Aeric Endoaquept Research Articles

The relationship between soil chemical properties and phytochemical contents of non-centrifugal cane brown sugar in Thailand

In Thailand, NCS products from sugarcane are traditionally produced by the evaporation of raw cane juice obtained from a pressing machine. NCS products enhance flavor and supply both energy and nutritional value through the vitamins, minerals and bioactive compounds which occur naturally in sugarcane produced without molasses removal. Soil quality and choice of cane cultivar affect the nutraceutical components of brown cane sugar products grown in diverse areas. Differences in nutraceutical components of NCS products obtained by traditional processes were investigated form sugarcane planted in two different areas of Sukhothai Province, with varied soil qualities based on the same cane variety (LK-92-11). The soil classification was carried out according to the Staff Soil Survey (2014) and classified as Aquic Haplustalfs and Aeric Endoaquepts soil types. NCS products from sugarcane planted in Aquic Haplustalfs contained high nutraceuticals and antioxidant activities compared with sugarcane planted in Aeric Endoaquepts. EC and potassium content of the soils showed significant negative correlation with policosanols, total phenolics, total flavonoid contents, and antioxidant activities of the NCS products. Pearson’s correlation indicated that higher electrical conductivity and potassium content of the soils were attributable to lower amounts of policosanols, total phenolics, and total flavonoid contents as well as antioxidant activities. We suggested that electrical conductivity and potassium content of soil should be concerned and monitored to obtain high level of nutraceutical of NCS product made from sugarcane

Land suitability evaluation according to agroecological zone information for agricultural commodity development in coastal area of Tegal Central Java Indonesia

The Agroecological Zone (AEZ) is an information system to determine the potential of land resources. Based on that, the suitability of plants and their land management technology can be identified. The evaluation of land suitability of coastal areas in Tegal District was carried out using matching method between growing requirements for commodities and land characteristics of AEZ data. AEZ identification results show that the coastal area consists of three zones, namely Zone A, alluvial plains with Typic Endoaquepts and Aeric Endoaquepts soil types; Zone B, Fluvio-marine plains with Typic Endoaquepts soil types; and Zone C, coastal areas with Typic Udipsamments soil types. Based on the agroecological characteristics, the coastal area is suitable for crops development and fisheries. The suitable agricultural commodities namely rice, water melon, sugar cane and jasmine, which correspond to class 1 (S1) for zones A and B; red chilies and shallots, class 2 (S2) which is suitable for zones A and B. While zone C is identified as less suitable for food crops or horticulture, due to limiting factors such as poor oxygen availability and poor root conditions.

Effect of Tillage and Water Management on Aggregate Stability of a Gleyic Cambisols

The objective of this study was to determine the effect of tillage and water management on the physical stability of irrigated lowland rice field, in Kwalkwalawa, Sokoto State. The experiment was carried out in a farmer`s field, near the Usmanu Danfodiyo University Teaching and Research Farm, Kwalkwalawa, Sokoto State. The coordinates of the area were taken using global positioning system (GPS) model Garmin etrex 20.0, which shows that the area is located on (N13°05.963”E005°12.650” and at 252 m asl). The soils of the study area were classified as Aeric Endoaquepts at subgroup level in the USDA Soil Taxonomy System which correlated with Gleyic Cambisols in the World Reference Base. The treatments consisted of factorial combination of two tillage systems (conventional tillage (CT) and reduced tillage (RT), three irrigation water managements (Alternate one, two and three days irrigation intervals, which were carried out from one week after transplanting to hard dough stage) and three rice varieties (FARO 44, 60 and 61) all laid in a split-plot design and replicated three times. After harvest, disturbed soil samples were collected with the aid of soil auger, prepared and passed through 5 mm sieve for aggregate stability determination. Result reveals that a consistent trend in aggregate size fraction was observed between the two tillage systems in both years, were a significant decrease in values of aggregate fractions of both the CT and RT in 2019 compared to in 2018. Aggregate size fraction of 5-2 mm had a significantly high value of RT compared to CT, 2-0.25 mm fractions were at par (0.41) while a greater value of aggregate fractions for CT in both 0.25-0.005 mm and ˂0.005 mm were observed compared to RT. Alternate days to irrigation and sampling depths increase with a corresponding in all the aggregate size classes in the two years of this study. A significant difference in mean weight diameter (MWD) and geometric mean diameter (GMD) between the two tillage, water management and depth was noticed in both years of the trial where RT and alternate one day had high value while MWD and GMD increase with increasing depth.

