[Short-term effects of different tillage modes combined with straw-returning on the soil labile organic carbon components in a farmland with rice-wheat double cropping].

A two-year (2009-2011) field experiment was conducted to study the effects of different tillage modes, straw-returning, and their interactions on the soil total organic carbon (TOC) and labile organic carbon (LOC) components (easily oxidizable organic carbon (EOC), water-soluble organic carbon (WSOC), and microbial biomass carbon (MBC)) at the soil depths of 0-7, 7-14, and 14-21 cm in a farmland with rice-wheat double cropping. In all treatments of straw-returning, the TOC and LOC contents in each soil layer were significantly higher than those without straw-returning. Under plowing tillage, the MBC content in 0-7 cm soil layer was significantly higher than that under rotary tillage, but the EOC content was in adverse. Rotary tillage made the TOC content in 7 - 14 cm soil layer being significantly higher, as compared with plowing tillage. The TOC, WSOC, and MBC contents in 14-21 cm soil layer under plowing tillage were significantly higher than those under rotary tillage. Plowing tillage combined with rice and wheat straws-returning made the soil TOC content being higher than the other treatments.

[Effects of nitrogen fertilization and root separation on the plant growth and grain yield of maize and its rhizosphere microorganisms].

A field experiment with root separation was conducted to study the effects of root interaction in maize-soybean intercropping system on the plant growth and grain yield of maize and its rhizosphere microorganisms under different nitrogen fertilization levels (0.1, 0.3, 0.5, and 0.7 g x kg(-1)). Root interaction and nitrogen fertilization had positive effects on the plant height, leaf length and width, and leaf chlorophyll content of maize. Less difference was observed in the root dry mass of maize at maturing stage between the treatments root separation and no root separation. However, as compared with root separation, no root separation under the nitrogen fertilization levels 0.1, 0.3, 0.5, and 0.7 g x kg(-1) increased the biomass per maize plant by 8.8%, 6.3%, 3.6%, and 0.7%, and the economic yield per maize plant by 17.7%, 10.0%, 8.2%, and 0.9%, respectively. No root separation increased the quantity of rhizosphere fungi and azotobacteria significantly, as compared with root separation. With increasing nitrogen fertilization level, the quantity of rhizosphere bacteria, fungi, and actinomycetes presented an increasing trend, while that of rhizosphere azotobacteria decreased after an initial increase. The root-shoot ratio of maize at maturing stage was significantly negatively correlated with the quantity of rhizosphere bacteria, fungi, and actinomycetes, but less correlated with the quantity of rhizosphere azotobacteria. It was suggested that the root interaction in maize-soybean intercropping system could improve the plant growth of maize and increase the maize yield and rhizosphere microbial quantity, but the effect would be decreased with increasing nitrogen fertilization level.

[Eco-fitness of county-level agricultural leading industry structure: assessment and development prediction].

Based on the 'three critical points' theory of eco-fitness, and by using dynamic weighting and fitting methods, an assessment system for the eco-fitness of county-level agricultural leading industry structure was constructed, and, taking Zhangqiu of Shandong Province, East China as a case, the eco-fitness of county-level agricultural leading industry structure was assessed and predicted. Due to the limited agro-ecological resources, the comprehensive eco-fitness index of four kinds of agricultural leading industry in Zhangqiu presented an upward trend from 2005 to 2010, but a downward trend from 2011 to 2015. The eco-fitness indices of oil crops and fruits would be negative in 2015. The applied research in Zhangqiu confirmed the validity of the assessment system constructed for the eco-fitness of county-level agriculture leading industry structure and the rationality of the prediction model.

[Effects of different fertilization modes on paddy field topsoil organic carbon content and carbon sequestration duration in South China].

