Changes in cytokinin activity during flower development in Cosmos sulphureus Cav

Endogenous cytokinin activity was determined in the flowers of Cosmos sulphureus Cav. from bud emergence to full bloom using the soybean callus bioassay. Cytokinin activity was low early in flower development but increased prior to full bloom. In Sephadex LH-20 column chromatography of flower extracts, the cytokinins present co-eluted with zeatin, zeatin riboside and glucoside cytokinin. While the former two predominated prior to full bloom, cytokinin glucoside activity appeared to be at a maximum at full bloom. The possible relevance of these findings is discussed in relation to flower development.     

花卉植物对Cd、As、Pb污染农田的修复及其精油应用

为提高植物修复的经济价值,该文选取孔雀草、波斯菊和矢车菊三种附加值较高的花卉植物,考察其对广西某矿区Cd、As、Pb复合污染农田的修复潜力,测定分析三种花卉植物对重金属的富集和转运能力,并从修复后植物的地上部提取精油,研究植物精油对病原菌埃希氏大肠杆菌(Escherichia coli)、金黄色葡萄球菌(Staphyloccocus aureus)、伤寒沙门氏菌(Salmonella typhimurium)的生长抑制效果,进一步探索植物精油作为洗手液添加剂的应用能力。结果表明:(1)试验区域内土壤污染严重,Cd、As全量超过风险管制值,Pb全量超过风险筛选值,属于Cd、As、Pb重度污染。(2)选取的三种花卉植物均可在试验区域较好地生长,其中孔雀草和波斯菊对Cd、Pb的富集与转运能力较强,对As的富集能力最弱但转运能力较强。与孔雀草和波斯菊相比,矢车菊除对Cd的转运能力较强外,对其他重金属的富集和转运能力均较弱。三种植物重金属富集能力大小排序为孔雀草>波斯菊>矢车菊,不同花卉对重金属富集偏好顺序依次为Cd>Pb>As。(3)从修复后的植物地上部提取精油进行研究分析发现,孔雀草精油对三种病原菌都具有良好的生长抑制效果(<10 CFU·mL^-1),且孔雀草体内富集的重金属并未影响精油中的重金属含量。另外,添加了孔雀草精油的洗手液,对金黄色葡萄球菌的生长抑制效果可延长至480 min。因此,孔雀草不仅可作为重金属复合污染农田的修复植物,而且修复后还可从植物体内提取精油作为抑菌剂。该研究结果为修复后重金属富集生物质的新型资源化利用提供了理论基础。     

Phytoextraction of Cadmium and Zinc By Sedum plumbizincicola Using Different Nitrogen Fertilizers,a Nitrification Inhibitor and a Urease Inhibitor

Cadmium (Cd) and zinc (Zn) phytoavailability and their phytoextraction by Sedum plumbizincicola using different nitrogen fertilizers, nitrification inhibitor (dicyandiamide, DCD) and urease inhibitor (N-(n-Butyl) thiophosphoric triamide, NBPT) were investigated in pot experiments where the soil was contaminated with 0.99 mg kg^?1 of Cd and 241 mg kg^?1 Zn. The soil solution pH varied between 7.30 and 8.25 during plant growth which was little affected by the type of N fertilizer. The (NH₄)₂SO₄+DCD treatment produced higher NH₄⁺?N concentrations in soil solution than the (NH₄)₂SO₄ and NaNO₃ treatment which indicated that DCD addition inhibited the nitrification process. Shoot Cd and Zn concentrations across all treatments showed ranges of 52.9–88.3 and 2691–4276 mg kg^?1, respectively. The (NH₄)₂SO₄+DCD treatment produced slightly higher but not significant Cd and Zn concentrations in the xylem sap than the NaNO₃ treatment. Plant shoots grown with NaNO₃ had higher Cd concentrations than (NH₄)₂SO₄+DCD treatment at 24.0 and 15.4 mg kg^?1, respectively. N fertilizer application had no significant effect on shoot dry biomass. Total Cd uptake in the urea+DCD treatment was higher than in the control, urea+NBPT, urea+NBPT+DCD, or urea treatments, by about 17.5, 23.3, 10.7, and 25.1%, respectively.     

