Peat in the inoculation medium induces fusarium susceptibility in melons

The effect of peat moss on fusarium wilt of melon ( Cucumis melo L.) was studied in order to improve the selection process of resistant melons during breeding programmes. Disease symptoms were evident earlier and disease progress was faster in seedlings that were transplanted to peat following inoculation than in those transplanted to sand. The resistant breeding line used as a control did not show any wilt symptoms in either medium. Mixing the peat with sand or perlite reduced the disease development rate and the final disease incidence. The effects of peat and sand on disease progress were evaluated with two segregating melon populations in which the expected susceptible : resistant ratio was 25 : 75. In both populations, disease incidence was higher in the peat, which enables breeders to identify resistant plants and to lower the risk of using escapees as resistant plants. The mechanism of disease enhancement may include both biotic and abiotic components. There is an indication that peat induces plant susceptibility before inoculation. Melon seedlings germinated in peat and transplanted into sand exhibited significantly greater wilt incidence than those that germinated in sand and were transplanted into sand following the inoculation. Disease progress in sterile peat was significantly slower than that in non-sterile peat, which suggests the possible involvement of microbial activity.     

不同基质对闭鞘姜生长发育和光合作用的影响

采用随机区组设计,研究不同配比的红壤、泥炭、椰糠和珍珠岩6种基质配方对闭鞘姜生长的影响。测定6种基质的物理和化学性质,观测萌芽率、叶片数、茎粗、株高、株幅、光合日变化、根茎鲜重和根茎干重。结果显示,基质S4（泥炭+椰糠+珍珠岩=1∶2∶2）的植株净光合速率（P_n）显著高于其他基质处理。在6种基质生长的植株叶片净光合速率曲线呈单峰或双峰变化,而蒸腾速率曲线呈单峰变化。最大株高、最大根茎鲜重和根茎干重也出现在基质S4种植的植株。从以上结果可知,基质S4比较适合闭鞘姜的生长和根状茎干物质积累。     

草炭对土壤中尿素中氮的动态影响

采用室内培养,研究了两种草炭对尿素在土壤中转化后的铵态氮和碱解动态变化的影响以及其原因。表明,不论是石河子草炭或是加拿大草炭,在抑制尿素硝化产生硝态氮的同时对氨的挥发有一定的抑制作用,土壤在较长的内（２周内）保持较高的铵态氮含量,草炭的加入活跃了土壤中微生物,减少了肥料氮素的损失。     

The carbon content of soil and its geographical distribution in Great Britain

Abstract. England and Wales have 155 314 1 × 1 km squares, of which 140049 have more than 50% soil cover. The total soil organic carbon content, based on the dominant soil series and dominant land cover type, is estimated to be 2773 × 10⁶ t C. Scotland has 84929 1 × 1 km squares, of which 82 420 have a nominated dominant soil series. The total soil organic carbon content is estimated to be 19011 × 10⁶ t C, 6.85 times the total organic carbon content of the soil of England and Wales. The total organic carbon content of the soil of Great Britain is estimated to be 21 784 × 10⁶ t C, of which 87% is in Scottish soils and 75% is in Scottish peats. A map of the mean soil organic carbon content of 10 × 10 km squares of the National Grid using classes of equal range illustrates the narrow range of organic carbon contents of the soils of England and Wales and the dominance of organic carbon in Scottish soils. A map using the same data, but with classes of unequal ranges increasing in size with increasing carbon content, is better for showing detailed differences within England and Wales.     

A method for modelling peat depth in blanket peatlands

Inventories of peat volume and carbon storage often include general values for peat depth, but more spatially explicit and accurate estimates are required if carbon management strategies are to be developed at scales appropriate for the management. This article presents a methodology for estimating peat depth for large blanket peat areas using field sampling and GIS modelling to map peat depth on Dartmoor in south‐west England. The study area was divided into carbon unit areas (CUAs) based on soil and vegetation. Approximately 1000 peat depth measurements were taken, each consisting of a mean (n = 5) from depths within a 32 m² area. Sampling points were stratified according to CUA area and proportional extent of slope and elevation classes. Regression analyses were used to determine the relationships between slope, elevation and peat depth within each CUA. The strongest relationship was for blanket peat (r² = 0.53), with weaker ones for areas where peat was shallow and depth was less variable. A digital elevation model was used in a GIS to model peat depths for the whole of Dartmoor. Results were tested against a data set of 200 peat depths on a 250 m grid covering 1325 ha. We conclude that peat depth can be modelled using easily available topographic data combined with well‐designed field sampling over larger spatial scales. The approach can result in accurate mapping of peat depth and carbon storage for blanket peatlands in the United Kingdom and perhaps also elsewhere.     

