For developing the site-specific fertilizer management strategies of crop, it is essential to know the spatial variability of soil factors and to assess their influence on the variability of crop growth and yield. In 2002 and 2003 cropping seasons within-field spatial variability of rice growth and yield was examined in relation to spatial variation of soil properties in the· two paddy fields having each area of ca. 6,600m2 in Suwon, Korea. The fields were managed without fertilizer or with uniform application of N, P, and K fertilizer under direct-seeded and transplanted rice. Stable soil properties such as content of clay (Clay), total nitrogen (TN), organic mater (OM), silica (Si), cation exchange capacity (CEC), and rice growth and yield were measured in each grid of 10~times10m . The two fields showed quite similar spatial variation in soil properties, showing the smallest coefficient of variation (CV) in Clay (7.6~%) and the largest in Si (21.4~%) . The CV of plant growth parameters measured at panicle initiation (PIS) and heading stage (HD) ranged from 6 to 38~% , and that of rice yield ranged from 11 to 21~% . CEC, OM, TN, and available Si showed significant correlations with rice growth and yield. Multiple linear regression model with stepwise procedure selected independent variables of N fertilizer level, climate condition and soil properties, explaining as much as 76~% of yield variability, of which 21.6~% is ascribed to soil properties. Among the soil properties, the most important soil factors causing yield spatial variability was OM, followed by Si, TN, and CEC. Boundary line response of rice yield to soil properties was represented well by Mitcherich equation (negative exponential equation) that was used to quantify the influence of soil properties on rice yield, and then the Law of the Minimum was used to identify the soil limiting factor for each grid. This boundary line approach using five stable soil properties as limiting factor explained an average of about 50~% of the spatial yield variability. Although the determination coefficient was not very high, an advantage of the method was that it identified clearly which soil parameter was yield limiting factor and where it was distributed in the field.
Rice yield and protein content have been shown to be highly variable across paddy fields. In order to characterize this spatial variability of rice within a field, two-year experiments were conducted in 2002 and 2003 in a large-scale rice field of 6,600m2 In year 2004, an experiment was conducted to know if variable rate treatment (VRT) of N fertilizer, that was prescribed for site-specific management at panicle initiation stage, could reduce spatial variation in yield and protein content of rice while increasing yield compared to conventional uniform N topdressing (UN, 33kg N/ha at PIS) method. VRT nitrogen prescription for each grid was calculated based on the nitrogen (N) uptake (from panicle initiation to harvest) required for target rice protein content of 6.8~% , natural soil N supply, and recovery of top-dressed N fertilizer. The required N uptake for target rice protein content was calculated from the equations to predict rice yield and protein content from plant growth parameters at panicle initiation stage (PIS) and N uptake from PIS to harvest. This model· equations were developed from the data obtained from the previous two-year experiments. The plant growth parameters for the calculation of the required N were predicted non-destructively by canopy reflectance measurement. Soil N supply for each grid was obtained from the experiment of year 2003, and N recovery was assumed to be 60~% according to the previous reports. The prescribed VRT N ranged from 0 to 110kg N/ha with an average of 57kg/ha that was higher than 33 kg/ha of UN. The results showed that VRT application successfully worked not only to reduce spatial variability of rice yield and protein content but also to increase rough rice yield by 960kg/ha. The coefficient of variation (CV) for rice yield and protein content was reduced significantly to 8.1~% and 7.1~% in VRT from 14.6~% and 13.0~% in UN, respectively. And also the average protein content of milled rice in VRT showed very similar value of target protein content of 6.8~% . In conclusion the procedure used in this paper was believed to be reliable and promising method for reducing within-field spatial variability of rice yield and protein content. However, inexpensive, reliable, and fast estimation methods of natural N supply and plant growth and nutrition status should be prepared before this method could be practically used for site-specific crop management in large-scale rice field.
ice yield and plant growth response to nitrogen (N) fertilizer may vary within a field, probably due to spatially variable soil conditions. An experiment designed for studying the response of rice yield to different rates of N in combination with variable soil conditions was carried out at a field where spatial variation in soil properties, plant growth, and yield across the field was documented from our previous studies for two years. The field with area of 6,600 m2 was divided into six strips running east-west so that variable soil conditions could be included in each strip. Each strip was subjected to different N application level (six levels from 0 to 165kg/ha), and schematically divided into 12 grids (10m ~times10m~;for~;each~;grid) for sampling and measurement of plant growth and rice grain yield. Most of plant growth parameters and rice yield showed high variations even at the same N fertilizer level due to the spatially variable soil condition. However, the maximum plant growth and yield response to N fertilizer rate that was analyzed using boundary line analysis followed the Mitcherlich equation (negative exponential function), approaching a maximum value with increasing N fertilizer rate. Assuming the obtainable maximum rice yield is constrained by a limiting soil property, the following model to predict rice grain yield was obtained: Y=107651-0.4704*EXP(-0.0117*FN)*MIN(I-clay,~;Iom,~;Icec,~;ITN,~; ISi) where FN is N fertilizer rate (kg/ha), I is index for subscripted soil properties, and MIN is an operator for selecting the minimum value. The observed and predicted yield was well fitted to 1:1 line (Y=X) with determination coefficient of 0.564. As this result was obtained in a very limited condition and did not explain the yield variability so high, this result may not be applied to practical N management. However, this approach has potential for quantifying the grain yield response to N fertilizer rate under variable soil conditions and formulating the site-specific N prescription for the management of spatial yield variability in a field if sufficient data set is acquired for boundary line analysis.
