Biochar addition drives soil aggregation and carbon sequestration in aggregate fractions from an intensive agricultural system

Purpose

Biochar application is deemed to modify soil properties, but current research has been mostly conducted on the degraded land in tropical regions. Using six consecutive years of biochar field trial, we investigated effects of biochar on soil aggregates, structural stability, and soil organic carbon (SOC) and black C (BC) concentrations in aggregate fractions. The findings have important implications in managing soil structure and SOC sequestration in high fertility soils of the temperate areas.

Materials and methods

The study had four treatments: control; biochar rate at 4.5 (B4.5) and biochar rate at 9.0 t ha^?1 year^?1 (B9.0); and straw return (SR). Soil samples were collected from 0–10-cm layer, and aggregate size distribution was determined with the wet-sieving method. Then, the mean weight diameter (MWD) of aggregates and the aggregate ratio (AR), i.e., the ratio of the >250 μm to the 53–250 μm size were calculated to assess the structural stability. Total SOC and BC concentrations in bulk soil (<2 mm) and separated fractions (i.e., >2000, 250–2000, 53–250, and <53 μm) were measured.

Results and discussion

The B4.5 and B9.0 significantly increased macroaggregate (250–2000 μm) and MWD and AR indices relative to the control. Comparing to the SR, the improvements in soil aggregation under biochar treatments were limited. Additionally, more SOC in larger fractions (>2000, 250–2000, and 53–250 μm) and BC in extracted fractions under biochar soils were observed. These results implied that biochar addition enhanced both native SOC and BC physical protection by aggregation.

Conclusions

Biochar application is effective in mediating soil aggregation, and thus improves both native SOC and BC stabilization in an intensive cropping system of North China.

     

Effect of Chromium and Lead on Yield,Chemical Composition of Essential Oil,and Accumulation of Heavy Metals of Mint Species

A pot culture experiment was conducted to investigate the effect of increasing levels (30.0 and 60.0 mg kg^?1 soil) of chromium and lead on the yield, chemical composition of essential oil, and phytoaccumulation of heavy metals of three mint species (Mentha arvensis, M. piperita, and M. citrata). The fresh herbage yield of M. arvensis was not significantly affected by the application of chromium and lead, but its essential oil yield was significantly decreased by the application of chromium and lead as compared to the control. The fresh herbage, root yield, and essential oil yield of M. piperita were significantly increased and those of M. citrata were decreased by the increase in the levels of chromium and lead applications. The levels of α-pinene, β-pinene, sabinene, β-myrcene, limonene, menthone, and isomenthone in M. arvensis and M. piperita oil and of sabinene, pinene, and linalyl acetate in M. citrata oil were considerably affected by the application of chromium and lead to soils as compared to control plants. The concentrations of chromium in shoots and roots of mint species significantly increased as the levels of chromium in soil increased. The increases in the levels of lead in soil enhanced the concentrations of lead in the shoots and roots of mint species as compared to the control. The accumulations of chromium and lead were greater in the roots than in the shoots in all the three species of mint. Mentha piperita was found to be the most suitable crop for cultivation in the chromium- and lead-contaminated soils, followed by M. arvensis and M. citrata.     

Analyzing the Relation between Loss-on-Ignition and Other Methods of Soil Organic Carbon Determination in a Tropical Cloud Forest (Mexico)

The objective of this study was to analyze the relationship between soil organic carbon content, determined by dry combustion (%OC_LECO) and the Walkley–Black method (%OC_WB), and loss on ignition (LOI). Soil samples were collected from noncalcareous O and A1 horizons within a tropical cloud forest. Linear regression equations were developed to estimate organic carbon from LOI. The applicability of the predictive equations was evaluated by comparison of measured and predicted organic carbon data for independent soil samples. The results showed that the LOI method produced a better linear relationship with the %OC_LECO (R ² = 0.96, P < 0.001) than with the %OC_WB (R ² = 0.88, P <0.001) method. These results also showed that %OC_WB and %OC_LECO prediction equations underestimate and overestimate soil organic carbon by 0.74% and 0.56%, respectively. This study suggests that LOI may be a good estimator of soil organic carbon for noncalcareous O and A1 horizons in a tropical cloud forest.     