蚯蚓处理椰子废弃物和畜禽粪混合物的研究

通过将椰糠、椰子枯落叶分别与牛粪、鸡粪混合．按10条／hg风干堆料接种蚯蚓后．在相同的条件下饲养，分别于10、20、30、40d时测定蚯蚓的生长繁殖情况．以及测定蚯蚓处理有机肥前后的理化性状。结果表明，随着时间的增加，蚯蚓的均重、日增重、日繁殖倍数均呈现先增加后减少的趋势．且不同时期、不同组合间均差异显著（P〈O．05），以椰糠、椰子枯落叶和牛粪组合的生长繁殖优于椰子凋落叶和鸡粪组合：蚯蚓处理后有机肥的pH、有机碳含鼍和C／N下降，全氮和全磷含量上升，且碳含量和C／N在处理前后均达到显著水平．但pH和磷含量在蚯蚓处理前后均无显著差异。     

施用草炭对科尔沁沙地土壤的改良效果

用草炭在科尔沁沙地上进行土壤改良田间试验,结果表明,施用有机质含量高、含有丰富的植物所需营养元素的草炭,可以有效地改善沙地土壤理化性质,提高其保水、保肥能力,增加作物产量。这为科尔沁沙地土壤改良开辟了一条新的途径。     

Effect of nitrogen,phosphorus and potassium on yields and nutrient levels in cabbage grown on sphagnum peat

Abstract

Fertilizer treatments for cabbage, grown on sphagnum peat, consisted of an N, a P and a K series. Each nutrient was applied at four rates in combination with constant rates of the other two.

Results indicated that 270 kg N/ha, the highest rate used, may not have been adequate whereas P and K at 80 and 150 kg/ha respectively were. In the N, the P, and the K series, highest head weights coincided with midribs containing 2.06% N, 0.48% P and 4.18% K respectively.     

泥炭营养块压制成型的试验研究

介绍了泥炭营养块压制成型研究的试验过程与结果分析，采用正交试验设计方法讨论了水分对泥炭营养块压制成型的影响。试验表明，基质填充量、颗粒配比对泥炭营养块压制成型的影响显著。在兼顾生产效率、生产条件和不影响泥炭营养块品质的情况下，减少基质填充量、提高成型压力、选择合理的粒径配比可提高泥炭营养块的抗压强度和压实密度。     

Quantification of Poinsettia Root Growth by Image Scans or X-ray Computed Tomography Scans in Three Propagation Substrates at Varied Moisture Levels

ABSTRACT

The objective was to refine protocols to quantify rooting of plant cuttings and the water/air microenvironment of substrates using x-ray computed tomography (CT). Poinsettia (Euphorbia pulcherrima) cuttings were propagated in three substrates (peat, rockwool, and phenolic foam) at varied moisture levels. In Experiment 1, adventitious rooting occurred in cuttings grown in rockwool or foam from 12% to 86% volumetric water content (VWC) and 12% to 80% volumetric air content (VAC). The highest root growth occurred in rockwool at 59% VWC and 33% VAC. There was an advantage to quantifying root growth by CT in rockwool and foam, in contrast to peat, because of clear differences in material density between root and substrate during image processing. In Experiment 2, root growth was quantified in peat by two-dimensional image scans under similar growth chamber environments, with rapid root growth from 52% to 63% VWC and 16% to 26% VAC. In Experiment 3, CT was used to quantify the substrate microenvironment at 0.5 cm slices to further describe the environment at the base of the plant cutting. Rapid rooting occurred in microenvironments above 56% VWC and 14% VAC, whereas the low 3% VAC in foam at high moisture may limit root growth.

Abbreviations: volumetric water content (VWC), volumetric air content (VAC), volumetric solid content (VSC)