Effects of nano Fe/SiO2 fertilizers on germination and growth of barley and maize

Iron (Fe) nanoparticles (NPs), with 30–40 nm diameter, were stabilized on sand. The resulting synthesized Fe/SiO₂ NPs, with different Fe contents (0–25 mg kg^?1) were employed as fertilizers in probing the mean germination time (MGT), growth and dry matter of barley and maize and their comparison with common Fe/SiO₂ in a completely randomized design (CRD) experiment. The results showed that our fertilizers had significant effects on MGT, with the lowest of 0.58 day for barley and 0.79 day for maize; at 15 and 5 mg kg^?1 nano Fe/SiO₂, respectively. Application of 15 mg kg^?1 of nano Fe/SiO₂ increased the shoot length: 8.25% and 20.8% for barley and maize, respectively. However, the concentration of 25 mg kg^?1 had a negative impact on shoot length in barley. Increasing the concentrations of both nano and common Fe/SiO₂ particles, increased the root lengths in both plants, however this increase was higher with the application of nano Fe/SiO₂. Likewise, seedling length enlarged with the concentration increase of both Fe/SiO₂ particles and was more pronounced with nano Fe/SiO₂. The application of nano Fe/SiO₂ was more effective compared with the common Fe/SiO₂ in encouraging barley and maize growth. The positive impact was higher in maize than barley.     

Co-situs application of controlled-release fertilizers to alleviate iron chlorosis of paddy rice grown in calcareous soil

Abstract

Co-situs is the placement with one application of a sufficient amount of controlled-release fertilizer for an entire growing season at any site, together with seeds or seedlings, without causing fertilizer salt injury. An experiment was conducted to find an efficient method for ameliorating Fe deficiency in two rice cultivars (cv. Tsukinohikari and cv. Sasanishiki) grown in a calcareous soil (pH 9.2, CaCO₃ 384 g kg^?1), which was poor in organic matter (0.1 g kg^?1) and available Fe (3.0 μg g^?1 soil). The field treatments consisted of co-situs application of the following fertilizers: 1) controlled-release NPK fertilizer (CRF-NPK) containing no micronutrients; 2) controlled-release NPK fertilizer containing micronutrients (CRF-M1); and 3) controlled-release NPK fertilizer containing micronutrients (CRF-M2). The main difference between CRF-M1 and CRF-M2 was that the former had larger granules than the latter. All the fertilizers were placed in contact with the roots of rice seedlings at transplanting time. Plants in the CRF-M1 and CRF-M2 treatments had similar lengths, number of stems, leaf age, and leaf color (SPAR value) during the cultivation period. By contrast, plants from the CRF-NPK treatments grew poorly, showed severe chlorosis symptoms of Fe deficiency, and all died on 30 DAT. Plants of both cultivars accumulated more macroand micronutrients with the CRF-M2 treatment than with the CRF-M1 treatment. The grain yield of cv. Tsukinohikari was 0.0, 1,910, and 2,160 kg ha^?1 for the CRF-NPK, CRF-M1, and CRF-M2 treatments, respectively, and 0.0, 2,490, and 2,860 kg ha^?1 for the same treatments for cv. Nihonbare. Chlorosis due to iron deficiency was successfully ameliorated and world-average grain yields were obtained with the co-sites application of both controlled-release fertilizers.     

Availability and extractability of soil manganese in a liming experiment

Abstract

The availability of soil Mn to corn in relation to extractability of soil Mn by EDTA, Mg(NO₃)₂, CH₃COONH₄, hydroquinone, H₃PO₄, and NH₄H₂PO₄ as affected by liming was evaluated under field conditions on a single soil type. EDTA, Mg(NO₃)₂ and CH₃COONH₄‐extractable Mn were related inversely to available Mn. No useful relationships were found between hydroquinone, H₃PO₄, and NH₄H₂PO₄‐extractable soil Mn and Mn uptake by sweet corn.     