Effects of Lead Forms and Organic Acids on the Growth and Uptake of Lead in Hydroponically Grown Wheat

This study investigated the effects of lead (Pb) form (free or complexed) and type and concentration of chelants [citric acid and ethylenediaminetetraacetic acid (EDTA)] on the growth and ability of wheat to accumulate Pb. Wheat variety Auqab-2000 was exposed to four levels of EDTA and citric acid (0, 500, 1000, and 1500 μM) in the presence of Pb (1000 μM). Both the free Pb (1000 μM) and high concentration (1500 μM) of EDTA and citric acid reduced the plant biomass. Without the addition of chelants, only a little Pb was accumulated by wheat shoots. This demonstrates that organic acids used in enhanced phytoextraction applications do not merely serve to increase metal mobility and plant availability but also can help to increase translocation rates of metals absorbed by the plant roots. Greater translocation of Pb from roots to shoots was observed with EDTA than that with citric acid.     

Soil porosity in physically separated fractions and its role in SOC protection

Purpose

Processes that lead to soil organic carbon (SOC) protection depend on both soil porosity and structure organization, as well as chemical and biological properties. In particular, the soil micro-nano porosity (<30 μm) regulates microorganism accessibility to the soil pore system and offers surfaces for organic carbon adsorption and intercalation into soil minerals. The aim of this work was to investigate how pore size distribution can selectively protect specific carbon pools in different aggregate size fractions, by considering the effects of long-term application of farmyard manure (FYM) and mineral (Min) fertilization.

Materials and methods

Macroaggregates (250–2000 μm), microaggregates (53–250 μm), and silt–clay (<53 μm) fractions of three different soils (clayey, peaty, and sandy) were separated by wet sieving technique and then subjected to chemical and physical analysis. Sample porosity and pore size distribution were analyzed using mercury intrusion porosimetry (MIP), while SOC chemical structure was characterized by means of nuclear magnetic resonance (¹³C cross-polarization–magic angle spinning nuclear magnetic resonance (CP MAS ¹³C NMR)) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopies.

Results and discussion

Results showed that FYM increased organic (OC) and humic carbon (HC) content compared to the Min fertilization and unfertilized soils. However, it caused a gradual decrease in O,N-alkyl C, and alkyl C of humic C from macroaggregate to silt–clay fractions, suggesting an advanced state of humic component degradation as revealed by CP MAS ¹³C NMR, DRIFT analyses. MIP analysis showed a clear increase of micropores (5–30 μm) and cryptopores (0.0035–0.1 μm) from macroaggregate to silt–clay fractions, while minor differences were observed among the treatments. The application of principal component analysis to mineral soil fractions identified the formation of three main clusters, where (i) macroaggregates of clayey soil were mainly associated to cryptopores and OC and (ii) microaggregates and silt–clay fraction were mainly isolated by carbonyl C, ultramicropores, and total porosity. The third cluster was associated with medium and fine sand of the sand soil fraction as coupled with O,N-alkyl C, anomeric C, mesopores, and HC/OC ratio.

Conclusions

Overall, this study indicates that pore size distribution may be a valuable indicator of soil capacity to sequester carbon, due to its direct influence on SOC linkages with soil aggregates and the positive effects against SOC decomposition phenomena. In this context, micropore- to nanopore-dominated structures (e.g., clayey soil) were able to protect OC compounds by interacting with mineral surfaces and intercalation with phyllosilicates, while meso/macropore-dominated structures (i.e., sandy soil) exhibited their low ability to protect the organic components.

