Methane oxidation in non-flooded soils as affected by crop production — invited paper

Methane is an important greenhouse gas, which contributes approximately 20% to global warming. The atmospheric CH₄ concentration is increasing rapidly, resulting from an imbalance between CH₄ production and consumption. The only known biological CH₄ sinks are soils where methanotrophic bacteria consume CH₄ by oxidizing it. For several reasons the CH₄ uptake potential, particularly of arable soils and grassland, is only partly exploited, as several agricultural practices have adverse impacts on the activity of the CH₄ oxidizing bacteria. The kind of land use in general has a remarkable influence with much higher oxidation rates under forest than under grassland or arable soil. Regular soil cultivation by ploughing and fertilization with ammonium or urea have been identified as main factors. Immediately after ammonium application the methanotrophic enzyme system is blocked, resulting in an inhibition of CH₄ oxidation. In addition to this short-term effect a long-term effect exists after repeated ammonium fertilization, which is most likely caused by a shift in the population of soil microbes. Crop residues affect CH₄ oxidation differently, depending on their C/N ratio: with a wide C/N ratio no effects are expected, whereas with a narrow C/N ratio strong inhibition was observed. Animal manure, particularly slurry, can cause CH₄ emission immediately after application, whereas in the long run farmyard manure does not seem to have adverse impacts on CH₄ oxidation. The methanotrophic activity decreased markedly with soil pH, although in many cases liming of acidified soils did not show a positive effect. Arable soils have a rather small pH range which allows CH₄ oxidation, and the inhibitory effect of ammonium can partly result from a concomitant decrease in soil pH. Reduced tillage was identified as a measure to improve the methanotrophic activity of arable land, set aside of formerly ploughed soil points into the same direction. Plant growth itself is not primarily responsible for observed effects on CH₄ oxidation, but secondary factors like differential pesticide treatments, changes in pH, or cultivation effects are more likely involved. Although for the overall CH₄ fluxes the oxidation processes in agricultural soils are of minor importance, all available possibilities should be exhausted to improve or at least preserve their ability to oxidize CH₄.     

pH、抗坏血酸对硫酸亚铁化学状态的影响

本研究对不同ｐＨ值下，不同抗坏血酸水平及不同时间内硫酸亚铁溶液中以不同化学状态存在的铁进行了定量分析和研究。结果表明，低ｐＨ有利于硫酸亚铁以溶解、离子化及二价形式存在，ｐＨ的升高则具有相反的作用，特别是随时间的延长更加明显。抗坏血酸的存在可以促进硫酸亚铁的溶解，促进其离子化以及保持离子态铁稳定地以二价形式存在，有效地防止了硫酸亚铁在高ｐＨ环境下的不溶及二价铁被氧化为三价铁。抗坏血酸的这些作用是通过其还原及络合作用实现的。     

智能滴灌施肥控制系统中 pH调节品质的优化

利用遗传神经网络,通过对其权值的训练,优化权系数和网络结构.由可测的输出变量,将诸多有关作物 pH值调节的扰动推算出来,实现最优控制.仿真结果表明它能使加酸施肥系统控制偏差不超过± 2%,优化了调节品质.     

温度和pH对面粉和硼润土粘合性能的影响

将面粉和硼润土2种粘结剂分别以4%添加到配合饲料中,经pH分别为4.00、5.20、6.20、7.45、8.00、9.00、10.00的缓冲液调制后制成颗粒,再分别在30℃、55℃和85℃的烘箱中干燥,最后测定各处理饲料在水中的稳定时间、沉降速度和粗蛋白溶失率。结果表明:随着烘干温度的升高,2种粘结剂粘合性能明显增强;当pH为4～6.2时,粘结剂粘合性能没有明显变化,但当pH>7.45时,随着pH的升高,2种粘结剂的粘合性有增强的趋势,粗蛋白的溶失率也明显降低。     

区分松材线虫病材与健康材的研究

通过对南京地区黑松、马尾松松材线虫病材的化学成分的研究，发展病材的主要化学成分与健康材相比无明显差异，但苯醇抽出物和乙醚抽出物含量却显著减少。病材乙醚抽出物含量的明显减少是松材遭受松材线虫侵袭的特征之一。在乙醚抽出物的组成上病材和健康材也存在差别，此外两者的ｐＨ值也不相同，因而可选用适当的指示剂通过显色反应加以区分。     

