[Effects of P fertilizer on female strobilus and needle N and P nutrition of clones with different fruiting abilities].

In order to realize precise fertilization and high yield management of clonal seed orchard, clones with different fruiting abilities were used as the materials. Four P fertilization levels were at 0, 400, 800 and 1600 g per plant (P, P, P and P respectively). Fertilization was applied before floral primordia formation and after cone picked, respectively. The effects of P fertilizer on the female strobilus of clones and the changes of N, P contents in needles of different positions during floral primordia formation stage and early stage of flower bud differentiation were investigated. The results showed that compared with P, the female strobilus of P and P were significantly increased by 67.4% and 61.2% in 2018 and 28.9% and 14.1% in 2019, respectively. There was a significant negative correlation between the female strobilus with the N content and N/P, a significant positive correlation between the female strobilus and the P content in needles. The responses of N and P contents in needles to P fertilization differed in clones with different fruiting abilities. In floral primordia formation stage, the N content of clones with weak fruiting ability was high, and the N/P was 11.5-12.5, while the P content of clones with strong fruiting abilities was high, and the N/P was 9.5-10.5. During this period, the P content of most clones under P treatment was the highest, while the N/P was lowest. In the early stage of flower bud differentiation, the N/P of two fruiting clones was 15.3-17.0 and 13.2-15.1, respectively. The P content in upside layer was significantly higher while N/P was significantly lower than that in middle and lower layers. In conclusion, the 800 g P fertilization per plant could increase the P content and reduce the N/P of needles during the floral primordia formation stage of clones with diffe-rent fruiting abilities, which was beneficial to the formation of female strobilus and promote the yield of clone seed orchards.