[Effects of Mulching and Slow-release Fertilizer Application Reduction on Soil Microbial Community Structure in Rapeseed Field Under Two Different Rainfall Conditions].

In order to investigate the effects of furrow and ridge rainwater harvesting, straw mulching, and reduced and slow-release fertilizer on soil microbial community structure of rapeseed, a two-year field study was conducted in rainy (2016-2017) and drought (2017-2018) seasons, which included three cultivation patterns:1 conventional flat planting, 2 straw mulching, and 3 ridge-furrow rainfall harvesting system and four fertilization patterns:1 conventional fertilization (100% of the amount), 2 reduced slow-release fertilizer Ⅰ (80% of the amount), 3 reduced slow-release fertilizer Ⅱ (60% of the amount), and 4 no fertilizer. The results indicated that it was rainy in 2016-2017, with seasonal drought during the nutritional growth stage in 2017-2018. The two technologies (straw mulching+80% slow-release fertilizer, J80 and ridge-furrow rainfall harvesting system+80% slow-release fertilizer, M80) were beneficial to boost the soil microbial activity. J80 and M80 increased the microbial biomass carbon by 9.94% and 10.32% and microbial biomass nitrogen by 2.38% and 1.19%, respectively, compared with that of the local cultivation pattern under two different climate conditions. The total amount of microbial phospholipid fatty acid (PLFA) decreased by 30.75% in the rainy year compared with that in the drought year, and mulching technology could effectively increase the total amount of soil PLFA. The PLFA contents of soil bacteria and fungi in the rainy year were 33.67% and 53.21%, respectively, lower than those in the drought year. However, the PLFA content of actinomycetes increased by 13.04%. Microbial communities were sensitive to abnormal precipitation. The bacteria/fungi ratio increased in rainy weather. The drought climate heighted the ratio of straight chain saturated fatty acid/straight chain monounsaturated fatty acid and straight chain monounsaturated fatty acid/cyclopropane acid. In conclusion, adopting the optimal cultivation technologies can stabilize the soil microenvironment under abnormal precipitation, relieve water and nutrient stress, and provide an effective means for rapeseed sustainable development.

[Responses of soil moisture and photosynthetic characteristics to mulching materials and ridge-to-furrow ratios in rapeseed fields in southwest dryland of China]. / è¥¿å—æ—±åœ°æ²¹èœç”°åœŸå£¤æ°´åˆ†å’Œä½œç‰©å ‰åˆç‰¹å¾å¯¹è¦†ç›–ææ–™å’Œåž„æ²Ÿæ¯”çš„å“åº”.

In order to deal with the frequent seasonal drought and improve water use efficiency and crop photosynthetic efficiency in drylands of southwest China, a field experiment was conducted to investigate the effects of different mulching materials (common white film, common black film, biodegradable film and no film) and ridge-to-furrow ratios (40 cm:40 cm and 40 cm:80 cm) on soil water storage, as well as photosynthetic characteristics, fluorescence parameters and chlorophyll relative content (SPAD) of rapeseed, with the flat planting as the control. The results showed that the average soil water storage under different mulching materials followed the order: ridge with common black film (BR) ≈ ridge with common white film (WR) ≈ ridge with biodegradable film (BDR) ＞ ridge with no film (NR) ＞ flat planting (FP). Meanwhile, ridge-to-furrow ratios did not affect soil water storage. The net photosynthetic rate, stomatal conductance and fluorescence para-meters (Fm, Fv, Fv/Fm, Fv/Fo, qP and qN) of rapeseed under ridge-furrow with film mulching was higher than those under flat planting. Compared with control, SPAD value was improved by 6.1%, 8.6%, 8.5% and 3.6% under WR, BR, BDR and NR, while instantaneous water use efficiency (IWUE) was increased by 18.3%, 11.4%, 16.3% and 10.4% under those treatments, respectively. Rapeseed yield under BR, WR and BDR was significantly higher than that in control, while NR did not increase yield. The treatment of ridge with common black film + 40 cm:40 cm as ridge-to-furrow ratio could gain the highest economic benefit. Ridge-furrow planting of rainfall harvesting could improve soil moisture, increase crop photosynthetic capacity, and raise yield and economic income in rapeseed fields in drylands of southwest China.

