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21.
V. P. Shabaev 《Plant and Soil》1986,91(2):249-256
Summary Fertilizer/soil N balance of cropped and fallow soil has been studied in a pot experiment carried out with grey forest soil (southern part of Moscow region) at increasing rates of15N labelled ammonium sulfate (0; 8; 16; 32 mg N/100 g of soil). The fertilizer15N balance has been shown to depend upon its application rate and the presence of growing plants. Fertilizer N uptake efficiency was maximum (72.5%) and gaseous losses-minimum (12.5%) at the application rate of 16 mg N/100 g of soil. Fertilizer N losses from the fallow soil were 130–220% versus those from the cropped soil. At the application of fertilizer N the plant uptake of soil N was 170–240% and the amount of soil N as N–NH4 exchangeable + N–NO3 in fallow was 350–440% as compared to the control treatment without nitrogen (PK).After cropping without or with N fertilizer application at the rates of 8 and 32 mg N/100 g of soil, a positive nitrogen balance has been found which is likely due to nonsymbiotic (associative) N-fixation. It has been shown that biologically fixed nitrogen contributes to plant nutrition. 相似文献
22.
23.
Summary Phosphate sorption isotherms were developed for five Philippine wetland rice soils using the conventional technique and a modified one. In the conventional method, P requirements of soils varied between 280 and 810 g P/g soil. In the modified method, they varied from 160 to 540 g P/g soil at 0.2 ppm P in solution. Soils with high P-sorption capacities had vermiculite and halloysite as the dominant clay minerals. Soil reduction by flooding decreased P-sorption by 28–70 percent at 0.2 ppm P in solution. The decrease in P-sorption due to soil reduction was greatest in a crystalline soil with vermiculite and halloysite as the dominant clay minerals and least in a soil with dominant X-ray amorphous silicates in the clay fraction.Desorption of freshly adsorbed P under reduction was greater in HCO
3
–
solution than in CaCl2 and it increased with level of applied P. Desorption patterns of freshly adsorbed P were similar to adsorption patterns but values of P in solution were lower at desorption. Soils varied with respect to desorption of freshly sorbed P. Desorption studies indicate that soils vary in intensity factor with respect to P and thus influence P availability to plants. Use of P-sorption and P-desorption data obtained under reduced soil condition was proposed for detecting P needs of submerged rice soils.Results of a pot study with IR36 at different levels of solution P (reduced) in one soil indicated a high degree of correlation between adjusted P levels and the measured growth parameters. About 0.12 ppm P in the soil solution or 0.46 ppm P desorbed in HCO
3
–
solution (equivalent to 100 mg P/kg soil) was adequate for near-maximum plant height, tiller production, total dry matter yield, plant P content, and total P uptake. 相似文献
24.
Nature and properties of humic acid prepared from different sources and its effect on nutrient availability 总被引:1,自引:0,他引:1
Summary Effect of sources, moisture levels and extractants on extraction, analytical properties, IR-spectra, macromolecular characteristics, interaction with cations and physiological properties of the extracted material (humic acid) were studied. Among the three variables, extractant influenced the degree of humification, IR-spectra, nature and properties of humic acids to a greater extent though the other two had significant contribution. Sodium pyrophosphate found to be an ideal extractant for humic acid. Reduced viscosity of humic acids increased with dilution particularly below 0.1 g/dl and decreased with increasing H+ concentration between pH 6.5 and 8.5 irrespective of source, moisture level and extractant. The amount of proton released and drop in initial pH of humic acids on addition of different metal ions indicated formation of mono-, di-hydroxy metal-HA complexes which broke down at pH 8.0 and above. HA-Fe2+ and HA-Cu2+ complexes were found to be most stable. Humic acids from different sources varied significantly in their effect on available nutrient status of soils though, the latter is main determining factor particularly for calcium and magnesium. 相似文献
25.
