Long-term fertilization and plastic film mulching modify temporal incorporation of 13C/15N-labelled particulate organic matter

Plastic film mulching (PFM) is critical for agricultural planting and maximizing production in semiarid and arid areas. Particulate organic matter (POM) is assumed to be a sensitive indicator for evaluating the effects of different agricultural practices on soil fertility and the soil organic carbon (SOC) pool. Soil aggregates have the function of ‘wrap’ and protect the POM stored in them. However, there is limited information regarding how PFM and fertilization jointly influence the dynamic changes of newly added stalk-derived POM in brown earth. Consequently, an in-depth study of the fate of carbon (C) and nitrogen (N) derived from maize stalk residues within the particulate organic carbon (POC) and particulate organic nitrogen (PON) fractions in soil aggregates was undertaken. Its outcome would contribute to better predictions on the active organic matter components sequestered in the soil. The dynamics and accumulation of newly added maize stalk C and N as POC and PON in different soil aggregates (using the dry sieving method divided into >2, 1–2, 0.25–1 and <0.25 mm) were analysed by an in situ ¹³C/¹⁵N-tracing technique under PFM and different fertilization treatments. Over 360 days of cultivation, the POC and PON contents were significantly (p < 0.05) larger in the nitrogen (N) and organic manure (M) treatments than in the MN (manure combined with nitrogen) and Control treatments. The PFM treatment accelerated the decomposition of maize stalk C in the N fertilizer treatment, with an increase of 64% in stalk-derived POC after the 1-day cultivation period. Stalk-derived POM tended to accumulate in <0.25 mm microaggregates in the early cultivation period and then decreased rapidly with the extension of the cultivation period affected by PFM coupled with fertilization. However, stalk-derived POM accumulation in macroaggregates (>0.25 mm) fluctuated over the 360-day cultivation period. Accordingly, PFM application and fertilization practices had important effects on the accumulation of newly added stalk-derived POM in soil aggregates. We conclude that the accumulation of maize residue POM was primarily affected by soil fertilization type, rather than by the presence or absence of PFM. These results provide new insights into agricultural management strategies for improving soil carbon sequestration capacity.     

玉米秸秆覆盖量对土壤质量影响的试验研究

秸秆覆盖还田是保护性耕作技术的核心技术之一,可以有效减少环境污染和大田水分蒸发,提高作物产量,而不同秸秆覆盖量对土质状况又有不同的影响。为此,就不同玉米秸秆覆盖处理对土壤质量的影响进行了试验,并在小麦全生育期的3个阶段进行采样,分析了不同时期不同处理下土壤质量的变化,然后进行模糊综合评价。结果表明,较优的秸秆处理方案为50％覆盖有腐解剂,较优的秸秆覆盖量为50％覆盖,即半覆盖量。     

培育措施对人工林樟子松木材力学性质的影响

研究了不同培育措施(初植密度、间伐强度、坡向、坡位)对人工林樟子松(Pinus sylvestris var.mongolica)木材的密度和力学性质(横纹抗弯强度、抗弯弹性模量、顺纹抗压强度、冲击韧性、端面硬度)的影响。初植密度(1.5m×1.0m,1.5m×2.0m和1.5m×2.5m)对木材密度和抗弯弹性模量有显著的影响。初植密度为1.5m×1.0m时,木材主要力学指标值最大。适当间伐可提高木材的抗弯弹性模量和顺纹抗压强度,但重度间伐则会降低木材的力学强度。坡向(阳坡和阴坡)对木材的抗弯弹性模量影响显著,阳坡高于阴坡。坡位(上坡位和下坡位)对除端面硬度外的木材力学性质指标影响都显著,各项力学指标值均是坡下高于坡上。表5参9。     

熏蒸剂的使用受限促进气调技术的发展

熏蒸药剂残留对食品、环境的危害问题使得相关标准制定单位采取措施严格限制熏蒸剂的使用.二十年前曾经使用的多数熏蒸剂如今已所剩无几.甲基溴具有较高效的杀虫效果,但是由于它对臭氧层的破坏严重,发达国家已于2005年淘汰使用,发展中国家也将于2015年之前淘汰甲基溴.比较而言,现今使用普遍的仍是磷化氢,然而近年来害虫对磷化氢的抗性问题显得日益严重.这些熏蒸药剂的种种局限,已经向食品企业提出了新的全球性的挑战,要求致力于寻找新的熏蒸剂,开发新的替代技术.目前,被提及的新的熏蒸剂有硫酰氟、氧硫化碳(carbonyl sulphide)、环氧丙烷(propylene oxide)、甲基碘(methyl jodide)、臭氧(ozone)、甲酸甲酯(ethyl formate)和氢氰酸(hydrogen cyanide).硫酰氟被认为是很有前景的熏蒸剂替代品,可用来有效地保护储藏食品、食品加工设备免受害虫危害,而且还可以作为一种检疫用的熏蒸剂.其它一些新开发的熏蒸剂由于只对特定种类的储藏物品有效或在特定条件下才有效,所以使用的局限性很大.试验证明:具有挥发性的植物提取剂有较好的使用前景,但还需要大量的商业生产验证试验,而且在投入生产实践之前还需要一系列的认证程序.可成功替代熏蒸药剂的众多气体处理技术有:气调技术、高温结合气调技术以及进一步开发用作特定用途的高压二氧化碳技术.当前研究开发的是低压环境下的气调技术.这些研究证明气调技术很有市场前景,应当作为全球开发的新方法的一个典范.     

