Fulltext search in archive

Plant's nitrogen (N) requirement that is not fulfilled by available N in soil has to be supplied externally through chemical fertilizers. A reliable estimate of soil N-supplying capacity (NSC) is therefore essential for efficient fertilizer use. In this study involving a pot experiment with twenty acidic soils varying widely in properties, we evaluated six chemical indices of soil N-availability viz. organic carbon (C_org), total N (N_tot), acid and alkaline-KMnO₄ extractable-N, hot KCl extractable-N (KCl-N) and phosphate-borate buffer extractable-N (PBB-N), based on their strength of correlation with available-N values obtained through aerobic incubation (AI-N) and anaerobic incubation (ANI-N), and also with the dry matter yield (DMY), N percentage and plant (maize) N uptake (PNU). In general, the soils showed large variability in NSC as indicated by variability in PNU which ranged from 598 to 1026 mg/pot. Correlations of the N-availability indices with AI-N and ANI-N decreased in the order: PBB-N (r = 0.784** and 0.901**) > KCl-N (r = 0.773** and 0.743**) > acid KMnO₄-N (r = 0.575** and 0.651**) ≥ C_org (r = 0.591** and 0.531**) ≥ alkaline KMnO₄-N (r = 0.394** and 0.548**) > N_tot (r = 0.297** and 0.273*). Of all the indices evaluated, PBB-N showed the best correlations with plant parameters as well (r = 0.790** and 0.793** for DMY and PNU, respectively). Based on the highest correlations of PBB-N with biological indices as well as plant responses, we propose PBB-N as an appropriate index of N-availability in the acidic soils of India and other regions with similar soils.

To investigate the environmental advantages of using grass-clover binary mixtures over pure stands as winter cover crops, a serial of five field experiments (each designed as randomized complete blocks with four replicates) was carried out in eastern Slovenia. Trifolium incarnatum L. and Lolium multiflorum Lam. were sown in late summer as pure stands and binary mixtures. Pooled data calculated from all the experiments revealed that the soil mineral N in spring and accumulation of N by plants decreased with decreasing proportion of T. incarnatum in the binary mixtures, while the C:N ratio of cover crop organic matter increased. C accumulation was the highest when the seeding ratio of the binary mixture of T. incarnatum and L. multiflorum was 50:50. In the C and N environmentally sustainable management efficiency coefficients, three important traits of winter cover crops for environmental pro-tection were given equal importance (low soil mineral N content in spring, high C accumulation in plants, and high N accumulation in plants). The coefficient was higher for binary mixtures of T. incarnatum and L. multiflorum than for pure stands of these crops, proving the complex environmental advantages of binary mixtures over pure stands.

Soil samples were collected at both jointing and maturing stages of maize and wheat to compare the effects of 4-year no-tillage (NT) and conventional tillage (CT) on seasonal variations of microbial biomass carbon (C), metabolic quotient, and invertase activity in a sandy loam soil in North China. Soil invertase activity significantly increased (P < 0.05) from summer to spring of the next year and then significantly decreased (P < 0.05) from spring to summer. With a delay of about 3 months, soil microbial biomass C and basal respiration altered in a similar pattern, while microbial metabolic quotient changed on the contrary. Compared with CT, the NT practice significantly increased (P < 0.05) soil organic C content, and tended to result in higher soil microbial biomass C and invertase activity, as well as lower soil microbial metabolic quotient, especially at the jointing stage of maize. Our results indicated that NT might play an important role in the improvement of soil microbial efficiency, especially at the maize seedling season.

A field study was conducted to ascertain the effect of three zinc (Zn) levels: 0, 20 kg ZnSO₄/ha and 20 kg ZnSO₄/ha + foliar spray of 0.5% ZnSO₄, on wheat grain Zn content and factors contributing to or hindering in its bioavailability. Increasing Zn levels were established as serviceable in improving the nutritional status of genotypes. Soil application + foliar spray proved to be paramount for all the traits leading to an 80% increase in grain Zn content, 61.3% in methionine content and a decrease of 23.2% in phytic acid as an average of all genotypes and both years. The genotype UP 2382 was found more suited to Zn fertilization in allocating Zn and maintaining a lower phytate to Zn molar ratio.

