Relative Dry Matter Yield Research Articles

Chemical treatment and mobilization of reserves of soybean seeds under water deficit

Abstract: Seed treatments with chemical phytosanitary products can compromise mobilization of seed reserves for the seedlings under water deficit conditions. The aim of this study was to evaluate the physiological quality, the initial seedling development, and the mobilization of reserves in soybean seeds treated with phytosanitary products under water deficit. The trial was set up in a completely randomized design in a 4 × 4 factorial arrangement: chemical treatments (control, Thiamethoxam, Fludioxonil + Metalaxyl-M, and Fipronil + Pyraclostrobin + Tiophanate-methyl) × osmotic potentials (0, -0.1, -0.2, and -0.3 MPa). We analyzed the following variables: germination; hypocotyl length, root length, and total seedling length; seedling length vigor index; cotyledon dry matter weight; seedling dry matter yield; seed reserve reduction; relative dry matter yield; seed reserve reduction rate; and conversion efficiency of seed reserves into seedling dry matter. Seed quality and seedling development decline under water deficit conditions. The treatment with Fipronil + Pyraclostrobin + Thiophanate-methyl results in lower phytotoxicity. The estimated cotyledon dry matter (CDM) weight is an indicator of phytotoxicity and water deficit. Mobilization of reserves is compromised in seeds treated with insecticides, reducing the capacity of conversion of reserves into dry matter. There is an inversely proportional relationship between the reduction in conversion and the efficiency of conversion of reserves of treated soybean seeds under water deficit.

Productivity of pigeon pea, cowpea and maize under sole cropping, legume–legume and legume–cereal intercrops on Alfisols in Central Malawi

A study was conducted in Lilongwe and Dowa districts of central Malawi to assess the performance and productivity of pigeon pea (PP), cowpea (CP) and maize (MZ) when grown as sole crops, legume–legume and legume–cereal intercrops. The experiment was arranged in a randomized complete block design (RCBD). Analysis of variance for yields was carried out on a per plant basis and the productivity was assessed by using various competition indices including the land equivalent ratio (LER), relative dry matter yield (RDY), relative nutrient yields and the monetary advantage index (MAI). Results showed significantly higher (P 1) and monetary gains (positive MAI values) in all the intercropping systems than sole cropping, at both study sites. Furthermore, the PP + MZ intercrop was the most productive system in terms of yields and monetary gains as it produced the highest LER and MAI values. From this study it is noted that prudent implementation of legume-based diversified intercropping systems including pigeon pea–cowpea and pigeon pea–maize intercrops can play a crucial role in sustaining the intensification of agriculture in smallholder dominated systems.

Reserve mobilization in soybean seeds under water restriction after storage

Abstract: Germination does not guarantee plant establishment if there is no efficient and enough reserve mobilization from seeds to the initial seedling growth, mainly in adverse situations. Therefore, this study aimed to evaluate the mobilization of reserves in soybean seeds under water restriction. Four soybean seed lots previously stored for one year were used in the study. To simulate water stress, we used polyethylene glycol (PEG) solutions at concentrations of 0.0, -0.1, and -0.2 MPa. The number of normal, infected and abnormal seedlings were evaluated, along with the number of dead and hard seeds. The radicle, hypocotyl, and cotyledons were separated to determine the dry weight based on the total seed reserve available for mobilization. From this value, the seed reserve reduction, relative dry matter yield, seed reserve reduction rate, and reserve conversion efficiency into dry seedling weight were determined. The increase in water restriction elevates the reserve consumption during the germination process. Vigorous seeds are more efficient in mobilizing and converting grains reserve in dry seedling mass. In less vigorous seeds, mainly those on water restriction, the increase in reserve consumption does not result in conversion into dry seedling mass.