The experiment was conducted at the Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur to study the response of chickpea (Cicer arietinum L) to dual inoculation of Rhizobium and arbuscular mycorrhiza, poultry litter, nitrogen, and phosphorus on spore population and colonization, nodulation, growth, yield attributes, and yield. The performance of Rhizobium inoculant alone was superior to control in all the parameters of the crop studied. Among the treatments dual inoculation of Rhizobium and arbuscular mycorrhiza in presence of poultry litter performed best in recording number and dry weight of nodules, dry weight of shoots and roots, number of pods/plant, number of seeds/pod, and seed yields of chickpea. The highest seed yield of 3.96g/plant was obtained by inoculating chickpea plants with dual inoculation of Rhizobium and arbuscular mycorrhiza in association with poultry litter. Treatments receiving dual inoculation of Rhizobium and arbuscular mycorrhiza in presence of nitrogen and phosphorus, Rhizobium inoculant in presence of nitrogen and phosphorus, and that of arbuscular mycorrhiza in presence of nitrogen and phosphorus were similar as that of treatment receiving dual inoculation of Rhizobium and arbuscular mycorrhiza in presence of poultry litter. From the view point of nodulation, growth, yield attributes, and yields of chickpea, dual inoculation of Rhizobium inoculant and arbuscular mycorrhiza along with poultry litter was considered to be the balanced combination of nutrients for achieving the maximum output from cultivation of chickpea in Shallow Red Brown Terrace Soil of Bangladesh.
A study on genetic variability and association of yield attributing characters with grain yield was carried out using 35 deepwater rice genotypes. High genotypic co-efficient of variation (GCV) was observed for plot yield, EBT/m2 , plant height and days to 50~% flowering (DFF). For all the traits, estimates of the phenotypic co-efficient of variation (PCV) were higher than GCV, indicating presence of environmental influence. High heritability and genetic advance was observed for plot yield, EBT/m2 and plant height. Plot yield had significant positive association with test weight, EBT/m2 and DFF. However, test weight had the maximum direct effect on grain yield
Study on effectiveness of Bradyrhizobium japonicum on soybean [Glycine max (L.) Merr.], local cultivar 'Sathiya' were carried out in the garden soil of Trib-huvan University. Different parameters like nodulation, chlorophyll content in fresh leaves and growth of plant in inoculated and uninoculated plant was studied. Pot experiment was conducted in the green house to evaluate the effectiveness of B. japonicum on soybean. It was observed that B. japonicum inoculation increased the number of nodules, shoot length of plant and total chlorophyll content in fresh leaves of soybean plant. However, root length was decreased in all inoculated plants.
Early predictions of crop yields call provide information to producers to take advantages of opportunities into market places, to assess national food security, and to provide early food shortage warning. The objectives of this study were to identify the most useful parameters for estimating yields and to compare two model selection methods for finding the 'best' model developed by multiple linear regression. This research was conducted in two 65ha corn/soybean rotation fields located in east central South Dakota. Data used to develop models were small temporal variability information (STVI: elevation, apparent electrical conductivity (ECa) , slope), large temporal variability information (LTVI : inorganic N, Olsen P, soil moisture), and remote sensing information (green, red, and NIR bands and normalized difference vegetation index (NDVI), green normalized difference vegetation index (GDVI)). Second order Akaike's Information Criterion (AICc) and Stepwise multiple regression were used to develop the best-fitting equations in each system (information groups). The models with δi~leq2 were selected and 22 and 37 models were selected at Moody and Brookings, respectively. Based on the results, the most useful variables to estimate corn yield were different in each field. Elevation and ECa were consistently the most useful variables in both fields and most of the systems. Model selection was different in each field. Different number of variables were selected in different fields. These results might be contributed to different landscapes and management histories of the study fields. The most common variables selected by AICc and Stepwise were different. In validation, Stepwise was slightly better than AICc at Moody and at Brookings AICc was slightly better than Stepwise. Results suggest that the Alec approach can be used to identify the most useful information and select the 'best' yield models for production fields.