To investigate the effects of returning wheat straw to croplands on soil compaction and nutrient availability, this trial was designed: (1) planted crops without fertilization (NF); (2) natural land without human activities (CT); (3) applied mineral fertilizers in combination with 7500 kg/ha wheat straw (WS-NPK); (4) applied mineral fertilizers in combination with 3750 kg/ha wheat straw (1/2WS-NPK); and (5) applied mineral fertilizers alone (NPK). It is found that, compared with NPK, the soil bulk density in 1/2WS-NPK and WS-NPK both decreased by more than 10% in the 0 cm to 15 cm layer, and by 6.93% and 9.14% in the 15 cm to 20 cm, respectively. Furthermore, in contrast to NPK, the soil available nitrogen in the 0 cm to 25 cm layer in 1/2WS-NPK and WS-NPK were higher by 17.43% and 35.19%, and the soil available potassium were higher by 7.66% and 17.47%, respectively. For soil available phosphorus in the depth of 5 cm to 25 cm, it was higher by 18.51% in 1/2WS-NPK and by 56.97% in WS-NPK, respectively. Therefore, returning wheat straw to croplands effectively improves soil compaction and nutrients availability, and the improvement in soil nitrogen and phosphorus availability is closely related to the amount of wheat straw.

A litterbag experiment was conducted to investigate the changes of tannins and nutrients in branchlets at different decomposition stages of Casuarina equisetifolia in southern subtropical coastal zone, China, using the colorimetric assays. The time required for the loss of half of the initial dry weight (t₅₀) was 9.13 months. Total phenolics (TP), extractable condensed tannins (ECT), protein-bound condensed tannins (PBCT), total condensed tannins (TCT) and protein precipitation capacity (PPC) of branchlets litter decreased rapidly, while fibre-bound condensed tannins (FBCT) increased during decomposition. Nitrogen and phosphorus concentration of the branchlet litter both increased gradually during decay. Negative correlations between TP and nitrogen or phosphorus, as well as TCT and nitrogen or phosphorus were found. These chemical changes enhanced the current knowledge on the potential ecological role of nutrient transformation in tannins in C. equisetifolia plantations.

To investigate the effect of low soil pH caused by fertilization on soil available zinc in calcareous soil, this study was conducted based on a long-term experiment consisting of: (a) no fertilization (CT); (b) mineral fertilizer application coupled with 7500 kg/ha of wheat straw (WS-NPK); (c) mineral fertilizer application coupled with 3750 kg/ha of wheat straw (1/2WS-NPK); (d) mineral fertilizer application alone (NPK). Long-term fertilization results in a significant increase in soil DTPA-extractable zinc. However, the increased soil DTPA-extractable zinc is unavailable to crops and mainly confined to 0.25 mm > and 0.25 mm to 1 mm aggregates. Compared to CT, soil DTPA-extractable zinc under fertilization is more than 9.67% and 122.36% higher in 0.25 mm > and 0.25 mm to 1 mm aggregates, respectively. Furthermore, plant-available zinc in the 0-15 cm soil layer and wheat grain zinc are both significantly positive related to soil DTPA-extractable zinc in > 2 mm aggregates. Therefore, plant-available zinc in the 0-15 cm layer is closely associated with DTPA-extractable zinc in > 2 mm aggregates, and the low soil pH caused by long-term fertilization could not enhance plant-available zinc in the surface soil layer nor elevate wheat grain zinc concentration because of the occlusive effect of soil aggregates.