Electron donors and acceptors influence anaerobic soil organic matter mineralization in tidal marshes

Anaerobic decomposition in wetland soils is carried out by several interacting microbial processes that influence carbon storage and greenhouse gas emissions. To understand the role of wetlands in the global carbon cycle, it is critical to understand how differences in both electron donor (i.e., organic carbon) and terminal electron acceptor (TEA) availability influence anaerobic mineralization of soil organic matter. In this study we manipulated electron donors and acceptors to examine how these factors influence total rates of carbon mineralization and the pathways of microbial respiration (e.g., sulfate reduction versus methanogenesis). Using a field-based reciprocal transplant of soils from brackish and freshwater tidal marshes, in conjunction with laboratory amendments of TEAs, we examined how rates of organic carbon mineralization changed when soils with different carbon contents were exposed to different TEAs. Total mineralization (the sum of CO₂ + CH₄ produced) on a per gram soil basis was greater in the brackish marsh soils, which had higher soil organic matter content; however, on a per gram carbon basis, mineralization was greater in the freshwater soils, suggesting that the quality of carbon inputs from the freshwater plants was higher. Overall anaerobic metabolism was higher for both soil types incubated at the brackish site where SO₄²⁻ was the dominant TEA. When soils were amended with TEAs in the laboratory, more thermodynamically favorable respiration pathways typically resulted in greater organic matter mineralization (Fe(III) respiration > SO₄²⁻ reduction > methanogenesis). These results suggest that both electron donors and acceptors play important roles in regulating anaerobic microbial mineralization of soil organic matter.     

Influence of PGPR-enriched liquid organic fertilizers on the growth and nutrients uptake of maize under drought condition in calcareous soil

In order to study the effect of water deficit stress (WDS), plant growth promoting rhizobacteria (PGPR)-enriched and non-enriched vermicompost tea(VT) and vermiwash(V) on the growth and nutrients uptakes of maize, a greenhouse experiment was conducted. The two-factor experiment was set up in a completely randomized design with three replications. The factors included: 1) liquid organic fertilizers (LOFs) with five levels (control, VT, V, vermicompost tea enriched with bacterium (VTB) and vermiwash enriched with bacterium (VB)) and 2) WDS with three levels (Field Capacity (FC), 80% FC and 60% FC(. At each irrigation interval, the volume of the used LOFs was equivalent to 60% of the volume of water required for 60% FC. At 60% FC, shoot dry matter (SDW), shoot N, P, Zn, Cu, and Fe uptake significantly decreased compared with those of FC and 80% FC, whereas shoot K uptake significantly increased. At all WDS levels, application of LOFs led to increase in SDW and shoot nutrients uptake. The highest amount of studied traits was obtained in VTB and VT treatments. Generally, VT treatments were more effective than V. Furthermore, PGPR-enriched LOFs were more effective than non-enriched ones. Application of LOFs may be considered as a practical approach for amplifying drought tolerance and reducing the risk of water scarcity in maize cultivation.     

DIFFERENTIAL TRANSLOCATION OF 59IRON IN IRON SUFFICIENT AND DEFICIENT SORGHUM PLANTS

Radioactively labeled iron (⁵⁹Fe) was used to study differential uptake in sorghum plants in the recovery stage of chlorosis. Radio-labeled ⁵⁹Fe was supplied through root feeding in nutrient solution experiment (48 hrs, pH 6.2) to non-chlorotic and chlorotic plants. Chlorotic plants were further treated with foliar spray [ferrous sulfate (FeSO₄), FeSO₄ + thiourea (TU), FeSO₄ + citric acid (CA), FeSO₄ + thioglycollic acid (TGA)] to study the uptake of radio-labeled ⁵⁹Fe through root feeding during recovery process of chlorosis. Under iron deficiency, the differential uptake of ⁵⁹Fe was markedly increased in leaves and stem of chlorotic control (-Fe) sorghum plants as compared to non-chlorotic control (+Fe) and foliar sprayed (FeSO₄, FeSO₄ + TU, FeSO₄ + CA, and FeSO₄ + TGA) plants. The lowest uptake of ⁵⁹Fe was observed in younger leaves (24.33 nmol, g^?1 fresh weight h^?1) and stem (1.98 nmol, g^?1 fresh weight h^?1) of non-chlorotic control followed by foliar sprayed plants in comparison to chlorotic control, respectively. Similarly less ⁵⁹Fe uptake was observed in the older leaves of FeSO₄ + CA sprayed (21.70 nmol, g^?1 fresh weight h^?1) plants in comparison to chlorotic control (35.60 nmol, g^?1 fresh weight h^?1). The highest differential ⁵⁹Fe uptake through nutrient medium was in the roots of plants, which were foliar sprayed with FeSO₄ along with TU. The role of iron alone and along with citric acid and thiol compounds is discussed in recovery of chlorosis.     