[Effects of Chinese milk vetch intercropped with rape under straw mulching on soil aggregate and organic carbon character]. / 秸秆覆盖条件下紫云英间作油菜的土壤团聚体及有机碳特征.

There are severe soil erosion, shallow soil, reduction of soil organic matter, and poor soil and water conservation in purple soil areas in Southwest China, which become the main limiting factors for the sustainable development of agriculture. A series of buckets and field experiments in the field were employed to explore the soil aggregate and soil organic carbon in response to Chinese milk vetch intercropped with rape under straw mulching, aiming to improve soil aggregate structure and increase organic carbon content. Results showed that intercropped Chinese milk vetch increased soil micro-aggregate content in rape rhizosphere, and reduced soil aggregate mean mass diameter. The change of soil macro-aggregate in rape rhizosphere was mainly caused by the change of content of soil aggregate on 10-5 mm and 5-2 mm, while the soil micro-aggregate was mainly caused by soil aggregate on 0.25-0.053 mm. Intercropped Chinese milk vetch and straw mulching significantly increased soil organic carbon content after corn growing season, with increasing the content of soil organic carbon on 10-20 cm and 20-30 cm. Though intercropped Chinese milk vetch and straw mulching had less effect on soil total organic carbon in rape season, more and more significant effect on 0-10 cm, 10-20 cm, and 20-30 cm with rape growing, especially in stem elongation stage, flowering stage, and harvest stage. Our results showed that the characteristic of soil aggregate in rape rhizosphere could be changed by intercropped Chinese milk vetch, and that the content of soil organic carbon could be increased by Chinese milk vetch intercropped with rape under straw mul-ching.

[Diversity of the Microbial Community in Rice Paddy Soil with Biogas Slurry Irrigation Analyzed by Illumina Sequencing Technology].

In order to explore the variation in soil microbial community diversity in paddy fields with different irrigation periods, we collected in situ rice field soils during different biogas irrigation periods and analyzed the microbial community structures of these soils by high-throughput sequencing. The results showed that as the biogas irrigation period increased, the soil pH decreased gradually, while organic matter, nitrate nitrogen, phosphate, and other nutrients were accumulated. Years of continued biogas irrigation was not conducive to improving rice yields. The results showed that as the biogas irrigation period increased, the richness in microbial species in paddy soils decreased gradually, and the diversity in the microbial communities was also reduced. Proteobacteria accounts for the largest proportion in rice paddy soil with biogas slurry irrigation. With the increase of biogas irrigation years, the proportion of ß-Proteobacteria, Bacteroidia, Bacteroidales, Burkholderiales, Bacteroides, and Thiobacillus increased, while the proportion of Gemmatimonadetes and α-Proteobacteria decreased gradually. Dissolved organic carbon (F=2.67, P=0.09) had the greatest effect on microbial community structures in the studied paddy soils.

[Effects of intercropping Chinese milk vetch on functional characteristics of soil microbial community in rape rhizosphere]. / é—´ä½œç´«äº‘è‹±ä¸‹æ²¹èœæ ¹é™ åœŸå£¤å¾®ç”Ÿç‰©ç¾¤è½åŠŸèƒ½ç‰¹å¾.