     

Wheat straw and its biochar have contrasting effects on inorganic N retention and N2O production in a cultivated Black Chernozem

A laboratory incubation experiment was conducted to investigate the effects of direct incorporation of either wheat straw or its biochar into a cultivated Chernozem on gross N transformations calculated by the ¹⁵N pool dilution technique and nitrous oxide (N₂O) production rates. Incorporation of wheat straw stimulated gross NH ₄ ⁺ (ammonium) and NO ₃ ^? (nitrate) immobilization rates by 302 and 95.2?%, respectively, suppressed gross nitrification rates by 32.2?%, and increased N₂O production by 37.7?%. In contrast, the addition of a biochar produced from the wheat straw did not influence any of the above N cycling processes. Therefore, application of biochar could be a possible management strategy for long-term C sequestration (through soil storage of stable C contained in the biochar) in soils without increasing N₂O production rates, but could not effectively immobilize NO ₃ ^? in the soil.     

Effect of Long-Term Fertilizer Management and Crop Rotations on Accumulation and Downward Movement of Phosphorus in Semi-Arid Subtropical Irrigated Soils

Crop species and their varieties vary in phosphorus (P) requirements for optimum production and response to P application. As crop recovery of added P often ranges from 10 to 40%, the rest accumulates in soil and may create potential for P leaching, depending upon the soil characteristics, duration of P applications, and cropping systems. Accumulation and distribution of Olsen P (plant-available labile P), total inorganic P, and total organic P were investigated in soil profiles of three field experiments differing in rate (9–44 kg P ha^–1), frequency (applied once or twice annually), and duration (4–34 years) of fertilizer P applications, crop rotations, soil characteristics, and irrigation pattern (upland irrigated and flooded-rice crop) in a subtropical region. Profile samples were collected from soil depths of 0–15, 15–30, 30–60, 60–90, 90–120, and 120–150 cm of different treatments in these experiments and analyzed for different forms of P and soil characteristics. The results revealed that (i) annual applications of fertilizer P either to one crop (alternative-applied P) or to both crops (cumulative) led to the accumulation of residual fertilizer P in the form of Olsen P, varying from 44 to 148 kg P ha^–1, and the magnitude of accumulation was proportional to applied fertilizer P rate, frequency, and duration; (ii) majority of residual fertilizer P accumulated as inorganic P (74–89%) followed by organic P (11–26%) and Olsen P (9–19%), illustrating that the inorganic P pool is a major sink for fertilizer P; (iii) application of fertilizer nitrogen (N) and potassium (K) alone or in combination with fertilizer P did not affect residual fertilizer P accumulation in soil profile; (iv) incorporation of farmyard manure enhanced the P enrichment of soil profile; (v) irrigation pattern, soil pH (7.1–7.7), and calcium carbonate (CaCO₃) (trace–0.33%) did not influence P movement to deeper soil layers; silt, clay, and soil organic C (SOC) showed strong relationships with Olsen P (r = 0.827, 0.938, and 0.464, P < 0.01) and enhanced the retention of labile P in the plow layer; and (vi) only 6–29% total residual P moved beyond 30 cm deep in fine-textured soils under 22-year rice (Oryza sativa L.)–wheat (Triticum aestivum L.) and 34-year maize (Zea maize L.)–wheat rotations, whereas 41, 27, 20, 9, and 3% were located in soil layers 0–30, 30–60, 60–90, 90–120, and 120–150 cm deep, respectively, in coarse-textured soil profile under 4-year peanut (Arachis hypogaea L.)–sunflower (Helianthus annuus L.) field. These findings confirmed that interplay between the fertilizer P management (alternative vis-à-vis cumulative P application and optimal vis-à-vis excessive rates of fertilizer P in different crop rotations), amount of labile P accumulated in soil profile, and soil characteristics (silt, clay, and SOC) largely controlled the downward movement and resultant potential for P leaching in subtropical irrigated soils.     