Responses by iron-efficient and inefficient oat cultivars to inoculation with siderophore-producing bacteria in a calcareous soil

Rhizosphere bacteria may enhance plant uptake of Fe by producing siderophores that chelate sparingly soluble Fe³⁺ in calcareous soils. To evaluate the extent to which plants benefit from colonization of the roots by prolific siderophore-producing bacteria, we inoculated two oat cultivars with six strains of bacteria that produced high concentrations of siderophores under Felimiting conditions in vitro. Oat cv Coker 227, an Fe-efficient cultivar, which produces the phytosiderophore avenic acid, and cv TAM 0-312, and Fe-inefficient cultivar, which does not produce the phytosiderophore, were grown in a calcareous soil (Weswood silt loam) on a light bench in the laboratory. Half of the plants were fertilized with a nutrient solution containing 5 mM Fe and half with a nutrient solution containing no Fe. After 6 weeks of growth, we compared colonization of the roots by the inoculant bacteria and the dry weight and Fe content of roots and shoots. Three species of Pseudomonas colonized the roots of both oat cultivars in high numbers (10⁶ cells g^-1 root dry weight), whereas the remaining bacteria colonized the roots in substantially lower numbers (10⁴ cells g^-1 root dry weight). Plants fertilized with 5 mM Fe were larger and supported greater numbers or rhizosphere bacteria per gram of root than plants not supplied with Fe. Comparisons of the Fe content and dry weight of roots and shoots revealed few significant differences between inoculated and uninoculated plants, or among the plants inoculated with the different strains of siderophore-producing bacteria. The differences that were observed revealed no consistent response to inoculation. We conclude that inoculation of the roots of the two oat cultivars with bacteria that produce high concentrations of siderophores in response to an Fe deficiency had little or no effect on Fe acquisition by the plants.     

Evapotranspiraton estimation based on scaling up from leaf stomatal conductance to canopy conductance

Evapotranspiraton (ET) estimation based on scaling up from leaf stomatal conductance (g_s) to canopy conductance (g_c) is important in improving effective use and evaluation of agricultural water resources. Taking a summer maize field in north China as an example, after the response of g_s to main environmental factors was analyzed based on the measured value, the Jarvis model for g_s was established and calibrated. Then the weighted integration model (WI model) was established on the basis of weighted model (W model) after considering the difference of intercept diffuse radiation by shaded leaves in different canopy heights and nonlinear relationship between g_s and the photosynthetically active radiation (PAR) to improve g_c estimation for shaded leaves using integration equation. Meanwhile the estimation accuracy of W and WI models for g_c was compared, and then field ET was estimated using the Penman-Monteith equation. Results indicate that the variation of g_s was similar to that of PAR and the Jarvis model could better express the response of g_s to PAR, vapour pressure deficit and air temperature. Compared to the W model, WI model could effectively improve the estimation accuracy of g_c, with the relative error of 4.4%. Penman-Monteith equation overestimated λET by 9.4% using the estimated g_c by the W model, but underestimated λET by 2.3% using the estimated g_c by the WI model. Therefore, Penman-Monteith equation can estimate maize field ET using the estimated g_c by WI model in the region.     