E. Krahulec 《Plant Ecology》1985,59(1-3):119-123
Two types of Nardus-rich communities may be distinguished in Europe according to their geographic pattern:I. Communities of high mountains showing discontinuous variation. Different florogenesis in island-like high mountains results in a number of alliances characteristic for particular mountain systems: Trifolion humilis Quézel 57 (Atlas, N Africa), Plantaginion thalackeri Quézel 53 (Sierra Nevada), Campanulo-Nardion Rivaz-Martinez 63 (mountains of the central Iberian peninsula), Nardion Br.-Bl. 26 (from Pyrenees, Auvergne to W and E Carpathians), Potentillo ternatae-Nardion Simon 58 (S Carpathians, Pirin, Rila), Jasionion orbiculatae Lakui 66 (Dinarids), Trifolion parnassi Quézel 64 (S Greece), Nardo-Caricion rigidae Nordhagen 37 (Iceland, Scotland, Scandinavia, W Sudeten).II. Communities at lower altitudes with continuous variation, where particular syntaxa are difficult to distinguish. Along the climatic gradient from a subatlantic to a subcontinental climate, a cline in floristic composition of the communities under discussion is found. Towards the eastern borderline, the communities are poorer in characteristic species. Here only one alliance is considered-Violion caninae Schwickerath 44. A Similar situation occurs along the altitudinal gradient in mountains. Only in mountains with a belt of alpine communities the montane Nardeta are saturated with alpine species. This thpe of communities was described as Nardo-Agrostion tenuis by Sillinger (1933). 相似文献
26.
Animal community structure as a function of stream size 总被引:1,自引:1,他引:0
Christer Brönmark Jan Herrmann Björn Malmqvist Christian Otto Per Sjöström 《Hydrobiologia》1984,112(1):73-79
The species-area relationship of the island biogeography theory was calculated for macroinvertebrates in 22 coastal, adjacent streams. A z-value of 0.19 was obtained. The low z-value was probably a consequence of the short distances between streams as well as high dispersal rates. In addition, a cluster analysis based on the dissimilarity of species assemblages showed that stream size was of prime importance in categorizing the streams. To a smaller extent water quality affected the community structure in the streams. 相似文献
27.
E. C. Jorgenson 《Journal of nematology》1984,16(2):154-158
Granular and liquid commercial humates, with micronutrients, and a microbial fermentation product were compared in several combinations with nematicides for their effects on cotton lint yield and root-knot nematode suppression. Fumigant nematicides effectively reduced cotton root galling caused by root-knot nematodes, and cotton lint yields increased. Organophosphates and carbamates were not effective. Occasionally, cotton lint yields were increased or maintained with combination treatments o f humates, micronutrients, and a microbial fermentation product, but galling o f cotton roots by root-knot nematodes was usually not reduced by these treatments. 相似文献
28.
Bragg soybeans were planted in nematicide-treated and nontreated plots on 15 May, 15 June, 1 July, and 15 July in 1980 and 1981 to determine the influence of planting date on damage caused by H. glycines. Although earlier studies showed the nematode was sensitive to high soil temperatures (> 34 C), late planting did not reduce damage caused by the nematode. Yields from plots treated with 1, 2-dibromo-3-chloropropane (57.5 kg a.i./ha) were 48, 118, 395, and 403% higher than yields from nontreated plots with planting dates of 15 May, 15 June, 1 July, and 15 July, respectively, when data were averaged over the 2 years. Increase in both seed size and number accounted for the yield increases in treated plots. Soil temperatures were highest during July in 1980, averaging 8.9 and 6.5 hours per day above 34 C at 10- and 20-cm depths, respectively. Larvae populations of H. glycines were reduced by the nematicide but not by late planting. These results indicate that damage caused by H. glycines may actually increase with later planting and that nematicides may be more beneficial when soybeans are planted late in a double-cropped production system. 相似文献
29.
The plant-communities from habitats of the metallophyte species Minuartia verna and Thlaspi alpestre (T. caerulescens) at sites disturbed and undisturbed by mining are described. Four communities were delineated by cluster and principal component analysis. Group 1 comprised species-poor communities on disturbed non-calcareous soils; group 2, relatively species-rich communities on disturbed calcareous soils; group 3, species-rich communities in the main on undisturbed calcareous soils. Group 4 consisted of species-rich communities with an alpine element, in damp habitats on base-rich soils derived from igneous rocks. Total and exchangeable elements As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Zn were determined for the soils of these sites. Levels of soil Ca, Cd, Pb and Zn accounted for most of the variation along the first axis of the PCA and soil nutrient levels were probably the main predictor along the second.Abbreviations PCA
Principal Component Analysis 相似文献
30.
The increase in bare patch of cereals associated with minimum tillage practices prompted an investigation of the relationship between soil compaction and saprophytic growth of Rhizoctonia solani. In soils wetter than 10 kPa there was a greater density of hyphae in compacted than in non-compacted soil. In relatively dry soil, however, there was wider exploration by hyphae in non-compacted than in compacted soil. The implications of these findings for disease management are discussed. 相似文献