The uptake of As, Cd, Pb, and Zn and potential phytoremediation efficiency of five high biomass producing crops, white sweetclover (Melilotus alba L.), red clover (Trifolium pratense L.), curled mallow (Malva verticillata L.), safflower (Carthamus tinctorius L.) and hemp (Cannabis sativa L.) commonly used as grazing and/or energy crops was evaluated in both pot and field experiments at soils with different level of element contamination. In pot experiment the highest phytoremediation efficiency was demonstrated by C. tinctorius where 4.8% of Cd and 1.1% of Zn were removed from the moderately contaminated soil in one vegetation period when repeated harvest of aboveground biomass was performed. The removal of As and Pb was negligible for all the investigated plant species. At the highest element content in soil inhibition of plant growth due to the element phytotoxicity to plants was reported in most of cases. In the precise field experiment lower phytoremediation efficiency (biennial phytoremediation factors did not exceed 0.2% for Pb and Zn and 0.3% for Cd for C. tinctorius) was determined but yield suppress was not observed. Thus, free space for manipulation with element mobility in soil to increase element uptake by plants remains for further research.

<b>The effects of fertilization, irrigation and crop rotation on the major soil parameters and microbiological soil properties were studied at Debrecen-Látókép in the 16</b> ^th <i> and 17</i> ^th <i> years of the fertilization experiment on calcareous chernozem soil. The results can be summarized as follows: In the examination period the moisture content of the experimental soil increased by 2-3% due to irrigation. With increasing fertilizer doses, the pH value of soils reduced both in aqueous and <i>M</i> KCl suspension, but it did not change considerably at medium and high fertilizer doses. The hydrolytic acidity increased with decreasing pH values. The nitrate-N, AL-soluble phosphorus and potassium contents increased gradually with increasing fertilizer doses. Among the soil microbial parameters, the total number of germs increased slightly, while the amount of nitrifying bacteria was significantly higher due to fertilization. As a result of <i>fertilization</i> , a significant increase was detected in the phosphatase and urease activityin both crop rotations and irrigation treatments. The activity of saccharase and catalase was reduced at medium and high fertilizer doses. In addition to changing the moisture content of soils irrigationincreased the total number of germs and the amount of nitrifying and cellulose decomposing bacteria. Irrigation provided more favourable conditions for CO ₂ production, increasing the microbial biomass C content and for the functioning of phosphatase and urease enzymes. </i> In triculture the number of nitrogen-fixing and cellulose decomposing bacteria was higher than in monoculture, especially in the case of medium and high fertilizer doses. The activity of phosphatase, saccharase and urease enzymes was significantly higher in triculture than in monoculture.

The effects of fertilization, irrigation and crop rotation on the major soil parameters and microbiological soil properties were studied at Debrecen-Látókép in the 16 ᵗʰ and 17 ᵗʰ years of the fertilization experiment on calcareous chernozem soil. The results can be summarized as follows: In the examination period the moisture content of the experimental soil increased by 2-3% due to irrigation. With increasing fertilizer doses, the pH value of soils reduced both in aqueous and M KCl suspension, but it did not change considerably at medium and high fertilizer doses. The hydrolytic acidity increased with decreasing pH values. The nitrate-N, AL-soluble phosphorus and potassium contents increased gradually with increasing fertilizer doses. Among the soil microbial parameters, the total number of germs increased slightly, while the amount of nitrifying bacteria was significantly higher due to fertilization. As a result of fertilization , a significant increase was detected in the phosphatase and urease activityin both crop rotations and irrigation treatments. The activity of saccharase and catalase was reduced at medium and high fertilizer doses. In addition to changing the moisture content of soils irrigationincreased the total number of germs and the amount of nitrifying and cellulose decomposing bacteria. Irrigation provided more favourable conditions for CO ₂ production, increasing the microbial biomass C content and for the functioning of phosphatase and urease enzymes. In triculture the number of nitrogen-fixing and cellulose decomposing bacteria was higher than in monoculture, especially in the case of medium and high fertilizer doses. The activity of phosphatase, saccharase and urease enzymes was significantly higher in triculture than in monoculture.

Soil microbial biomass is an active part of soil organic matter that plays a key role in the decomposition of organic materials, nutrient cycling, and formation of soil structure. Measurement of soil microbial biomass has been proposed with a number of biochemical procedures, which vary in their sensitivity, procedural complications, and relationship to other active soil organic matter pools. Across a number of soils, the flush of CO2 following rewetting of dried soil was closely related to (1) the flush of CO2 following fumigation with chloroform, (2) potential C mineralization, and (3) potential N mineralization. Both chloroform fumigation-incubation and rewetting of dried soil utilize the activity of the surviving native soil microbial community to evaluate the soil microbial biomass. We describe how the flush of CO2 can be used to discriminate changes in soil biological quality induced by various agricultural management practices under different soil conditions.