Characterization and Classification of Different Rice Growing Soils with Special Emphasis on Soil Organic Carbon Stock in Rajnagar Block of Birbhum District, West Bengal

Characterization and classification of rice growing soils of rainfed region of West Bengal is having an utmost importance for developing optimal agricultural land use planning. In the context of ever increasing food demand under dwindling agricultural land availability, rainfed areas have got the attention for enhancing food grain production for the national food basket. Hence, in the present study, we made an effort to characterize six rice growing soils placed in six different landform situations (plateau top, dissected plateau, plateau fringe, undulating upland, alluvial plains and valley fill) and classify accordingly for resource inventory of Rajnagar block, Birbhum district, West Bengal. Results depicted that, rice is grown mainly in Alfisols and Inceptisols in this block with varying morphological and physico-chemical characteristics. The soils are moderately deep to very deep with sandy loam to clay loam surface texture. Soils of plateau top, dissected plateau, plateau fringe, undulating upland, alluvial plains and valley fill were classified as Typic Haplustalfs, Aeric Endoaqualfs, Typic Haplustalfs, Typic Haplustepts, Aeric Endoaquepts, Typic Haplustalfs, respectively. The double crop rice ecology (rice-mustard) showed significantly (P=0.05) higher surface soil organic carbon (SOC) stock in surface as compared to the other monocrop rice ecologies. Among all the landforms compared, soils of valley fill region had the highest surface SOC stock (14.5 Mg ha-1) followed by plains (10.4 Mg ha-1), plateau fringe (7.7 Mg ha-1), plateau top (8.1 Mg ha-1), dissected plateau (7.2 Mg ha-1) and upland (6.9 Mg ha-1). Significantly (P=0.05) higher total profile SOC stock suggested a better soil health in valley fill and plains as compared to other areas that enhances our understanding about the need of the implementation of carbon management based land use planning for higher future productivity of these soils under environmental sustenance.

Phosphate sorption indices as affected by the calcareousness of soils

An experiment was carried out to study the effects of calcareousness on phosphate sorption indices of soils using three representative calcareous soils, namely Sara (Aquic Eutrochrept), Gopalpur (Aquic Eutrochrept), and Ishurdi (Aeric Haplaquept) series of Bangladesh. Three non-calcareous soils, namely Belabo (Typic dystrudepts), Sonatala (Aeric Endoaquepts) and Ghatail (Aeric Haplaquept) series were also selected for comparison purposes. Phosphate sorption indices of soils were calculated using Langmuir and Freundlich isotherms. Isotherms were constructed taking one gram of air-dried sieved (< 2 mm) soil into a 50 ml centrifuge tube, and subsequently adding seven initial P concentrations, namely 0, 1, 10, 25, 50, 100 and 150 μg/ml to each centrifuge tube employing a soil/solution ratio of 1 : 20 (w/v). According to the Langmuir equation, the amount of phosphate sorbed followed the order: Sonatala > Ghatail > Sara = Gopalpur > Ishurdi > Belabo. The abundance of amorphous iron rather than the calcareousness was putatively responsible for the high phosphate sorption capacity of soils. Maximum phosphorus buffering capacity (MPBC) of the calcareous soils ranged from 33.4 - 62.8 l/kg. Langmuir and Freundlich equations produced different values for soil P requirements (SPR) at 0.2 and 1.0 mg P/l. Calcareous soils would require 27 - 44 mg P/kg soil to attain 0.2 mg P/l soil solution, which is deemed sufficient for crop growth. The soils would require 32 - 58 mg P/kg soil to reach 1.0 mg P/l soil solution, which is regarded to be safe for soils in terms of susceptibility to P losses. The calculated Langmuir constant b values were higher than the threshold value of 0.07 l/mg for two of the calcareous soils. Therefore, even though the non-calcareous soils sorbed more phosphate, higher bonding energy of P sorption for calcareous soils makes them less vulnerable to loss via surface runoff.
 Dhaka Univ. J. Biol. Sci. 28(1): 93-110, 2019 (January)