Low temperature is one of the most severe abiotic stress factors limiting growth, productivity and distribution of winter cereals. Reliable field screening method, which can detect small differences in winter survival, is important for the effective selection and development of plants to identity superior cold tolerant winter cereal genotypes. This study was undertaken to provide improved screening method of winter hardiness in the field by increasing the accuracy in evaluating winter hardiness of barley (Hordeum vulgare L.). We introduced furrow in field screening of winter survival. By sowing the plants at the ridge and base, we could minimize the effect of topographic variation in a field by giving higher and lower level of stress at the same time. This method could be used by breeders to conduct accurate evaluation of winter hardiness by selecting the better treatment, which shows close to normal distribution, among the winter survival rate from the ridge, base and mean survival rate of the two in a screening field.
Pod dehiscence (PD), defined as the opening of pods along both the dorsal and ventral sutures, causes the seed to shatter in the field before harvesting and results in loss of seed yields. However, breeding for resistance to PD is difficult due to the complicated genetic behavior and environmental interaction. The objective of the present research was to analyze the genetic behavior of PD for improving the breeding efficiency of resistance to PD in soybean. PD after oven-drying the sampled pod at 40~circC for 24 hours was the most reliable to predict the degree of PD tested in the field. Keunolkong, a dehiscent parent, was crossed with non-dehiscent parents, Sinpaldalkong and Iksan 10. Using their F1~;and~;F2 seeds, PD was measured after oven drying the pod at 40~circC for 24 hours. The gene conferring PD behaved in different manners depending on the genetic populations. In the Keunolkong~times Sinpaldalkong population, PD seemed to be governed by single major recessive gene and minor genes, while several genes were probably involved in the resistance to pod dehiscence in the Keunolkong~times Iksan 10 population. Heritability for PD estimated in F2 population showed over 90~% in the two populations. High heritability of PD indicated that selection for resistance to PD should be effective in a breeding program. In addition, genetic mapping of quantitative locus (QTL) for PD in both populations may reveal that genes conferring PD are population-specific
Ascorbate peroxidase (APX) plays a crucial role in the detoxification of hydrogen peroxide. APX activity is maintained significantly higher in the paraquattreated leaves of the paraquat-tolerant Rehmannia glutinos. This study was conducted to understand structural and regulatory characteristics of APX gene in R. glutinosa. A putative APX cDNA clone (RgAPX1) was isolated from a leaf cDNA library using a partially sequenced expressed sequence tag clone. RgAPX1 is consisted of 1148 bp nucleotides and contains an open reading frame encoding a 250 amino acid-long polypeptide. Deduced RgAPX1 amino acid sequence shares higher sequence similarity to cytosolic APXs. RgAPX1. expression was higher in the leaf than in the flower and root. Southern blot result indicates the presence of one or two RgAPX1-related genes in R. glutinosa genome. RgAPX1 transcription was affected differentially by various stresses and phytohormone. The results indicate that RgAPXl is constitutively expressed in most tissues and its expression is modulated for the immediate and efficient detoxification of H2O2 under normal and stress conditions.
This study was focuses on the variation of isoflavone contents during seed development and their interaction with major chemical components such as protein, amino acids, saccaharides, lipid and fatty acids. During maturing, lipid, protein, and amino acid contents in soybean seeds showed the highest values at R7 stages, but isoflavone contents were increased until R8 stage. It was noted that malonyl glucosides (64.2~%) are predominant forms among conjugated isoflavones followed by glucosides (30.7~%) , acetyl glucosides (4.1~%) and aglycones (0.9~%) . Sucrose and stachyose were presented as a major saccharide in soybean seeds. As maturing days progressed, they were constantly increased and the highest contents were observed at R8 stage. While small quantities of raffinose, fructose, glucose, maltose, DP3 (DP: degree of polymerization), DP6, and DP7 were detected. These results showed that saccharide composition at the beginning of seed development is primarily monosaccharides with little sucrose and oligosaccharides, but as maturing days proceeds, sucrose and starch increase with concomitant decrease in monosaccharides. Sucrose and stachyose were positively correlated with isoflavone (r=0.780, 0.764 at p<0.01, respectively), while fructose, glucose, maltose, and DP7 were negatively correlated (r=-0.651, -0.653, -0.602, and -0.586 at p<0.05, respectively). Soybeans at R8 stage were high in protein and amino acid, but low in free amino acid contents. Protein and amino acid contents showed positively significant correlations with isoflavone (r=0.571 and 0.599 at p<0.05, respectively), but free amino acid content were negatively correlation with isoflavone (r=-0.673, p<0.01). The lipid content reaches its final content relatively early stage of seed development and remains constant as compared with other chemical components. Among the fatty acids, although varietal difference was presented, stearic acid and linolenic acid were gradually decreased, while oleic and linoleic acid were increased as seed maturing progressed. Lipid was significantly correlated (r=0.754, p<0.01) with isoflavones. However, neither saturated fatty acid nor unsaturated fatty acids significantly affected the isoflavone contents of maturing soybean seeds.