Soil characteristics in teak plantations and natural forests in Ashanti Region,Ghana

Abstract

The goal of this study to was compare soils of natural forests converted to teak (Tectona grandis Linn. F) plantations (21.3±5.1 years) in the Offinso and Juaso Forest Districts in the Ashanti region, Ghana. Sites selected for this study were in the moist semi‐deciduous forest zone and had nearly identical physiographic characteristics. In each of three natural forest stands and three teak plantations, 16 soil pits were examined and soil samples from the 0–20 (major rooting zone) and 20–40 cm depths were analyzed for selected chemical and physical properties. In the 0–20 cm depths bulk density significantly increased (1.17 to 1.30 g cm^‐3), but soil organic matter (OM) content (13 to 11%), total nitrogen (0.3 to 0.2 %), available phosphorus (4.2 to 1.2 mg kg^‐1), and exchangeable potassium (0.4 to 0.3 cmol(+)kg^‐1), calcium (17.0 to 12.4 cmol(+)kg^‐1), and magnesium (3.8 to 3.2 cmol(+)kg^‐1) significantly decreased in soils where natural forests were replaced with teak plantations. Similar results also were found for the 20–40 cm soil depths. The higher nutrient contents in soils under the natural forest may have been due to more litter contributions from understorey vegetation observed there. In the teak plantations nutrient leaching losses may have accelerated due to increased mineralization and the inability of teak to use the increase in available nutrient.     

Nutrients balance for improvement of phytoremediation ability of teak seedlings (Tectona grandis)

As a green technique, plant-based remediation systems can be used to remove nitrogen (N) pollutants from N-rich wastewaters. However, the excess amount of N and shortage of other nutrients in this system limits the plant growth and affects the plant remediation efficiency. In this study, the effect of adding phosphorus (P) and potassium (K) to the N-enriched wastewater on growth and N-removal efficiency of teak seedlings (Tectona grandis) was evaluated. Twelve ratios of N:P:K were applied to teak seedlings and the related effects were compared with those in control solution containing only N. The results indicated that a ratio of 1N:0.5P:1K increased dry matter accumulation in teak seedlings by improving the balance of nutrients in plants. Teak seedlings grown in nutritionally-improved system eliminated 33.8% N more than those grown in only N solution. The water loss through plant uptake was also enhanced in the improved system up to 56%.     

Optimizing Fly‐Ash Dose for Better Tree Growth and Nutrient Supply in an Agroforestry System in Semi-arid Tropical India

Abstract

Research on fly‐ash utilization in dryland Alfisols in semi‐arid tropical India may help successful establishment of agroforestry systems. A field study was conducted during 2001–2004 with the objective of evaluating fly-ash using different levels (0, 17, 33, and 66% v/v) in tree microsites along with compost and tank silt mixtures. Specifically, the focus was to find the optimum dose of fly‐ash mixtures for tree growth and nutrient release with time of both essential and heavy elements in fly-ash and soil: phosphorus (P), potassium (K), calcium (Ca), sodium (Na), aluminium (Al), zinc (Zn), and cadmium (Cd) and their effect on plant tissues with respect to copper (Cu), Zn, Cd, nickel (Ni), chromium (Cr), and lead (Pb). The changes in plant‐available or extractable status of elements and the growth of two major tree species [viz., teak (Tectona grandis) and leucaena (Leucaena leucocephala)] were monitored at 6‐month intervals during 2002–2004 in an agrisilvicultural system. Pit mixtures with 66% fly‐ash by volume of pit significantly increased the tree growth of teak throughout the study period. For leucaena, it positively influenced the growth at initial stages. The dose increased the status of available P, K, Ca, and Na during the study period. The exchangeable Al and available Zn content of microsites corresponding to the dose significantly increased during 2001–2003 but the levels were less than the toxic limits. The available Cd content showed an increase only during the initial stage of the study period. The variation in heavy‐metal content (Cu, Cd, Cr, Ni, Pb, and Zn) in plant tissues among the different treatments was found to be nonsignificant.     