Measuring potassium fractions is not sufficient to assess the long-term impact of fertilization and manuring on soil’s potassium supplying capacity

Potassium (K)-fractions, thresholds of K release and fixation, quantity-intensity (Q/I) parameters of K, K-release kinetics, and K-fixation capacity were compared for their effectiveness in differentiating the effect of various nutrient management practices on K supplying capacity of an Aeric Endoaquept soil after 45 years of puddled rice cultivation. Soil samples (0–15 cm) were collected after the completion of 45 rice-rice cycles from an on-going long-term fertilizer experiment located in ICAR-National Rice Research Institute, Cuttack, India. The treatments involved control (unfertilized), N (nitrogen fertilizer), NP (N+ phosphorus fertilizer), NK (N+ potassium fertilizer), NPK (N + P + K fertilizer), FYM (farmyard manure), N + FYM, NP + FYM, NK + FYM, and NPK + FYM. Rice cultivation without K fertilizer application resulted in lower values of soil K parameters than the K-fertilized treatments. Treatment effects were most prominent on release threshold concentration (RTC), followed by cumulative K release, K-release rate constants, and K-fixation capacity. Parameters of K-release kinetics and Q/I relationships showed better correlation with rice grain yields than soil-K fractions. Soil K thresholds were closely related with exchangeable (Kex) and non-exchangeable K (Knx), but not clay minerals. Among the soil K parameters, RTC, cumulative K release (Kf) with 0.01 M CaCl2, release rate constants (b R and b S ) of parabolic diffusion equation, and K-fixation capacity were most effective in revealing the nutrient management induced variations in soil K fertility. In the studied soil, K-thresholds were significantly related to Kex and Knx.

Interspecific Differences of the Capacities on Excessive Soil Moisture Stress for Upland Crops in Converted Paddy Field

The interspecific estimation for tolerance capacities of upland crop species to excessive soil water stress in paddy field is significant in agricultural practices. Most of upland crops can be damaged by either excessive soil water or capillary rise of the water table during rainy season in paddy fields. The major objective of this study was to evaluate water stress of upland crops under different drainage classes in converted paddy field. This experiment was carried out in poorly drained soil (PDS) and imperfectly drained soil (IDS) of alluvial sloping area located at Toero-ri, Bubuk-myeon, Miryang-si, Gyeongsangnam-do. The soil was Gagog series, which was a member of the fine silty, mixed, nonacid, mesic family of Aeric Endoaquepts (Low Humic-Gley soils). Two drainage methods, namely under Open ditch drainage methods (ODM) and, Closed pipe drainage methods (PDM) were installed within 1-m position at the lower edge of the upper paddy fields. The results showed that sum of excess water days (SWD30), which was used to represent the moisture stress index, was 42 days (the lowest) in the PDM compared with 110 days in the ODM. Most of upland crops were more susceptible to excessive soil water during panicle initial stage on more PDS than on IDS. Yield of upland crops in the PDM was continuously increased by the rate of 15.1% on sorghum, 15.4% foxtail millet, 53.6% proso millet, 49.6% soybean and 47.9% adzuki bean as compared in the ODM. The capacity for tolerance by excessive soil water based on yield of each upland crop in the poorly drained sloping paddy fields was the order of sorghum, soybean, foxtail millet, proso millet and adzuki bean. Therefore, Sorghum is relatively tolerant to excessive soil water conditions and, may be grown successfully in converted paddy field.