施肥对两种苋菜吸收积累镉的影响

通过盆栽试验,研究了生长在5 mg/kg镉(Cd)污染土壤中的两种苋菜(红苋(Amaranthus Paniculatus L.)和绿苋(Amaranthus Paniculatus L.))在3种施肥处理下(N、NP和NPK)的生长状况和对Cd的吸收积累情况。结果表明,两种苋菜能够在污染土壤中正常生长,各器官中叶Cd含量最高,范围为124.1—225.9 mg/kg;根中次之,范围为57.1—100.6 mg/kg;茎中最低,范围为56.2—87.6 mg/kg;富集系数高达22.4—40.2。施加N,NP,NPK肥对两种苋菜器官中的Cd含量和生物量有显著影响。其中,施加NPK肥使红苋和绿苋的生物量分别达到不施肥(对照)处理的3.5和3.2倍,单株提取Cd的总量是对照3.2和5.0倍。综上表明,两种苋菜(红苋和绿苋)具有生物量大、易栽培、施加NPK肥能够大幅增加生物量的同时不减少器官对Cd的吸收等优点,作为Cd污染土壤的修复植物有巨大应用前景。     

Long-term manuring and fertilization effects on soil organic carbon pools under a wheat–maize cropping system in North China Plain

The effects of organic manure and chemical fertilizer on total soil organic carbon (C _T), water-soluble organic C (C _WS), microbial biomass C (C _MB), labile C (C _L), C mineralization, C storage and sequestration, and the role of carbon management index (CMI) in soil quality evaluation were studied under a wheat–maize cropping system in a long-term experiment, which was established in 1989 in the North China Plain. The experiment included seven treatments: (1) OM: application of organic manure; (2) 1/2OMN: application of half organic manure plus chemical fertilizer NPK; (3) NPK: balanced application of chemical fertilizer NPK; (4) NP: application of chemical fertilizer NP; (5) PK: application of chemical fertilizer PK; (6) NK: application of chemical fertilizer NK; and (7) CK: unfertilized control. Application of organic manure (OM and 1/2OMN) was more effective for increasing C _T, C _WS, C _MB, C _L, C mineralization, and CMI, as compared with application of chemical fertilizer alone. For the chemical fertilizer treatments, balanced application of NPK (treatment 3) showed higher C _T, C _WS, C _MB, C _L, C mineralization, and CMI than the unbalanced use of fertilizers (treatments 4, 5, and 6). The C storage in the OM and 1/2OMN treatments were increased by 58.0% and 26.6%, respectively, over the NPK treatment, which had 5.9–25.4% more C storage than unbalanced use of fertilizers. The contents of C _WS, C _MB, and C _L in organic manure treatments (treatments 1 and 2) were increased by 139.7–260.5%, 136.7–225.7%, and 150.0–240.5%, respectively, as compared to the CK treatment. The CMI was found to be a useful index to assess the changes of soil quality induced by soil management practices due to its significant correlation with soil bulk density and C fractions. The OM and 1/2OMN treatments were not a feasible option for farmers, but a feasible option for sequestering soil carbon, especially for the OM treatment. The NPK treatment was important for increasing crop yields, organic material inputs, and soil C fractions, so it could increase the sustainability of cropping system in the North China Plain.     

Interaction of Purine Nucleotides with Cobalt-Hexammine,Cobalt-Pentammine and Cobalt- Tetrammine Cations. Evidence for the Rigidity of Adenosine and Flexibility of Guanosine and Deoxyguanosine Sugar Conformations

Abstract

The interaction of adenosine-5′-monophosphate (5′-AMP), guanosine-5′-monophosphate (5′-GMP) and 2′-deoxyguanosine-5′-monophosphate (5′-dGMP) with the [Co(NH₃)₆]³⁺, [CO(NH₃)₅C1]²⁺ and [CO(NH₃)₄C1₂]⁺ cations has been investigated in aqueous solution with metal/nucleotide ratios (r) of 1/2, 1 and 2 at neutral pH. The solid complexes have been isolated and characterized by FT-IR and ¹H-NMR spectroscopy.