Nutrient competition and requirement in finger millet-haricot bean intercropping system

There is not a special recommended fertilizer rate for component crops in intercropping systems. Rather, soil nutrient applications for intercropped crops are mainly based on recommended rates for the respective individual crops. A field experiment was conducted at two sites in northwestern Ethiopia to assess the nutrient competition and requirement for finger millet-haricot bean intercropping. Factorial combinations of three cropping systems (sole finger millet, sole haricot bean, and their intercropping) and five fertilizer levels (0, 50%, 100%, 150%, and 200% of the recommended NP fertilizer rate of each sole crop) were laid out in randomized complete block design with three replications. Results revealed that maximum nitrogen (N) and phosphorus (P) uptake by finger millet and haricot bean were recorded in finger millet-haricot bean intercropping (FM + HB) at 150% and 200% NP, respectively. Greater relative N yield (RNY) than relative dry matter yield (RDMY) was obtained at 150% NP to both component crops indicating that N at this treatment was not limited to both crops in FM + HB. The relative P yield (RPY) was greater than RDMY of finger millet at all but 200% NP, while RPY of haricot bean was less than RDMY at all fertilizer levels. Thus, it can be concluded that FM + HB at 2:1 row ratio and 150% NP increased the nutrient and land use efficiency more than sole cropping.

Correction and standardization of critical limit of zinc for maize (Zea mays L.) crop: Bangladesh perspective

Critical limit (CL) determination of zinc (Zn) is very important for predicting response of maize crop to its application in soils and for the crop’s actual fertilizer requirement. This study was conducted at Bangladesh Agricultural Research Institute, Gazipur, to determine the CL of Zn for maize grown in 20 soils collected from the five Agro–Ecological Zones during January to March, and April to June of 2017. The available Zn content of soils and maize biomass were estimated utilizing the extraction method with 0.005 M diethylene triamine pentaacetic acid (DTPA). During January to March and April to June 2017, the amount of DTPA extractable Zn in different soils ranged from 0.60–3.25 mg kg−1 and 0.50–1.68 mg kg−1, respectively. During both periods of crop growth (January to March and April to June, 2017), the soil available zinc was negatively significantly correlated with soil pH, available P, exchangeable Ca, exchangeable Mg and positively significantly correlated with relative dry matter (DM) yield. Soil Zn also positively significantly correlated with maize tissue Zn content (r = 0.521*). However, the CL of Zn were estimated to be 0.84 mg kg−1 in soils and 26.1 mg kg−1 in maize tissue for maize cropping as determined by Cate and Nelson’s (1965) graphical procedure. Maize crop may respond to Zn application in soils containing Zn at/below the above level. This data may be used for predicting plant response to Zn fertilizer and development of crop Zn nutrition guide for maximum production.

Diverse Grain‐Filling Dynamics Affect Harvest Management of Forage Barley and Triticale Cultivars

Core Ideas Decision‐making criteria are needed to optimize silage production in barley and triticale.The critical factors, yield, forage quality, and dry matter interact in the grain‐filling period.Optimization of factors is required and the indicator for harvest may differ between species.Comparison on a growing degree day scale during grain filling provided an assessment of dynamics.Triticale needed more degree days than barley to optimize yield and dry matter shown by dough stage. Harvest time for small‐grain forage is impacted by changes in yield, dry matter concentration (DMC) and forage quality during grain‐filling. Little information exists for hulless and two‐rowed barley (Hordeum vulgare L.) and triticale (X Triticosecale Wittmack) grown in Alberta. Two barley and two triticale cultivars were grown at three planting dates and two locations over 2 yr at Lacombe, AB, Canada. Forage was harvested five times after boot stage at 7‐ and 10‐d intervals for barley and triticale, respectively. Relationships were developed by regressing variables with growing degree days (GDD) after the boot stage for triticale cultivars, combined, and each barley cultivar (‘Falcon’ and ‘Gadsby’). Comparisons were made at GDD positions. Triticale out‐yielded and dried slower than barley and had higher DMC for 560 GDD after the boot stage; Gadsby out‐yielded Falcon. The soft dough stage (DS 85) indicated optimum yield, 93% of relative dry matter yield (RDMY) at less than 400 g kg−1 DMC for barley and triticale, but occurred at 400 and 500 GDD after the boot stage, respectively. Triticale had lower in vitro true digestibility (IVTD) and higher fiber levels than barley at boot stage; but triticale IVTD decreased slower than barley and Falcon declined faster than Gadsby. Starch accumulated more rapidly for Gadsby than Falcon, while triticale increased slowly initially, then rapidly later in the grain filling period. Delaying harvest by 100 GDD for triticale compared to barley (both at DS 85) resulted in the higher triticale yield, while allowing more starch to accumulate.