Based on the organic carbon data of 222 topsoil samples taken from 38 paddy field experiment sites in South China, calculations were made on the relative annual change of topsoil organic carbon content (RAC) and carbon sequestration duration in the paddy fields in South China under five fertilization modes (inorganic nitrogen fertilization, N; inorganic nitrogen and phosphorus fertilization, NP; inorganic nitrogen, phosphorus, and potassium fertilization, NPK; organic fertilization, O; and inorganic plus organic fertilization, OF). The RAC under the fertilizations was 0-0.4 g x kg(-1) x a(-1), with an increment of 0.20 and 0.26 g x kg(-1) x a(-1) in double and triple cropping systems, respectively. The RAC was higher in treatments O and OF than in treatments N, NP, and NPK, being the highest (0.32 g x kg(-1) x a(-1)) in treatment OF. The topsoil organic carbon accumulation rate decreased with increasing time, and the carbon sequestration duration in treatments N, NP, NPK, O, and OF was about 22, 28, 38, 57, and 54 years, respectively. Inorganic plus organic fertilization was the most effective practice for soil carbon sequestration in the paddy fields in South China.

[Effects of domestic wastewater slow infiltration on the growth of poplar 'Zhonglin 2001' plantation].

A slow infiltration experiment with different hydraulic loads (0, 3, 6, 9, 12, and 15 cm per week) of domestic wastewater was conducted in a 'Zhonglin 2001' poplar plantation to study the effects of the wastewater slow infiltration on the growth of the plantation. Comparing with the control (0 cm), the other five treatments increased the soil organic matter, total N, total P, total K, and Na+ contents in the plantation averagely by 1.940 g x kg(-1), 0.115 g x kg(-1), 0.029 g x kg(-1), 1.454 g x kg(-1) and 0.030 g x kg(-1), respectively. At lower hydraulic loads (3-12 cm per week), the poplar biomass growth and the N, P and Na+ contents in different poplar organs averagely increased by 17.583 t x hm(-2) x a(-1), 3.086 g x kg(-1), 0.645 g x kg(-1), and 0.121 g x kg(-1), with the maximum (36.252 t x hm(-2) x a(-1), 13.162 g x kg(-1), 5.137 g x kg(-1), and 0.361 g x kg(-1), respectively) at hydraulic loads 6-12 cm per week. The further increase of the hydraulic load decreased the poplar biomass growth and the N, P and Na+ contents in different poplar organs. The K content in different poplar organs decreased with increasing hydraulic load. Treating with domestic wastewater increased the leaf length, decreased the leaf asymmetry, and delayed leaf-falling. At high hydraulic load (15 cm per week), the higher soil Na+ and water contents would threat the poplar growth. The proper domestic wastewater hydraulic loads for the growth of poplar 'Zhonglin 2001' plantation would be 3-12 cm per week.

[Identification of the prior regions for agricultural and rural pollution control in Changshu].

The characteristics such as wide area, dispersion and randomness of agricultural and rural pollution make it difficult to seize the key to pollution control in rural areas. On the scale of township, using inventory analysis, accounting for emissions and emission intensity of the chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) in Changshu, Jiangsu Province, which exists in a total of 4 classes and 6 kinds of agricultural and rural sources such as farmland cultivation (chemical fertilizer application and crop straw abandoned), animal breeding, aquaculture, rural life (domestic sewage and human waste, solid waste), using cluster analysis, identify the prior regions and the prior pollution sources for agricultural and rural pollution control by the sensitivity evaluation, and make agricultural and rural pollution control and management measures more focused. It shows that: in 2007, COD, TN and TP emissions of agricultural and rural pollution sources were 5496.07, 4161.03, and 647.54 t x a(-1), and the emission intensity of COD, TN and TP was 48.84, 36.98, and 5.75 kg x hm(-2). The main pollution source of COD was rural life and aquaculture, and the contribution rate was more than 75%; the main pollution source of TN and TP was agricultural cultivation and aquaculture, and the contribution rate was more than 80%. The sensitivity evaluation identified that the town of Guli and Shajiabang were the prior regions for agricultural and rural pollution control in Changshu; farmland cultivation and aquaculture were the prior pollution sources in the two areas.

[Temperature differences of air-rice plant under different irrigated water depths at spiking stage].