The application of green manure is facing serious problems in purple soil region of southwest China. With the aim to explore the potential application of green manure, we examined the functional characteristics of soil microbial community in a system of Chinese milk vetch intercropped with rape. The innovations are the application of Chinese milk vetch in dry land of the southwest China and the establishment of new planting pattern of rape by providing empirical data. Results showed that the intercropping with Chinese milk vetch decreased the carbon resource use efficiency of microbial community in rape rhizosphere, especially for the utilization of carbohydrates. At the same time, Shannon index, Simpson index, and richness were reduced, but evenness index was increased by intercropping. Those results from cluster analysis and principal component analysis suggest that the soil microbial community composition was significantly different between monocropping and intercropping. The carbohydrates, amino acids and carboxylic acids were the sensitive carbon sources for differentiating the changes of the microbial community induced by monocropping and intercropping. Intercropping Chinese milk vetch could decrease functional activity, change community composition, and reduce diversity of soil microbial community in rape rhizosphere.

[Characteristics of Soil Respiration and Soil Organic Carbon in Fava Bean Farmland Under Ridge Tillage and Straw Mulching in Southwest China].

Soil respiration is an important process for carbon emission. A field study was conducted with four treatments including T (traditional tillage+straw mulching level 0 kg·hm-2), R (ridge tillage+straw mulching level 0 kg·hm-2), RS1 (ridge tillage+straw mulching level 3750 kg·hm-2), and RS2 (ridge tillage+straw mulching level 7500 kg·hm-2), so as to probe the effects of ridge tillage and straw mulching amount on soil respiration and soil organic carbon(SOC) and the relationships of soil respiration rate with soil temperature and water content (SWC) during the growth period of fava bean in the triple intercropping system of fava bean/maize/sweat pomato in dryland region of southwest China known as the purple hilly region. The changes of soil respiration rate were in accordance with crop growing, being firstly increased and then decreased during the whole growth period of fava bean, and there were significant differences in soil respiration rate among different treatments, which could be ranked as RS2[3.365 g·(m2·d)-1] > RS1[2.935 g·(m2·d)-1] > T[2.683 g·(m2·d)-1] > R[2.263 g·(m2·d)-1]. Ridge tillage reduced soil respiration in fava bean farmland, whereas straw mulching treatment increased it, whose variation trend was in accordance with that of straw mulching levels. There was a significant exponential relationship between soil respiration and soil temperature at 5 cm and 10 cm depth, and the exponential model at 10 cm produced better fitness than that at 5 cm. The temperature sensitivity (Q10) at 10 cm could be ranked as RS2 > RS1 > R > T, being 1.751,1.665,1.616, and 1.35, respectively. The combined exponential model indicated that soil temperature and water content (SWC) could jointly explain 68%(R), 79%(RS1) and 76%(RS2) of variation in soil respiration. This study results suggested that ridge tillage and straw mulching significantly increased SOC of 0-5 cm, 5-10 cm, 10-20 cm and 20-30 cm soil layers, and the increase of SOC was in accordance with that of straw mulching levels. The SOC was significantly increased in 5-10 cm and 10-20 cm soil layers, which could be ranked as RS2 > RS1 > R > T, and the increases in SOC at 5-10 cm were especially notable. The weighted average of particulate organic carbon (POC) at 0-30 cm was significantly increased, but the proportion of POC in SOC did not show significant influence.

[Effects of Green Manure Intercropping and Straw Mulching on Winter Rape Rhizosphere Soil Organic Carbon and Soil Respiration].

Under the background of global warming, the farmland soil respiration has become the main way of agricultural carbon emissions. And green manure has great potential to curb greenhouse gas emissions and achieve energy conservation and emissions reduction. However, in purple soil region of Southwest, China, soil respiration under green manure remains unclear, especially in the winter and intercropping. Through the green manure ( Chinese milk vetch) intercropping with rape, therefore, we compared the effects of rape rhizosphere under straw mulching. The soil organic carbon and soil respiration were examined. The results showed, compared with straw mulching, root separation was the major influencing factors of soil organic carbon on rape rhizosphere. Soil organic carbon was significantly decreased by root interaction. In addition, straw mulching promoted while green manure intercropping inhibited the soil respiration. Soil respiration presented the general characteristics of fall-rise-fall due to the strong influence of rape growth period. Therefore, it showed a cubic curve relationship with soil temperature.