RESIDUES OF FORAGE SPECIES AFFECT PHOTOSYNTHETIC CHARACTERISTICS OF THE PEQUIZEIRO

ABSTRACT Some forages release allelopathic substances into the environment, and may prevent consortium with arboreal species in pastures. The objective of this work was to evaluate photosynthetic characteristics of pequizeiro plants (hereafter pequi) influenced by concentrations of residues of the forage species Urocholoa decumbens, Melinis minutiflora and Paspalum notatum. The treatments consisted of pequi cultivation under aerial residues of the three forage species mixed to the substrate in four concentrations (1, 2, 3 and 4% mass/mass), plus an additional treatment (comparative control) with pequi cultivated on the substrate without waste. The following parameters were evaluated: photosynthetic rate, stomatal conductance, transpiration rate, relationship between internal and external CO2 concentration (Ci/Ca), maximum quantum yield, effective quantum yield of FS II, electron transport rate, nonchemical quenching and chlorophyll index, concerning the content of chlorophyll a, b and total in pequi plants at 50 and 100 days after transplanting (DAT), and the relative production of dry matter at 100 DAT. At 50 DAT, the following photosynthetic variables were affected in pequi plants: A, gs, chlorophyll a, chlorophyll b and total chlorophyll when cultivated in the presence of forage residues. At 100 DAT, the following photosynthetic variables were affected in pequi plants: A, Fv/Fm, ETR, NPQ, chlorophyll a, chlorophyll b and total chlorophyll, when cultivated in the presence of forage residues. Pequi plants had reduced relative dry matter yield when grown in the presence of U. decumbens. This variable was also affected when pequi was grown in increasing concentrations of residues of the species U. decumbens, M. minutiflora and P. notatum.

Ethiopian Mustard–Chickpea Intercropping System is a Viable Option for Yield Advantage in Dryland Condition of North India-Part II

Cereal with legume intercropping is common but oilseed and legume crops are not tested in the form of intercropping with a suitable nutrient management and moisture conservation practices. Hence, present study was conducted during 2008–2009 and 2009–2010 in Ethiopian mustard and chickpea intercropping system with moisture conservation practices and different levels of phosphorus and sulphur in order to evaluate the intercropping system and analyze the competition and the interrelationship between component crops than their pure stands. Relative dry matter yield of Ethiopian mustard throughout the growth stages was greater than that of chickpea at all levels of phosphorus and sulphur nutrition. Ethiopian mustard/chickpea intercropping system recorded higher mustard equivalent yield over sole mustard and sole chickpea with the application of moisture conservation and phosphorus and sulphur fertilizer. The relative yield total, relative crowding coefficient, actual yield loss (AYL), and system productivity index values were greater with moisture conservation practices and higher dose of phosphorus and sulphur nutrition indicating an advantage of intercropping. In intercropping, the values of relative crowding coefficient, AYL, aggressivity, and competitive ratio indicated that the Ethiopian mustard was more competitive than chickpea. This study suggests that Ethiopian mustard/chickpea intercropping system was more productive and profitable with phosphorus and sulphur nutrition if proper moisture conservation practice could be adopted by the farmers as alternative options under moisture scarce conditions.