Alleviation of seeding chlorosis by plant growth regulators in drip-irrigated rice

Drip irrigation can produce high rice yields with significant water savings; therefore, it extends rapidly in water-scarce northern China. However, drip-irrigated rice seedlings often exhibit Fe chlorosis. The objective of this field experiment was thus to determine the ability of plant growth regulators to alleviate chlorosis in drip-irrigated rice seedlings. The study compared three plant growth regulators (1-naphthylacetic acid, NAA; sodium nitrophenolate, CSN; and diethyl aminoethyl hexanoate, DA-6) applied in two ways (seed-soaking and drip-application). The results showed that CSN increased root oxidation activity by 37% in the seed-soaking treatment and by 45% in the soil-application treatment. Seed soaking with NAA, CSN, and DA-6 increased the active Fe content in leaves by 8.8%, 17.5%, and 11.4%, respectively, compared with untreated seedlings. Iron absorption and SPAD values were both greater in the soil-application plots than in the seed-soaking plots. Among the plant growth regulators, CSN resulted in the highest yield (2.2% greater than untreated rice in the seed-soaking treatment and 12.8% greater than untreated rice in the soil-application treatment). In conclusion, CSN significantly improved root Fe uptake at the seedling stage and reduced chlorosis in drip-irrigated rice. Therefore, CSN drip application can be recommended for alleviating rice chlorosis in practical use.     

An examination of the total analysis of major elements in soil samples

Recently conventional chemical analyses were mostly replaced by instrumental analysis. Although results from both methods were examined in details after the samples had been solubilized or extracted by appropriate techniques, the solubilization method was considerably altered so as to be convenient for the following analysis. In atomic absorption spectrophotometry (AAS), for example, fusion technique was mostly inadequate because of the higher salts concentration in the obtained solution. The use of H₂SO₄ must also be avoided in acid digestion for SO₄ ^2- precipitates with Sr²⁺ or La³⁺ which must be added to eliminate interferences in the succeeding procedure. Therefore, it is essential to consider the whole scheme including sample treatments to evaluate the suitability of instrumental analysis. In this experiment, the suitability of the methods which have been employed in our laboratory was examined by analyzing 9 rock standards.     

Current Situation of Fertilizer in Japan

Nitrogenous Fertilizer

The production of nitrogenous fertilizer in 1953 Fertilizer Year (August 1953–July 1954) showed an increase of 293.000 metric tons or 11.4% over the preceding year through furtherance of rationalization of the industry as well as better conditions of electricity. This increase was attributable to that of ammonia form fertilizer, which was 331,000 tons over preceding year, while calcium cyanamide showed a slight decrease as per Table 1.     

The adverse effects of soil salinization on the growth of Trifolium alexandrinum L. and associated microbial and biochemical properties in a soil from Iran

The aim of this study was to determine the effects of increasing concentrations of salt solutions (including 0.12, 2, 6, and 10 dS m⁻¹) on the growth of berseem clover (Trifolium alexandrinum L.) and related soil microbial activity, biomass and enzyme activities. Results showed that the dry weights of root and shoot decreased with an increase in the concentrations of salt solutions. Soil salinization depressed the microbiological activities including soil respiration and enzyme activities. Substrate-induced respiration was consistently lower in salinized soils, whereas microbial biomass C did not vary among salinity levels. Higher metabolic quotients (qCO₂) and unaffected microbial biomass C at high EC values may indicate that salinity is a stressful factor, inducing either a shift in the microbial community with less catabolic activity or reduced efficiency of substrate utilization. Acid phosphatase and alkaline phosphatase activities decreased with increasing soil salinity. We found significant, positive correlations between the activities of phosphatase enzymes and plant's root mass, suggesting that any decrease in the activities of the two enzymes could be attributed to the reduced root biomass under saline conditions.     