Targeted yield based fertilizer prescriptions for autumn rice (<italic>Oryza sativa</italic> L.) in inceptisols of Assam, India

Soil Test Crop Response (STCR) study was conducted during 2010-11 for autumn rice under integrated plant nutrition system (IPNS) in Inceptisols (Aeric Endoaquepts) in Jorhat district of Assam. The basic parameters were computed from the STCR data, and the fertilizer prescription equations were developed for recommending fertilizer doses in autumn rice. The nutrient requirement (NR) for producing one quintal of autumn rice was found to be 2.40 kg, 0.84 kg and 2.25 kg of N, P<sub>2</sub>O<sub>5</sub> and K<sub>2</sub>O, respectively. The percent contribution of nutrients from soil (CS), fertilizer (CF) and FYM (CO) were calculated as 12.49, 45.31 and 32.92 for N, 13.42, 28.52 and 11.84 for P<sub>2</sub>O<sub>5</sub> and 21.99, 47.58 and 29.76 for K<sub>2</sub>O, respectively. These equations were validated in farmers’ fields during 2012 and the variation between actual yield and targeted yield ranged from +1.36 to +5.33.The fertilizer estimates under STCR-IPNS for 3000 and 4000 kg ha<sup>−1</sup> targeted yield recorded maximum response ratio and economic benefit in the field trial and confirmed the validity of proposed fertilizer prescription equations for autumn rice.

Effect of Integrated Nutrient Management on Soil Enzymes, Microbial Biomass Carbon and Soil Chemical Properties after Eight Years of Rice (Oryza sativa) Cultivation in an Aeric Endoaquept

Soil enzymes, microbial biomass carbon (MBC), microbial population and selected soil chemical properties were evaluated in a field experiment involving integrated nutrient management (INM) for eight years of rice cultivation in an Aeric Endoaquept. Persistent application of biofertilizers for eight years illustrated the clear increase in fluorescein di-acetate (FDA) hydrolase (10.51 μg fluorescein g−1 h−1) and arylsulfatase (ARS) (43.8 μg p-nitrophenol g−1 h−1) activities with 50% of NP fertilizer. Application of enriched compost (EC) (2 t ha−1) demonstrated clear increase in dehydrogenase (DH) (220.0 μg TPF g−1 d−1) and phosphomonoesterase (PME) (388.8 μg p-nitrophenol g−1 h−1) activities with only 25% of recommended nitrogenous (N) and phosphatic (P) fertilizer. The integration of biofertilizers or EC with reduction of 75 to 50% NP fertilizers resulted the higher MBC in between 270.6 and 323.3 μg g−1 compared to chemical fertilizer alone. Similarly, maximum accretion (11.2 g kg−1) of organic carbon (OC) was observed with the application of EC (1 t ha−1) amid sizeable cut (50% NP) of chemical fertilizers after eight crops. Abundance of Azospirillum (5.76 to 5.84 log cfu g−1) and PSB (5.82 to 5.90 log cfu g−1) were observed with application of either biofertilizers or EC (1 t ha−1) and 50% NP fertilizers. The MBC and OC displayed significant correlation with intracellular and extracellular soil enzymes and microbial populations in rice soil following INM. The overall multifaceted effects of different INM treatments facilitated beneficial soil conditions in the present study reflected the significant increase in the grain yield of rice (4.07 t ha−1) which is equivalent to the 100% NPK (3.86 t ha−1). The application of biofertilizers with 50% NP showed highest value (234.3 kg ha−1) of available N, whereas highest available P (25.8 kg ha−1) was obtained in the INM treatment that contained EC (2 t ha−1).

Soil Test based Fertilizer Prescriptions under Integrated Plant Nutrient Supply for Rice-Rice Cropping Sequence in Inceptisols of Assam

Field experiments were conducted during 2010–12 to assess the fertilizer requirements for rice-rice sequence under integrated plant nutrient supply on Inceptisols (Aeric Endoaquepts) in Jorhat district of Assam. Following Ramamoorthy's Inductive cum targeted yield model, the nutrient requirement per quintal of grain production and contribution from soil, fertilizer and farmyard manure (FYM) were calculated for both autumn and winter rice. The per cent contribution of nutrients from soil (CS), fertilizer (CF) and FYM (CFYM) were found to be 12.49, 45.31 and 32.92 for N, 13.42, 28.52 and 11.84 for P2O5 and 21.99, 47.58 and 29.76 for K2O, respectively for autumn rice. The same for winter rice was 24.60, 33.15 and 48.28 for N, 30.69, 32.15 and 14.38 for P2O5, and 41.00, 56.87 and 31.59 for K2O, respectively. The fertilizer prescription equations were developed and nomograms were formulated based on the equations for a range of soil test values and desired yield target for rice. Under NPK + FYM @ 5.0 t ha−1, 17, 6,14 and 35, 7 and 12 kg ha−1 of fertilizer N, P2O5 and K2O, respectively could be saved for attaining target yield of 40 q ha−1 for autumn rice and 60 q ha−1 for winter rice as compared to NPK fertilizers alone.

