Inherent soil productivity and yield-increasing potential of potato in main production areas in Inner Mongolia

Objectives Inner Mongolia is one of the main potato production areas in China. The indigenous soil productivities (ISP) and their effects on potato yields with and without fertilization in the main production areas of Inner Mongolia were evaluated, which would provide theoretical basis for tailoring fertilization in different ecological regions.

Methods Yield data were collected from the 1118 potato field trials located at the southern foot of Yin Mountain (SYMt), northern foot of Yin Mountain (NYMt), the hilly area of Yan Mountain (HYMt) and the northern foot of Greater Khingan Range (NGKR) in Inner Mongolia during 2006 to 2015. The potato yields in the treatment of no fertilization were used to calculate the indigenous soil productivities (ISPs) and their contribution to potato yields in the fertilization treatment. Yield increase potential of potato was predicted by the boundary line fitting method. And the yield gaps between the predicted maximum yield and the current yield under recommended fertilization were calculated. The stability and sustainability indexes were used to assess the effect of ISP on potato yield stability and sustainability.

Results The yield of ISP in SYMt, NYMt, HYMt and NGKR were 13.10, 14.67, 15.71 and 16.45 t/hm²; the fertilization yields were 20.90, 23.17, 25.34, 26.54 t/hm²; the corresponding contribution of ISP to potato yield were 57.6%, 62.7%, 63.9% and 66.2%, respectively. With the improvement of inherent soil productivity, the contribution rate of soil base fertility to yield increased gradually. The potato yields obtained with fertilization were significantly and positively correlated with inherent soil productivity, and the linear fitting coefficient between potato yield and ISP were 0.769, 0.876, 0.770 and 0.790 (P < 0.0001) in SYMt, NYMt, HYMt and NGKR, respectively. With the improvement of inherent soil productivity, the yield gaps between the predicted maximum yields. And the current fertilization yields decreased, and the stability index decreased while the sustainability index increased for yield under fertilization.

Conclusions The inherent soil productivity, yield under fertilization and contribution rate of soil productivity are varied among the four main potato production areas in Inner Mongolia, and those in HYMt and NGKR areas are significantly higher than those in SYMt. The predicted highest potato yield by fertilization in SYMt, NYMt, HYMt and NGKR are 53.68、62.87、65.39 and 69.65 t/hm², respectively. There is a significant negative correlation between inherent soil productivity and the current yield potential. The improvement of inherent soil productivity will decrease the stability index and increase the sustainability index of potato yield by fertilization.