This paper focuses on Eremanthus incanus Less. (Asteraceae), a common species of highland regions in Brazil. The effect of arbuscular mycorrhizal (AM) inoculation on plant growth (height and diameter) was evaluated. Roots were examined from individuals randomly selected from undisturbed areas of highland vegetation and from an experimental restored site. Results showed that E. incanus presented high AM colonization both in restored and undisturbed sites. Moreover, AM colonization was significantly higher in the inoculated treatment than in the non-inoculated one. The species presented Arum-type colonization and frequent production of vesicles, especially in the restored site. Arbuscular mycorrhizal inoculation stimulated plant growth (height and diameter). Ten AM fungi (AMF) taxa were found in the studied rooting zones: Acaulospora spinosa, A. elegans, A. foveata, Acaulospora sp., Gigaspora margarita, Glomus sp., Dentiscutata biornata, D. cerradensis, Dentiscutata sp. and Racocetra verrucosa. These results revealed that AMF is a common and important component in highland vegetation in Brazil, and should be included in future restoration programs.

Fast-growing woody plants that can be grown under short-rotation systems offer an alternative to food production on arable land, and serve as a potential source of renewable energy. In order to establish the feasibility of future large scale production under the conditions of the Czech-Moravian highland, a high density experimental field plantation including a range of available clones of Populus sp. and Salix sp. with the total area of 1.5 ha was established in early 2001 in Domanínek (Czech Republic, 49°32'N, 16°15'E and altitude 530 m). The clone experiment of Populus sp. covered 0.3 ha in the center of the plantation and included 13 clones in total, with hardwood cuttings of only 6 clones available in numbers allowing 4-replicate experiment. The plantation was established on agricultural land and the trees were planted in a double row design with a density of 10 000 trees/ha. The trial was weeded by mechanical methods, and no irrigation, fertilization, or herbicides were applied. The experiment site was harvested at the end of 2006. It was found that the biomass yields of the tested clones of Populus sp. were in the higher range of results from national and European studies in case of hybrid clones. The satisfactory survival rate in the first year, when mortality tends to be highest, was supported by relatively wet weather conditions after plantation establishment. At the end of the first rotation, the highest yields were obtained from clones J-105 and J-104 (P. nigra × P. maximowiczii) and P-494 (P. maximowiczii × P. berolinensis) with J-105 showing a mean annual increment of dry matter close to 14 t/ha. Additional experiments seem to suggest that well managed poplar plantation might produce even better values if higher survival rates can be achieved.

Two osmoprotectants (proline - Pro; trehalose - Tre) were exogenously supplied to seedlings of rice cvs. Pokkali (PK - salt-tolerant) and Khao Dawk Mali 105 (KDML105 - salt-sensitive) to investigate their effects on plants exposed to 200 mmol/L NaCl for 6 days and 5 days after recovery from stress. The reduction of growth, increase in Na⁺ to K⁺ ratio, high level of hydrogen peroxide (H₂O₂) content, enhanced activity of antioxidant enzymes (superoxide dismutase - SOD, peroxidase - POX, catalase - CAT and ascorbate peroxidase - APX) were observed in both rice cultivars under NaCl treatments. Exogenous Pro and Tre supplement to NaCl-stressed plants did not mitigate the reduction of growth during salt-stress. Nevertheless, during recovery plants previously supplied with Tre showed markedly higher percentage of growth recovery than those treated with NaCl alone or supplied with Pro. The beneficial effect of Tre on growth recovery was clearly demonstrated in KDML105 in which growth enhancement was related to reduction in Na⁺ to K⁺ ratio. Exogenous Pro was able to reduce H₂O₂ in both cultivars during salt stress whereas Tre could reduce it only in KDML105. Exogenous Tre did not enhance any antioxidant enzymes during stress but enhanced APX activity in KDML105 during recovery. Exogenous Pro enhanced the activity of APX in PK, and POX, CAT and APX in KDML105 during both stress and recovery period.

A field experiment was conducted to illustrate the different degree and dynamics of microbial community structure and function in the rhizosphere across four growing stages (before plantation and three growth stages) using a combination of biochemical (enzyme assay and microbial biomass carbon) and molecular approaches of qPCR and PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis). Rice plant cultivation promoted higher enzyme activities (invertase and urease), microbial biomass carbon (C_mic), bacterial (16S rRNA) and fungal (ITS rRNA) genes abundances in the rhizosphere compared to unplanted soil. Principal component analyses of PCR-DGGE profile also revealed that structures of bacterial and fungal communities of rice planted soil were well distinct from unplanted soil. Moreover, enzyme activities showed a significant positive correlation with the total microbial biomass in the rhizosphere throughout growth stages of rice plant. Relative fungal: bacterial ratios were significantly higher in rice planted soil compared to unplanted soil, suggesting rice plantation enhanced the fungal community in the rice rhizosphere environment. These results further suggest a significant linkage between the microbial community dynamics and function in the rhizosphere associated with rice plant over time.