Nitrogen availability from dairy cow dung and urine applied to forage grasses in eastern Canada

Bélanger, G., Rochette, P., Chantigny, M., Ziadi, N., Angers, D., Charbonneau, E., Pellerin, D. and Liang, C. 2015. Nitrogen availability from dairy cow dung and urine applied to forage grasses in eastern Canada. Can. J. Plant Sci. 95: 55–65. Nitrogen availability from dung and urine excreted by dairy cows has been studied extensively but few studies have been conducted in areas with short growing seasons and cold winters. We assessed N availability from dairy cow urine and dung applied to forage grasses under the cool conditions of eastern Canada, with a focus on soil- and plant-based indicators. The experiment was conducted with timothy (Phleum pratense L.)-dominated swards on two soil types (clay, sandy loam) with three periods of application (mid-September, early June, early July) and four treatments: Control, Dung (1.75 kg fresh weight m−2), Diluted urine (U-50; 50 g N m−2), and Urine (U-100; 100 g N m−2) from lactating cows. Dry matter (DM) yield and N concentration were measured from several successive clippings. Ion exchange membranes (IEM) and crop N nutrition index (NNI) were used, respectively, as soil-based and plant-based indicators of N availability. Relative cumulative DM yields, calculated as cumulative DM yield over all clippings for a given treatment divided by maximum cumulative DM yield among the four treatments, increased from Control (clay: 31 - 69%; sandy loam: 21–63%) to Dung (clay: 39–84%; sandy loam: 46–86%) and U-50 (clay: 81–83%; sandy loam: 78–100%). Relative values of cumulative N uptake were close to those of DM yields. The percentage of applied N taken up by the crop from all clippings was greater with urine (8–28%) than with dung (3–12%) on both soil types. Nitrogen from dung and urine was available to timothy at all periods of application, but urine N availability was greater than that of dung N. Nitrogen exposure, calculated as cumulative mineral N on IEMs, and NNI were both related to relative DM yield (R 2>0.61; P<0.001), confirming their capacity to assess N availability to forage grasses receiving dung and urine excreted by dairy cows.

Comparative Effect of City Finished Compost and NPK Fertilizer on Growth and Availability of Phosphorus to Radish (<i>Raphanus sativus</i> L.)

A pot experiment was carried out to investigate the comparative effect of city finished compost and NPK fertilizer on the growth and availability of phosphorus to radish (Raphanus sativus L.). An air dried sandy loam soil was mixed with five rates of city finished compost (CFC) equivalent to 0, 5, 10, 20, 40 ton ha–1 and three rates of NPK fertilizer equivalent to 50% (N-P-K = 69-16-35 kg ha–1), 100% (N-P-K = 137-32-70 kg ha–1 K) and 150% (N-P-K = 206-48-105 kg ha–1). Four plants were harvested at 45 days of growth and remaining one plant was harvested at 90 days of growth and separated into leaves and bulbs. After harvest, soil samples were collected from each pot to measure soil pH and available P extracted by Olsen, Mehlich-3, Kelowna and Bray & Kurtz-1 extractants. The growth parameters (length of leaves and bulbs, fresh and dry weight of leaves and bulbs), relative dry matter yield, plant P concentrations, P uptake by radish, soil pH, and available P increased by the rates of CFC and NPK fertilizer treatments. Among the treatments, growth performance of radish was better with the highest rate of 40 t ha–1 CFC treatments. The results obtained from the 5 and 10 t ha–1 CFC treatment were comparable with the results of 50% and 100% NPK fertilizer treatments respectively. Similar effects of amendments were obtained in the case of plant P concentration, uptake of P by plant, soil pH and available soil P concentration. Available P and soil pH showed very strong and positive correlation (P < 0.001) with dry matter yield, P uptake by plant. The P extracted by various extractants also showed strong positive correlation (r = 0.973 to 0.994; P < 0.001 ) each other indicating the suitability of any of the extractants to predict available P. Results of the present study indicated that 10 t ha–1 city finished compost could be used instead of 100% to obtain similar yield and to improve soil conditions.

ROOT ZONE TEMPERATURE INFLUENCES ZINC REQUIREMENT OF MAIZE CULTIVARS ON A CALCAREOUS LOAM SOIL

The zinc (Zn) requirement of a maize (Zea mays L.) hybrid (‘FHY-396’) and an indigenous variety (‘EV-7004’) was measured at low (22.4 ± 5°C) and high (28.8 ± 5°C) root-zone temperatures (RZT). Four Zn rates (0, 3, 9 and 27 mg kg−1 soil) were applied to a calcareous loam soil in pots for the glasshouse study. Shoot and root dry matter yields were significantly more at the higher RZT. Regardless the RZT, maximum relative shoot dry matter yield in hybrid and variety was produced, respectively, at 9 and 3 mg Zn kg−1 soil. Zinc concentration in roots and shoots of both the cultivars increased with Zn rates and it was significantly more at the higher RZT. Cultivars differed in critical Zn concentration (CZnC) required for maximum shoot dry matter yield. The CZnC ranged from 25 to 39 μg Zn g−1 plant tissue for optimum growth of both the cultivars at low and high RZT.

