Efficiency of producing bioflocs with aquaculture waste by using poly-β-hydroxybutyric acid as a carbon source in suspended growth bioreactors

With additional organic carbon, fish waste can be used as a substrate to produce bioflocs, a protein source for aquaculture animals. In choosing a carbon source, one should consider convenience, cost and biodegradability. This study investigates the efficiency of poly-β-hydroxybutyric acid (PHB), a biologically degradable polymer, as a carbon source to produce bioflocs in suspended growth bioreactors (SGRs), PHB-SGRs, compared with glucose (GLU-SGRs). The C:N ratio in PHB-SGRs could be maintained around 15:1. The volatile suspended solids (VSS) yield was 2.94 ± 0.72 gVSS/g fish waste for PHB-SGRS and 4.90 ± 0.23 gVSS/g fish waste for GLU-SGRs. The recycling rate of nitrogen in aquaculture solid waste was 56 ± 2% and 87 ± 7% for the PHB-SGRs and Glu-SGRs. No significant differences were found in the bioflocs produced and in the crude protein content of the produced bioflocs between PHB-SGRs and GLU-SGRs. PHB-SGRs and GLU-SGRs could remove dissolved inorganic nitrogen from aquaculture wastewater, with average values of 11.82 ± 8.95 and 16.27 ± 3.95 mg/g TSS/d. Because the calculation of the added amount of carbon and the multiple additions of carbon was avoided, PHB is considered to be a good choice as an organic carbon source for this process, even though not all parameters used for assessment were better than those of GLU-SGRs.     

Organic carbon pools in a Luvisol under agroforestry and conventional farming systems in the semi-arid region of Ceará, Brazil

Many environmental benefits have been attributed to agroforestry systems in various ecosystems around the world. However, there is a limited amount of information to evaluate this agricultural system in the semi-arid region, specifically in the region of Ceará, Brazil. The objective of this work was to evaluate five agricultural (four agroforestry and one conventional) systems in order to test the hypothesis that the agroforestry systems promote an increase in the soil organic carbon stocks and organic carbon pools, thus improving soil quality. The following treatments were tested: agrosilvopasture (AGP), silvopasture (SILV), traditional agroforestry (TRAG), intensive cropping (IC), and native forest (NF). The soil samples were collected at four depths: 0–6, 6–12, 12–20 and 20–40 cm. Total soil organic carbon stocks and the organic carbon pools (microbial biomass-C, mineralizable-C, oxidizable-C, free, occluded light fraction organic matter, and C in the humic substances) were analyzed. After 5 years of experimental cultivation, the soil under the SILV system presented the best results for the attributes studied, preserving, and in some cases, improving these attributes, when compared to the other conditions. The traditional agroforestry system (TRAG) reduced total organic carbon stocks and, consequently, C in some organic matter compartments, indicating that the fallow period was not sufficient to maintain soil quality. The AGP and IC systems presented significant losses in some of the soil organic matter (SOM) pools, suggesting that the soil environment had been degraded. The most labile SOM components were considered sensitive indicators of change in the soil quality. The silvopasture system can, therefore, be recommended as an alternative soil management strategy for food production and for the maintenance of soil quality and agricultural sustainability in the semiarid region of Ceará state.     

化肥与有机物料配施对作物产量及土壤有机质的影响

通过对北京褐潮土土壤肥力和肥料效益监测基地10年定位微区试验的调查分析表明：在土壤肥力水平较低的情况下施用氮、磷、钾化肥及氮磷钾化肥与有机物料配施，具有显著提高粮食产量的作用，并较大幅度提高土壤有机质含量；随着有机物料施用量的增加，效果更为明显。有机物料效果以有机肥最佳，其次为小麦秸秆，玉米秸秆与化肥配施效果与单一施化肥相近。     

有机无机氮肥配施对典型菜地土壤微生物和酶活性的影响

为了比较不同种类有机无机氮(N)肥配施后典型菜地土壤微生物和酶活性的差异,揭示施用有机物料后微生物在调节土壤肥力中的作用,以猪粪、沼渣沼液和猪粪堆肥为供试材料,采用田间小区试验,设置不施肥(CK)、不施N肥(PK)、纯施化肥(NPK)、有机无机肥配施1(20%猪粪N+80%化肥N,NPKM1)、有机无机肥配施2(20%沼渣沼液N+80%化肥N,NPKM2)和有机无机肥配施3(20%猪粪堆肥N+80%化肥N,NPKM3)等6种施肥模式,连续3年(2011-2013年)研究不同有机无机N肥配施对典型菜地土壤微生物和酶活性的影响。结果表明:小白菜季和莴苣季生育期间土壤细菌数量呈上升趋势,土壤真菌、放线菌数量呈先升后降趋势,且栽培后季较前季高。与NPK处理相比,NPKM1、NPKM2、NPKM3处理土壤细菌数量提高2.27%~26.16%(小白菜季),15.06%~40.82%(莴苣季);真菌数量提高33.62%~47.10%(小白菜季),39.64%~52.27%(莴苣季);放线菌数量提高6.59%~38.21%(小白菜季),20.97%~29.66%(莴苣季)。有机无机N肥配施可以促进菜地土壤微生物大量繁殖。与NPK处理相比,NPKM1、NPKM2、NPKM3处理提高土壤脲酶、磷酸酶、过氧化氢酶、纤维素酶的活性。有机无机N肥配施可以促进菜地土壤酶活性的提高。各处理蔬菜产量分别为6.73~22.50 t/hm2(小白菜),21.54~47.79 t/hm2(莴苣),大小均表现为NPKM3NPKM1NPKM2NPKPKCK。相关分析表明,小白菜和莴苣产量与土壤微生物数量和酶活性之间均存在密切关系。总之,有机无机N肥配施可以有效提高土壤中微生物数量和酶活性,维持菜地较高的土壤肥力,有利于蔬菜种植的可持续和高效生产,以猪粪堆肥配施效果最佳。     