The present study was undertaken to quantify changes in the status of soil nutrients, their depletion and build-up after continuous long intensive cropping for last 36 years in a permanent manorial trial which has been in progress since 1972 in an alfisol of western Himalayas. The rotation was maize-wheat which included various combinations of N, P, K, Zn and FYM (farmyard manure). Continuous cultivation influenced pH, OC (organic carbon), available N (nitrogen), P (phosphorus) and K (potassium). An increase in the status of organic carbon was observed in 100% NPK + FYM treatments for more than three decades from initial value of 7.9 to 12.0 g/kg. The use of either FYM or lime alongwith 100% NPK sustained crop productivity or improved nutrient status. However, imbalanced use of nutrients i.e. NP or N alone is adversely affecting the fertility of soil by aggravating the problem of soil acidity. Application of S free P fertilizer DAP (diammonium phosphate) drastically reduced the yield of both the crops. Thus, continuous use of balanced fertilizers is necessary for sustaining soil fertility and productivity of crops.

Field experiments were conducted at two different locations (Barani Agricultural Research Institute Chakwal and farm field Talagang, district Chakwal) for two crop-growing seasons in northern rainfed Punjab, Pakistan to assess the yield and micronutrient uptake of chickpea (Cicer arietinum). The treatments were four combinations of two levels of sulfur (15 and 30 kg/ha) from two sources (gypsum and ammonium sulfate) and a no-sulfur control. Application of sulfur resulted in a significant increase in seed yield up to 17% over control. Ammonium sulfate was a more efficient source of sulfur as compared to gypsum at both the locations. Sulfur application resulted in a significant increase in micronutrient uptake by plant; however effect of sulfur application on soil pH at the end of experiment was not significant. Availability of soil zinc and copper increased with sulfur application at the end of two year experiment. Tissue copper and iron and soil available copper and iron correlated negatively with soil pH. Sulfur should be applied to chickpea grown under rainfed conditions in order to increase seed yield, to improve nutritional composition of product and to enhance efficiency of other fertilizers.

Little information is available on how fertilizer application affects concentration of many elements in peeled potato (Solanum tuberosum) tubers and peels. We analyzed how long-term application of cattle slurry and mineral N, P and K fertilizers affects the yield of tubers, their dry matter content and concentrations of elements. In 2009, potatoes tubers were collected in control, cattle slurry (CS), mineral N₄P₂K₂ and combined CSN₄P₂K₂ treatment of the Ruzyně Fertilizer and Crop Rotation Experiment established on Illimerized Luvisol in Prague (Czech Republic) in 1955. Amount of N, P and K supplied by CS was 138, 30 and 172 kg/ha and the amount supplied by N₄P₂K₂ was 110, 31 and 186 kg/ha. Yield of fresh potatoes ranged from 20.6 in the control up to 31.2 t/ha in CSN₄P₂K₂ treatment. Dry matter content of unpeeled tubers, peeled tubers and potato peels was not significantly affected by fertilizer treatments probably because of not excessive N application. Normal cropping practices with application of CS and mineral N, P and K fertilizers did not significantly increase concentrations of trace elements in peeled tubers or potato peels on neutral soil with low trace elements availability. Concentrations of many elements (N, P, K, Ca, Mg, Cd, Cr, Cu, Mn, Ni, and Zn) were higher in potato peels than in peeled tubers, but the differences in the case of trace elements were relatively small.