Response of soil enzymes to Linear Alkylbenzene Sulfonate (LAS) addition in soil microcosms

Soil enzymatic activities (phosphatases, arylsulphatase and dehydrogenase) were measured in microcosm systems designed for the study of the impact of a commercial mixture of Linear Alkylbenzene Sulphonate (LAS) homologues on a xerofluvent agricultural soil. The soil microcosms consisted of glass columns filled with 800 g of dry soil which were fed with sterile commercial LAS solutions at concentrations of 10 or 50 mg l⁻¹ for periods of time up to 21 days. A soil microcosm fed with sterile distilled water was included in this study and considered as control. Our results showed that the continuous application of the anionic surfactant to soil increased the values of the enzymes acid and alkaline phosphatases and arylsulphatase. On the contrary, the dehydrogenase activity was decreased by the continuous application of 10 or 50 mg l⁻¹ LAS when compared with control microcosms. In addition, a statistically negative correlation was found between this enzymatic activity in the upper portion of the soil columns amended with LAS and the viable counts of heterotrophic aerobic microorganisms. Moreover, in order to test the influence of LAS on nutrient availability and, consequently, on bacteria populations and soil biological activities, phosphate concentration was regularly determined in the microcosm leachates. The phosphate concentration tested in the leachate of the microcosm continuously amended with 50 mg l⁻¹ LAS solution was significantly lower than the concentrations detected in the leachate of the microcosms continuously amended with 10 mg l⁻¹ LAS throughout the experiment.     

Effects of acid rain on leaf-litter decomposition in a beech forest on calcareous soil

Summary The effects of simulated acid rain on litter decomposition in a calcareous soil (pH_{H 2 O} 5.8) were studied. Litterbags (45 m and 1 mm mesh size) containing freshly fallen beech leaf litter were exposed to different concentrations of acid in a beech forest on limestone (Göttinger Wald. Germany) for 1 year. Loss of C, the ash content, and CO₂–C production were measured at the end of the experiment. Further tests measured the ability of the litter-colonizing microflora to metabolize ¹⁴C-labelled beech leaf litter and hyphae. The simulated acid rain strongly reduced CO₂–C and ¹⁴CO₂–C production in the litter. This depression in production was very strong when the input of protons was 1.5 times greater than the normal acid deposition, but comparatively low when the input was 32 times greater. acid deposition may thus cause a very strong accumulation of primary and secondary C compounds in the litter layer of base-rich soils, even with a moderate increase in proton input. The presence of mesofauna significantly reduced the ability of the acid rain to inhibit C mineralization. The ash content to the 1-mm litterbags indicated that this was largely due to transport of base-rich mineral soil into the litter.     

Modeling aerobic decomposition of rice straw during the off-rice season in an Andisol paddy soil in a cold temperate region of Japan: Effects of soil temperature and moisture

Submerged rice paddies are a major source of methane (CH₄) which is the second most important greenhouse gas after carbon dioxide (CO₂). Accelerating rice straw decomposition during the off-rice season could help to reduce CH₄ emission from rice paddies during the single rice-growth season in cold temperate regions. For understanding how both temperature and moisture can affect the rate of rice straw decomposition during the off-rice season in the cold temperate region of Tohoku district, Japan, a modeling incubation experiment was carried out in the laboratory. Bulk soil and soil mixed with 2% of δ¹³C-labeled rice straw with a full factorial combination of four temperature levels (?5 to 5, 5, 15, 25°C) and two moisture levels (60% and 100% WFPS) were incubated for 24 weeks. The daily change from ?5 to 5°C was used to model the freezing–thawing cycles occurring during the winter season. The rates of rice straw decomposition were calculated by (i) CO₂ production; (ii) change in the soil organic carbon (SOC) content; and (iii) change in the δ¹³C value of SOC. The results indicated that both temperature and moisture affected the rate of rice straw decomposition during the 24-week aerobic incubation period. Rates of rice straw decomposition increased not only with high temperature, but also with high moisture conditions. The rates of rice straw decomposition were more accurately calculated by CO₂ production compared to those calculated by the change in the SOC content, or in its δ¹³C value. Under high moisture at 100% WFPS condition, the rates of rice straw decomposition were 14.0, 22.2, 33.5 and 46.2% at ?5 to 5, 5, 15 and 25°C temperature treatments, respectively. While under low moisture at 60% WFPS condition, these rates were 12.7, 18.3, 31.2 and 38.4%, respectively. The Q₁₀ of rice straw decomposition was higher between ?5 to 5 and 5°C than that between 5 and 15°C and that between 15 and 25°C. Daily freezing–thawing cycles (from ?5 to 5°C) did not stimulate rice straw decomposition compared with low temperature at 5°C. This study implies that to reduce CH₄ emission from rice paddies during the single rice-growth season in the cold temperate regions, enhancing rice straw decomposition during the high temperature period is very important.     