Soil‐Test Methods for Florida Sands Treated with an Aluminum–Water Treatment Residual and Various Phosphorus Sources

Use of aluminum (Al)–rich water treatment residuals (Al‐WTR) has been suggested as a practice to immobilize excessive phosphorus (P) in Florida soils that could represent an environmental hazard. Fertilizer P requirements can differ in WTR‐amended and unamended soil, so careful selection of soil‐testing methodology is necessary. Acidic extractants can dissolve WTR sorbed P and overestimate plant‐available P. We evaluated the suitability of the Mehlich 1 P (M‐1P) and other agronomic soil‐test procedures in an Al‐WTR‐treated Florida soil. Bahiagrass (paspalum notatum Fluggae), ryegrass (Lolium perenne L.), and a second bahiagrass crop were grown in succession in a Florida topsoil amended with four sources of P at 44 kg P ha^?1 (P‐based rates) and 179 kg PAN ha^?1 [nitrogen (N)–based rates] and three WTR rates (0, 10, and 25 g kg^?1 oven‐dry basis). Both water‐extractable P (WEP) and iron (Fe) strip P (ISP), but not M‐1P, values of soil sampled at planting of each grass were greater in the absence than in the presence of WTR. Total plant P uptake correlated with WEP (r² = 0.82^***) and ISP (r² = 0.75^***), but not M‐1P (r² = 0.34^***). Correlations of the dry‐matter yield, P concentration, and P uptake of the first bahiagrass were also better with WEP and ISP than with M‐1P values. However, regression of plant responses with M‐1P improved after the first crop of bahiagrass. Both WEP and ISP values were better predictors of available soil P than M‐1P in a field study with same four P sources surface applied to established bahiagrass at the same two P rates, with and without WTR. Both WEP and ISP are recommended as predictors of P adequacy in soils treated with WTR, especially for soils recently (< 5 months) treated with Al‐WTR.     

Genotypic variation in foliar nutrient concentrations, δ13C,and chlorophyll fluorescence in relation to tree growth of radiata pine clones in a serpentine soil

This study investigated the genotypic variation in foliar nutrient concentrations, isotopic signature (δ¹³C), and chlorophyll fluorescence (F_v/F_m) and tree growth of 40 radiata pine clones grown on a New Zealand serpentine soil, and the relationships between growth and physiological traits of these clones from improved and unimproved groups. Genotypic variation in growth and physiological traits existed within (i.e., clonal) and between groups, with larger variation among clones. The clonal repeatabilities were greater for foliar nitrogen (N), calcium (Ca), magnesium (Mg), boron (B) concentrations, δ¹³C, and Ca : Mg ratio (0.35–0.64) than for growth traits (0.14–0.27) and other physiological traits (0.08–0.24). Significant phenotypic correlations were found between growth traits and foliar phosphorus (P), potassium (K), sulfur (S), iron (Fe), and K : Mg and Ca : Mg ratios and F_v/F_m (positive), and foliar Mg (negative). This study indicates that the trees on this serpentine soil generally suffered from multiple nutrient deficiencies and imbalances and the clonal variation in growth performance was more related to their capabilities of acclimation to nutrient than water stresses. Overall, the clones that absorbed more P, K, S, and Fe and less Mg from the soil grew better on this serpentine soil. For unimproved clones, the most limiting nutrients for tree growth were foliar K and Fe, while for improved clones it was foliar K.     

Phosphat-Düngerbedarf von Getreide und Zuckerrüben im südniedersächsischen Lößgebiet

Phosphate fertilizer requirement of cereals and sugar beets on “loess soils” in the Southern part of Lower Saxony (F.R. of Germany) In the years 1984 to 1986 105 P-fertilizer experiments with winter wheat, winter barley and sugar beets were carried out on “loess soils” in the Southern part of Lower Saxony (F. R. of Germany). The mineral P fertilization applied as “Triplephosphat” varied between 0 and 250 kg P₂O₅/ha. Soil test values (P-H₂O method) of the sites ranged from 6 to 38 and were on the average 18 ± 8 mg P/kg. Besides the P-H₂O-extraction the following methods were used: CAL, DL, NaHCO₃ and EUF. In no case P-application increased yields of cereals and sugar beets, although in 1986 there was no P fertilization for three years. Results of plant analysis (0.3–0.6% P i. dm) also showed a sufficient P-status. Furthermore an increase of P content of soils (+20 mg P-H₂O/kg on average) by a fertilizer rate of 1500 kg P₂O₅/ha did not effect yield in the following years. Thus, on these fields with P levels of 5 mg P-H₂/kg soil (5 mg P₂O₅-CAL/100 g) and more a P fertilization corresponding to the P removal by the crop rotation of sugar beets and 2x cereals of about 180 kg P₂O₅/ha in three years is recommended, if crop residues remain on the field. At P levels higher than 12–14 mg P-H₂O/kg soil P fertilization can be below P-removal or omitted.     