Soil quality and fertility are associated with its productivity, and this in turn is connected to the soil biological activity. To study these effects, well designed long-term field experiments that provide comprehensive data sets are the most applicable. Four treatments (tillage methods) were set up: (1) conventional tillage (CT); (2) no tillage (NT); (3) minimum tillage + straw (MTS), and (4) no tillage + mulch (NTM). Our objective was to assess the relationships between soil microbial characteristics and winter wheat yields under these different techniques of conservation tillage within a field experiment, originally established in 1995. The differences in average grain yields over time period 2002-2009 between the variants were not statistically significant. Organic carbon in the topsoil was higher in plots with conservation tillage (NT, MTS, and NTM), than in the conventional tillage plots. There was a statistically significant correlation (P ≤ 0.01) between the grain yields and organic C content in topsoil.

This study was undertaken in order to test whether the development of nodule density over the vegetation period is different in lucerne stands grown for 1, 2 or 3 years continuously. For rapidly assessing nodule density in the field, a modified profile wall method was applied. Nodules were counted on a vertical profile wall, after spraying away a 2 cm layer of soil. For validating this method nodule density was determined on roots washed from monolith samples. Field data indicate that there is a shift of nodulation towards deeper soil layers with increasing maturity of lucerne stands. In 1-year lucerne nodulation was limited virtually to the top 15 cm of soil. In the 15-30 cm soil layer and in the subsoil (30-80 cm), nodule density increased with the cropping duration (1 year < 2 years < 3 years). Temporal decreases in nodule density during the vegetation period associated with dry spells were more pronounced for 2-years as compared with 3-years lucerne.

The main aim of this study was to determine the intensity of hydrophobic/hydrophilic components of the soil's organic matter as well as its hydrophobicity. Non-destructive Fourier Transform Infrared (FTIR) spectroscopy was used for the diagnosis and characterization of the basic classes of the chemical groups (hydrophilic and hydrophobic components) from which the organic matter in the soils is formed. Soil samples (depth 0-30 cm) were taken from the topsoil of the 70 sampling sites from the experimental field at Prague-Ruzyne (Czech Republic) during 2007-2009, where a conventional soil tillage technology was used. It was found that the variability of the intensity of the hydrophobic components is greater (27.6%) than that of the intensity of the hydrophilic components (6.2%), which correlated significantly with the C_org (r = 0.58; P < 0.05) and N_t (r = 0.65; P < 0.05) in the soil. It was proven that the soil samples with a higher proportion of coarse grains are more hydrophobic than those with higher proportions of clay. Data about soil hydrophobicity can help to evaluate the soil quality parameters as well as the soil fertility.

Relatively little is known about potassium leaching losses following harvest of silage maize. While direct negative impacts on the environment are unlikely, losses of K with leaching need to be known for accurate balancing, especially on coarse textured soils, where K can be a critical element. In a four-year field experiment the effects of fertilizer forms (inorganic, cattle slurry and pig slurry) and four levels of N input (0, 80, 160, 240 kg N/ha) with corresponding amounts of K on the nutrient balances and leaching of K from silage maize grown on a sandy soil were investigated using suction cups. After four years, surplus of K from cattle slurry led to higher lactate-soluble K in the topsoil. Potassium leaching differed between years with different amounts of rainfall during winter. Annual leaching losses of K increased with N and K input and amounted to 38 kg K/ha, while fertilizer form had no significant effect. Losses of K increased with increasing N leaching (R² = 0.69). We conclude that in maize production on coarse textured soils and under conditions of high N leaching (86-152 kg N/ha), K leaching can be large (6-84 kg K/ha) and constitutes a relevant part of K balances (-84 to +127 kg K/ha).

This study aims to explore the optimum nitrogen (N) application method by analyzing effects of variable N application stages and ratios on the N absorption and translocation of high-yield summer maize (DH661). The study included field experiments and ¹⁵N isotopic dilutions for pot experiments. Results showed that the yield was not increased in a one-off N application at the jointing stage. The uptake of fertilizer-derived N in the grain increased with the increasing of N applied times. Compared to a single or double application, total N uptake (N_up) and biomass increased significantly by supplying N at the six-leaf stage (V6), ten-leaf stage (V10) and 10 days after anthesis in ratios of 3:5:2 and 2:4:4. The fertilizer-derived recovery rates were 67.5% and 78.1%, respectively. The uptake and utilization of fertilizer-derived N was enhanced by increasing the recovery rate of N supplied after anthesis, and reducing the absorption of soil-derived N. Therefore, the 2:4:4 application ratios was the optimal N application method.