Assessment of nutrient competition and nutrient requirement in soybean/sorghum intercropping system

Intercropping system of cereals with legume is common in semi-arid tropics of India. However, little attention has been paid to assessing nutrient competition in the system. Seasonal changes in relative dry matter yield (RDY), relative nitrogen yield (RNY), relative phosphorus yield (RPY) and relative potassium yield (RKY) are useful indices to estimate the N, P and K status in intercropping system. The competitive effect of soybean ( Glycine max L.) in association with sorghum ( Sorghum bicolor L. Moench) was assessed using these indices under six nutrient treatments (0, 75% NPK, 100% NPK, 75% NPK + 5 Mg farmyard manure, 75% NPK + 5 Mg phosphocompost and 75% NPK + 1.5 Mg poultry manure) from a 5-year field experiment conducted in a N and P deficient Vertisol of Central India. The RDY and RNY of sorghum were greater than the values of RDY and RNY of soybean indicating inter-species competition for N between component crops, peak competition being at 80 days after sowing (DAS). Using the concept of RDY and RNY, it was observed that having coincided the maturity period and peak demand for N of both the crops, soil N was exhausted by sorghum because of its strong competitive ability and N was liming for soybean at 80 DAS. Strong competitive ability of sorghum was also evident from higher biomass, root mass, root length density and contribution to the mixture yield. Once sorghum entered its maturity phase, its competitive effect on soybean was greatly reduced. Competition for P between two species is more prominent up to 60 DAS and P was not limiting to none of the species after 60 DAS as the RPY values were equal to corresponding RDY values. Based on RKY value, none of the component species suffered from K deficiency at any stage even if it was not applied. This implied that competition exists for soil N and P but not for K up to 60–80 DAS in soybean/sorghum intercropping system. The result showed that competition between two crops measured in terms of RNY, RPY and RKY under organic-fertilizer was less; however, recorded higher soybean equivalent yield and monetary advantage index than inorganic-fertilizer. The study thus suggests that in soybean/sorghum intercropping system to minimize competition between two crops in N and P deficient Vertisol, application of 75% NPK + FYM/poultry manure/phosphocompost is a viable nutrient management option.

Modeling Vegetative Stage Response of Canola (Brassica napus L.) to Combined Salinity and Boron tresses

Boron (B) is essential to growth at low concentrations and limits growth and yield when in excess. Little is known regarding plant response to excess B and salinity occurring simultaneously. In this study, two models of Leibig-Sprengel (LS) and Mitscherlich-Baule (MB), originally proposed to explain plant response to nutrients only, were modified to evaluate canola yield response to combined levels of B and salinity stresses. The water salinity treatments were consisted of non-saline water, 3, 6, 9 and 12 dS m -1 . The B treatments were 0, 10, 20 and 30 mg kg -1 added to soil as H3BO3. It was revealed that modified LS model can satisfactorily predict canola dry matter yield. The calculated statistics: Maximum Error, Root Mean Square Error, Modeling Efficiency, Coefficient of Determination and Coefficient of Residual Mass, indicated that the estimated relative dry matter yield for soil B concentrations and salinity levels by modified LS model compared to modified MB model was closer to the measured relative yield. Therefore, the use of modified LS model for estimating canola relative yield in salinity and B stresses is recommended. The threshold value of salinity increased with higher B concentration and maximum dry matter yields decreased with increasing B concentration. Excess B was found to decrease dry matter yield of canola. This effect was inhibited when plants were exposed to simultaneous B and salinity stresses. Both irrigation water salinity and B concentration influenced water use efficiency (WUE) of plant, however, only B concenteration influenced canola yield in in the same manner.