Analytical studies on the productive efficiency of nitrogen in rice

The concept of productive efficiency of nutrients has been discussed at length by Kimura and Chiba (1943)¹⁾. Considering that the effect of a nutrient for the production of grain and straw may be divided into several growing periods of plant.life, Kimura and Chiba (1943) conducted water culture experiments to study the effect of nitrogen absorbed at a definite period on the production of grain and straw. The total productive efficiency was divided into several partial efficiencies based upon the growing period of the rice plant. The following is a summary of their findings.     

Agronomic Implications of the Application of Lime plus Gypsum By‐products to a Hyperdistric Acrisol from Western Spain

Abstract: A laboratory experiment involving the use of leaching columns reproducing the topmost portion of a Hyperdystric Acrisol (FAO 1998 FAO. 1998. World reference base for soil resources, Rome: FAO, ISRIC, and ISSS. (World Soil Resources Report No. 84) [Google Scholar]) or plinthic Palexerult (Soil Survey Staff 2003 Soil Survey Staff. 2003. Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys, Washington, D.C.: U.S. Government Printing Office. (Agriculture Handbook No. 436) [Google Scholar]) treated in its Ap horizon with sugar foam wastes and phosphogypsum was conducted. The amendments increased the contents in exchangeable calcium (Ca) of the Ap horizon and, to a lesser extent, also that of the AB horizon. However, the contents in exchangeable magnesium (Mg) and sodium (Na) decreased as much in Ap as they did in AB; by contrast, the potassium (K) content exhibited a less marked decrease. The potassium chloride (KCl)–extractable aluminium (Al) of the Ap horizon was dramatically decreased much more than that of the AB horizon by the amendments. In the soil solution from Ap, the amendments raised the pH and decreased the Al concentration; in that from AB, however, they caused an initial pH decrease, a tendency that reversed as the gypsum was leached and eventually led to the pH exceeding that in the soil solution from control. The first few water extractions exhibited increased Mg concentration. This trend was reversed in the second leaching cycle, where the concentrations of Mg in the amended columns were lower than those in the controls. In the soil solution, the variation of the Ca and sulphate (SO₄ ^2–) concentrations was influenced by the salt‐sorption effect. The total Al content in soil solution from AB increased during the first leaching cycle and then decreased during the second. The amendments decreased the activities of Al³⁺, AlOH⁺², and Al(OH)₂ ⁺ in the Ap horizon and increased those of Al³⁺, AlSO₄ ⁺, Al(SO₄)₂ ^?, and AlF⁺² in the first leaching cycle in the AB horizon. The productivity of the Ap horizon after the treatments was assessed using a wheat crop (T. aestivum, var. ‘Jabato’) in a greenhouse.     

Dynamics of Forms of Inorganic Phosphorus in Soil under Coffee Plants as a Function of Successive Annual Additions of the Nutrient

Phosphorus (P) dynamics and availability in soils are influenced by P fertilization. This paper aimed to evaluate inorganic P fractions bonded to calcium (Ca), iron (Fe), and aluminum (Al), associating them with soil mineralogy. The experiment was carried out using an acidic kaolinitic–oxidic soil, located in an irrigated area cultivated with coffee plants (Coffee arabica L.), submitted to successive annual fertilizations with triple superphosphate doses of 0, 50, 100 200, and 400 kg ha^?1 phosphorus pentoxide (P₂O₅) in randomized blocks with three replications. Phosphorus fractions were determined in soil samples collected at two depths, 0–10 and 10–20 cm, according to the methodology used by Chang and Jackson (1957 Chang, S. C. and Jackson, M. L. 1957. Fractionation of soil phosphorus. Soil Science, 84: 133–144. [Crossref] , [Google Scholar]). The inorganic P fractions presented the following sequence: P-Al > P-Fe > P-Ca. The dynamics of forms of inorganic P showed that P-Al is controlling the P bioavailability as a result of an acidic pH and a very simple and thermodynamically stable clay mineralogy, typical of very weathered and old tropical soils.     