Wheat yield prediction by zero sink and equilibrium-type soil phosphorus tests

Diffusive gradients in thin films (DGT) measurements have been shown to outperform other phosphorus (P) tests in soils with strong P sorption, but this has not been confirmed for moderately weathered European soils. We compared the performance of DGT in predicting wheat grain yield in Swedish long-term fertility experiments with those of standard intensity (water-extractable P (P-H₂O)) and quantity (ammonium lactate-extractable P (P-AL)) tests. A Mitscherlich-type model was used to fit wheat yield response to P application rates (0, 15, 30 or 35, and 45 kg P ha^-1 year^-1) in each individual trial replicate to estimate the maximum yield. For trials with clear plateau-type yield responses and the goodness of fit (R²) > 0.75, relative yields (RYs) were calculated for each P treatment and plotted against the soil P test results (n=143). The goodness of the Mitscherlich-type fits decreased in the following order:DGT-measured P (P-DGT) (R²=0.35) > P-H₂O (R²=0.18) > P-AL (R²=0.13). When excluding soils with P-AL:P-DGT ≥ 0.1 L g^-1, R² was considerably improved to 0.55 for P-AL, 0.46 for P-H₂O, and 0.65 for P-DGT (n=61). At 95% of maximum yield, the upper limit of P deficiency for P-DGT was 44.8 (the soils with P-AL:P-DGT < 0.1 L g^-1) and 61.9 μg L^-1 (all soils), falling within the range reported for other European and Australian soils (6.0-142 μg L^-1). We show that in the investigated Swedish soils, DGT performed better than the quantity and intensity tests, which is attributed to its ability to capture P diffusion and resupply from the soil solid phase, similar to plant roots in the rhizosphere.     

Effect of tillage and residue management on enzyme activities in soils

Recent interest in soil tillage and residue management has focused on low-input sustainable agriculture. In this study we investigated the effect of three tillage systems (no-till, chisel plow, and moldboard plow) and four residue placements (bare, normal, mulch, and double mulch) on the activities of four amidohydrolases (amidase, L-asparaginase, L-glutaminase, and urease) in soils from four replicated field-plots. Correlation coefficients (r) for linear regressions between the activities of each of the enzymes and organic C or pH and between all possible paired amidohydrolases were also calculated. The results showed that the effects of tillage and residue management on pH in the 28 surface soil (0–15 cm) samples were not significant. The organic C content, however, was affected significantly by the different tillage and residue-management practices studied, being the greatest in soils with notill/double mulch treatment, and the least with no-till/bare and moldboard/normal treatments. Within the same tillage system, mulch treatment resulted in greater organic C content compared with normal or bare treatment. The activities of the amidohydrolases studied were generally greater in mulch-treated plots than in non-treated plots, and were significantly correlated with organic C contents of soils, with r values ranging from 0.70^*** to 0.90^***. Linear regression analyses of enzyme activities on pH values (in 0.01 M CaCl₂) of the 28 surface soils showed significant correlations for L-asparaginase, L-glutaminase, and urease, with r values of 0.74^***, 0.77^***, and 0.72^***, respectively, but not for amidase (r=0.24). The activities of the four amidohydrolases studied in the 40 soil samples tested were significantly intercorrelated, with r values ranging from 0.72^*** to 0.92^***. The activities of the four amidohydrolases decreased with increasing soil depth of the plow layer, and were accompanied by a decrease in organic C content.     