Water and nitrogen managements are both very important to increase crop yield. An experiment was carried out in split plot design to study the effects of urea types (normal urea and coated urea) and irrigation on soil and fertilizer nitrogen use in maize (Zea mays L.) field in 2006 and 2007. Irrigation was used as main plot, and urea types were used as split-plot. Two irrigation levels, no irrigation in the whole growth duration and 85 mm irrigation at the blister stage, were designed. There were five nitrogen treatments, which were no nitrogen used as control (N0), normal urea 75 kg N/ha (N1), normal urea 150 kg N/ha (N2), coated urea 75 kg N/ha (C1) and coated urea 150 kg N/ha (C2). The results showed that, at the same level of irrigation and nitrogen, the soil nitrogen contents of the treatments with coated urea (CU) applied were higher in 0~40 cm soil layers, but lower in deeper soil layers, than those with normal urea (NU) applied. Irrigation increased the nitrate losing, but the nitrate loss of CU was lower than those of NU. Using CU with irrigation could increase the nitrogen uptake by maize, and more nitrogen was transfered to grain. At the same nitrogen level, CU had higher N recovery efficiency but lower soil N dependent rate than NU. When applied with CU, the nitrogen release rate was lower and the nitrogen was quickly absorbed by maize, which reduced the risk of nitrogen loss and increased the use efficiency of soil and fertilizer nitrogen. These results suggest that coated urea combined with deficit irrigation should be applied for high yield and nitrogen use efficiency of maize on the North China Plain.

Soil arsenic (As) levels are particularly high in parts of China, where wheat and rape are widely grown. Understanding the effects of As concentration on the growth of these two major crops is of significance for food production and security in China. A pot experiment was carried out to study the uptake of As and phosphorus (P), and the soil As bioavailability at different growth stages of wheat and rape. The results indicated that winter wheat was much more sensitive to As stress than rape. Wheat yields were elevated at low rates of As addition (< 60 mg/kg) but reduced at high rates of As concentrations (80-100 mg/kg); while the growth of rape hadn't showed significant responses to As addition. Phosphorus concentrations in wheat at jointing and ear sprouting stages increased with increasing soil As concentrations, and these increases were assumed to contribute a lot to enhanced growth of wheat at low As treatments. Arsenic did not significantly affect P concentrations in rape either. The highest As concentrations in wheat shoot and rape leaf were 8.31 and 3.63 mg/kg, respectively. Arsenic concentrations in wheat and rape grains did not exceed the maximum permissible limit for food stuffs of 1.0 mg/kg. When soil As concentration was less than 60 mg/kg, both wheat and rape could grow satisfactorily without adverse effects; when soil As concentration was 80-100 mg/kg, rape was more suitable to be planted than wheat.

Over 2004-2006, effects of mineral fertilisers (60 N + 30 P + 60 K kg/ha or 120 N + 30 P + 60 K kg/ha) and farmyard manure (12 or 24 t/ha) application on biological and chemical properties of soil were studied in seminatural grassland. The research trial was established at Radvaň site, central Slovakia (altitude 480 m, loamy to sandy-loamy Cambisol). These parameters were investigated during the growing seasons: CO₂ production, intensity of total N mineralisation (TMN), the rate of nitrification (NIT), total C content in microbial biomass (MB-C), C_ox, N_t, P, K, Mg and the humic acids to fulvic acids ratio (HA:FA). At the application of mineral fertilisers, the highest N rate significantly increased TMN and NIT, mainly in 2004 and 2005. The manure application showed the strongest effects on the biological parameters. The manure rate of 12 t/ha significantly increased the soil respiration in 2005 and 2006 as well as TMN and NIT throughout the research. The manure application increased also the soil pH, MB-C, N_t, Mg, P and C_ox.