The complexes are polymeric in nature both in the crystalline solid and aqueous solution. The binding of the cobalt-hexammine cation is indirectly (via NH₃) through the N-7 and the PO₃ ^2- groups of the AMP and via O-6, N-7 and the PO₃ ^2- of the GMP and dGMP anions (outer-sphere). The cobalt-pentammine and cobalt-tetrammine bindings are through the phosphate groups (inner-sphere) and the N-7 site (outer-sphere) of these nucleotide anions. The ribose moiety shows C2′-endo/anti conformation, in the free AMP and GMP anions as well as in the cobalt-ammine - AMP complexes, whereas a mixture of the C2′-endo/anti and C3′-endo/anti sugar puckers were observed for the Co(NH₃)₆-GMP, Co(NH₃)₅-GMP and a C3′-endo/anti conformer for the Co(NH₃)₄-GMP complexes. The deoxyribose showed an O4′-endo/anti conformation for the free dGMP anion and a C3′-endo/anti for the Co(NH₃)₆-dGMP, Co(NH₃)₅-dGMP and Co(NH₃)₄-dGMP complexes.     

Impact of long-term additions of chemical fertilizers and farm yard manure on carbon and nitrogen sequestration under rice-cowpea cropping system in semi-arid tropics

Restoration of soil organic carbon (SOC) in arable lands represents potential sink for atmospheric CO₂. The strategies for restoration of SOC include the appropriate land use management, cropping sequence, fertilizer and organic manures application. To achieve this goal, the dynamics of SOC and nitrogen (N) in soils needs to be better understood for which the long-term experiments are an important tool. A study was thus conducted to determine SOC and nitrogen dynamics in a long-term experiment in relation to inorganic, integrated and organic fertilizer application in rice-cowpea system on a sandy loam soil (Typic Rhodualf). The fertilizer treatments during rice included (i) 100% N (@ 100 kg N ha^?1), (ii) 100% NP (100 kg N and 50 kg P₂O₅ ha^?1), (iii) 100% NPK (100 kg N, 50 kg P₂O₅ and 50 kg K₂O ha^?1) as inorganic fertilizers, (iv) 50% NPK + 50% farm yard manure (FYM) (@ 5 t ha^?1) and (v) FYM alone @ 10 t ha^?1 compared with (vi) control treatment i.e. without any fertilization. The N alone or N and P did not have any significant effect on soil carbon and nitrogen. The light fraction carbon was 53% higher in NPK + FYM plots and 56% higher in FYM plots than in control plots, in comparison to 30% increase with inorganic fertilizers alone. The microbial biomass carbon and water-soluble carbon were relatively higher both in FYM or NPK + FYM plots. The clay fraction had highest concentration of C and N followed by silt, fine sand and coarse sand fractions in both surface (0–15 cm) and subsurface soil layers (15–30 cm). The C:N ratio was lowest in the clay fraction and increased with increase in particle size. The C and N enrichment ratio was highest for the clay fraction followed by silt and both the sand fractions. Relative decrease in enrichment ratio of clay in treatments receiving NPK and or FYM indicates comparatively greater accumulation of C and N in soil fractions other than clay.     

Biological Control Agents in Combination with Fertilization or Fumigation to Reduce Sclerotial Viability of Sclerotium rolfsii and Disease of Snap Beans in the Greenhouse