Suitability of extractant for soil available silicon and silicon response to upland paddy grown on alkaline soils of central India

Abstract

Several silicon (Si) extractants are being employed in different countries mostly for lowland acidic soils. Present investigation was conducted to evaluate suitable extractants for upland paddy grown on alkaline soils. Available Si was extracted by using ten different extractants. Tris buffer pH 7.0 (1:10) in Inceptisols showed positively highest and significant correlation with grain yield (r?=?0.870), grain Si uptake (r?=?0.887), straw yield (r?=?0.852), and straw Si uptake (r?=?0.919). However, 0.5?M acetic acid (1:2.5) in Vertisols showed positively highest and significant correlation with grain yield (r?=?0.810), grain Si uptake (r?=?0.852), straw yield (r?=?0.850), and straw Si uptake (r?=?0.929). The application of Si @ 200?kg ha^?1 along with chemical fertilizers significantly increased yield and nutrient uptake of upland paddy on Vertisols. Tris buffer pH 7.0 (1:10) and 0.5?M acetic acid (1:2.5) were suitable extractant for Inceptisols and Vertisols, respectively based on its correlation with yield and nutrient uptake.     

Nitrogen Transformation as Influenced by Soil Microbial Nitrogen under Carbon Dioxide Enrichment Induced in Created Riparian Wetlands

Limited research has been conducted on how atmospheric carbon dioxide (CO₂) affects water and soil nitrogen (N) transformation in wetland ecosystems. A stable isotope technique is suitable for conducting a detailed investigation of mechanistic nutrient transformations. Nutrient ammonium sulfate (NH₄)₂SO₄ input in culture water under elevated CO₂ (700 μL L^?1) and ambient CO₂ (380 μL L^?1) was studied to analyze N transformations with N blanks for both water and soil. It was measured by ¹⁵N pool dilution using analytical equations in a riparian wetland during a 3-month period. Soil gross ammonium (NH₄ ⁺) mineralization and consumption rates increased significantly by 22% and 404%, Whereas those of water decreased greatly by??57% and??57% respectively in enriched CO₂. In contrast, gross nitrate (NO₃ ^?) consumption and nitrification rates of soil decreased by??11% and??14% and those of water increased by 29% and 27% respectively in enrichment CO₂. These may be due to the extremely high soil microbial biomass nitrogen (MBN), which increased by 94% in elevated soil. The results can show when CO₂ concentrations are going to rise in the future. Consequently soil microbial activity initiates the decreased N concentration in sediment and increased N concentration in overlying water in riparian wetland ecosystems.     

Landscape Scale Variation in Nitrous Oxide Flux Along a Typical Northeastern US Topographic Gradient in the Early Summer

Most previous studies investigating controls on nitrous oxide (N₂O) emissions have relied on plot-scale experiments and focused on relative homogeneous biotic and abiotic factors such as soil, vegetation, and moisture. We studied soil N₂O flux at 11 chamber sites along a 620 m topographic gradient in upstate New York, USA, aiming at identifying patterns of N₂O flux and correlating them to hydrological factors and soil substrate properties along the gradient. The topographic gradient is a complex slope with an overall gradient of 8%, covering plant communities of pasture, forest, alfalfa field, and riparian area from the top to the bottom. Mean fluxes of N₂O measured from late March to May ranged from 4.45 to 343 μg N m^?2 h^?1, and these fluxes were not significantly different among chamber sites located in different communities. With the descending of the slope, N₂O fluxes increased with the increase of soil water content, except for the riparian site. Statistically, N₂O fluxes were not strongly correlated with soil temperature, soil bulk density, and water filled pore space (p?>?0.05). Instead, strong correlations (p?2O fluxes and soil C and N content including NO ₃ ^? , NH ₄ ⁺ , total organic carbon, and C/N ratio. Multiple linear regression analyses including both soil physical and substrate properties highlighted the significance of soil NO ₃ ^? content and C/N ratio in regulating N₂O fluxes along the gradient.     

