A modelling approach for analysis of agro pastoral activity at the one-farm level

A model was developed to represent the general functioning of a low input farming system in order to dispose of a tool able to simulate the effects of changes in productive and social organisation in traditional Andean rural communities. The model analyses daily agro pastoral activities of different members of an Andean peasant family, and farm crop production, across a 1-year timeframe, according to climate and labour organisation. The modelling approach uses object-oriented language, describes the objects and their relations with a unified modelling language formalism and manages time as illustrated by a sample potato crop. To demonstrate this methodology, one-farm observed and simulated data are compared within two frameworks: the cattle-feeding system, and the labour allocation system detailed by task and by gender. Results show good reliance in the first case study and, in the second case, a satisfactory overview of the agro pastoral calendar of household member workers, regarding the priorities given by peasants according to climate, land-use constraints, social organisation and out-farm activities. Due to its modularity, the object-oriented modelling approach appears to improve understanding of the general functioning of agro pastoral households by allowing multi-purpose simulations and exploring the links between social and productive activities.     

生物炭对砒砂岩与沙复配土壤理化性状及辣椒生长的影响

为探究生物炭对砒砂岩与沙复配土壤肥力提升和作物生长的影响。通过盆栽试验,研究不同添加量的生物炭对辣椒生物学性状、产量以及复配土壤理化性状的影响。结果表明:复配土比例为1∶1时,A2处理使茎叶鲜质量、干质量增加81.4%、80.5%,单果长、单果茎粗增加15.1%、21.0%,土壤有效磷含量增加11.08 mg·kg-1,对土壤pH和全盐量影响不大。复配土比例为1∶2时,B2处理下果实鲜质量、干质量增加39.7%、40.2%,茎叶鲜质量、干质量增加28.1%、29.5%、根鲜质量、干质量增加35.0%、22.0%,单果长、单果茎粗分别增加12.1%、13.0%,单株结果数增加119.8%,产量最高且土壤pH和盐分变化不大。复配土为1∶5时,添加生物炭对辣椒生长发育和产量积累产生抑制。因此,该试验条件下,建议1∶1和1∶2的复配土生物炭添加量为2%,1∶5的复配土不建议施用生物炭。     

红壤旱地一株自生固氮菌的筛选鉴定及其固氮能力评估

为了鉴定从红壤中分离得到的一株自生固氮菌,并探讨其固氮能力。采用形态观察、生理生化测定和16S rDNA基因序列分析的方法研究了菌株的分类地位,采用乙炔还原法测定其固氮酶活性,并在室内培养条件下,通过花生、玉米的幼苗盆栽试验研究菌株对土壤MBN、矿化氮和植株氮素积累量的影响。结果表明：从种植于红壤的玉米根际,筛选出15株自生固氮菌,以菌株CM12固氮能力最强,初步鉴定CM12为伯霍尔德杆菌属(Burkholderia sp.),固氮酶活性达C₂H₄ 39.1 nmol/(h·mL)。室内培养试验结果表明,接种CM12菌株的处理,花生和玉米土壤MBN含量较CK处理分别提高了2.38和2.37倍,其中种植花生体系中,接菌处理与施用化学氮肥处理土壤MBN含量无显著差异。接种固氮菌影响了旱地红壤NO₃^--N和NH₄⁺-N比例,降低了土壤中NO₃^--N含量,且种植玉米体系中土壤NO₃^--N含量降低较明显。固氮菌短期接种增加了花生根系和玉米地上植株的氮素积累量。研究结果为该菌株在红壤旱地实际生产中的应用提供了理论基础。     

Evaluation of optical sensor measurements of canopy reflectance and of leaf flavonols and chlorophyll contents to assess crop nitrogen status of muskmelon