化肥减量条件下不同有机肥用量对油菜养分利用和产量的影响

以油菜品种湘油420为供试材料,采用田间试验,研究了化肥减量25%条件下,配施不同用量（1125~4500kg/hm²）有机肥对油菜产量、干物质积累以及养分积累的影响,以常规施肥,即化肥不减量且不施有机肥为对照。结果表明,化肥减量25%配施有机肥可显著提高单株角果数、植株干物质和养分积累量,从而提高油菜产量,且随着有机肥用量的增加而增加,而经济效益仅在有机肥用量较低时（1125kg/hm²）有所增加。化肥减量25%配施有机肥处理比常规施肥（FFP）处理增产25.2%~78.5%,比化肥减量25%未配施有机肥（F75%）处理增产43.9%~105.1%;根据有机肥用量与产量之间的回归方程,化肥减量25%时仅配施675kg/hm²有机肥可弥补因化肥减量带来的产量损失。与FFP和F75%处理相比,化肥减量25%配施有机肥处理均显著增加油菜干物质和氮磷钾积累量。化肥减量25%配施1125kg/hm²有机肥处理的经济效益最高,为5789元/hm²,比FFP处理增加74元/hm²,比F75%处理增加519元/hm²。综上可得,有机无机肥配施可促进养分积累和油菜生长,提高菜籽产量,通过配施有机肥可实现化肥减量25%的目标,且本区域有机肥配施的适宜用量为1125kg/hm²。     

北方日光温室土壤有机质累积特征研究

对山西日光温室有机肥施用状况和土壤有机质累积特征进行了调查和取样分析,研究结果表明:山西日光温室土壤有机肥施用量较低;日光温室土壤有机质含量处于缺乏水平,变幅为6.69~37.23g/kg;日光温室土壤有机质累积出现“南高北低”的变化趋势;设施生产中的“土壤”有失去原有功能而变为“载体”的趋势。     

仓式好氧堆肥中影响有机物发酵降解的主要因素

在实验室条件下进行了仓式好氧堆肥实验,研究了城市有机固体废物堆肥物料种类、温度、含水率、固体颗粒粒度、碳氮比等因素对堆肥过程中有机物降解的影响．实验结果表明最佳堆肥实验条件为：温度40～50℃,含水率50％,粒径30mm,C/N质量比30：1．实验结果显示为了保证仓式好氧堆肥反应的顺利进行,上述几个因素应当被严格地控制在适当范围内．另外,通过正交实验对各影响因素进行了比较,发现在研究的4个主要影响因素中含水率的影响作用最大,C／N质量比其次,温度和物料的粒径所起的影响作用最小、     

Light and atmospheric pollution affect photosynthesis of street trees in urban environments

The gas exchange of leaves of the Ilex rotunda trees planted at thirteen sites in the city of Fukuoka, Japan, with various sun light conditions and air pollutant concentrations was studied. The highest maximum photosynthetic rate and the stomatal conductance of single leaves were measured under controlled conditions and analyzed with the environmental variables by correlation analysis. The photosynthetic rate of the urban core was highest and that of the suburban area was lowest. The results from the correlation analysis showed that the photosynthetic rate was negatively correlated with sun light conditions and positively correlated with air pollutant concentrations. The reasons for the higher photosynthetic rate in the urban core with poor sun light condition and higher air pollutant concentrations were discussed in relation to stimulation by air pollutant and avoidance of photoinhibition.     

A comparison of production and management between Wisconsin organic and conventional dairy herds

An observational study was conducted in Wisconsin to compare production and management on organic and conventional dairy farms. Thirty organic dairy herds, where antimicrobials are rarely used for calves and never used for cows, were compared with 30 neighboring conventional dairy farms on which antimicrobials were routinely used for animals of all ages. A seven-page questionnaire regarding milk production, milking practices, housing, incidence of the major dairy diseases and medical treatments was used to assess management and production during 2000-2001. Body condition scores (BCS) of lactating cows and environmental and animal sanitation scores (EASS) were also collected on each of two occasions. The organic herds had significantly fewer cattle than did the conventional herds (P=0.017). The average daily milk production per cow in organic dairy herds (20.2 kg/day) was lower than that of conventional herds (23.7 kg/day). The incidence of clinical mastitis (CM) on organic farms (28 cases per 100 cow-years at risk) was not statistically different from that of on conventional farms (32 cases per 100 cow-years at risk). No significant difference in bulk tank somatic cell count (BTSCC) was observed between organic farms (262,000 cells/ml) and conventional farms (285,000 cells/ml). The average annual cull rate was 18.0 cases per 100 cow-years for the conventional farms and 17.2 for the organic farms (P=0.426). Our paired t-test results indicated significantly higher parasite burden on organic dairy farms; however, no significant difference between the two farm types when controlling for season (March and September), grazing intensity (no grazing, little grazing, grazing with access to housing and grazing only) and herd average milk production per cow. There was little evidence of other fundamental differences between the two farm types in other management and production parameters.