Influence of boron and organic matter on the changes in soil biological properties and yield of rape (Brassica campestris) in an aeric endoaquept

Field experiments were conducted during winter seasons of 2006 -07 and 2007-08 to study the influence of boron and organic matter application on the changes in soil biological properties in an aeric endoaquept (pH,7.5;organic carbon content, 0.61%; CaCl2–extractable boron 0.32 mg/kg) growing rape (Brassica campestris L.) as a test crop. The results reveal that non-symbiotic nitrogen fixing bacteria (NFB), non symbiotic nitrogen fixing capacity, phosphate solubilising micro-organisms (PSM), phosphate solubilising capacity (PSC) and microbial biomass carbon (MBC) have been found to be influenced with different treatments, being recorded highest (90.45, 69.29 × 105/g soil; 11.73, 9.63; 80.29, 63.28 mg of N2 fixed/g of soil/g of sucrose; 0.038, 0.032 mg/g dry soil and 159.48, 149.58 µg/g dry soil respectively) in the treatment T4 where lower level (0.5 kg/ha) of boron as calbor and organic matter at 5 tonnes/ha was applied along with recommended levels of N, P2O5 and K2O (80:40:40) in both rhizosphere (R) and non- rhizosphere (NR) soils. The yield of rape was also recorded highest (8.95 q/ha) in the treatment T4 ( lower level (0.5 kg/ha) of boron as calbor,organic matter at 5 tonnes/ha and recommended levels of N, P2O5 and K2O ( 80:40:40 ). From the stepwise technique of multiple regression it was revealed that the NFB at R and NR, PSC at R and NR, PSM at R and NR and MBC at NR are only important predictors which can explain 99 % of total variance.

Influence of Zinc on the yield and nutrition of wet season rice (Oryza sativa) grown under aeric endoaquept

A field experiment on wet season kharif rice (Oryza sativa L.) cv IET 4094 was conducted during the year 2010- 11 and 2011-12 in an aeric endoaquept to study the influence of applied zinc on the growth, yield and nutrition of rice. The results show that the application of chelated zinc (Zn-EDTA) increased N, P, K and Zn concentration in dry matter and grains of rice. The highest amount of N, P,K and Zn in rice dry matter and grain have been found to be recorded in the treatment where the recommended levels of NPK (80:40:40) and chelated zinc in two splits (one at basal and the second one at grand tillering stage) were applied. The percent increase in the yield of grain (43.20) and straw (68.50) were also recorded highest in the treatment where Zn-EDTA was applied in two splits (0.5 kg/ha as basal + 0.5 kg/ha at grand tillering stage) over that of the control, while that of the same percent increase of the applied Zn–EDTA was highest in rice grain yield (18.40) over that of the corresponding highest level of ZnSO4.7H2O (20 kg/ha) at two splits.

Influence of elevated carbon dioxide and temperature on belowground carbon allocation and enzyme activities in tropical flooded soil planted with rice

Changes in the soil labile carbon fractions and soil biochemical properties to elevated carbon dioxide (CO2) and temperature reflect the changes in the functional capacity of soil ecosystems. The belowground root system and root-derived carbon products are the key factors for the rhizospheric carbon dynamics under elevated CO2 condition. However, the relationship between interactive effects of elevated CO2 and temperature on belowground soil carbon accrual is not very clear. To address this issue, a field experiment was laid out to study the changes of carbon allocation in tropical rice soil (Aeric Endoaquept) under elevated CO2 and elevated CO2 + elevated temperature conditions in open top chambers (OTCs). There were significant increase of root biomass by 39 and 44% under elevated CO2 and elevated CO2 + temperature compared to ambient condition, respectively. A significant increase (55%) of total organic carbon in the root exudates under elevated CO2 + temperature was noticed. Carbon dioxide enrichment associated with elevated temperature significantly increased soil labile carbon, microbial biomass carbon, and activities of carbon-transforming enzyme like β-glucosidase. Highly significant correlations were noticed among the different soil enzymes and soil labile carbon fractions.