Cumulative Effect of Soil and Foliar Application of Nitrogen,Phosphorus, and Sulfur on Growth,Physico-Biochemical Parameters,Yield Attributes,and Fatty Acid Composition in Oil of Erucic Acid-Free Rapeseed-Mustard Genotypes

ABSTRACT

The feasibility of split (soil + foliar) applications of nitrogen (N) and phosphorus (P) and addition of a small quantity of sulfur (S) in the spray was tested for improving performance of rapeseed-mustard genotypes in a factorial randomized field experiment. Three genotypes (two erucic acid free, viz. Brassica napus L. cv. ‘Hyola PAC – 401’ and Brassica juncea L. Czern. and Coss. cv. ‘TERI (0E) M 21-Swarna’, and one best performing high yielding Brassica juncea L. cv. ‘Rohini’ as a check) were grown with four soil (B) plus foliar (F) applications of N, P, and S with uniform basal 30 kg potassium (K) ha^{? 1} (K₃₀), viz. (i) the optimum soil-applied treatment supplemented with the spray of deionized water (B_N90P30 + Fw) comprising control, (ii) B_N70P30 + F _N20, (iii) B_N70P28 + F_N20P2, and (iv) B_N70P28 + F_N20P2S2. Soil Plus foliar application of nutrients, particularly B_N70P28 + F_N20P2S2, improved their performance with respect to growth characteristics (shoot length plant^{? 1}, leaf number plant^{? 1}, area leaf^{? 1}, leaf area index, fresh weight plant^{? 1}, and dry weight plant^{? 1}), physico-biochemical parameters (net photosynthetic rate, stomatal conductance, carboxylation efficiency, water use efficiency, carbonic anhydrase activity, leaf NPK content, and N use efficiency), yield attributes (pod number plant^{? 1}, seed number pod^{? 1}, 1000-seed weight, seed yield ha^{? 1}, oil content, and oil yield ha^{? 1}), and fatty acid composition in oil of these genotypes. The cultivar ‘Hyola PAC-401’ performed best particularly with B_N70P28 + F_N20P2S2. The improvement in the response of genotypes to the split application of nutrients may be attributed to their ready availability through foliar application.     

Foliar Applied Phosphorous Enhanced Growth,Chlorophyll Contents,Gas Exchange Attributes and PUE in Wheat (Triticum aestivum L.)

A pot experiment was conducted to evaluate the foliar applied phosphorous with and without pre-plant dose (50 kg hac.^?1) of phosphorous on growth, chlorophyll contents, gas exchange parameters and phosphorous use efficiency (PUE) of wheat. The experiment was conducted in net house at Department of Crop Physiology, University of Agriculture Faisalabad, Pakistan. Two promising wheat cultivar AARI 2011 and FSD 2008 were used as a test crop with 5 foliar phosphorus (P) rates (0, 2, 4, 6, 8 kg ha^?1). The foliar applied P with pre-plant performed better than without pre-plant and control treatments. Foliar treatment of phosphorus at 6 kg ha^?1 P proved to be the best among other foliar treatments followed by 8 kg ha^?1 P. The foliar application of phosphorous at 6 kg hac.^?1 with pre-plant soil applied P increased the shoot length, root length, shoot fresh weight, root fresh weight, shoot dry weight and root dry weight. The chlorophyll contents (Chl. a and b) were increased with the foliar application of phosphorous. The gas exchange parameters (net carbon dioxide (CO₂) assimilation rate, transpiration rate, stomatal conductance and sub-stomatal CO₂ rate) were significantly improved by foliar applied P. The maximum values of net CO₂ assimilation rate (5.27 μ mol m^?2 sec.^?1), transpiration rate (3.44 μ mol m^?2 sec.^?1), stomatal conductance (0.81 μ mol m^?2 sec.^?1) and sub-stomatal CO₂ (271.67 μ mol m^?2 sec.^?1), were recorded in the treatment where P was foliar applied at 6 kg hac.^?1 with pre-plant soil applied Phosphorous. The foliar application of phosphorous with pre-plant soil applied P enhanced Phosphorous use efficiency (PUE) in both varieties. The maximum value of PUE (15.42%) was recorded in the treatment where foliar feeding of P was done at 6 kg hac.^?1 with pre-plant soil applied P in both genotypes.     