Nitrogen losses from intensive vegetal production systems are commonly associated with contamination of water bodies. Sustainable and optimal economic N management requires correct and timely on-farm assessment of crop N status to detect N deficiency or excess. Optical sensors are promising tools for the assessment of crop N status throughout a crop or at critical times. We evaluated optical sensor measurement of canopy reflectance and of leaf flavonols and chlorophyll contents to assess crop N status weekly throughout a muskmelon crop. The Crop Circle ACS 470 was used for reflectance measurement, the SPAD 502 for leaf chlorophyll, and the DUALEX 4 Scientific for leaf chlorophyll and flavonols. Four indices of canopy reflectance (NDVI, GNDVI, RVI, GVI), leaf flavonols and chlorophyll contents and the nitrogen balance index (NBI), the ratio of chlorophyll to flavonols contents, were linearly related to crop N content and to crop Nitrogen Nutrition Index (NNI) throughout most of the crop. NBI most accurately predicted crop N status; in five consecutive weekly measurements, R² values were 0.80–0.95. For NDVI during the same period, R² values were 0.76–0.87 in the first three measurements but R² values in the last two measurements were 0.39–0.45. Similar relationships were found with the three other reflectance indices. Generally, the relationships with NNI were equal to or slightly better than those with crop N content. These optical sensor measurements provided (i) estimation of crop N content in the range 1.5–4.5%, and (ii) an assessment of whether crop N content was sufficient or excessive for optimal crop growth for NNI ranges of 0.8–2.0. Composite equations that integrated the relationships between successive measurements with the optical sensors and crop N content or NNI for periods of ≥2 weeks (often 2–3 weeks) were derived for most indices/parameters. Overall, these results demonstrated the potential for the use of these optical sensor measurements for on-farm monitoring of crop N status in muskmelon.     

缓释肥侧位深施及用量对油菜产量和肥料利用率的影响

为明确红壤稻田直播油菜缓释肥（N-P2O5-K2O:25-7-8）侧位深施效果及适宜用量，该研究连续2 a在两熟制和三熟制2种种植模式下开展缓释肥侧位深施效果对比试验（设置不施肥、土表撒施和侧位深施3个施肥方式）和施用量试验（设置0、300、450、600、750和900 kg/hm2 共6个施肥水平），研究缓释肥侧位深施及不同用量对油菜产量形成和肥料利用率的影响。结果表明，施肥方式对红壤稻田油菜产量形成和肥料利用率均有显著影响，且对两熟制油菜影响更为显著。相比传统土表撒施，侧位深施显著促进了油菜产量和肥料利用率的提高。缓释肥侧位深施明显提高了各时期油菜干物质量，尤其是显著增加了初花期至成熟期的干物质积累量，促进了花后根部与地上部干物质同步增长；促进了根系对N、P、K的吸收，提高了油菜产量和肥料利用率。菜籽产量与缓释肥用量呈线性加平台关系，适宜施肥量可保证较大的收获密度，并协同产生较多的每株角果数和每角粒数，从而提高籽粒产量、肥料利用率和经济效益。两熟制和三熟制油菜缓释肥侧位深施的适宜用量分别为715和585 kg/hm2，产量潜力可分别达2 450和1 700 kg/hm2。研究表明，侧位深施适量缓释肥可显著提高红壤稻田直播油菜生产力，建议结合机械化种植因地制宜推广应用。     

Age-related abscission patterns of cotton fruiting forms: timing of the end of abscission susceptibility in relation to water content and growth of the boll

The susceptibility of cotton fruiting forms (squares or bolls) to abscission is age dependent. After flower opening, abscission probability peaks and then decreases rapidly, suggesting the existence of a stage beyond which boll abscission does not occur. However, the timing and characterization of this stage need further refinement. This paper compares the susceptibility to abscission of fruiting forms with age according to sympodial position, and relates abscission probability of bolls to the time-course patterns of boll diameter, seed-cotton weight and water content. Square appearance, flower opening and abscission events were monitored in three experiments conducted with high inputs and in one experiment receiving no fertilizer. In the latter, the duration of fruiting and the appearance rates of fruiting forms were lower than in the high-input experiments. For a given age-class of fruiting form, the abscission rate increased from the innermost to the outermost position on the sympodium but the relative pattern of susceptibility with age did not change. Abscission followed a bimodal pattern with squares and bolls abscising most during early stages of development (≤80 Degree Days from appearance for squares, and ≤160 DD from flower opening for bolls). Applying a 60% light reduction for four or eight days during the late flowering period increased the abscission rate in proportion to the duration of shading. However, the frequency distribution of abscission with age was not affected by shading. In general, there was a consistent period at 200–240 DD after flower opening beyond which abscission ceased to occur. This period corresponded to a change in boll water content, which fell below 0.80 g g⁻¹, and in seed-cotton dry weight which started to increase linearly and rapidly. Boll diameter was found to be a convenient measure to delimit this transition period. In our experimental conditions a critical diameter of 30 mm marked the end of abscission sensitivity of bolls.     