Comparison of Responses to Mn Deficiency Between the UK Wheat Genotypes Maris Butler, Paragon and the Australian Wheat Genotype C8MM

Wheat grown in Mn-deficient soil has been widely observed to produce much reduced yields. Breeding for Mn-efficient wheat genotypes adapted to Mn-deficient soils would represent a long-term solution for wheat agronomy. To characterize the physiological basis of Mn efficiency in wheat genotypes would facilitate the breeding programs for producing Mn-efficient wheat. Using a solution culture and a soil culture system in the present study, a Mn-efficient UK wheat genotype Maris Butler and a Mn-inefficient UK wheat genotype Paragon have been compared with a Mn-efficient Australian wheat genotype C8MM in the responses to Mn deficiency in order to characterize the Mn efficiency in these wheat genotypes. Results showed that in solution culture, Maris Butler grown under Mn deficiency had 77% relative dry matter yield of control plants that were grown under Mn sufficiency, whereas C8MM and Paragon had 60% and 58% relative dry matter yield of their respective controls. Results from the soil culture demonstrated that relative dry matter yield remained high for Maris Butler and C8MM (53% and 56%, respectively), whereas the value for Paragon dropped to 33%. In terms of dry matter yield and photosynthetic efficiency, Maris Butler demonstrated Mn efficiency in both solution culture and soil culture, whereas C8MM showed Mn efficiency only in soil culture. Results also demonstrated that under Mn-depleted supply in soil, plants of C8MM had a significantly higher ability in Mn uptake, whereas plants of Maris Butler showed a higher internal Mn use efficiency in comparison with plants of Paragon. Results from the present study indicate that the ability of C8MM to accumulate higher amounts of Mn is the basis of the improved Mn efficiency of this genotype in comparison with Paragon, and in Maris Butler there is a higher internal use of Mn expressed as an improved photosynthetic efficiency in conferring its Mn efficiency. It is suggested that more than one mechanism has arisen in wheat to confer tolerance to Mn deficiency.

Comparison of Seven Kinetic Equations for K Release and Application of Kinetic Parameters

Corn field experiments with two treatments, NP and NPK, where N in the form of urea, P in the form of calcium phosphate, and K in the form of KC1 were applied at rates of 187.5, 33.3, and 125 kg ha −1, respectively, on soils derived from Quaternary red clay were conducted in the hilly red soil region of Zhejiang Province, China. Plant grains and stalks were collected for determination of K content. Seven equations were used to describe the kinetics of K release from surface soil samples taken before the corn experiments under electric field strengths of 44.4 and 88.8 V cm −1 by means of electro-ultrafiltration (EUF) and to determine if their parameters had a practical application. The second-order and Elovich equations excellently described K release; the first-order, power function, and parabolic diffusion equations also described K release well; but the zero-order and exponential equations were not so good at reflecting K release. Five reference standards from the field experiments, including relative grain yield (yield of the NP treatment/yield of the NPK treatment), relative dry matter yield (dry matter of the NP treatment/dry matter of the NPK treatment), quantity of K uptake in the NP treatment (no K application), soil exchangeable K, and soil HNO 3-soluble K, were used to test the effectiveness of equation parameters obtained from the slope or intercept of these equations. Correlations of the ymax (the maximum desorbable quantity of K) in the second-order equation and the constant b in the first-order and Elovich equations to all five reference standards were highly significant (P≤ 0.01). The constant a in the power function equation was highly significant (P≤ 0.01) for four of the five reference standards with the fifth being significant (P≤ 0.05). The constant b in the parabolic equation was also significantly correlated (P≤ 0.05) to the relative grain yield and soil HNO 3-soluble K. These suggested that all of these parameters could be used to estimate the soil K supplying capacity and the crop response to K fertilizer.