Field trials were conducted at two sites Troubsko near Brno and Prague-Ruzyně in 1996-1999 with three varieties of safflower (Gila, CW-74, Sironaria). Three rates of nitrogen fertilization were used: N0 = no fertilization, N₁ = 40 kg/ha, N₂ = 80 kg/ha. Sowing rates were 50 and 70 germinable seeds per m2. The average values of oil content were highest in seeds of CW-74 variety (27.2%). Gila had on average the lowest oil content (24.5%). Linoleic acid was dominant in all three safflower varieties. Variation in content of linoleic acid in different years was not so high as in oil content. The highest average content of linoleic acid was found in Gila variety (81.2%), the lowest in Sironaria (77.4%). At Ruzyně average seed yield on dry basis was 2.7 t/ha and average straw yield was 7.56 t/ha. At Troubsko seed yield was 2.56 t/ha and straw yield was 3.69 t/ha (by 50% lower than at Ruzyně). The effect of year of growing and site on seed yields and on other parameters was highly significant. N fertilization increased safflower seed yield at Troubsko site only, where the dose of 40 kg/ha N increased the yield by 0.08 t/ha on average of years and the dose of 80 kg/ha N increased the seed yield by 0.2 t/ha in comparison with no nitrogen fertilization treatments. Increased N rates and especially higher plant density resulted in an increase in straw yields. Neither were thousand seed weight nor number of flower heads influenced significantly by different N rates or the above-mentioned differences in plant density.

Overgrazing affects typical steppe community in ways similar to grasslands in other areas. Exclusion of livestock grazing is one of the main management practices used to protect grasslands. However, it is not known if long-term exclusion of livestock grazing has positive effect on above- and belowground community properties in typical steppe of the Loess Plateau. We studied the long-term (20-year) cumulative effects of exclusion of livestock grazing on above- and belowground community properties compared with that before exclusion of livestock grazing in a typical steppe of the Loess Plateau, NW China. Our results show that twenty-year exclusion of livestock grazing significantly increased above- and belowground biomass, species richness, cover and height for five different communities. Most of belowground biomass was in the 0-20 cm horizon and grazing exclusion increased biomass especially at the depth of 0-10 cm. Our study suggests that long-term exclusion of livestock grazing can greatly improve community properties of typical steppe in the Loess Plateau.

The present investigation was undertaken to find out efficient strains of arbuscular mycorrhiza (AM fungi) alone or in combinations with Trichoderma viride for inoculation Dendrocalamus strictus L. seedlings. The inoculated seedlings showed good response having higher plant height, phosphorous ions content in root and shoot, AM spore number and root colonization than non-inoculated (control) seedlings in both single (alone) and co-inoculation (combined consortium) experiments. T. viride showed significant growth followed by Glomus mosseae, G. fasciculatum and mixed AM with single inoculation. In co-inoculation, the best growth responses were observed with G. fasciculatum + T. viride followed by G. mosseae + T. viride, mixed vesicular arbuscular mycorrhizas (VAM) + T. viride, G. mosseae + G. fasciculatum + T. viride + mixed VAM, G. mosseae + G. fasciculatum + T. viride and G. mosseae + G. fasciculatum after 120 days and also depicted maximum increase in phosphorus content of shoot and root when compared with other inoculated seedlings. However, all the inoculated seedlings showed significant increase in phosphorus content when compared with control seedlings.

Grazing-induced variations in vegetation may either accelerate or reduce soil carbon storage through changes in litter quantity and quality. Here, a three-year field study (2005-2007) was conducted in Tibetan alpine meadow to address the responses of surface soil (0-15 cm) organic carbon (SOC) storage in the plant growing season (from May to September) to varying grazing intensity (represented by the residual aboveground biomass, with G₀, G₁, G₂, and G₃ standing for 100%, 66%, 55%, and 30% biomass residual, respectively), and to explore whether grazing-induced vegetation changes depress or facilitate SOC storage. Our results showed that: (i) Higher grazing intensity resulted in lower biomass of grasses and sedges, lower root biomass, and in a change in plant community composition from palatable grasses and sedges to less palatable forbs. (ii) Increased grazing reduced the SOC content and storage with only G₃ showing an SOC loss during the plant growing season. (iii) Soil organic carbon storage exhibited a highly positive correlation with the residual aboveground biomass and root biomass. Our results imply that a grazing-induced reduction in plant biomass productivity and changes in species composition would depress soil carbon storage, and that an increase in grazing pressure can lead to a gradual change of alpine meadow soils from being 'carbon sinks' to become 'carbon sources'.