Our aim was to determine whether the soil microbial biomass, which has developed naturally over many years in a given ecosystem, is specially adapted to metabolize the plant-derived substrate C of the ecosystem within which it developed or whether the nature of recently added substrate is the more important factor. To examine this, soils from three sites in close proximity (woodland, grassland and arable from the Broadbalk Experiment at Rothamsted Research, Harpenden, UK) were each amended with air-dried wheat straw (Triticum aestivum), ryegrass leaves (Lolium perenne) or woodland leaf litter (mainly Quercus robur and Fagus sylvatica) in a fully replicated 3 [multiplication] 3 factorial laboratory experiment. The initial mineralization rates (evolved CO₂-C) were determined during the first 6.5 hours and again, together with the amount of microbial biomass synthesized (microbial biomass C), at 7, 14, 21, 30 and 49 days of incubation. The hourly rate of CO₂-C production during the first 6.5 hours was slowest following leaf litter addition, while the added grass gave the fastest rates of CO₂-C evolution both within and between soils. Ryegrass addition to the arable soil led to approximately four times more CO₂-C being evolved than when it was added to the woodland soil, at an overall rate in the arable soils of 41 [mu]g C g[superscript [-]1] soil hour[superscript [-]1]. In each soil, the net amounts of CO₂-C produced were in the order grass > straw > leaf litter. In each case, the amount produced by the added leaf litter was significantly less (P < 0.05) than either the added grass or straw. Overall, the trend was for much slower rates of mineralization of all substrates in the woodland soil than in either the arable or grassland soils. During 49 days of incubation in the woodland and grassland soils, the net total amounts of CO₂-C evolved differed significantly (P < 0.01), with grass > straw > leaf litter, respectively. In the arable soil, the amounts of CO₂-C evolved from added grass and straw were significantly larger (P < 0.01) than from the leaf litter treatment. Our findings indicated that the amounts of CO₂-C evolved were not related to soil management or to the size of the original biomass but to the substrate type. The amount of biomass C synthesized was also in the order grass > straw > leaf litter, at all stages of incubation in the woodland and grassland soil. In the arable soil, the same effect was observed up to 14 days, and for the rest of the incubation the biomass C synthesized was in the order grass > straw > leaf litter. Up to three times more biomass C was synthesized from the added grass than from the other substrates in all soils throughout the incubation. The maximum biomass synthesis efficiency was obtained with grass (7% of added C). Overall, the woodland soil was most efficient at synthesizing biomass C and the arable soil the least. We conclude that substrate type was the overriding factor that determined the amount of new soil microbial biomass synthesized. Mineralization of substrate C by soil microorganisms was also influenced mainly by substrate type and less by soil management or size of original biomass.

The assessment of a degree of biological degradation of drained peat soils in the Brest Poles'e by level of total biomass soil microorganisms is given. The powerful peat soil as characterized by a maximum biomass of bacteria, actinomyces and fungi: (724,20 +-48,40)x10-5g/g. Total biomass of microorganisms in the degrading-peat and peat-mineral soil having a medium degree of mineralization was less by 5,43 times (p0,05) in comparison with the biomass in the powerful peat soil. This has allowed to evaluate the first soil by biological criterion as degraded one having the degree of degradation of 1 (in the 0-4 scale). The remaining varieties of the investigated soils (humus-peat, humus-gley, humus-peat-gley and mean-power peat) had degradaton degree by biological criterion equal zero

Quantification of root biomass through the conventional root excavation and washing method is inefficient. A pot experiment was conducted to estimate root-derived carbon (C) in soil. Spring wheat (Triticum aestivum L. cv. 'Quantum') was grown in plastic containers (6 L) filled with sterilized sandy soil in a greenhouse. Plants were enriched with 13CO2 in a glass chamber twice at growth stages GS-37 and GS-59 for 70 min at each time. In one treatment, roots were separated from soil at crop maturity, washed and dried for the determination of biomass. Isotope ratios were then separately analyzed for roots and soil. In a second treatment, roots were thoroughly mixed with the whole soil and representative samples were analyzed for 13C abundance at crop maturity. Control plants were untreated with 13C, in which roots were separated from soil. The root biomass was calculated based on the root-derived C, which was measured through 13C abundance in the soil and root mixed samples. A substantial amount of root-derived C (24%) was unaccounted while separating the roots from soil. Similarly, about 36% of the root biomass was underestimated if conventional root excavation and washing method is used. It has been shown that root biomass can be estimated more accurately from the root-derived C using 13C tracer method than the estimates made by the conventional excavation and washing method. We propose this as an alternative method for the estimation of root-derived C in soil, based on which root biomass can be estimated.

Land leveling is a government-subsidized, water-conserving agricultural practice common in the Mississippi River Delta region of the midsouthern United States. Though practiced to more uniformly deliver irrigation water, land leveling is a severe soil disturbance that alters the quasi-equilibrium among near-surface soil biogeochemical properties. The objectives of this study were to characterize the short-term impacts of land leveling on the magnitude, variance, and spatial variability and distributions of soil physical and biological properties and to evaluate the impact of land leveling on the relationships among soil properties in a Sharkey clay (very-fine, smectitic, thermic Chromic Epiaquert) used for irrigated soybean [Glycine max (L.) Merr.] and rice (Oryza sativa L.) production in the Mississippi Delta region of northeast Arkansas. Bulk density and clay increased (P < 0.001), while sand, silt, fungal biomass, and fungal/bacterial biomass ratio decreased (P < 0.001) as a result of land leveling. Despite the effect on the fungal/bacterial biomass ratio, hence a significant alteration of the soil microbial community structure, soil bacterial biomass was unaffected by land leveling. The variance associated with silt increased (P < 0.01), while the variance for fungal biomass and the fungal/bacterial biomass ratio increased (P < 0.001) as a result of land leveling. Spatial variability and distributions of soil physical and biological properties and relationships among them were noticeably altered by land leveling. Increased variations in soil physical and biological properties as a result of any soil disturbance will make uniform field management difficult. Compared to a similar study, the magnitudes of near-surface soil physical and biological property change as a result of land leveling were lower on a clayey Vertisol than on a silt-loam Alfisol.