Effect of long-term application of organic amendment on C storage in relation to global warming potential and biological activities in tropical flooded soil planted to rice

The impact of long term organic amendments on the functional microbial activities, soil carbon (C) storage in relation to greenhouse gas (GHG) emission from rice field was investigated in a tropical Aeric Endoaquept. The treatments included unamended control, farmyard manure (FYM), green manure (GM) (Sesbania aculeata), FYM + GM and rice straw (RS) + GM combination. Our results suggest that the FYM + GM treatment has increased the global warming potential (GWP) by 110 % as well decreased the C efficiency ratio by 24 % in comparison to control. On the other hand, under RS + GM treatment the soil organic C and total C contents were significantly higher to the tune of 34 and 53 %, respectively. Our studies clearly reveal that the application of RS + GM at 1:1 [Nitrogen (N) basis] could probably be the best soil amendment to sequester the soil organic C. Such amendments may not only have practical application value but also lead to higher yield capacity and minimize emission of GHG under flooded tropical rice soil systems.

Evaluation of Extractants for Boron under the Influence of Organic Matter and Applied Boron in Rhizosphere and Nonrhizosphere Soils Growing Rape (Brassica campestris L.)

Field experiments during 2006–07 and 2007–08 were conducted in an Aeric Endoaquept to evaluate extractants suitable for boron (B) under the influence of organic matter and B in both rhizosphere (R) and nonrhizosphere (NR) soils with rape (Brassica campestris L.) as a test crop. The results reveal that the average B content in Mehlich 3 (MH-3) B was greatest (0.791 mg kg−1) in NR soil, while that of the same in R soil was greatest (0.785 mg kg−1) with Mannitol–calcium chloride (CaCl2) (MCC) followed by hot -CaCl2 (HCC, 0.750 mg kg−1) in the treatment T4 where NPK (80:40:40), B at 0.5 kg ha−1, and farmyard manure (FYM) at 5 t ha−1 were applied together. Based on linear regressions and correlations between different extractants and yield responses, the MH-3 extractant gave the greatest value of co-efficient of determination (R2 = 0.36**, r = 0.598**) and has proved to be a superior extracting solution for B in NR in an Aeric Endoaquept. The results further suggested that the extractability of B with these three extractants did not have any control over rhizosphere soil zone.

Interaction effects of elevated CO2 and temperature on microbial biomass and enzyme activities in tropical rice soils

The impacts of elevated CO(2) and temperature on microbial biomass and soil enzyme activities in four physicochemically different types of tropical rice soils (Aeric Endoaquept, Aeric Tropoaquept, Ultic Haplustalf and Udic Rhodostalf) were investigated in a laboratory incubation study. Soil samples were incubated under 400, 500 and 600 μmol mol(-1) CO(2) concentration at 25°C, 35°C and 45°C for 2 months. Elevated CO(2) significantly increased the mean microbial biomass carbon (MBC) content, across the soils, over control by 6.2%, 38.0% and 49.2% at 400, 500 and 600 μmol mol(-1) CO(2) concentration, respectively. Soil enzyme activities (fluorescein diacetate hydrolase, dehydrogenase, β-glucosidase, urease, alkaline and acid phosphatases) also increased significantly ranging from 1.3% (urease) to 53.2% (alkaline phosphatase) under high CO(2) in the soils studied. Both MBC and soil enzyme activities were further stimulated at high temperatures suggesting elevated CO(2) and high temperature interaction accelerated the general turnover of the organic C fractions of the soil and through increase in microbially mediated processes.