The use of biological control agents in combination with fertilization or fumigation to reduce sclerotial viability of Sclerotium rolfsii and the disease it causes on snap bean was investigated in the greenhouse. The fertilizers ammonium sulphate [(NH₄)₂SO₄], ammonium nitrate (NH₄NO₃), diammonium phosphate [(NH₄)₂HPO₄], or urea applied to soil at a field rate of 135 kg/ha, 15 cm deep of nitrogen (N) (0.09 mg of N/g) or Gliocladium virens (Gl-3) biomass at a rate of 7.5 kg/ha, 15 cm deep (0.05 mg/g) did not reduce the viability of sclerotia of S. rolfsii (Sr-1) when each was applied alone. However, treatment with fertilizer together with the low rate of Gl-3 biomass significantly reduced the sclerotial viability. The treatments that were effective in reducing the viability by more than 75% were the application of (NH₄)₂SO₄ or (NH₄)₂PO₄ and the low rate of Gl-3 biomass. Application of the high rate (0.25 mg/g) of Gl-3 biomass alone only reduced the sclerotial viability by 25%. The addition of any of the fertilizers with the low rate of biomass generally resulted in bean seed germination in the pathogen-infested soil that was higher than that achieved with each individual component. The disease severity (DSI) on beans was appreciable (<3.0) in pathogen-infested soil treated with or without the fertilizer (NH₄)₂SO₄ and in pathogen-infested soil without fertilizer but with a low rate of Gl-3. However, in pathogen-infested soil treated with the fertilizer and the low rate of Gl-3 biomass together, the disease was reduced to a DSI value of less than 1.0. In fumigation studies with metham sodium (Vapam), a dose-response study to investigate the viability of sclerotia of S. rolfsii (Sr-3) indicated that fumigant rates of less than 23.3 μ g/g of soil were sublethal. It was also shown that 5.4 μ g/g of metham sodium was inhibitory to Gl-3 biomass but not to conidia. Consequently, the conidia of isolates Gl-3, Thm-4 of Trichoderma hamatum, and Tv-1 of Trichoderma viride were used together with metham sodium at 17.1 μ g/g of soil. Conidia that were applied to the soil 2 days prior to metham sodium reduced the viability of sclerotia more than each individual component. The results of this study suggest the feasibility of effective disease reduction with an approach utilizing biological control in combination with fertilization or fumigation.     

Enhancing crop growth, nutrients availability, economics and beneficial rhizosphere microflora through organic and biofertilizers

Field experiment was conducted on fodder maize to explore the potential of integrated use of chemical, organic and biofertilizers for improving maize growth, beneficial microflora in the rhizosphere and the economic returns. The treatments were designed to make comparison of NPK fertilizer with different combinations of half dose of NP with organic and biofertilizers viz. biological potassium fertilizer (BPF), Biopower, effective microorganisms (EM) and green force compost (GFC). Data reflected maximum crop growth in terms of plant height, leaf area and fresh biomass with the treatment of full NPK; and it was followed by BPF+full NP. The highest uptake of NPK nutrients by crop was recorded as: N under half NP+Biopower; P in BPF+full NP; and K from full NPK. The rhizosphere microflora enumeration revealed that Biopower+EM applied along with half dose of GFC soil conditioner (SC) or NP fertilizer gave the highest count of N-fixing bacteria (Azotobacter, Azospirillum, Azoarcus andZoogloea). Regarding the P-solubilizing bacteria,Bacillus was having maximum population with Biopower+BPF+half NP, andPseudomonas under Biopower+EM+half NP treatment. It was concluded that integration of half dose of NP fertilizer with Biopower+BPF / EM can give similar crop yield as with full rate of NP fertilizer; and through reduced use of fertilizers the production cost is minimized and the net return maximized. However, the integration of half dose of NP fertilizer with biofertilizers and compost did not give maize fodder growth and yield comparable to that from full dose of NPK fertilizers.     

Arbuscular mycorrhizal fungal community structure and diversity in response to long-term fertilization: a field case from China

The influences of different fertilizer treatments on spore community structure and diversity of arbuscular mycorrhizal (AM) fungi (AMF) were investigated in a long-term fertilization experiment with seven treatments: organic manure (OM), half organic manure N plus half fertilizer N (1/2 OMN), fertilizer NPK, fertilizer NP, fertilizer NK, fertilizer PK, and the control (without fertilization). Fertilization generally increased the nutrient contained in the fertilizer and treatments with NPK and 1/2 OMN produced the highest crop yields. Thirty-five species of AMF within 6 genera, including 8 previously undescribed species, were recovered. Similarly in all seven treatments, the most abundant genus was Glomus, and followed by Acaulospora. All the fertilization treatments changed AM species composition, and NK treatment had the slightest influence. Fertilization with fertilizers NP, PK and NPK markedly increased AM fungal spore density, while 1/2 OMN, OM and NK treatments showed no significant influences. All the fertilizer treatments, especially OM, significantly decreased species richness and species diversity (Shannon-Weiner index). There were no significant correlations between AM fungal parameters (spore density, species richness and species diversity) and soil properties. The findings indicate that long-term fertilization all can change AM fungal community structure and decrease species diversity, while balanced fertilization with NPK or 1/2 OMN is the most suitable fertilization regime if taking both crop yields and AM species diversity into account.     