Improved management of mango fruit though orchard and packinghouse treatments to reduce lenticel discoloration and prevent decay

Mango fruit are exposed to complex postharvest handling management, intended to improve postharvest quality retention during export shipment. Susceptibility to lenticel discoloration and to Alternaria side rots and Phomopsis stem-end rot under current handling conditions led us to re-evaluate and modify the chain of postharvest treatments, from the orchard to the packinghouse. The previously developed hot-water brushing (HWB) treatment was found effective in reducing incidence of Alternaria and stem-end rots, but it significantly induced development of red lenticels. Two factors were key to improving fruit quality, by simultaneously reducing lenticel discoloration and decay development: (a) postharvest water and/or NaOH washes in the orchard, and (b) hot-water spray (HWS) applied over rollers without brushes in the packinghouse. The present results indicate that optimal management involves combinations of water washes in the orchard with packinghouse HWS treatment; this significantly reduced the severity of lenticel discoloration by 50–60%, and the incidence and extent of postharvest side rots caused by Alternaria by 60% or more. These results indicate that appropriate handling of fruit can appreciably improve their quality during prolonged storage and shipment.     

秸秆还田地不同水氮条件对水稻产量及土壤肥力的影响

[目的]研究秸秆还田地不同水氮管理对水稻产量、土壤养分以及土壤酶活性的影响,为发展优质、高效生态农业提供理论支持。[方法]通过田间小区试验,设计了3种灌溉方式共9个处理,并设置3个麦秆不还田处理为对照。[结果]施氮量为225kg/hm2时,浅湿调控灌溉模式有利于控制水稻茎蘖量,降低水稻株高,形成合理的群体结构;不同水氮管理对水稻产量构成因素中的每穗总粒数、结实率无显著影响,水稻有效穗数受灌溉措施及施氮量的影响较大,浅湿调控灌溉可以显著提高水稻有效穗数和千粒重,从而提高水稻产量;施氮量为225kg/hm2时,浅湿调控灌溉可以有效提高土壤有机质、全氮、有效磷、有效钾的含量。秸秆还田可以显著提高土壤蔗糖酶活性,降低土壤脲酶活性,而对土壤过氧化氢酶活性无显著影响。秸秆还田地施氮量为225kg/hm2时,浅湿调控灌溉对土壤蔗糖酶活性的提高最为显著,而不同水氮条件对土壤脲酶活性的影响并不显著。[结论]在秸秆还田地,当施氮量为225kg/hm2时,浅湿调控灌溉可以有效提高水稻产量及土壤肥力。     

Low-intensity light cycles improve the quality of lamb's lettuce (Valerianella olitoria [L.] Pollich) during storage at low temperature

The influence of light on fresh-cut vegetables during storage is controversial, since both positive and negative effects on shelf-life and quality of such products have been observed. In this work, the effect of low-intensity light treatments on lamb's lettuce, a fresh-cut leafy and ready-to-eat vegetable, was investigated during storage at low temperature (6 °C), in comparison with conventional storage (in the dark at 4 °C). Although continuous light treatment (1 cycle of 8 h per day) was deleterious, cycles of light treatments (8 cycles of 1 h per day; 16 cycles of 0.5 h per day) showed positive effects, assessed by evaluating the content of chlorophylls, carotenoids, ATP, glucose and ascorbate. These analyses were performed at the beginning and after 6 days of storage, in comparison with samples stored in the dark at 4 °C. Under low-intensity light treatments, even if performed at a higher temperature (6 °C), the content of such bioactive compounds increased or was at least similar to that found in samples stored in the dark at the same temperature. We suggest that continuous low-intensity light treatments during cold storage of lamb's lettuce are able to promote photosynthesis but, at the same time, induce photo-damage. On the contrary, under intermittent low-intensity light cycles, photosynthesis is only partially activated, while the metabolism of the green tissues is still able to provide carbon moieties for the synthesis of bioactive molecules involved in delaying senescence. Therefore, low-intensity light cycles at 6 °C could contribute to maintain quality of lamb's lettuce, with respect to samples stored in the dark at both 6 and 4 °C. Finally, setting the temperature at 6 °C allows reduction of refrigerator energy consumption during storage.     

田菁翻压还田对滩涂土壤碳氮及微生物生物量的影响

为探讨不同施肥处理下田菁翻压还田对滩涂土壤的改良效果,通过田间小区试验对不同施肥处理(CK、SN1、SN2、SN3、SN4及SN4+OF对应的施氮量分别为N 0、90、135、180、225 kg/hm~2及N 225 kg/hm~2+有机肥)下田菁生物量、碳氮养分含量及翻压还田对土壤碳氮、微生物生物量的影响及各指标间的相关性进行了研究。结果表明:SN3处理对提高田菁总生物量及两次刈割地上部碳氮含量效果明显。SN4+OF处理下田菁翻压还田后土壤有机碳、全氮及固定态铵含量明显提升,分别为6.44 g/kg、0.62 g/kg和40.1mg/kg,土壤活性有机碳、硝态氮、铵态氮、微生物生物量碳氮(MBC、MBN)含量及碳库管理指数(CPMI)均以SN2处理下田菁翻压还田效果较优。土壤C/N、MBC/MBN比值分别以SN4+OF和SN2处理下田菁翻压还田最高。因此,SN3处理可明显提高田菁生物量和碳氮养分含量,而田菁翻压还田效果则以SN2及SN4+OF处理较优。