腐植酸产品特性及其对真菌和植物生长的影响

天然腐植酸主要来自风化煤和褐煤等,其产品主要有Pak腐植酸盐、腐植酸盐肥料、Pak Humax、Humkara和Humide等,它们在使用之前必须了解其功效。本研究比较了4种腐植酸肥料的理化性质、光学特性以及对小麦(栽培品种Sehr)、绿豆(绿豆-54)、玉米(C-12)和田菁种子萌发和生长的影响,同时研究了它们对4种真菌的影响。4种腐植酸肥料的含水量为52%~71.11%,溶解度为30.2%~98.2%,密度为1.67~4.17 g/mL,2%腐植酸肥料水溶液pH值为5.39~10.11,EC值为3.140~1.143 mS/cm。4种腐植酸肥料的碳含量为22.95%~36.56%、氮含量为0.658%~1.183%,相应的C/N比为30.91~44.16。将4种腐植酸肥料用0.1 mol/L NaOH溶液溶解,分离获得腐植酸和黄腐酸,按含碳量计算,含碳量40.3%~77.5%的为腐植酸,含碳量22.5%~59.7%的为黄腐酸。对腐植酸在400 nm、500 nm、600 nm和700 nm下的光学性质进行了研究,并对465 nm和665 nm条件下的吸光度进行测量,计算其比值E4/E6(即消光系数)。结果表明,E4/E6比值变化在3.64~5.48之间,且光密度随着波长的增加而降低,与腐殖质的碳含量具有显著相关性。供试的4株真菌中,根据菌落直径观察,Trichoderma harzianum,T.hamatum和Alternaria alternate3种真菌在0.025%腐植酸培养基上生长最好。4种腐植酸肥料对小麦、玉米、绿豆种子萌发都有抑制作用,但对田菁种子萌发具有促进作用;对小麦和玉米的根具有促进生长的作用,同时可以提高小麦和玉米芽的干物质含量,而对绿豆和田菁没有影响。研究发现,巴基斯坦市场上销售的腐植酸肥料差异很大,为保障使用者的利益,对这些肥料进行质量监测十分必要。

Characterization of Commercial Humic Acid Samples and Their Impact on Growth of Fungi and Plants

Naturally occurring humates like leonardite and brown coal or lignite are marketed under different brand names e.g. Pak Humates, Humate Fertilizer, Pak Humax, Humkara and Humide etc. However, their efifcacy is needed to be conifrmed before their use. Different studies were conducted for the comparison of four commercial humates for their physico-chemical, optical properties, plant growth promoting ability in terms of seed germination and seedling vigour in＆amp;nbsp;wheat （cv Sehr）, mung bean （Mung-54）, maize （C-12） and sesbania and their effect on growth of some fungi. Moisture content of four humates varied from 0.52%to 71.11%, while solubility in water varied from 30.2%to 98.2%and den-sity differed from 1.67 to 4.17 g/mL. A 2%solution of humates had pH and EC varying from 5.39 to 10.11 and 3.140 to 1.143 mS/cm, respectively. Carbon and nitrogen concentrations varied from 22.95%to 36.56%and 0.658%to 1.183%, respectively with a C/N ratio of 30.91 to 44.16. Humates dissolved in 0.1N NaOH were partitioned into humic acid and fulvic acid fractions. Of the total C in humates, 40.3%to 77.5%was ranged in humic acid and 22.5%to 59.7%in fulvic acid fraction. The HA was also studied for optical properties at 400 nm, 500 nm, 600 nm and 700 nm besides that at 465 nm and 665 nm to calculate E4/E6（extinction coefifcient）;the later varied between 3.64 and 5.48. Optical density of the humic acid decreased at increasing wavelength and was correlated signiifcantly with the carbon contents of humic com-pounds. Three fungi, Trichoderma harzianum, T. hamatum and Alternaria alternate showed maximum growth at 0.025%HA in the growth medium on the basis of colony diameter. Humates inhibited seed germination in wheat, maize and mung bean except for sesbania. Root length and shoot dry matter increased in wheat and maize but no effect was found in mung bean and sesbania. The studies revealed that humates available in the market vary widely and therefore some sort of quality monitoring is required for the beneift of end users.