Toxic Effect of Cadmium on Rice as Affected by Nitrogen Fertilizer Form

A nutrient solution experiment was conducted to determine the influence of N forms on growth, oxidative stress, and Cd and N uptake in rice plants. The treatments were consisted of two Cd levels (0 and 1 μmol) and three N forms (NH₄)₂SO₄, NH₄NO₃ and Ca(NO₃)₂. The results indicated that without Cd addition in the culture solution, the N forms had no significant effect on all measured parameters, including plant growth, photosynthetic traits, malondialdehyde (MDA) concentration, superoxide dismutase (SOD) activity, and Cd and N concentration, while Cd addition in the medium resulted in significant differences in measured parameters among the three forms of N fertilizers. The least inhibition of growth was noted in (NH₄)₂SO₄-fed plants, and the largest in Ca(NO₃)₂-fed plants, when plants were exposed to Cd stress. The highest photosynthetic rate and chlorophyll content was also recorded in (NH₄)₂SO₄-fed plants. Addition of Cd caused a remarkable increase in SOD activity and MDA content in plants, and the extent of increase varied with N form, with (NH₄)₂SO₄-fed plants being smallest. In comparison with the control plants, the N concentration in roots and shoots was not significantly affected in (NH₄)₂SO₄-fed plants, but significant decrease in root N concentration was found for the NH₄NO₃ and Ca(NO₃)₂-fed plants under Cd stress. Moreover, the significant differences were also noted among the three N forms in both root and shoot Cd concentrations, with (NH₄)₂SO₄-fed plants being the lowest. The results indicated that the toxic effect of Cd on rice varied with the form of N fertilizer.     

Comparison of the efficiency of urea,aqueous ammonia and ammonium sulphate as nitrogen fertilizers

Summary Nitrogen-15 labelled urea, aqueous NH₃ and (NH₄)₂SO₄ were applied to soils contained in pots. The fertilizers were injected in 5 cm³ of solution, 3.5 cm below the soil surface, to simulate a fertilizer band in the field. Ryegrass (Lolium perenne) was planted, and several cuttings and roots were harvested. Efficiency was determined as the recovery of fertilizer-N in the plant tissues and soil.Total recovery varied from 94 to 100%. There was no significant difference between the total recovery of the 3 fertilizer forms, although recovery in the soil component was lower for (NH₄)₂SO₄ than for urea or NH₃. There was a significant difference in total recovery between soils due to the soil component. Only small amounts of¹⁵N were not recovered, whereas laboratory experiments reported elsewhere had demonstrated that substantial gaseous losses of N as N₂, N₂O and NO +NO₂ occurred in these soils during nitrification of added NH₃ fertilizer.     

Net annual global warming potential and greenhouse gas intensity in Chinese double rice‐cropping systems: a 3‐year field measurement in long‐term fertilizer experiments

