Relationship of crop yield and soil organic carbon and nitrogen under long term fertilization in black loessial soil region on the Loess Plateau in China.

The feedbacks between crop yield and soil organic carbon and total nitrogen contents were examined in a long-term experiment, which was established on black loessial soil on the Loess Pla-teau in China. There were six treatments, including CK (no fertilizer), N (single nitrogen fertilizer), NP (chemical fertilizers NP), SNP (straw and chemical fertilizers NP), M (organic manure) and MNP (organic manure and chemical fertilizers NP). Results showed that balanced application of chemical fertilizers, single application of organic manure, the combined application of chemical fertilizers with organic manure and chemical fertilizers coupled with straw returning to the field all significantly increased crop yield and its stability compared with control (CK).

[Soil Olsen-P content changing trend and its relationship with phosphorus surplus and crop yield under long-term fertilization in loessial soil region on the Loess Plateau, China].

The changing trend of soil available phosphorus (Olsen-P) content in soil and its relationship with soil phosphorus surplus and crop yield are fundamental when making appropriate phosphate fertilizer recommendations. In this paper, the influences of long-term fertilization on crops phosphorus uptake, soil phosphorus surplus, changing trend of soil available phosphorus content and relationships of soil available phosphorus content with soil phosphorus surplus and crop yield were investigated through 34 years (1981-2015) long-term trial in loessial soil region on the Loess Plateau. The experiment had a completely-randomized-block split-plot design in triplicate.

[Effects of long-term fertilization on nitrogen fertilizer use efficiency in loessial soil region on the Loess Plateau, Northwest China].

Nitrogen fertilizer use efficiency is a key parameter to determine recommended nitrogen fertilizer amount and evaluate the effects of nitrogen fertilizer application. The effects of long-term fertilization on annual and accumulated nitrogen fertilizer use efficiency and the relationship between them were studied using a 34-year fertilization experiment (1981-2015) in loessial soil region. The results showed that fertilization had significant influence on annual and accumulated nitrogen ferti-lizer use efficiency of wheat, rape and flax in the period of 1983-2015.