Abstract:

Hairy vetch （Vicia villosa） is one of China’s most important fertilizer and forage dual-purpose green manure crops. In this study， we investigated differences in phosphorus （P） acquisition and rhizosphere properties among different genotypes of hairy vetch to provide baseline knowledge about phosphorus utilization in hairy vetch. A pot experiment was carried out in Xining city， Qinghai Province， testing two factors： Hairy vetch cultivars and phosphate fertilizer types. Two P-efficient and two P-inefficient hairy vetch cultivars were screened in a field test. The phosphate fertilizers were calcium superphosphate and rock phosphate， and the control had no phosphate fertilizer added. We analyzed P uptake， soil P fractions， soil organic acid contents， root acid phosphatase （RACP） and soil acid and alkaline phosphatase activities （ACP and ALP）， and the abundance of genes encoding soil acid and alkaline phosphatases （phoC and phoD） at the full-bloom stage of hairy vetch. The results showed that the ranges of total P-uptake and P-utilization rates of hairy vetch cultivars were 7.45-46.07 mg·pot^-1 and 7.12%-22.49%， respectively. The total P-uptake and P-fertilizer utilization rates were significantly higher in P-efficient cultivars than in P-inefficient cultivars， by 0.91%-61.20% and 12.52%-60.25%， respectively. Compared with P-inefficient cultivars， P-efficient cultivars contained higher proportions of labile P and moderately labile P and lower proportions of stable P. The proportions of labile P and moderately labile P in P-efficient cultivars were 6.14-26.14 times higher and 1.04-1.54 times higher， respectively， than those in P-inefficient cultivars. The proportion of stable P was 2.92-7.91 times higher in P-inefficient cultivars than in P-efficient cultivars. Soil total organic acid and oxalic acid contents， and the activities of RACP， ACP， and ALP were significantly higher in P-efficient cultivars than in P-inefficient cultivars by 117.45%-254.60%， 19.40%-50.75%， 16.37%-146.40%， 6.19%-104.19%， and 6.16%-35.06%， respectively. The abundance of phoC and phoD was 1.07-2.58 times higher and 1.46-3.64 times higher， respectively， in P-efficient cultivars than in P-inefficient cultivars. Linear regression analyses showed that soil total organic acid and oxalic acid contents and RACP and ACP activities were significantly positively correlated with soil labile P （determination coefficients of 0.40， 0.46， 0.13， and 0.19， respectively）， but significantly or very significantly negatively correlated with stable P （determination coefficients of 0.75， 0.58， 0.41， and 0.49， respectively）. In summary， compared with the P-inefficient cultivars， the P-efficient hairy vetch cultivars showed stronger abilities to acquire insoluble P and had higher P-uptake and P-fertilizer utilization rates. The P-efficient hairy vetch cultivars acquired immobile P by increasing organic acid （mainly oxalic acid） contents and phosphatase activity， accompanied by increased abundance of phoC and phoD genes in the soil， which in turn increased the proportions of labile P and moderately labile P and promoted P absorption and utilization.

Key words: hairy vetch cultivars （lines）, soil phosphorus fractions, organic acid, phosphatase activity, phosphatase gene