The impact of agricultural management on global warming potential (GWP) and greenhouse gas intensity (GHGI) is not well documented. A long‐term fertilizer experiment in Chinese double rice‐cropping systems initiated in 1990 was used in this study to gain an insight into a complete greenhouse gas accounting of GWP and GHGI. The six fertilizer treatments included inorganic fertilizer [nitrogen and phosphorus fertilizer (NP), nitrogen and potassium fertilizer (NK), and balanced inorganic fertilizer (NPK)], combined inorganic/organic fertilizers at full and reduced rate (FOM and ROM), and no fertilizer application as a control. Methane (CH₄) and nitrous oxide (N₂O) fluxes were measured using static chamber method from November 2006 through October 2009, and the net ecosystem carbon balance was estimated by the changes in topsoil (0–20 cm) organic carbon (SOC) density over the 10‐year period 1999–2009. Long‐term fertilizer application significantly increased grain yields, except for no difference between the NK and control plots. Annual topsoil SOC sequestration rate was estimated to be 0.96 t C ha^?1 yr^?1 for the control and 1.01–1.43 t C ha^?1 yr^?1 for the fertilizer plots. Long‐term inorganic fertilizer application tended to increase CH₄ emissions during the flooded rice season and significantly increased N₂O emissions from drained soils during the nonrice season. Annual mean CH₄ emissions ranged from 621 kg CH₄ ha^?1 for the control to 1175 kg CH₄ ha^?1 for the FOM plots, 63–83% of which derived from the late‐rice season. Annual N₂O emission averaged 1.15–4.11 kg N₂O–N ha^?1 in the double rice‐cropping systems. Compared with the control, inorganic fertilizer application slightly increased the net annual GWPs, while they were remarkably increased by combined inorganic/organic fertilizer application. The GHGI was lowest for the NP and NPK plots and highest for the FOM and ROM plots. The results of this study suggest that agricultural economic viability and GHGs mitigation can be simultaneously achieved by balanced fertilizer application.     

The agrochemical effectiveness of some phosphorus-nitrogen compounds with the direct P−N bond

Phosphorus-nitrogen compounds characterized by the direct P?N bond, represented by trimeric and tetrameric phosphorus nitridoamide—[PN(NH₂)₂]_3–4, phosphorus oxytriamide—PO(NH₂)₃ and ammonium diamidophosphate—NH₄PO₂(NH₂)₂, were applied as fertilizers in a vessel experiment with barley and their agrochemical effectiveness was compared with that of ammonium phosphate—(NH₄)₂HPO₄. The results obtained indicate that the above compounds are of nutritive value for plants.     

Belowground competitive suppression of seedling growth by grass in an African savanna

Coexistence of N₂-fixing legumes and non-legume trees with grasses in African savannas results in intense competition between these life-forms. We hypothesised that belowground competition might induce different nutritional constraints in N₂- versus non-N₂-fixing species. A field (Hluhluwe-imFolozi nature reserve, South Africa) competition experiment with two N₂-fixing legume species (Acacia burkei and Acacia karroo) and two non-N₂-fixing species (Schotia brachypetala and Spirostachys africana) both with clipped grass and without grass was established. Plants were supplied with no fertilizer, or generous amounts of fertilizer (200?kg?N?ha^?1, 100?kg P₂O₅ ha^?1, 7.1?kg K₂O ha^?1) supplied as either 28?C10 (N?CK), P or a combination of these fertilizers (NPK). Regularly clipped grass suppressed growth (by more than 90?%) of both N₂- and non-N₂-fixing seedlings equally. Biomass accumulation of seedlings grown with grass and the grasses themselves responded positively to NK and/or NPK, but not P, although P-fertilization did have effects on foliar [N] and ??¹⁵N values of trees and grasses showing that plants accessed the fertilizer. Tree ??¹⁵N values and foliar [N] were also modified by NPK, demonstrating access to fertilizer. However, the ameliorative effects of NPK on grass competition-induced biomass suppression were only partial. This may be due to ??non-resource competition?? (i.e. root gaps) imposed by dense grass roots. The fact that nutrients were able to partially ameliorate the effects of grass competition, however, indicates that such ??non-resource competition?? may be partially overcome by even more generous supply of fertilizers.     

