>1 a>5 a>2 a>4 a>6 a>7 a>8 a. 2) In order of phonological stages, the equal relational grade sequence is fruit forming stage>fruit maturity stage>postharvest growth stage>flowering stage>leaf expansion stage>seedling emergence stage>defoliation stage>dormancy stage, and the sequence of the weighted grade analysis was fruit forming stage>postharvest growth stage>fruit maturity stage>flowering period>leaf expansion stage>defoliation stage>seedling emergence stage>dormancy stage. In conclusion, the optimum harvest time of C. microphylla for forage is the fruit forming stage while branches are in 3 a, when it is also the best time for trunk cutting.