Bioresource Nutrient Recycling and Its Relationship with Biofertility Indicators of Soil Health and Nutrient Dynamics in Rice–Wheat Cropping System

A field experiment was conducted for 3 years during 2006–2009 in India to study the effects of plant nutrient recycling through crop residue management, green manuring, and fertility levels on yield attributes, crop productivity, nutrient uptake, and biofertility indicators of soil health in a rice–wheat cropping system. The study revealed that soil microbial biomass carbon (SMBC) and carbon dioxide (CO₂) evolution were significantly greatest under crop residue incorporation (CRI) + Sesbania green manuring (SGM) treatment and were found at levels of 364 μg g^?1 soil and 1.75 μg g^?1 soil h^?1, respectively; these were increased significantly by recycling of organic residues. Activities of dehydrogenase and phosphatase enzymes increased significantly after 3 years, with maximum activity under CRI + SGM treatment. The CRI with or without SGM significantly influenced the plant height, number of tillers m^?2, number of grains panicle^?1 or ear^?1, and 1000-grain weight. Mean yield data of rice and wheat revealed that CRI or crop residue burning (CRB) resulted in slightly greater yield over crop residue removal (CRR) treatment. The CRI + SGM treatment again observed significantly greatest grain yields of 7.54 and 5.84 t ha^?1 and straw yields of 8.42 and 6.36 t ha^?1 in rice and wheat, respectively, over other crop residue management treatments. Total nitrogen (N), phosphorus (P) and potassium (K) uptake in rice–wheat system was greatest with amounts of 206.7, 37.2, and 205.6 kg ha^?1, respectively, in CRI + SGM treatment. Fertility levels significantly influenced the rice and wheat yield with greatest grain yields of 6.66 and 5.68 t ha^?1 and straw yields of 7.94 and 5.89 t ha^?1 in rice and wheat, respectively, with the application of 150% of recommended NPK. Total NPK uptake in rice–wheat system also increased significantly with increase in fertility levels with greatest magnitude by supplying 150% of recommended NPK. Overall, nutrient recycling through incorporation of crop residues and Sesbania green manuring along with inorganics greatly improved the crop productivity, nutrient uptake, and biofertility indicators of soil health with substantial influence on SMBC, CO₂ evolution, and dehydrogenase and phosphatase enzyme activities. This indicates that crop residue management along with Sesbania green manuring practice could be a better option for nutrient recycling to sustain the crop productivity and soil health in intensive rice–wheat cropping system in India as well as in similar global agroecological situations, especially in China, Pakistan, and Bangladesh.     

Impact of organic matter addition on pH change of paddy soils

Purpose

The objective of the present study was to explore the effect of initial pH on the decomposition rate of plant residues and the effect of residue type on soil pH change in three different paddy soils.

Materials and methods

Two variable charge paddy soils (Psammaquent soil and Plinthudult soil) and one constant charge paddy soil (Paleudalfs soil) were used to be incubated at 45 % of field capacity for 105 days at 25 °C in the dark after three plant residues (Chinese milk vetch, wheat straw, and rice straw) were separately added at a level of 12 g?kg^?1 soil. Soil pH, CO₂ escaped, DOC, DON, MBC, MBN, NH ₄ ⁺ , and NO ₃ ^? during the incubation period were dynamically determined.

Results and discussion

Addition of the residues increased soil pH by 0.1–0.8 U, and pH reached a maximum in the Psammaquent and Plinthudult soils with low initial pH at day 105 but at day 3 in the Paleudalfs soil with high initial pH. Incorporation of Chinese milk vetch which had higher concentration of alkalinity (excess cations) and nitrogen increased soil pH more as compared with incorporation of rice and wheat straws. Microbial activity was the highest in Chinese milk vetch treatment, which resulted in the highest increase of soil pH as compared with addition of rice and wheat straws. However, nitrification seemed to be inhibited in the variable charge soils of Psammaquent and Plinthudult but not in the constant charge soil of Paleudalfs.

