| The experiment was conducted in Pingyuan country, Dezhou City, Shandong Province China from 2013 to 2014. Recommended cultivars for the region that were grown in this study were Ji mai 22 and Zheng dan 958 for wheat and maize, respectively. The experiment comprised of four treatments in a randomized block design with three replications. The five treatments were:(1) cattle manure, (2) biogas slurry, (3) crushed maize straw, (4) chemical fertilizer. In ordered to provide a theoretical basis for the efficient utilization of straw resources and increase the fertility of soil, the effect of returning different organic materials on soil organic carbon fractions and crop yield in wheat-maize rotation system was analyzed. The main results were as follows:L The effects of inputting different organic materials on soil moistureAs compared with chemical fertilizer, soil water content was increased after organic materials inputted into soil in wheat-maize system. In wheat season, the order of organic materials exerted on soil water content was:manure (15.81%)> biogas slurry (15.29%)> crushed maize straw (14.84%)> chemical fertilizer (14.05%), especially in 20～40 cm soil layer. When the depth was more than 40 cm, the difference among different treatments was decreased gradually. The organic materials played a significant role in 0～10 cm soil layer and the treatment of manure (21.26%) with the best effect during maize growth.In wheat season the range of pondage was 27.14-53.89 mm, whereas in maize season it was 37.91～66.15 mm. In 0～20 cm soil layer, the greatest water storage was observed in piogas slurry (43.26 mm) during wheat growth while it was manure (56.69 mm) when the crop was maize; In 20～40 cm soil layer, the greatest values were observed in manure (35.77 and 49.44 mm) treatment both in wheat and maize season. In 40～60 cm soil layer, the treatments, manure (41.39 mm) and crushed maize straw (55.30 mm), showed the greatest value.2 The effects of inputting different organic materials on soil bulk densityAfter organic materials returned into soil, they had decreased soil bulk density(SBD) and improved soil structure. We observed this phenomenon especially in 0-20 cm soil layer. When the soil depth was 0～20cm the treatment of crushed maize straw had the minimal SBD 1.11～1.16 g/cm3) while in 20～40 cm it was manure (1.21～1.32 g/cm3). However, the difference was not obvious when the depth was 40-60 cm.With the wheat growing the SBD increased gradually and reached the maximum in mature stage of wheat. However, the effect of organic materials on SBD in maize season was weaken.3 The effects of inputting different organic materials on soil organic carbon, its fractions and sensitivityThe organic materials promoted soil organic carbon and its fractions (MBC, ROC, DOC and HWC) cluster stratification and gathering in 0-60 cm. Meanwhile, the contents of soil 3rganic carbon fractions in wheat season were higher than in maize season. The range of SOC during wheat season was:5.76～12.13 g/kg (0～20 cm),0.84～6.48 g/kg (20～40 cm) and 3.99～6.58 g/kg (40～60 cm). The order of treatments was:manure> biogas slurry> crushed maize straw> chemical fertilizer. And this phenomenon was decreased with wheat growth. However, the range of SOC was in maize season was:5.53～12.43 g/kg (0～20 cm),0.84～7.25 g/kg (20～40 cm) and 0.65-6.49 g/kg (40～60 cm) and the optimal treatment was changed when maize growth stage changed.The highest MBC (513.12 and 427.40 mg/kg) was observed in manure both in wheat and maize seasons. And it had 45.33% and 41.64% higher than chemical fertilizer, respectively. The treatment of biogas slurry (4.61 g/kg) had the greatest soil readily oxidable carbon ( ROC) in 0-20 cm in wheat season, while during maize growth it was crushed maize straw treatment (3.77 g/kg). In wheat season, the best effect of organic materials on the contents of DOC and HWC was accord to wheat stage. However the treatments of crushed maize straw and manure showed a significant role in DOC. As for HWC, we observed the best treatment in wheat and maize season were manure and crushed maize straw, respectively.4 The relationship between soil organic carbon and its fractionsThe order of soil organic carbon fractions accounted for soil organic carbon during our experiment was:ROC> MBC> HWC> DOC, especially the treatments of the organic and biogas slurry inputted (P<0.05). ROC, MBC, DOC and HWC accounted SOC for 10.96%～39.03%,2.60%～9.46%,1.98%～4.77% and 3.76～6.98% respectively in 0～60cm in all treatments during wheat season, while in the maize season they were:9.36%-39.38%, 2.79%～7.20%,2.57%～6.82% and 2.57%～9.50%, respectively. According to regression analysis, ROC and SOC’s relevance was the biggest, followed by MBC. In different seasons, the sensitivity of different organic carbon fractions to organic materials was various. In wheat season, MBC was the most sensitive index to organic materials, whereas it was HWC during maize season. However, with the depth increased the effect was weakened gradually.5 The effects of inputting different organic materials on yields in wheat-maize systemThe treatment of manure with the highest wheat yield (7887.36 kg/hm2) in 2012～2013 when we compared different organic materials. It had 12.38% and 5.12% higher than biogas slurry and crushed maize straw. Meanwhile, the highest maize yield was also observed in it and reached significant level (P<0.05). As compared with 2013, the yield of wheat and maize under all treatments had increased in 2014. When compared with, the treatments of manure, biogas slurry and crushed maize straw had 34.92%,15.19% and 26.55% respectively higher for wheat yield than fertilizer and for maize yield the value were 19.47%,8.48% and 10.69%, respectively. |
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