渗透压与pH值对常温保存山羊精液的影响

本文研究了山羊精液在高倍稀释（１：３０），常温（１３—１５℃）保存条件下，稀释液渗透压与ｐＨ值对精子存活时间的影响。试验选用两种稀释液，渗透压调为较高的３４１和３３９渗压毫克分子浓度与较低的２６３和２８０渗压毫克分子浓度，ｐＨ值分别调为６．５和７．０。结果表明：在渗透压类同的条件下，ｐＨ为６．５，精子总存活时数比ｐＨ为７．０时长（ｐ＜０．０１）。生存指数高（Ｐ＜０．０１）。在ｐＨ值相同的条件下，较高渗透压的稀释液保存效果好。渗透压与ｐＨ值对精子共同作用下，在ｐＨ６．５时，不论渗透压较高或较低，精子活力维持在０．３以上的时数为３０小时左右，而ｐＨ７．０时只有１６小时左右。较低渗透压使精子顶体完整率下降轻快（Ｐ＜０．０１）。     

不同酸化饲料对断奶仔猪影响的研究

本试验选用168头平均35 d断奶的种仔猪,随机分成3组,每组3个重复,每组分别饲喂不同处理的酸化日粮,以酸结合力(BC)和pH表示。其中基础日粮组(第3组)的BC/pH为23.3/6.11,2个试验组(第2组和第1组)的BC/pH分别是14.9/4.9和11.9/4.51。研究酸化日粮对断奶仔猪生产性能、肠道组织结构及生理指标等的影响。结果表明:饲喂不同BC/pH值饲料的仔猪采食量、日增重和饲料转化率差异不显著,但低BC/pH值日粮(11.9/4.51)降低了断奶仔猪的腹泻发生;对应激仔猪十二指肠绒毛高度影响差异显著(P<0.05);对结肠内容物中的大肠杆菌活菌数影响差异显著(P<0.05);对血液内电解质平衡值dEB影响差异不显著(P>0.05);对结肠内容物中的挥发性脂肪酸VFA含量影响差异不显著(P>0.05)。     

Continuous measurement of reticuloruminal pH values in dairy cows during the transition period from barn to pasture feeding using an indwelling wireless data transmitting unit

This study was performed to investigate the effect of the transition from barn feeding to pasture on the pattern of reticuloruminal pH values in 8 multiparous dairy cows. A indwelling wireless data transmitting system for pH measurement was given to 8 multiparous cows orally. Reticuloruminal pH values were measured every 600 s over a period of 42 days. After 7 days of barn feeding (period 1), all of the animals were pastured with increasing grazing times from 2 to 7 h/day over 7 days (period 2). From day 15 to day 21 (period 3), the cows spent 7 h/day on pasture. Beginning on day 22, the animals had 20 h/day access to pasture (day and night grazing). To study reticuloruminal adaptation to pasture feeding, the phase of day and night grazing was subdivided into another 3 weekly periods (periods 4–6). Despite a mild transition period from barn feeding to pasture, significant effects on reticuloruminal pH values were observed. During barn feeding, the mean reticuloruminal pH value for all of the cows was 6.44 ± 0.14, and the pH values decreased significantly (p < 0.001) during period 2 and 3 to 6.24 ± 0.17 and 6.21 ± 0.19 respectively. During periods 4, 5 and 6, the reticuloruminal pH values increased again (pH 6.25 ± 0.22; pH 6.31 ± 0.17; pH 6.37 ± 0.16). Our results showed that the animals had significantly lowered reticuloruminal pH during the periods of feed transition from barn to pasture feeding. Despite these significant changes, the decrease was not harmful, as indicated by data of feed intake and milk production.     

Commercial cuts and chemical and sensory attributes of meat from crossbred Boer goats fed sunflower cake‐based diets

This study aimed to evaluate sunflower cake feed in commercial cut yields and chemical and sensory attributes of goat meat. Thirty‐two castrated male goats were distributed in four levels (0, 8, 16 and 24%) of sunflower cake supplementation. The animals were slaughtered and the carcasses were placed in a cold chamber and sectioned into five anatomical regions corresponding to commercial cuts. Samples of the Longissimus lumborum muscle were analyzed for chemical composition and sensory quality. The chemical composition and pH were not affected by the treatments. The smell, taste and ‘goatiness’ of the aroma and flavor of the meat were also unaffected by the treatments. The appearance, tenderness and juiciness of the meat differed by treatment. The highest level (24%) of sunflower cake increased meat tenderness; however, according to the tasters there was reduced softness, although none of the samples were rejected by the tasters. Sunflower cake can be added to the diet at a level of up to 16% without altering the quantitative and qualitative attributes of the meat.