本试验以“甬优1540”为材料，通过2年的田间重复试验，在头季稻总施纯氮量（225.00kg·hm^-2）不变的前提下，设置头季不同氮肥运筹处理（基肥：第一次分蘖肥：第二次分蘖肥：穗肥比分别为3:1:2:4(N1)、3:2:1:4(N2)、3:3:0:4(N3)、4:3:0:3(N4)），从水稻群体分蘖特性、冠层结构特点、光合生理变化及干物质积累与运转规律入手，探讨了东南稻作区机械化栽培下头季稻氮肥运筹对再生稻产量形成的影响。结果表明，头季前氮后移施肥的N1处理有助于增加头季分蘖数，提高分蘖成穗率，N1处理成穗率高达70.18%，比基蘖肥比重高的当地常规施肥N4处理提高了9.15%。N1处理还有助于提高群体LAI值，其头季及再生季齐穗期LAI值分别比N4处理提高了16.52% 和29.87%。就茎鞘物质运转率及冠层光能截获率而言，N1处理下其头季稻茎鞘物质运转率比N4处理提高了50.57%，而其再生季齐穗期的冠层光能截获率比N4处理提高了5.07%。在本试验中,头季稻前氮后移的N1处理两季实际总产量最高，2年平均实际总产达17351.23 kg·hm^-2，比当地常规施肥N4处理提高了23.00%。由此可见，头季稻合理氮肥处理有利其提高健桩存量，从而为再生季作物的群体及产量形成奠定基础。在本研究中，低留桩机械化栽培下头季稻适当的前氮后移，不仅提高头季稻产量，而且还有利其再生腋芽的萌发，增加再生季成穗率，从而实现水稻一种两收目的。

Maize/peanut intercropping system shows the significant yield advantage. Soil microbes play major roles in soil nutrient cycling and were affected by intercropping plants. This experiment was carried out to evaluate the changing of rhizosphere microbial community composition, and the relationship between microbial community and soil enzymatic activities, soil nutrients in maize/peanut intercropping system under the following three treatments: maize (Zea mays L.) and peanut (Arachis hypogaea L.) were intercropped without any separation (NS), by half separation (HS) using a nylon net (50 μm) and complete separation (CS) by using a plastic sheet, respectively. The soil microbial communities were assessed by phospholipid fatty acid (PLFA). We found that soil available nutrients (available nitrogen (Avail N) and available phosphorus (Avail P)) and enzymatic activities (soil urase and phosphomonoesterase) in both crops were improved in NS and HS treatments as compared to CS. Both bacterial and fungal biomasses in both crops were increased in NS followed by HS. Furthermore, Gram-positive bacteria (G+) in maize soils were significant higher in NS and HS than CS, while the Gram-negative (G–) was significant higher in peanut soil. The ratio of normal saturated to monounsaturated PLFAs was significantly higher in rhizosphere of peanut under CS treatment than in any other treatments, which is an indicator of nutrient stress. Redundancy analysis and cluster analysis of PLFA showed rhizospheric microbial community of NS and HS of both plants tended to be consistent. The urase and Avail N were higher in NS and HS of both plants and positively correlated with bacteria, fungi (F) and total PLFAs, while negatively correlated with G+/G– and NS/MS. The findings suggest that belowground interactions in maize/peanut intercropping system play important roles in changing the soil microbial composition and the dominant microbial species, which was closely related with the improving of soil available nutrients (N and P) and enzymatic activities.

Continuous monoculture problems, or replanting diseases, are one of the key factors affecting productivity and quality ofChinese medicinal plants. The underlying mechanism is still being explored. Most of the studies on continuous monocultureof Rehmannia glutinosa L. are focused on plant nutritional physiology, root exudate, and its autotoxicity. However, thechanges in the diversity of microflora in the rhizosphere mediated by the continuous monoculture pattern have beenremained unknown. In this study, terminal restriction fragment length polymorphism (T-RFLP) technique was used forfingerprinting fungal diversity in the rhizosphere soil sampled from the fields of R. glutinosa monocultured for 1 and 2 yr. Theresults showed that the structure of fungal community in consecutively moncultured rhizosphere soil was different fromthat in control soil (no cropping soil), and varied with the consecutive monoculture years (1 and 2 yr). The comprehensiveevaluation index (D) of fungal community estimated by principal component analysis of fragment number, peak area,Shannon-Weiner index, and Margalef index was higher in 1 yr monoculture soil than that in 2 yr monoculture soil,suggesting that consecutive monoculture of R. glutinosa could be a causative agent to decrease the diversity of fungalcommunity in the rhizosphere soil.