Arylamidase and amidohydrolases in soils as affected by liming and tillage systems

This study investigated the long-term effect of lime application and tillage systems (no-till, ridge-till and chisel plow) on the activities of arylamidase and amidohydrolases involved in N cycling in soils at four long-term research sites in Iowa, USA. The activities of the following enzymes were assayed: arylamidase, -asparaginase, -glutaminase, amidase, urease, and -aspartase at their optimal pH values. The activities of the enzymes were significantly (P<0.001) and positively correlated with soil pH, with r values ranging from 0.42^* to 0.99^*** for arylamidase, 0.81^*** to 0.97^*** for -asparaginase, 0.62^*** to 0.97^*** for -glutaminase, 0.61^*** to 0.98^*** for amidase, 0.66^** to 0.96^*** for urease, and 0.80^*** to 0.99^*** for -aspartase. The Δactivity/ΔpH values were calculated to assess the sensitivity of the enzymes to changes in soil pH. The order of the sensitivity of enzymes was as follows: -

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-aspartase. The enzyme activities were greater in the samples of the 0–5 cm depth than those of the 0–15 cm samples under no-till treatment. Most of the enzyme activities were significantly (P<0.001) and positively correlated with microbial biomass C (C_mic) and N (N_mic). Lime application significantly affected the specific activities of the six enzymes studied. Results showed that soil management practices, including liming and type of tillage significantly affect soil biological and biochemical properties, which may lead to changes in nitrogen cycling, including N mineralization in soils.     

Nitrogen and carbon cycling associated with litterfall production in monoculture teak and mixed species teak and flueggea stands

Purpose

High demand for teak (Tectona grandis L.f.), a species of economic importance, was the reason Solomon Islands experienced a surge in community-wide planting of monoculture teak stands in the last two decades. Mixed species planting of teak and flueggea (Flueggea flexuosa Muell. Arg.) was introduced to overcome the reluctance of growers to thin their stands. However, there is lack of information on the effect of changing from monoculture to mixed species plantings on the cycling of nutrients especially carbon (C) and nitrogen (N).

Materials and methods

This study assessed litter quantity and quality, total C (TC), total N (TN), C:N ratio and C and N isotope compositions (δ¹³C and δ¹⁵N) over 18 months at two sites (Ringgi and Poitete). The treatments included teak planted at 833 stems per hectare (sph) (T1), teak planted in rows with two rows of flueggea at 833 sph (T2), 625 sph (T3) and 416 sph (T4), and teak planted in alternating rows with flueggea at 833 sph (T5).

Results and discussion

Treatment 1 (T1) produced significantly higher total litter than T4 at Ringgi. However, based on individual tree litterfall production, teak in T4 (lowest stocking rate) at both trials produced higher litter per tree than the teak in T3, T2, T5 and T1 while there was no significant difference with litter production of flueggea. An enrichment of litter δ¹⁵N was observed over time in either species, which suggested an increased N loss and transformations in both experimental sites. When comparing each treatment and using individual tree productivity, T4 significantly produced and returned higher litter TC and TN than T3, T2, T5 and T1.

Conclusions

Overall, individual tree productivity demonstrated that mixed species stands had a significant potential for cycling higher rates of C and N than monoculture teak stands. Therefore, establishment of mixed species stands, especially T4 and T3, was recommended as a practical measure to address the widely experienced problem of reluctance by growers to thin high value trees while preserving the balance of C and N inputs into the ground.

     

Are chlorophylls good indicators of nitrogen and phosphorus levels? 1

Aubergine plants (Solanum melongena cv. Bonica) were grown under controlled greenhouse conditions on a soil substrate supplied with organic fertilizers (15 kg/m²) mixed with calcium sulfate (CaSO₄ at 500 g/m²), with different doses of nitrogen (N as N₁ = 15, N₂ = 22.5, N₃ = 30 g/m²) in the form of ammonium nitrate (NH₄NO₃), and phosphorus (P as P₁ = 24, P₂ = 36 g/m²) as phosphorus acid H₃PO₄). Plants were sampled every 15 days, and the pigments chlorophyll a, chlorophyll b, total (a+b) and ratio (a/b), carotene, licopene, and anthocyanins were determined in the leaves. The results showed that increases in rhizosphere N led to increases in foliar concentrations of chlorophyll a and b, both individually and as total chlorophyll, independently of the dose of P applied. Total chlorophyll concentrations were directly correlated with the level of P fertilization. Carotene and licopenes reflected the influence of increasing doses of N, whereas P did not affect these pigments. Anthocyanin levels were affected by both N and P.     