Interpreting the dependence of soil respiration on soil temperature and water content in a boreal aspen stand

Continuous half-hourly measurements of soil CO₂ efflux made between January and December 2001 in a mature trembling aspen stand located at the southern edge of the boreal forest in Canada were used to investigate the seasonal and diurnal dependence of soil respiration (R_s) on soil temperature (T_s) and water content (θ). Daily mean R_s varied from a minimum of 0.1 μmol m⁻² s⁻¹ in February to a maximum of 9.2 μmol m⁻² s⁻¹ in mid-July. Daily mean T_s at the 2-cm depth was the primary variable accounting for the temporal variation of R_s and no differences between Arrhenius and Q₁₀ response functions were found to describe the seasonal relationship. R_s at 10 °C (R_s10) and the temperature sensitivity of R_s (Q_10Rs) calculated at the seasonal time scale were 3.8 μmol m⁻² s⁻¹ and 3.8, respectively. Temperature normalization of daily mean R_s (R_sN) revealed that θ in the 0–15 cm soil layer was the secondary variable accounting for the temporal variation of R_s during the growing season. Daily R_sN showed two distinctive phases with respect to soil water field capacity in the 0–15 cm layer (θ_fc, 0.30 m³ m⁻³): (1) R_sN was strongly reduced when θ decreased below θ_fc, which reflected a reduction in microbial decomposition, and (2) R_sN slightly decreased when θ increased above θ_fc, which reflected a restriction of CO₂ or O₂ transport in the soil profile.Diurnal variations of half-hourly R_s were usually out of phase with T_s at the 2-cm depth, which resulted in strong diurnal hysteresis between the two variables. Daily nighttime R_s10 and Q_10Rs parameters calculated from half-hourly nighttime measurements of R_s and T_s at the 2-cm depth (when there was steady cooling of the soil) varied greatly during the growing season and ranged from 6.8 to 1.6 μmol m⁻² s⁻¹ and 5.5 to 1.3, respectively. On average, daily nighttime R_s10 (4.5 μmol m⁻² s⁻¹) and Q_10Rs (2.8) were higher and lower, respectively, than the values obtained from the seasonal relationship. Seasonal variations of these daily parameters were highly correlated with variations of θ in the 0–15 cm soil layer, with a tendency of low R_s10 and Q_10Rs values at low θ. Overall, the use of seasonal R_s10 and Q_10Rs parameters led to an overestimation of daily ranges of half-hourly R_s (ΔR_s) during drought conditions, which supported findings that the short-term temperature sensitivity of R_s was lower during periods of low θ. The use of daily nighttime R_s10 and Q_10Rs parameters greatly helped at simulating ΔR_s during these periods but did not improve the estimation of half-hourly R_s throughout the year as it could not account for the diurnal hysteresis effect.     

