[Effects of different paddy-upland multiple cropping rotation systems on soil organic carbon and its fractions in paddy field]. / ä¸åŒæ°´æ—±å¤ç§è½®ä½œæ–¹å¼å¯¹ç¨»ç”°åœŸå£¤æœ‰æœºç¢³åŠå ¶ç»„åˆ†çš„å½±å“.

The variations of soil organic carbon and its fractions in different paddy-upland multiple cropping rotation systems were evaluated in field trials in two consecutive years. During paddy-upland multiple cropping rotations conducted over 2 years, the content of soil total organic carbon (TOC) first increased and then decreased. The content of readily oxidized organic carbon (ROC) was highest at the rice tillering stage and lowest at the mature stage. The soil microbial biomass carbon (SMBC) was highest at the tillering stage. The dissolved organic carbon (DOC) content was highest at the mature stage. The maximum and minimum differences were at the booting stage and mature stage for TOC content, at the greening stage and booting stage for ROC content, at the mature stage and the greening stage for DOC content, at the tillering stage and the greening stage for SMBC, respectively. The soil TOC and DOC contents showed the largest variations in the 'winter fallow-early rice-late rice → winter fallow-early rice-late rice' rotation. The soil ROC content showed the largest variation in the 'milk vetch-early rice-late rice → rape-peanut-late rice' rotation. The maximum variation of SMBC was in the 'vegetables-peanut/corn-late rice → milk vetch-early rice-late rice' rotation. The 'potato-maize/soybean-late rice → vegetables-peanut/corn-late rice' rotation resulted in higher soil TOC content at the booting stage. The pattern of 'milk vetch-early rice-late rice → oil rape-peanut-late rice' led to higher soil ROC contents in the early and middle growth stages of late rice. In the 'rape-peanut-late rice → potato-maize/soybean-late rice' rotation, the highest DOC contents were at the greening stage and the mature stage, and the highest SMBC were at the booting stage and the heading stage, respectively. All these diffe-rences were significant. The rank the contents of soil organic carbon fractions from highest to lowest followed the order: TOC>ROC>SMBC>DOC. The results suggested that paddy-upland multiple cropping rotation systems could increase the contents of soil organic carbon and its fractions and improve soil quality and fertility.

[Ecological evaluation of different multiple cropping systems in red soil drylands.] / 红壤旱地不同复种方式的生态功能评价.

In order to maximize the ecological function of red soil drylands and to determine the desirable multiple cropping systems, we evaluated the productivity, circulation of materials, energy and value flows in four multiple cropping systems on the basis of a consecutive three-year field experiment. Four multiple cropping systems were designed: treatment A (CK): wheat/soybean-sesame; treatment B: mixed green manure (rape × Chinese milk vetch × radish)-soybean ‖ maize-mung bean‖ sesame; treatment C: ryegrass-peanut‖ maize-millet‖ buckwheat; and treatment D: rape-mung bean‖ sweet potato; where interplanting was expressed as '/', intercropping as '‖', planting after harvest as '-', and mixed cropping as '×'. Thirteen variables were employed to compare economic, ecological, and social benefits among the four cropping systems using grey relational analysis. The results showed that 'mixed green manure (rape × Chinese milk vetch × radish)-soybean‖ maize-mung bean‖ sesame' exhibited the highest grey relational degrees in terms of economic, ecological, and social benefits, and a highest grey relational degree at 0.847 in the integrative benefit. This treatment was the best multiple cropping pattern suitable for red soil drylands. Thus, this cropping system could have a positive impact on the layout and optimization of the structure of agricultural production in red soil dryland regions in the future.

[Effects of nitrogen application and winter green manure on soil active organic carbon and the soil carbon pool management index].

Based on a cropping system of "winter green manure-double rice", the 4 x 4 two-factor test was used to study the effects of different nitrogen (N) application levels and winter green manure application on soil active organic carbon (AOC) and the C pool management index. The aim was to explore the ecological effects of winter green manure on soil improvement and determine the appropriate application levels of N fertilizer and winter green manure for improved rice yield. Results were as follows: 1) Compared with the control, the SOC and AOC contents increased by 22.2% and 26.7%, respectively, under the green manure only treatment, but the SOC contents decreased by 0.6%-3.4% under the single N fertilizer treatment. Compared with the control, the soil C pool management index increased by 24.55 and 15.17 under the green manure only and green manure plus N fertilizer treatments, respectively, and reduced by 2.59 under the single N fertilizer treatment. Compared with no fertilization, the average microbial biomass carbon (MBC) increased by 54.0%, 95.2% and 14.3% under the green manure, green manure plus N fertilizer and single N fertilizer treatments, respectively. 2) The soil AOC content was significantly positively correlated with the C pool management index (P < 0.01), and had a significant correlation with dis- solved organic C and MBC (P < 0.05). Rice yield was significantly positively correlated with AOC contents and the C pool management index, and the correlation coefficient was significantly greater than that with the total organic C. These results suggested that application of winter green manure at proper rates with inorganic fertilizer could increase SOC contents and the soil C pool management index, improve soil quality and fertility.

[Effects of different multiple cropping systems on paddy field weed community under long term paddy-upland rotation].

Based on a long term field experiment, this paper studied the effects of different multiple cropping systems on the weed community composition and species diversity under paddy-upland rotation. The multiple cropping rotation systems could significantly decrease weed density and inhibited weed growth. Among the rotation systems, the milk vetch-early rice-late maize --> milk vetchearly maize intercropped with early soybean-late rice (CCSR) had the lowest weed species dominance, which inhibited the dominant weeds and decreased their damage. Under different multiple cropping systems, the main weed community was all composed of Monochoia vaginalis, Echinochloa crusgalli, and Sagittaria pygmae, and the similarity of weed community was higher, with the highest similarity appeared in milk vetch-early rice-late maize intercropped with late soybean --> milk vetch-early maize-late rice (CSCR) and in CCSR. In sum, the multiple cropping rotations in paddy field could inhibit weeds to a certain extent, but attentions should be paid to the damage of some less important weeds.