Evaluation of soil P‐test values of canton Geneva/Switzerland in relation to P loss risks

The P status of the soils of Geneva is routinely determined by two independent chemical extractions. The P amounts extracted independently by an aqueous solution of ammonium acetate 0.5 M + EDTA 0.02 M (pH 4.65) (1:10 solid weight : solution volume, 60 minutes) and by H₂O (1 : 10 solid weight : solution volume, 60 minutes) were assumed to represent mobilizable and mobile phosphorus pools. The best correlations with the data from 1023 crop field soil samples in Geneva canton during the years 1994 to 2000 were obtained by power functions if the data were grouped in two distinct pH ranges: pH 4.6–6.5: (P‐AAE) = 16.436 (P‐H₂O) ^0.6083; R² = 0.625; n = 166, pH 6.6–8.6: (P‐AAE) = 25.582 (P‐H₂O) ^0.6518; R² = 0.47; n = 857. The derivatives of these functions are representative of apparent P‐buffering power. Environmentally sound threshold values for P‐H₂O and P‐AAE are estimated by calculating the change points first of these P‐AAE (quantity) against P‐H₂O (intensity) curves and second P‐buffering power against P‐H₂O or P‐AAE curves. The change points obtained from the smoothed quantity‐intensity data were: pH 4.6–6.5: P‐H₂O = 3.8 mg kg^–1 and P‐AAE = 16.436 (3.8)^0.6083 = 37.0 mg kg^–1; n = 166, pH 6.6–8.6: P‐H₂O = 2.5 mg kg^–1 and P‐AAE = 25.582 (2.5)^0.6518 = 46.5 mg kg^–1; n = 857. The change‐points for P‐buffering power curves occurred at pH 4.6–6.5: P‐H₂O = 1.3 mg kg^–1; P‐AAE = 19.7 mg kg^–1; n = 166, pH 6.6–8.6: P‐H₂O = 1.3 mg kg^–1; P‐AAE = 20.6 mg kg^–1; n = 857. The threshold buffering powers were: pH 4.6–6.5: d(P‐AAE)/d(P‐H₂O) = 9.998 (P‐H₂O) ^–0.3917 = 9.0, pH 6.6–8.6: d(P‐AAE)/d(P‐H₂O) = 16.674 (P‐H₂O) ^–0.3482 = 15.2. These results show that presently only about 25 % of the crop soils of Geneva canton were within these safe limits. The possibility of applying values of this magnitude which are significantly lower than officially recommended reference levels for phosphorus fertilizer recommendations is supported by recent agronomic investigations.     

Importance of organic nitrogen fractions in sandy soils,obtained by electro-ultrafiltration or CaCl2 extraction,for nitrogen mineralization and nitrogen uptake of rape

Summary Sandy soils have low reserves of mineral N in spring. Therefore organic-bound N is the most important pool available for crops. The objective of the present investigation was to study the importance of the organic-bound N extracted by electro-ultrafiltration and by a CaCl₂ solution for the supply of N to rape and for N mineralization. Mitscherlich-pot experiments carried out with 12 different sandy soils (Germany) showed a highly significant correlation between the organic N extracted (two fractions) and the N uptake by the rape (electroultrafiltration extract: r=0.76^***; CaCl₂ extract: r=0.76^***). Organic N extracted by both methods before the application of N fertilizer was also significantly correlated with N mineralization (electro-ultrafiltration extract: r=0.75^***; CaCl₂ extract: r=0.79^***). N uptake by the rape and the mineralization of organic N increased with soil pH and decreased with an increasing C:N ratio and an increasing proportion of sand in the soils. Ninety-eight percent of the variation in N uptake by the rape was determined by the differences in net mineralization of organic N. This show that in sandy soils with low mineral N reserves (NO _inf3 ^sup- -N, NH ₄ ⁺ -N) the organic soil N extracted by electro-ultrafiltration or CaCl₂ solutions indicates the variance in plant-available N. Total soil N was not related to the N uptake by plants nor to N mineralization.     

