| In order to provide the scientific basis for reasonable fertilization and improve crop yields, and to reveal the response patterns of carbon(C) and nitrogen(N) accumulation and distribution under various fertilization treatments. Furthermore, to elucidate the impact of soil microbial biomass carbon(SMBC), soil microbial biomass nitrogen(SMBN), and soil nutrition on crop C and N. The aboveground and underground biomass, carbon(C) and nitrogen(N) content, carbon nitrogen ratio, soil microbial biomass carbon(SMBC), soil microbial biomass nitrogen(SMBN), and soil nutrition(organic matter, total nitrogen, total phosphorus, total potassium, available phosphorus and available potassium) of wheat and maize at different growth stage under various fertilization treatments had been analyzed after 21 years of continuous long-term fertilization. There were ten fertilization treatments in total, including non-fertilization(Control), chemical nitrogen(N2), chemical nitrogen and phosphorus(N2P), chemical nitrogen and potassium(N2K), low chemical nitrogen, phosphorus and potassium(N1PK), chemical nitrogen, phosphorus and potassium(N2PK), N2 PK plus organic manure(N2PKM), high chemical nitrogen, phosphorus and potassium(N4PK), N2 PK plus maize straw(N2PKS), and middle chemical nitrogen, phosphorus and potassium(N3PK). The main results and conclusions as follows:1.The studies on C accumulation and N distribution of wheat showed that the aboveground C contents at mature stage were 13310, 10799 and 13242 kg/hm2 in N2 PK, N2 PKM and N2 PKS treatments, which were 239%, 175% and 237% higher than Control treatment, respectively. And the underground C contents in these treatments at this stage were 562, 376 and 592 kg/hm2, which were 186%, 91% and 201% higher than Control treatment, respectively. C contents during growth and mature stage ranged from 131-10799 kg/hm2 for aboveground part and 28.5-376 kg/hm2 for underground part in N2 PKM, 85.5-97.0% of which were distributed to the aboveground part. The aboveground N contents of wheat at mature stage were 413, 339 and 325 kg/hm2 in N2 PK, N2 PKM and N2 PKS treatments, of which were 294%, 223% and 209% higher than Control treatment, respectively. And the underground C contents in these treatments at this stage were 10.7, 8.39 and 2.54 kg/hm2, which were 9, 7 and 2 times higher than Control treatment, respectively. The N contents during wintering period and mature stage ranged from 12.5-339 kg/hm2 for aboveground and 1.44-8.39 kg/hm2 for underground in N2 PKM, of which 91.7-97.8% were distributed to the aboveground part. These results revealed that the C and N distribution proportion were different from various fertilization treatments. The wheat C and N contents can be improved efficiently by N2 PK and N2 PKM fertilization; Meanwhile, less of them can be distributed to the underground part, for which were helpful to enhance wheat yield and promote agricultural sustainable development.2.The studies on C accumulation and N distribution of maize showed that the aboveground C contents at mature stage were 7335, 6810 and 6893 kg/hm2 in N2 PK, N2 PKM and N2 PKS treatments, of which were 202%, 180% and 183% higher than Control treatment, respectively. While underground C contents were 258, 276 and 312 kg/hm2, which were 44%, 55% and 75% higher than Control, respectively. C contents during seeding and mature stage ranged from 49.1-6810 kg/hm2 for aboveground part and 15.2-276 kg/hm2 for underground part in N2 PKM, 74.4-95.9% of which were distributed to aboveground. The aboveground N contents of maize at mature stage were 306, 313 and 299 kg/hm2 in N2 PK, N2 PKM and N2 PKS treatments, of which were 164%, 170% and 158% higher than Control treatment, respectively. And the underground C contents in these treatments at this stage were 5.78, 5.59 and 6.23 kg/hm2, all of which were 3 times higher than Control. The N contents during seeding and mature stage ranged from 3.84-313 kg/hm2 for aboveground and 0.768-5.59 kg/hm2 for underground in N2 PKM, 82.8-98.1% of which were distributed to the aboveground part. N2 PK and N2 PKM treatments not only increased C and N contents of maize, but also reduced the distribution proportion of accumulated C and N and the C/N ratio to underground part. It revealed that N2 PK and N2 PKM fertilization treatments can improve the maize production and benefit to agricultural sustainable development.3.The studies on the soil microbial biomass carbon(SMBC) and soil microbial biomass nitrogen(SMBN) of wheat under long-term fertilization showed that at mature stage in 0-20 cm layer, SMBC contents were 154, 209 and 206 mg/kg in N2 PK, N2 PKM and N2 PKS, which were 29%, 75% and 73% higher than Control, respectively. While SMBN contents were 24, 28 and 36 mg/kg, of which were 89%, 115% and 176% higher than control, respectively. In 20-40 cm layer, SMBC contents were 175, 221 and 232 mg/kg at mature stage in N2 PK, N2 PKM and N2 PKS treatments, which were 35%, 70% and 79% higher than Control, respectively. While SMBN contents were 8, 22 and 18 mg/kg, all of which were insignificant in compare with Control. SMBC and SMBN were significantly increased in 0-20 cm layer in N2 PKM and N2 PKS treatments compared with Control treatment, but the differences were insignificant between N2 PKM and N2 PKS treatments.4.The studies on the soil microbial biomass carbon(SMBC) and soil microbial biomass nitrogen(SMBN) of maize under long-term fertilization showed that at mature stage in 0-20 cm layer, SMBC contents were 267, 343 and 329 mg/kg in N2 PK, N2 PKM and N2 PKS, which were 56%, 101% and 93% higher than Control, respectively. While SMBN contents were 43, 57 and 54 mg/kg, of which were 164%, 249% and 233% higher than control, respectively. In 20-40 cm layer, SMBC contents were 221, 243 and 249 mg/kg at mature stage in N2 PK, N2 PKM and N2 PKS treatments, which were 89%, 108% and 113% higher than Control, respectively. While SMBN contents were 38, 51 and 43 mg/kg in these treatments, and they were 4, 6 and 5 times higher than Control, respectively. SMBC and SMBN were significantly increased in 0-20 cm layer in N2 PKM and N2 PKS treatments compared with Control treatment, but the differences were insignificant between N2 PKM and N2 PKS treatments.5.The studies on C and N contents impacted by various soil factors under long-term fertilization showed that in these tested factors of SMBC, SMBN, soil nutrients and p H, the C content of wheat was directly impacted by SMBC, SMBN, total phosphorus, total potassium, available phosphorus and available potassium, the determination coefficient was 0.999. Among these factors, total phosphorus and available phosphorus were the most important affecting factors on C content of wheat, of which the direct path coefficient were 2.12 and-1.15, respectively. N content of wheat was most related with SMBC, SMBN, total phosphorus, total potassium, available phosphorus, the determination coefficient was 0.994, and the total phosphorus and available phosphorus were the most important affecting factors, the direct path coefficient were 2.50 and-1.23, respectively. C content of maize was most directly related with SMBC, SMBN, organic matter, total potassium and p H, the determination coefficient was 0.992, in which SMBC and organic matter were the most important impact factors, the direct path coefficient were 2.33 and-1.31, respectively. While N content of maize was most directly related with SMBC, SMBN, organic matter, total nitrogen and total potassium, the determination coefficient was 0.994, in which SMBC plays the most important role, with the direct path coefficient of 2.25. |
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