[Soil respiration and carbon balance in wheat field under conservation tillage].

In order to study the characteristics of carbon sources and sinks in the winter wheat farmland ecosystem in southwest hilly region of China, the LI6400-09 respiratory chamber was adopted in the experiment conducted in the experimental field in Southwest University in Chongqing. The soil respiration and plant growth dynamics were analyzed during the growth period of wheat in the triple intercropping system of wheat-maize-soybean. Four treatments including T (traditional tillage), R (ridge tillage), TS (traditional tillage + straw mulching), and RS (ridge tillage + straw mulching) were designed. Root biomass regression (RR) and root exclusion (RE) were used to compare the contribution of root respiration to total soil respiration. The results showed that the average soil respiration rate was 1.71 micromol x (m2 x s)(-1) with a variation of 0.62-2.91 micromol x (m2 x s)(-1). Significant differences in soil respiration rate were detected among different treatments. The average soil respiration rate of T, R, TS and RS were 1.29, 1.59, 1.99 and 1.96 micromol x (m2 x s)(-1), respectively. R treatment did not increase the soil respiration rate significantly until the jointing stage. Straw mulching treatment significantly increased soil respiration, with a steadily high rate during the whole growth period. During the 169 days of growth, the total soil respiration was 2 266.82, 2799.52, 3 483.73 and 3 443.89 kg x hm(-2) while the cumulative aboveground biomasses were 51 800.84, 59 563.20, 66 015.37 and 7 1331.63 kg x hm(-2). Compared with the control, the yield of R, TS and RS increased by 14.99%, 27.44% and 37.70%, respectively. The contribution of root respiration to total soil respiration was 47.05% by RBR, while it was 53.97% by RE. In the early growth period, the carbon source was weak. The capacity of carbon sink started to increase at the jointing stage and reached the maximum during the filling stage. The carbon budget of wheat field was 5 924.512, 6743.807, 8350.741, 8 876.115 kg x hm(-2), respectively. The results indicated that ridge tillage and straw mulching conservation tillage significantly improved the carbon sink in the wheat farmland ecosystem.

[Analysis of soil respiration and influence factors in wheat farmland under conservation tillage in southwest hilly region].

In order to investigate the effect of conservation tillage on soil respiration in dry cropping farmland in southwest purple hilly region, the LI6400-09 respiratory chamber was adopted in the experiment conducted in the experimental field in Southwest University in Beibei, Chongqing. The respiration and the hydrothermal and biotic factors of soil were measured and analyzed during the growth period of wheat in the triple intercropping system of wheat/maize/soybean. There were four treatments including T (traditional tillage), R (ridge tillage), TS (traditional tillage + straw mulching) and RS (ridge tillage + straw mulching), which were all in triplicates. The results indicated that the soil respiration rate changed in the range of 1.100-2.508 micromol x (m2 x s)(-1) during the reproductive growth stage of wheat. There were significant differences in soil respiration rate among different treatments, which could be ranked as RS > R > TS > T. The soil temperature in the 10cm layer was ranked as T > R > TS > RS. The relationship between soil respiration and soil temperature fitted well with an exponential function, in which the Q10 values were 1.25, 1.20, 1.31 and 1.26, respectively. The soil moisture in the 5cm layer was ranked as TS > RS > T > R. The best fitting model between soil moisture and soil respiration was a parabolic curve, indicating the presence of soil moisture with the strongest soil respiration. The response threshold of wheat to soil moisture was 14.80%-17.47% during the reproductive stage. The dominant groups of soil animals were Collembola and Acarina, which were correlated with soil respiration to some extent. The correlation was high in the treatments T and R, ranged from 0.669-0.921, whereas there was no remarkable correlation in the other treatments.