不同农业土壤中有效磷的变化与磷平衡的关系

Maintaining soil phosphorus(P) at adequate levels for plant growth requires assessing how the long-term P balance(viz., the difference between P inputs and outputs) results in changes in soil test P. The hypothesis that routinely measured soil properties can help predict the conversion factor of P balance into Olsen P was tested at 39 sites in agricultural areas of the Mediterranean region in Spain. A set of soil samples from each site was analyzed for Olsen P, inorganic P(P extracted using 0.5 mol L~(-1) H_2SO_4), pseudototal P(P extracted using 0.5 mol L~(-1) H_2SO_4 following ignition at 550℃), and organic P(the difference between pseudototal P and inorganic P). Organic and Olsen P were uncorrelated in most of the 39 soil sets, which suggests that organic P content changed little with P inputs and outputs. The slopes of the regression lines of Olsen P against pseudototal and inorganic P, which were used as two different measures of the conversion factor, ranged widely(from 0.03 to 0.25 approximately), with their average values(about 0.10) being similar to those found in long-term experiments conducted in temperate areas. Neither conversion factor was significantly correlated with any routinely measured soil property; however, the conversion factor for inorganic P was significantly lower for calcareous soils than for noncalcareous soils. Our negative results suggest the need to isolate the influence of soil properties from that of management systems and environmental factors relating to P dynamics in future studies.     

Sulphur mineralization and release of soluble organic sulphur from camp and non-camp soils of grazed pastures receiving long-term superphosphate applications

Summary Topsoils (0–75 mm) from four soil types with different sulphate retention capacities were collected from stock camp and non-camp (main grazing area) sites of grazed pastures in New Zealand which had been annually fertilized with superphosphate for more than 15 years. These soils were analysed for different S fractions and incubated at 30°C for 10 weeks using an open incubation technique in order to assess the extent of S mineralization and the release of soluble soil organic S from camp and non-camp soils during incubation. The soils were preleached with 0.01 M KCl, followed by 0.04 M Ca(H₂PO₄)₂ before being incubated. Pre-incubation leachates and weekly 0.01 M KCl leachates were analysed for mineralized S (i.e., hydriodic acid-reducible S) and total S. Soluble organic S was estimated as the difference between these two S fractions. Results obtained show higher cumulative amounts of all three S fractions in leachates over a 10-week incubation period in camp than in non-camp soils, suggesting that higher mineralization occurred in camp soils. Cumulative amounts of mineralized S from camp and non-camp soils showed a linear relationship with duration of incubation (R ²0.985^***), while the cumulative release of soluble organic S followed a quadratic relationship (R ²0.975^***). A significant proportion (14.6%–40.8%) of total S release in KCl leachates was soluble organic S, indcating that organic S should be taken into account when assessing S mineralization. Mineralized S and soluble organic S were best correlated with 0.01 M CaCl₂-extractable soil inorganic S (R ²=0.767^***) and 0.04 M Ca(H₂PO₄)₂-extractable soil inorganic S(R ²=0.823^***), respectively. Soil sulphate retention capacity was found to influence amounts of mineralized S and soluble organic S, and thus periodic leaching with KCl to remove mineralized S from soils may not adequately reflect the extent of soil S mineralization in high sulphate-retentive soils. In low (<10%) sulphateretentive soils, increasing the superphosphate applications from 188 to 376 kg ha^–1 year^–1 increased S mineralization but not amounts of C-bonded and hydriodic acid-reducible soil S fractions.     