The prevalence of Chlamydia psittaci infections in Belgian commercial turkey poults

The prevalence of Chlamydia psittaci infections in Belgian commericial turkey poults was examined and a follow-up study of one Belgian turkey flock was performed. Sera were examined for the presence of anti-chlamydia antibodies by immunoblotting. Cloacal and conjunctival swab smears and lung impression smears were examined for the presence of chlamydial antigen using the IMAGEN Chlamydia immunofluorescence test. Anti-chlamydia antibodies were found in 90 of 100 sera collected at slaughter from turkeys raised during the summer of 1992. The following winter, 73 of 100 sera reacted positively. On all twenty farms examined during 1992, turkeys were positive for anti-chlamydial antibodies. During 1993, chlamydial antigen was detected in swabs from 20 of 40 slaughterhouse turkeys tested. Antigen was found more often in the cloaca than in the conjunctiva. Chlamydial antigen was detected in samples from each of the 4 farms examined. The follow-up study on a turkey farm, sampling the birds at weekly intervals from one week old until 12 weeks of age, revealed that chlamydial antigen and anti-chlamydial antibodies were present during the whole period. During 1994, chlamydial antigen was detected in 45 of 60 lungs from slaughterhouse turkeys from all of 6 farms. During 1995, chlamydial antigen was detected in 41 of 54 lungs of 6 week old commercial turkey poults. The results of the present study indicate that Chlamydia psittaci infections are highly prevalent amongst Belgian commercial turkey poults with apparently little seasonal or year-to-year variation and that turkeys can contract the infection at an early age.     

FlorTree: A unifying modelling framework for estimating the species-specific pollution removal by individual trees and shrubs

Atmospheric pollution is a threatening problem around the world, with tropospheric ozone (O₃), nitrogen dioxide (NO₂) and particulate matter (PM₁₀) among the most harmful pollutants for citizens’ health. Nature-based solutions such as urban trees can cut down air concentrations of these pollutants thanks to stomatal uptake and dry deposition on their canopies and, in addition, uptake carbon dioxide (CO₂) and store carbon in their tissues. Unfortunately, some species emit biogenic Volatile Organic Compounds (bVOCs) that are O₃-precursors leading to air quality deterioration. As a proper selection of species is essential for urban greening, we developed an innovative single-tree model (FlorTree) to estimate the maximum flux of air pollutants. FlorTree considered species-specific parameters, such as tree morphology (height and crown leaf area), leaf/shoot structure, leaf habit (deciduous/evergreen) and eco-physiological responses to environmental factors, for 221 urban tree and shrub species. We applied the FlorTree model to examine i) which are the best species for air pollution removal in the case study of Florence (Italy) and ii) whether the species-specific removal performance is affected by different climate and air pollution conditions in other cities, namely Bucharest (Romania) and Tokyo (Japan). Results suggested that 24 tall trees (mainly broadleaves belonging to Tilia, Acer and Fraxinus genus) may be recommended for Florence due to their large crowns at maturity (50 years old), relatively high stomatal conductance and no bVOCs release. These general characteristics, however, were affected by climatic and pollutant conditions, suggesting that FlorTree must be applied to the local conditions. Therefore, our results demonstrated that FlorTree can be applied in any city for maximizing the air quality improvement by urban trees.     

Drainage performance and soil management

The performance of installed subsurface drainage systems is considerably influenced by soil management practices. These influences can be both positively and negatively. Cases of such influences are discussed in this paper. Optimal rootzone aeration and soil workability will often require a combination of drainage and soil management improvements.