Conclusions

The effectiveness of increasing soil pH after incorporation of the plant materials would be longer in low initial pH soils of Psammaquent and Plinthudult than in high initial pH soil of Paleudalfs. In order to achieve the same degree of pH improvement, higher amounts of plant residues should be applied in constant charge soils than in variable charge soils.     

Chemical Characterization of Rain and Fog Water in the Cervenohorske Sedlo (Hruby Jesenik Mountains, Czech Republic)

Field study at the Cervenohorske sedlo (1,013 m a.s.l.) (Hruby Jesenik Mountains, the Czech Republic, Central Europe) during 1999–2002 has been conducted in order to analyse the chemistry of rain/snow water using bulk and throughfall collector and fog/cloud water using modified passive Grunow collector. Fog water input to coniferous forest (Picea abies) was quantified using canopy balance method. For all samples pH, and the concentrations of $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ , Ca²⁺, K⁺, Mg²⁺, Na⁺, Cl^?, $ {\text{NO}}^{{\text{ - }}}_{{\text{3}}} $ , and $ {\text{SO}}^{{{\text{2 - }}}}_{{\text{4}}} $ were measured. The volume-weighted mean pH value varied from 4.92 to 5.43 in open bulk precipitation, from 4.30 to 4.71 in throughfall and from 4.66 to 5.23 in fog water. The fog droplets generally contain higher ion concentrations than rainwater. The related enrichment factors lie between 1.1 and 10.7 for the relevant species. The fog samples exhibit higher concentrations of $ {\text{NO}}^{{\text{ - }}}_{{\text{3}}} $ and $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ as compared to the bulk samples during 2000–2002. $ {\text{NO}}^{{\text{ - }}}_{{\text{3}}} $ are 5.7–10.7 times more concentrated in fog water and $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ are 3.4–7.2 times more concentrated in fog water. These differences may result from the height and characteristics of formation of the droplets. Based on canopy balance method, the annual fog water inputs were estimated to be 22 and 19% of rain and snow annual amounts in 1999 and 2000, respectively. For $ {\text{NO}}^{{\text{ - }}}_{{\text{3}}} $ , $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ , and $ {\text{SO}}^{{{\text{2 - }}}}_{{\text{4}}} $ , the contribution of fog deposition in total (bulk + fog) deposition is estimated as 54, 47, and 42%, respectively.     

Forms of phosphorus in soils of Rajasthan

Phosphorus in soils is found to be present in organic combinations, inorganic form or in adsorted form on clay complex. Different forms of soil phosphorus have different solubilities and consequent availability in soils. A knowledge about the content and types of soil phosphorus enables one to understand the organic behaviour and predict the response of added phosphatic material to crops (Parker 1953). The form in which phosphorus is present in soil is directly related to pH and CaCO₃ in the soil as well as the intensity of the development of the soil. Williams (1950) has found that in calcareous soils of South Australja most of the phosphorus was in combination with calcium, whereas in acid soils it forms compounds with alumina and iron. Hibbard (1931) concluded that in alkaline and calcareous soils, phosphorus exists mostly in the form of hydroxyapatite, chloroapatite, and the like. Kanwar and Grewal (1959) studied fractionation of phosphorus in Punjab soils and reported that differences in the nature and amounts of the phosphorus present in acid and alkaline soils of the State explain the causes of different phosphatic fertilizer responses to the crops. A similar report has been given by Goel and Agarwal (1959) who studied the fractionation of phosphorus in Kanpur soils and concluded that the mature soils are rich in iron and aluminium bound phosphorus and respond better to phosphatic fertilizer than the immature soils rich in Ca²⁺ and Mg²⁺ bound phosphorus. Chai Moo Cnoo and Caldwell (1959) reported that Fe³⁺ and Al³⁺ bound phosphorus was abundant in acid soils while Ca²⁺ and Mg²⁺ bound phosphorus content in alkaline soils, and organic phosphorus agreed, in general, with the content of organic matter, with some deviations.     

