[Responses of soil microbial biomass C and P to different long-term fertilization treatments in the yellow paddy soil]. / 黄壤稻田土壤微生物生物量碳磷对长期不同施肥的响应.

To explore the rational fertilization mode to improve the availability of soil phosphorus (P), we analyzed the changes and coupling characteristics of soil carbon (C) and P, microbial biomass C (MBC) and P (MBP) under different fertilization modes with a successive 22-year field experiment in yellow paddy soil. The experiment had 10 treatments, including no fertilization (CK), single application of nitrogen (N), combination of phosphorus and potassium (PK), combination of nitrogen and potassium (NK), combination of nitrogen and phosphorus (NP), combination of nitrogen, phosphorus and potassium (NPK), single application of organic fertilizer (M), and three organic-inorganic fertilizer combinations (1/4M+3/4NP, 0.5MNP, MNPK). The results showed that, compared with CK, the contents of total organic C (TOC), total P (TP), MBC and MBP in N and NK treatments decreased to some extent, while those in PK, NP and NPK treatments increased. Compared with the treatments of no fertilizer and inorganic fertilizer, the contents of TOC, MBC, MBP and MBP/TP ratio in treatments with manure significantly increased, among which M and MPNK treatments showed the strongest enhancement. The treatments with manure had the lowest MBC/MBP ratio, TOC/MBP ratio and MBC/TP ratio, while N treatment had the highest value. MBC, MBP, MBP/TP ratio, MBC/MBP ratio, TOC/MBP ratio and MBC/TP ratio were significantly correlated with TOC and available P, TOC was the direct factor affecting MBC, MBP, and MBP/TP ratio, while available P was the direct factor affecting MBC/MBP ratio, TOC/MBP ratio, MBC/TP ratio. In summary, soil MBP content and the coupling relationship between C and P could effectively distinguish the modes of production with single chemical fertilizer application and manure application, and could be used as biological indices in the evaluation of soil P fertility. Combined application of manure is an effective way to enhance P availability and increase its potential capacity and maintain soil biological health in yellow paddy soil.

Occurrence characteristics of Echinochloa and its response to long-term fertilization in paddy fields of yellow soil.

We studied the characteristics of Echinochloa and its response to variation of rice yield and soil properties under long-term fertilization in paddy field of yellow soil, based on a 23-year long-term fertilization experiment in Scientific Oberving and Experimental Station of Arable Land Conservation and Agricultural Environment (Guizhou), Ministry of Agriculture. The occurrence characteristics of Echinochloa (density, panicle number per plant, totle panicles, seed number per panicle, 1000-seed mass and seed mass per panicle) of ten treatments including CK, N, PK, NK, NP, NPK, 1/4MNP, 1/2MNP, M (manure), MNPK were examined. The results showed that the characteristics of Echinochloa significantly varied with long-term different fertilization. The highest density, panicle number per plant and total panicles of Echinochloa were attained in the MNPK treatment, followed by the 1/4MNP treatment. Compared with the NPK treatment, the density of Echinochloa was significantly decreased in no fertilizer treatment (CK) and unbalanced chemical fertilizer treatments (N, PK, NK, NP). The panicle number per plant significantly increased in organic fertilizer treatments (1/4MNP, 1/2MNP, M, MNPK). Both the density and total panicles of Echinochloa were positively correlated with rice yield. The occurrence characteristics of Echinochloa were positively correlated with soil organic matter, total N, total P, available N, available P and available K. Results from path analysis showed that soil total N had a direct positive effect on panicle number per plant and soil total P content was the main factor affecting the density and total panicles of Echinochloa. Soil available K content was the factor with strongest influence on seed number per panicle and seed mass per panicle. We concluded that the occurrence characteristics of Echinochloa varied with long-term different fertilization. The density, panicle number per plant and total panicles of Echinochloa could be increased with appling cow manure. Soil total P was the direct influencing factor for the variation of density and total panicle of Echinochloa in paddy field of yellow soil.