Effect of fertilizers on Cd uptake of Amaranthus hypochondriacus, a high biomass, fast growing and easily cultivated potential Cd hyperaccumulator

In a greenhouse pot experiment, we assessed the phytoextraction potential for Cd of three amaranth cultivars (Amaranthus hypochondriacus L. Cvs. K112, R104, and K472) and the effect of application of N, NP, and NPK fertilizer on Cd uptake of the three cultivars from soil contaminated with 5 mg kg(-1) Cd. All three amaranth cultivars had high levels of Cd concentration in their tissues, which ranged from 95.1 to 179.1 mg kg(-1) in leaves, 58.9 to 95.4 mg kg(-1) in stems, and 62.4 to 107.2 mg kg(-1) in roots, resulting in average bioaccumulation factors ranging from 17.7 to 29.7. Application of N, NP, or NPK fertilizers usually increased Cd content in leaves but decreased Cd content in stem and root. Fertilizers of N or NP combined did not substantially increase dry biomass of the 3 cultivars, leading to a limited increment of Cd accumulation. NPK fertilizer greatly increased dry biomass, by a factor of 2.7-3.8, resulting in a large increment of Cd accumulation. Amaranth cultivars (K112, R104, and K472) have great potential in phytoextraction of Cd contaminated soil. They have the merits of high Cd content in tissues, high biomass, easy cultivation and little effect on Cd uptake by fertilization.     

The effects of mineral fertilizer and organic manure on soil microbial community and diversity

The effects of mineral fertilizer (NPK) and organic manure on phospholipid fatty acid profiles and microbial functional diversity were investigated in a long-term (21-year) fertilizer experiment. The experiment included nine treatments: organic manure (OM), organic manure plus fertilizer NPK (OM + NPK), fertilizer NPK (NPK), fertilizer NP (NP), fertilizer NK (NK), fertilizer N (N), fertilizer P (P), fertilizer K (K), and the control (CK, without fertilization). The original soil was extremely eroded, characterized by low pH and deficiencies of nutrients, particularly N and P. The application of OM and OM + NPK greatly increased crop yields, soil pH, organic C, total N, P and K, available N, P and K content. Crop yields, soil pH, organic C, total N and available N were also clearly increased by the application of mineral NPK fertilizer. The amounts of total PLFAs, bacterial, Gram-negative and actinobacterial PLFAs were highest in the OM + NPK treatment, followed by the OM treatment, whilst least in the N treatment. The amounts of Gram-positive and anaerobic PLFAs were highest in the OM treatment whilst least in the P treatment and the control, respectively. The amounts of aerobic and fungal PLFAs were highest in the NPK treatment whilst least in the N and P treatment, respectively. The average well color development (AWCD) was significantly increased by the application of OM and OM + NPK, and the functional diversity indices including Shannon index (H ^′ ), Simpson index (D) and McIntosh index (U) were also significantly increased by the application of OM and OM + NPK. Principal component analysis (PCA) of PLFA profiles and C source utilization patterns were used to describe changes in microbial biomass and metabolic fingerprints from nine fertilizer treatments. The PLFA profiles from OM, OM + NPK, NP and NPK were significantly different from that of CK, N, P, K and NK, and C source utilization patterns from OM and OM + NPK were clearly different from organic manure deficient treatments (CK, N, P, K, NP, NK 6 and NPK). Stepwise multiple regression analysis showed that total N, available P and soil pH significantly affected PLFA profiles and microbial functional diversity. Our results could provide a better understanding of the importance of organic manure plus balanced fertilization with N, P and K in promoting the soil microbial biomass, activity and diversity and thus enhancing crop growth and production.     

Distribution and recovery of15N after fertilization of Douglas-fir saplings with different nitrogen sources

Summary Four-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) saplings planted in pots with a sand and peat mix (11) were fertilized at the rate of 200 kg N/ha of (¹⁵NH₂)₂CO (U-15),¹⁵NH₄NO₃ (A-15) and NH₄ ¹⁵NO₃(An-15). They were placed in a shadehouse and watered regularly to maintain soil moisture at field capacity over periods of one and two years. Quantity of¹⁵N in foliage generally increased from old to current growth, irrespective of the nitrogen source. Utilization of¹⁵N fertilizers by saplings after the first and second growing seasons following fertilization was greatest with nitrate labelled ammonium nitrate AN-15, and nearly equal for urea U-15 and ammonium labelled ammonium nitrate A-15. The soil immobilized more fertilizer nitrogen-15 from U-15 and A-15 than from AN-15. Data from the present study, in which leaching losses of fertilizer were minimized, demonstrated that in terms of nitrogen uptake by the saplings the nitrate fertilizer was superior to ammonium fertilizer.     