Determination of suitable chemical extraction methods for the available iron content of brown forest soils in Turkey

The aim of this research was to determine the available iron (Fe) content of brown forest soils of Edirne Province and the most suitable chemical extraction method. Eight chemical extraction methods (the 0.005 M DTPA + 0.01 M CaCl2 + 0.1 MTEA, 0.05 M HCl + 0.012 M H2SO4, 1 M NH4OAc (pH: 4.8), 0.01 M EDTA + 1 M NH4OAc, 1 M MgCl2, 0.01 M EDTA + 1 M (NH4)2CO3, 0.005 M DTPA + 1 M NH4HCO3, and 0.001 M EDDHA methods) and six biological indices (the dry matter yield, Fe concentration, Fe uptake, relative dry matter yield, relative Fe concentration, and relative Fe uptake) were compared. The biological indices were determined with barley (Hordeum vulgare L.) grown under greenhouse conditions. At the end of the experiment, the highest correlation coefficients (r) were determined to be between the 0.005 M DTPA + 0.01 M CaCl2 + 0.1 M TEA method and the biological indices and between the 0.005 M DTPA + 1 M NH4HCO3 method and the biological indices. The corresponding correlation coefficients (r) for the 0.005 M DTPA + 0.01 M CaCl2 + 0.1 M TEA method and the six biological indices were 0.621**, 0.823**, 0.810** 0.433**, 0.558**, and 0.640**, respectively. For the 0.005 M DTPA + 1 M NH4HCO3 method, these coefficients were equal to 0.618**, 0.520**, 0.679**, 0.521**, 0.492**, and 0.641**, respectively (** indicate the validity of the relationships at p < 0.01) These extraction methods, out of all the methods tested, were suggested for the determination of the available Fe content of the brown forest soils.

Potassium Internal Use Efficiency Relative to Growth Vigor, Potassium Distribution, and Carbohydrate Allocation in Rice Genotypes

Potassium (K) deficiency in soils is widespread and has become one of the most nutritional limiting factors for increasing rice yield in China and Asia. Improving K use efficiency by exploiting genetic potential largely depends on understanding physiological and genetic mechanisms underlying K efficiency in lowland rice. In this study, the K internal use efficiency (KIUE) at low K supply relative to K accumulation and distribution, tillering and grain filling rates, dry matter accumulation and allocation were examined under field conditions. The relative K concentrations in upper and lower leaves at booting and grain filling stages decreased with decreasing K internal use efficiency among the rice genotypes, indicating that K-efficient genotypes had greater K translocation ability than the K-inefficient genotypes at low K. The KIUE in biomass production at seedling and tillering stages was closely and positively correlated with the KIUE in grain production at the harvest stage. Significant positive correlations were noted between the KIUE at low K and the relative dry matter yield at the tillering stage and the harvest index among the rice genotypes. The K-efficient genotypes had a greater relative tillering rate during the tillering stage and a greater relative grain filling rate at the late grain filling stage, as compared with the inefficient genotypes. The relative net photosynthetic rate in the upper, and especially in the lower leaves was much lower in the K-inefficient genotypes than in the efficient ones at the grain filling stage, which may partly be due to the fact that the efficient genotype could maintain greater stomatal conductance and ribulose diphosphate carboxylase (RuBPcase) activity in functioning leaves under low K. The results indicate that (i) the K internal use efficiency could be an important index for measuring rice tolerance to low K stress, and (ii) K internal use efficiency is closely associated with efficient translocation and distribution of both K and carbohydrate within rice plants.

Imaging spectroscopy for early detection of nitrogen deficiency in grass swards

The potential of an experimental imaging spectroscopy system with high spatial (0.16–0.28 mm 2) and spectral resolution (5–13 nm) was explored for early detection of nitrogen (N) stress. From June through October 2000, a greenhouse experiment was conducted with 15 Lolium perenne L. mini-swards and 5 N treatments. Images were recorded twice a week. With the experimental system, spectra of grass leaves in the canopy can be obtained. Treatment effects on ground cover (GC) and changes in leaf spectral characteristics were studied separately. Leaf pixels with similar reflection intensity were grouped in intensity classes (IC). An index of reflection intensity (IRI) indicates the percentages of strongly reflecting grass pixels. Blue edge, green edge and red edge positions were calculated for each IC. Both GC and IRI increased until harvest, with largest increases for liberal N treatments. The width of the chlorophyll-dominated absorption band around 680 nm (CAW) increased up to a maximum of 133 nm for both liberal and limited N in the first two weeks after harvesting. CAW decreased for limited N in the second half of the growth period in contrast to liberal N. At harvest CAW explained 95% of the variation in relative dry matter (DM) yield between treatments. Principal component analyses showed an intertwined response of the principal components to both DM yield and N content. Edge positions changed strongly with IC. Possible effects of sensor characteristics, canopy geometry, leaf angle and changes in leaf characteristics with canopy position on the observed relation between IC and edge position are discussed.