酸性黄壤施用磷石膏对高粱营养生长和膜保护酶的影响

采用盆栽试验, 研究了贵州强酸性(pH 4.3)黄壤施用磷石膏对高粱生长、养分平衡、细胞膜保护酶活性的影响.结果表明, 在强酸性土壤上种植耐铝能力弱的高粱, 铝毒害明显, 即使施用足量的氮磷钾肥, 作物也生长不良.施用磷石膏和石灰后高粱出苗和生长正常, 各生物学性状均极显著优于对照, 施磷石膏高粱长势优于施石灰处理;高粱干物质量与磷石膏(X1)、石灰(X2)的施用量呈二次曲线变化(回归方程分别为: Yw=6.88+11.92X1-1.65X12, R=0.983**;Yw=6.88+6.39X2-0.72X22, R=0.996**);磷石膏降低酸性黄壤铝毒、提高植物钙含量的效果略逊于石灰, 在提高植物营养3要素(特别是磷、钾元素)的作用方面优于石灰, 施磷石膏植株磷含量是石灰处理的1.17～2.43倍;施高量磷石膏的高粱植株氮/磷、氮/钾、钾/磷比值分别为6.8～7.1、1.2～1.3和5.4～5.6, 比值适中、变幅小, 氮/铝、磷/铝、钾/铝、钙/铝比值提高, 改善和调节了高粱体内氮、磷、钾、钙养分的平衡.高粱叶片细胞膜保护酶(SOD、CAT和POD)活性分析表明, 施磷石膏、石灰后SOD和CAT活性增加, POD活性和脯氨酸含量下降, 施磷石膏效果优于石灰.     

Mobilität und Pflanzenverfügbarkeit von Phosphor aus organischen und anorganischen Formen in der Rhizosphäre von Lolium perenne

Mobility and availability of phosphorus from organic and inorganic forms in the rhizosphere of Lolium perenne 1.) In pots (sandwich-technique according to Helal and Sauerbeck), where the soil (A_p-horizon of an Alfisol-Udalf from loess) was separated into a root chamber and an outer chamber (up to 10 mm away from the root chamber), the phosphorus (P) availability of super-P, rock-P (Hyper-P) and organic P [myo-inositol-2-mono-P di(cyclohexylammonium) salt] was studied. P was applied at a rate of 50 mg P kg^?1 soil only in the outer chamber. This P fertilization resulted in significant increase of CAL- and water-extractable P in the treatment with organic P and super-P compared to the P₀ treatment. During 6 cuts of Lolium perenne organic P showed the same effect on the P-uptake of plants as super-P. Compared to the treatment without P, rock-P had no effect on the P-uptake. The higher P-uptake of Lolium perenne both in the super-P- and organic P-treatment was reflected at the end of the experiment only by the CAL-P content differences between root chamber and outer chamber. The highest activity of acid phosphatase, measured in air dried soil was found in the root chamber of the organic P treatment The content of EUF extractable organic P was significantly higher in the root chamber of the treatments with super-P and organic P than in the P₀- and rock-P-treatment. 2.) The P elution was studied with 2 soils (A_p-horizon of an Alfisol-Udalf from loess pH: 6.4; A_h-horizon of a basaltic brown soil pH: 5.4) under lab conditions in columns. In the super-P-and organic P-treatment leached P was mainly inorganic. In the soil with low pH value (5.4), P was leached in the treatment with super-P or organic P in a higher amount of organic P than in the soil with pH 6.4. The results of this experiment do not show in which form the applied organic P was moved to the roots or displaced in the soil.     

Assessment of ZN Interaction with Nutrient Cations in Alkaline Soil and its Effect on Plant Growth

An experiment was conducted to assess the zinc (Zn) availability to wheat in alkaline soils during Rabi 2009–2010. Wheat seedlings in pots having 2 kg alkaline sandy soil per pot were treated with 5, 10 and 15 kg Zn ha^?1 as soil and with 0.5 and 1.0% zinc sulfate (ZnSO₄) as foliar application. Results showed that Zn increasing levels in soil helped in phosphorus uptake up to boot stage but its conversion to grain portion lacked in Zn treated plants. Potassium (K) uptake also increased up to 6.24% in boot stage with treatment of 10 kg Zn ha^?1 + 1.0% ZnSO₄ foliar spray. Zinc (Zn) concentration increased in plant tissues with the increasing level of Zn application but this disturbed the phosphorus (P)-Zn interaction and, thus, both of the nutrients were found in lesser quantities in grains compared to the control. Despite of the apparent sufficient Zn level in soil (1.95 mg kg^?1), improvement in growth and yield parameters with Zn application indicate that the soil was Zn deplete in terms of plant available Zn. The above findings suggest that the figure Zn sufficiency in alkaline soil (1.0 mg kg^?1) should be revised in accordance to the nature and type of soils. Furthermore, foliar application of Zn up to 1.0% progressively increased yield but not significantly; and it was recommended that higher concentrations might be used to confirm foliar application of Zn as a successful strategy for increasing plant zinc levels.