Limitations of the Olsen method to assess plant-available phosphorus in reclaimed marsh soils

The aim was to assess the ability of bicarbonate-extractable P (Olsen P) to estimate total plant-available P (TPAP) in reclaimed marsh soils (Aeric Endoaquepts) which differed widely in P buffering capacity (PBC). Total plant-available P was estimated as the cumulative P uptake for a final concentration of 0.02 mg P/L in the soil solution which is the typical P requirement for field crops. The Olsen P estimated for that concentration was adopted as the critical level for crop production. We found that TPAP was better predicted by anion exchange resin-extractable P (AER-P) (65% of variance accounted for) than by Olsen P, probably because the effectiveness of the AER depends on the soil P buffering capacity, a factor that greatly influences the availability of P to plants. The critical Olsen P level was found to depend on those soil properties affecting the relationship between sorbed P and P in soil solution, viz. the P buffering capacity of soil, the Na/Ca mole ratio in the 1:1 soil:water extract, which explained 63 and 84% of the variance in the critical level, respectively, and the affinity of the sorbing surfaces for P. These properties must be taken into account when using Olsen P as the P index for fertilizer management.

Evaluation of Various Zinc Extractants in Lowland Rice Soil under the Influence of Zinc Sulfate and Chelated Zinc

Field experiments were conducted on rice (cv ‘IET 4094’) in an Aeric endoaquept (pH 7.2) to evaluate the various zinc (Zn) extractants in lowland rice soil under the influence of Zn sulfate and chelated Zn. The diethylenetriaminepentaacetic acid (DTPA), 0.1 N hydrochloric acid (HCl), and 0.05 N HCl‐extractable Zn concentrations in soil increased initially up to the Z29 stage of crop growth when Zn was applied as a single basal source, being greater with Zn ethylenediaminetetraacetic acid (Zn‐EDTA) compared to zinc sulfate (ZnSO4) application. Among the various extractants, the performance of 0.1 N HCl in extracting Zn was better than the other two extractants and followed the trend 0.1 N HCl > 0.005 M DTPA > 0.05 N HCl. The greatest increase in grain and straw yield of rice was 37.8 and 20.4%, respectively, over the control in the treatment T7 (1 kg Zn ha−1 as Zn‐EDTA at basal).

Effect of different sources of boron on its maintenance in soil in relation to rape (Brassica campestris L.)

Field experiments were conducted during Rabi (October to April) seasons of 2005 and 2006 in an Aeric Endoaquept taking rape (Brassica campestris L.) as a test crop using two sources of boron (calbor and borax) integrated with farmyard manure (FYM). The amount of 0.02 M CaCl2-extractable B content in soil was maintained at the highest level during crop growth in the treatment receiving calbor at 1 kg B ha−1. The B content in the plant was recorded highest (11.56 mg kg−1) at 90 days of crop growth in the treatment receiving integrated application of 0.5 kg B ha−1 as calbor and FYM (5 t ha−1). The yield of rapeseed was highest (890 kg ha−1) with B at 1 kg ha−1 as calbor compared to borax as a source of B.

Mobilisation of arsenic in soils and in rice (Oryza sativa L.) plants affected by organic matter and zinc application in irrigation water contaminated with arsenic

The experiments were conducted to study the effects of arsenic-contaminated irrigation water, zinc and organic matter on the mobilization of arsenic in an Aeric Endoaquept in relation to rice (cv. IET 4786). The results show that the amount of extractable arsenic increased with the progress of submergence decreased with zinc application. The magnitude of such decrease varied with the Zn amount, being greater (0.70 to 1.08 mg/kg) in the treatment where zinc was applied at the rate of 20 mg/kg. With regards to organic matter application, the arsenic content in soil markedly decreased, especially with farmyard manure application. The results of the greenhouse experiment with exposure of graded doses of arsenic to rice suggest that the upper toxic limit of arsenic in soil was 10 mg/kg for rice. The results of the field experiment show that the grain yield of continuous flooding (4.84 t/ha) and intermittent flooding up to 40 days after transplanting followed by continuous flooding (4.83 t/ha) with the application of ZnSO<sub>4</sub> at the rate of 25 kg/ha did not vary significantly. The lowest grain yield (3.65 t/ha) was recorded in the treatment where the intermittent flooding was maintained throughout the growth period without the application of zinc. The amount of arsenic was, however, much lower in the treatment where intermittent flooding was maintained throughout the growing period combined with zinc sulphate application.