Determination of Suitable Chemical Extraction Methods for Available Iron Content of the Soils from Edirne Province in Turkey

The aim of this research was to determine the available iron (Fe) content of the soils of Edirne Province and the most suitable chemical extraction method. Eight chemical extraction methods (0.005 M DTPA + 0.01 M CaCl2 + 0.1 M TEA; 0.05 M HCl + 0.012 M H2SO4; 1 M NH4OAc (pH: 4.8); 0.01 M EDTA + 1 M NH4OAc; 1 M MgCl2; 0.01 M EDTA + 1 M (NH4)2CO3; 0.005 M DTPA + 1 M NH4HCO3 and 0.001 M EDDHA methods) and six biological indices (dry matter yield, Fe concentration, Fe uptake, relative dry matter yield, relative Fe concentration, relative Fe uptake) were compared. Biological indices were determined with Barley (Hordeum vulgare L.) grown under greenhouse conditions. At the end of the experiment, the highest correlation coefficients (r) were determined to be between the 0.005 M DTPA + 0.01 M CaCl2 + 0.1 M TEA method and the biological indices and between the 0.005 M DTPA + 1 M NH4HCO3 method and the biological indices. The correlation coefficients (r) for the 0.005 M DTPA + 0.01 M CaCl2 +0.1 M TEA method were r=0.621**; r=0.823**; r=0.810**; r=0.433**; r=0.558** and r=0.640** and for the 0.005 M DTPA + 1 M NH4HCO3 method r=0.618** ; r=0.520**; r=0.679**; r=0.521**; r=0.492** and r=0.641**, (**:p<0.01) respectively. These extraction methods, among all the methods tested were suggested for the determination of available Fe content of Edirne Province soils.

DETERMINATION OF SUITABLE CHEMICAL EXTRACTION METHODS FOR AVAILABLE IRON CONTENT OF THE SOILS FROM EDIRNE PROVINCE IN TURKEY

The aim of this research was to determine the available iron (Fe) content of the soils of Edirne Province and the most suitable chemical extraction method. Eight chemical extraction methods (0.005 M DTPA + 0.01 M CaCl2 + 0.1 M TEA; 0.05 M HCl + 0.012 M H2SO4; 1 M NH4OAc (pH: 4.8); 0.01 M EDTA + 1 M NH4OAc; 1 M MgCl2; 0.01 M EDTA + 1 M (NH4)2CO3; 0.005 M DTPA + 1 M NH4HCO3 and 0.001 M EDDHA methods) and six biological indices (dry matter yield, Fe concentration, Fe uptake, relative dry matter yield, relative Fe concentration, relative Fe uptake) were compared. Biological indices were determined with Barley (Hordeum vulgare L.) grown under greenhouse conditions. At the end of the experiment, the highest correlation coefficients (r) were determined to be between the 0.005 M DTPA + 0.01 M CaCl2 + 0.1 M TEA method and the biological indices and between the 0.005 M DTPA + 1 M NH4HCO3 method and the biological indices. The correlation coefficients (r) for the 0.005 M DTPA + 0.01 M CaCl2 +0.1 M TEA method were r=0.621**; r=0.823**; r=0.810**; r=0.433**; r=0.558** and r=0.640** and for the 0.005 M DTPA + 1 M NH4HCO3 method r=0.618** ; r=0.520**; r=0.679**; r=0.521**; r=0.492** and r=0.641**, (**:p<0.01) respectively. These extraction methods, among all the methods tested were suggested for the determination of available Fe content of Edirne Province soils.