Interaction effect of nitrogen,phosphorus, and zinc fertilization on growth,yield, and nutrient contents of aromatic rice varieties

Abstract

Studies on nutrient interactions in aromatic rice are needed for proper understanding of impact of imbalanced use of nutrients in the era of multi and micro-nutrient deficiencies. A pot experiment was conducted during the rainy/wet season (June–October) of 2013 at New Delhi, to study the interaction effects of two levels each of nitrogen (N) (0 and 120?kg?ha^?1), phosphorus (P; 0 and 25.8?kg?ha^?1), and zinc (Zn; 0 and 5?kg?ha^?1) in two aromatic rice (Oryza sativa L.) varieties, viz. Pusa Rice Hybrid 10 and Pusa Basmati 1121. Application of N, P, and Zn resulted in increase of dry matter (0.91, 0.32, and 0.24?g plant^?1, respectively) 60?days after sowing (DAS) and grain yield of rice (3.68, 1.67, and 1.17?g plant^?1). The increase in yield of rice owing to N application was relatively higher by 0.98, 0.22, and 1.05?g plant^?1, respectively, when either P or Zn or both were applied with N than alone application of N, indicating synergetic effect of P and Zn application with N. The higher concentration and uptake of K in grain (0.25% vs 0.10%) and straw (1.32% vs 0.94%) were observed in the treatment received N than no N, though K was applied uniformly in all the treatments. It indicates positive interaction of N and K. The higher uptake of P in grain and straw was observed when P was applied with N and Zn (3.34 and 2.15?mg plant^?1), or with N (3.26 and 2.11?mg plant^?1) signifying positive effect of N on P uptake in rice.     

Formulation of humic substances coated fertilizer and its use to enhance K fertilizer use efficiency for tomato under greenhouse conditions

A greenhouse experiment was conducted at Land Resources Research Institute, NARC, Islamabad to examine the impact of humic substances (HSs) coating on potassium fertilizers use efficiency. Tomato variety “Rio Grande” was used. The treatments applied were T1= Control (N, P at 250 and100?mg kg^?1 respectively), T2?=?N, P?+?K at 200?mg kg^?1 as SOP, T3?=?N, P?+?K at 200?mg kg^?1 as NPK blend, T4?=?N, P?+?K at 200?mg kg^?1 HSs coated SOP) and T5?=?N, P?+?K at 200?mg kg^?1 HSs coated NPK blend. Results indicated a positive impact of sole and HSs coated products on agronomic traits, nutrient concentration, fruit quality traits, flower number, fruit umber, fruit weight, chlorophyll contents, fresh and dry biomass, tissue water contents, diameter and fruit mineral composition. The response of afore said traits to applied treatment varied.     

Prediction of potentially mineralizable N from amidohydrolase activities in a manure-applied, corn residue-amended soil

Prediction of potentially mineralizable N as an important N pool from soil amidohydrolases was investigated. Composite soil samples were collected from plots of a field experiment in which 0, 50 and 100 Mg cow manure ha⁻¹ year⁻¹ had been applied for five consecutive years. The soils were treated with corn shoots or roots or remained untreated in a factorial combination with the manure treatments, with three replications. The mineralized inorganic N was measured periodically in 20-week incubations and potentially mineralizable N (N₀) was calculated based on a first-order kinetic model. Urease, l-glutaminase and l-asparaginase activities were measured before and after incubation. The values of N₀ ranged from 208.6 in the controls to 388.4 in soils that had received 50 Mg ha⁻¹ year⁻¹ of cow manure and were amended with corn shoots. Corn residue amendment in the manure treated soils, increased the values of N₀ or changed the N mineralization kinetic pattern from a first-order to a zero-order model. According to a relative sensitivity index, l-asparaginase was the most sensitive enzyme to the treatments. Multiple regression analysis revealed that 92% of N₀ variations can be described by the activities of urease and l-asparaginase and therefore the soil amidohydrolase activities have the potential to evaluate potentially mineralizable N.