Effects of forest fertilization on nitrogen leaching and soil microbial properties in the Northern Calcareous Alps of Austria

Several boreal and alpine forests are depleted in nutrients due to acidification. Fertilization may be a remedy, but rapidly-soluble salts (N, P, K, Mg) may pose nitrate problems for the groundwater or decrease microbial activity.With the aim to investigate potential nitrogen leaching after fertilization we set up an experiment employing intact soil cores (11 cm diameter, 20–40 cm long) from a mixed forest and a Picea abies stand (soil type Rendsina) in the Northern Calcareous Alps of Austria. The cores were fertilized with a commercial NPK fertilizer or a methylene-urea-apatite-biotite (MuAB) fertilizer at a rate corresponding to 300 kg N ha^-1 and incubated for 28 weeks together with unfertilized controls. Both soil water (retrieved 5 cm below the soil surface) and leachate were analyzed for nitrate and ammonium in regular intervals. After the incubation, soil microbial biomass and basal repiration were determined and a nitrogen mineralization assay was performed.For the control, in the soil water and leachate maximum NH₄ ⁺ and NO₃ ^- concentrations of 5 and 11 mg N L^-1, respectively, were found. Compared to that, MuAB fertilizer resulted in a slow increase of NH₄ ⁺ and NO₃ ^- in the soil water (up to 11 and 35 mg N L^-1 respectively) and in the leachate (4 mg NH₄ ⁺-N L^-1 and 44 mg NO₃ ^--N L^-1). Highest nitrogen loads were found for the fast release NPK fertilizer, with NH₄ ⁺ and NO₃ ^- concentrations up to 170 and 270 mg N L^-1, respectively, in the soil water. NH₄ ⁺-N levels in the leachate remained below 5, while NO₃-N levels were up to 190 mg L^-1. Fast- release NPK caused a significant decrease of microbial biomass and basal respiration. These parameters were not affected by MuAB fertilizer.The results suggest that the MuAB fertilizer may be an ecologically appropriate alternative to fast-release mineral fertilizers for improving forest soils.     

Effects of Long-Term Fertilization on Leaf Photosynthetic Characteristics and Grain Yield in Winter Wheat

Based on a 20-year fertilization experiment with wheat-maize double cropping system, the effects of different long-term fertilization treatments on leaf photosynthetic characteristics and grain yield in different winter wheat (Triticum aestivum L.) cultivars were studied in the growing seasons of 2000–2001 and 2001–2002. A total of nine fertilization treatments were implemented, i.e. no fertilizer (CK), N fertilizer (N), N and P fertilizers (NP), N and K fertilizers (NK), N, P, and K fertilizers (NPK), only organic manure (M), organic manure and N fertilizer (MN), organic manure and N and P fertilizers (MNP), and organic manure and N, P, and K fertilizers (MNPK). With the treatments of combined organic manure and inorganic fertilizers (TMI), net photosynthetic rate (P _N), maximal activity of photosystem 2, PS2 (F_v/F_m), and chlorophyll content (SPAD value) of flag leaves and leaf area index (LAI) were much higher at the mid grain filling stage (20 or 23 d post anthesis, DPA), and exhibited slower declines at the late grain filling stage (30 DPA), compared with the treatments of only inorganic fertilizers (TI). The maximal canopy photosynthetic traits expressed as P _N×LAI and SPAD×LAI at the mid grain filling stage were also higher in TMI than those in TI, which resulted in different grain yields in TMI and TI. Among the treatments of TMI or among the treatments of TI, both flag leaf and canopy photosynthetic abilities and yield levels increased with the supplement of inorganic nutrients (N, P, and K fertilizers), except for the treatment of NK. Under NK, soil contents of N and K increased while that of P decreased. Hence the unbalanced nutrients in soil from the improper input of nutrients in NK treatment were probably responsible for the reduced flag leaf and canopy photosynthetic characteristics and LAI, and for the fast declining of flag leaf photosynthetic traits during grain filling, resulting in the reduced yield of NK similar to the level of CK.