In this experiment we proved an effect of dolomite limestone on chemical immobilization in soil contaminated by trace metals, namely Cd, Pb, and Zn. Primary, we set up lysimeter pot experiment to measure soil leaching without vegetation. Willow clone (S. × smithiana Willd) was cultivated in the second lysimeter pot as a new approach to monitor Pb, Cd and Zn leaching, which was affected by soil liming (used in 1% rate). At the time of both harvests, aboveground biomass increased significantly at the amended variant. After the second harvest aboveground biomass production increased by 80% in comparison with the first one, Cd and Zn concentration in biomass decreased 2-fold and 3-fold, respectively. Dolomite limestone as a process of liming: (i) restricted metals leaching from the soil substrate; (ii) reduced metal uptake by willow; and (iii) increased biomass production of willow. Liming also alleviated the plant stress imposed by risk elements resulting in better plant growth and lower levels of stress markers (total nitrogen content and the main amino acid metabolism parameters in the willow leaves) yet through different mechanisms.

Rhinanthus minor (yellow-rattle) can be used for restoration of species-rich grasslands but is vulnerable to competitive exclusion from high total aboveground biomass production of vascular plants. We asked (1) whether there is a threshold limit for total annual aboveground biomass production of vascular plants above which R. minor cannot establish viable population in grasslands and (2) how is cover of R. minor in grassland related to standing biomass of bryophytes. Data were collected in the Rengen Grassland Experiment (RGE) established in Germany in 1941 with following fertilizer treatments: unfertilized control, application of Ca, CaN, CaNP, CaNPKCl and CaNPK₂SO₄. Cover of R. minor and total annual aboveground biomass production of vascular plants were determined from 2005 to 2009. Further relationship between standing biomass of bryophytes and cover of R. minor was analyzed in 2006. Mean cover of R. minor over five years ranged from 0.7% to 12.3% in CaNPK₂SO₄ and control treatments, respectively. Cover of R. minor was significantly negatively related to total annual aboveground biomass production of vascular plants and cover of R. minor was below 3% in all plots with total annual aboveground dry matter biomass production of vascular plants higher than 5 t/ha. Although cover of R. minor was markedly reduced in highly productive plots in the RGE, high standing biomass of bryophytes (1.8 t/ha) in low productive control was not an obstacle for establishment of its viable population. We concluded, that viable population of R. minor can be established in grasslands only if total annual aboveground dry matter biomass production of vascular plants is below 5 t/ha regardless on standing biomass of bryophytes.

The root system of six-year-old winter jujube (Zizyphus jujuba Mill. cv. Zhanhua) trees were manually pruned at 3, 5 or 7 times trunk diameter distance along both inter-row sides, to study the effects of root pruning on physico-chemical characteristics and biological properties of winter jujube rhizosphere soil. The results showed that the root pruning of 3 and 5 times trunk diameter distance increased the available nitrogen, phosphorus, potassium^[concentrations and pH values in the rhizosphere soil and decreased organic matter concentrations, the contents of amino acids, organic acids and total sugars in the root exudates, the populations of bacteria, actinomyces and fungi, and inhibited the activities of catalase, invertase and urease enzymes in contrast to the control in early stage when root pruning was applied. The determined indexes presented a reverse trend as those in early stage after new roots appeared. Compared to the control, the trees by root pruning had higher pesticides residues of the rhizosphere soil in the whole experiment. No differences were noticed between 7 times trunk diameter distance and the control. It is proposed that root pruning had greater impacts on physico-chemical characteristics and biological properties of the rhizosphere soil depending on root pruning intensity.