Effects of floating Azolla on phosphorus fluxes and recovery from former agricultural lands in wetland microcosms

The long-term fertilization results in accumulation of phosphorus especially in the top layer of the soils. Inundation of agricultural lands leads to a switch to anaerobic soil condition, causing reduction of iron and leaching of phosphate simultaneously. From the ecological and environmental perspective, high nutrients flux especially phosphorus will increase the possibility of eutrophication in aquatic system. The fern Azolla had a good potential to adsorb phosphorus, it also has distinctive nitrogen-fixing capacity. We conducted a 10-week aquarium experiment to investigate the phosphorus release capacity from two agricultural soils in the Netherlands with different Fe and P concentrations but comparable Fe/P ratios. Besides, the research questions rose to whether Azolla could use the mobilized phosphate released from the soils for growth. We also tried to find an effective indicator to estimate the actually phosphate mobilization from sediment to water layer. Results showed that the soils with high Fe and P concentrations had higher phosphate release rate compared with the soil with low Fe and P concentrations. Pore water Fe: PO₄^3? ratios were valid to identify P release to surface water, when the Fe: PO₄^3? ratios less than 8 mol mol^?1 substantial phosphorus mobilization occurred. The conclusions showed that the actual mobilization of phosphate is more important than the phosphorus retained in the sediments for the internal PO₄^3? fluxes. From 10-week experimental results, we found that Azolla can reuse the phosphate retained in soils thus removed the mobilized phosphate in a moderately low surface water nutrient loading.     

Background level of nitrous oxide in the atmosphere in relation to flux from soil

According to Broadbent and Clark (3), there are numerous data indicating that denitrification leads to the emission of N₂O together with N₂, whereby loss of N is developed from soils. Nitrous oxide is also released from soils to the atmosphere during the nitrification of ammonium and ammonium-producing fertilizers under aerobic conditions (1). Relatively few attempts have been made to directly measure N₂O evolution under field conditions (6, 7, 10–12), although a number of laboratory studies have been reported. These studies are essential for determining the N balance between additions and losses of soil N.     

Evaluation of the soil fauna impact on decomposition in a simulated coniferous forest soil

Summary Long-term experiments (ca. 2 years) were carried out in laboratory systems that simulated the complexity of a coniferous forest floor. The test materials were partially sterilized by freezing and thawing, and reinoculated with (1) microbes alone or (2) microbes with fauna. Removable microcosms containing birch litter, spruce litter, or humus were inserted into a humus substrate. Two experiments used organic matter only, and another included a layer of mineral soil below the humus. Both were incubated in climate chambers that simulated both summer and winter conditions. The evolution of CO₂ was measured at regular intervals. In order to determine the C content of the leachates, the macrocosms and the microcosms were watered periodically.Soil fauna significantly increased respiration in the litter, but not in the microcosms containing humus. In the later phases of decomposition the presence of fauna had a negative effect. In the total systems the fauna consistently increased the respiration rate. The loss of mass was greater in the presence of fauna, especially during the middle phases (5–11 months), but it was higher in the controls later.Throughout the whole incubation period the decomposition rate was strongly influenced by the composition of the animal community. The interpretation of the results is affected by the fact that the controls, to which no fauna had been added, contained dense populations of microbial feeders (nematodes, rotifers, and protozoans).     

Absorption and transport of Na and Cl in rice cultivars differing in their tolerance to salinity: An examination of the effects of ammonium and potassium salts

The absorption and transport of Na and Cl from 0.1 mM and 10 mM ²²Na labelled NaCl or ³⁶Cl labelled KCl were examined in 15 days old seedlings of 3 cultivars of rice differing in their tolerance to salinity. Furthermore, the effects of 10, 100 and 1000 ppm (N)₂S on their uptake were studied. It was found that in general, the salt‐tolerant cultivars BR and PNL‐1 absorbed more Na and translocated a lesser proportion of it to the shoot, compared to the salt‐sensitive IR‐8, from 0.1 mM NaCl. The presence of (N)₂S reduced the uptake of Na in all the cultivars. It was also found that the presence of 100 ppm K, KN or NNreduced Na absorption from 0.1 mM NaCl significantly in all the cultivars, and the translocation to shoot in BR‐ Chloride transport from 0.1 mM NaCl was reduced by (N)₂S in all the cultivars. The 3 cultivars differed significantly in the rates of absorption and transport of Na and Cl. The results indicate that PNL‐1 which is a cross of IR‐8 X BR, has inherited the salt tolerance trait from BR. Lower rates of Na translocation to the shoot can be used as an index of salt tolerance in rice.