Objectives Soil fertility is the foundation for efficient crop production and scientific fertilization. The soil fertility and crop yield were monitored using a long-term experiment, to clarify their response to fertilization in the east Henan Province.
Methods Shangqiu City is located in the east part of Henan Province, where most farmland is fluvo-aquic soil. The long-term fertilization experiment in Shangqiu consists of 6 monitoring sites around the city, the soil samples in 0−20 cm and 20−40 cm layers were collected every year from all the monitoring sites for the determination of organic matter (OM), total nitrogen (TN), total phosphorus (TP), alkali hydrolyzable nitrogen (AN), available phosphorus (AP), available potassium (AK), slowly available potassium (SK), pH, and soil bulk density from 2006 to 2019. At the same time, the nitrogen, phosphorous, and potassium fertilizer input and crop yield were investigated. The soil fertility were evaluated using the modified Nemero index method, and the fertilizer contribution to soil fertility and crop yield were calculated using the path coefficient method.
Results During the 14 years from 2006 to 2019, the soil OM, TN, TP, AN, AK and SK, and the soil comprehensive fertility index (IFI) tended to increase in 0−20 cm soil layers, with the increase rate of 84.1%, 165.0%, 28.0%, 57.0%, 61.6%, 277.3%, and 0.37, respectively, while the AP did not changed significantly. The OM, TP, AN, AK and SK and IFI in the 20−40 cm soil layer kept increasing, and the TN and AP increased first and then decreased. The bulk density was in an increased trend in the 0−10 cm and 10−20 cm soil layers. The application amount of N and P fertilizers and the total amount of chemical fertilizers increased by 79.0%, 186.0% and 73.8%, respectively, and that of K fertilizer increased first and then decreased over the 14 years. The total output of wheat and maize was increased only by 4.2% over the 14 years, which was significantly lower than the increase of chemistry fertilizer input. According to the Path analysis, the contribution values of N, P and K fertilizers to soil fertility were 0.718, 0.710, and 0.710, and to crop yield were 1.091, 1.087, and 1.087 from 2006 to 2009. While the contribution to soil fertility was 0.523, 0.364, and −0.620, and that to crop yield were 0.911, 0.884, and −1.108 from 2010 to 2019 year, obvious lower than that from 2006 to 2009.
Conclusions During the 14 years period from 2006 to 2019, the chemical fertilizer input increased by 73.8%, while the crop yield increased by 4.2%, the contribution of N, P and K fertilizer input to soil fertility and crop yield showed a decreasing trend. The soil pH did not change obviously and the IFI was generally in middle level in 0−20 cm layer. The topsoil layer tended to be compacted and consolidated due to over application of chemical fertilizers after 2010. More study should be conducted to reduce chemical fertilizer input and alleviate soil compaction in the future.
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