With rice cultivars Yangdao 6, Yangjing 9538 and Wuxiangjing 14 as test materials, field experiment was conducted to study the effects of 3 irrigated water depths (0 cm, 2-4 cm, and > 10 cm) on the temperature of different parts of rice plant at spiking stage. The results showed that from 10:30 to 15:00 on sunny days, irrigated water depth on paddy field had significant effects on the temperature of field surface, middle part of rice plant, and rice spike. The higher the water depth on field surface, the lower the temperature of rice plant and rice spike. At the water level > 10 cm, the average temperature differences between air and the rice spike, middle part of rice plant and field surface of these three cultivars were 1.37, 2.98 and 4.12 degrees C higher than those at the water depth of 0 cm, and 0.67, 1.59 and 2.17 degrees C higher than those at the water depth of 2-4 cm, respectively. In addition, the temperature differences were 0.71, 1.39 and 1.95 degrees C higher at the water depth of 2-4 cm than those at the water depth of 0 cm, respectively. Obvious temperature differences of air-rice plant were also observed among the three rice varieties under different irrigated water depths. The analysis of the characteristics of temperature transfer among field surface, middle part of plant and rice spike indicated that the temperature transfer patterns under all test water management regimes accorded with the principles of energy transfer, suggesting that keeping proper water depth on the field surface at rice spiking stage contributed great to the decrease of rice spike temperature and the alleviation of rice heat injury.

[Effects of long-term continuous cropping of cotton and returning cotton stalk into field on soil biological activities].

The study on the effects of long-term continuous cropping of cotton and returning cotton stalk into field on the quantities of soil microbes and the activities of soil urease, invertase, catalase and diastase showed that the soil biological activities in cotton field were negatively affected by continuous cropping of cotton, but positively affected by the returning of cotton stocks into filed. The obstacle of short-term (5-10 years) continuous cropping was more obvious. After 5 and 10 years continuous cropping and stalk returning, the total quantity of soil microbes was decreased by 36.54% and 25.66%, and the quantities of bacteria and actinomyces were decreased by 61.12% and 70.16%, and 67.91%, 145.89%, respectively, while the quantity of fungi was increased, compared with those after 1 year cropping. The activities of soil urease and invertase after 5 and 10 years continuous cropping and stalk returning were decreased by 0.76% and 2.52%, and 28.12% and 11.44%, respectively, and the soil catalase activity after 5 years continuous cropping and stalk returning was decreased by 9.21%, compared with those after 1 year cropping. Under long-term continuous cropping and stalk returning, soil biological properties improved, and soil biological diversity index increased. Compared with those after 5 years continuous cropping and stalk returning, the quantities of bacteria and actinomyces after 15 and 20 years continuous cropping and stalk returning were increased by 71.52% and 61.03%, and 141.74%, 240.83%, respectively, with the proportion of fungi declined and the activities of urase, catalase and invertase increased. Soil amylase activity after 5, 10, and 20 years continuous cropping and stalk returning was increased by 11.38%, 10.41%, and 31.34%, respectively, compared with those after 1 year cropping.

[A modified method of ecological footprint and its application].

The Wackernagel's method of ecological footprint assumes that arable lands are cropped only once a year in a country or a region, which does not accord with the conception of ecological footprint referring to the area of productive land. In this paper, the method of cropland footprint was modified by regulating with multi-cropping index, and the ecological footprint calculated with the new method was for the area of cropland but not that of multi-cropping. The ecological economic systems in Binhai and Funing counties of Jiangsu Province from 1995 to 2003 were analyzed by the modified method, and the results showed that when calculated with conventional Wackernagel's method, the ecological footprints of Binhai and Funing were from 1.79 hm2 to 2.22 hm2 and from 1.38 hm2 to 2.81 hm2, and the percentages of cropland ecological footprint in total ecological footprints decreased from 42.65% to 38.81% and from 45.73% to 38.85%, respectively, while calculated with the modified method, the ecological footprints and the percentage of cropland ecological footprint in total ecological footprints were from 1.43 hm2 to 1.88 hm2 and from 1.12 hm2 to 2.43 hm2, and decreased from 28.45% to 22.89% and from 32.94% to 29.42%, respectively. It was indicated that the ecological footprint calculated with the new method was for the area of cropland, which more accorded with the eco-capacity and changed the size and composition of ecological footprints, being able to reflect the use of natural resources more precisely.