Terms Of Grain Research Articles

Nitrate Reductase Activity of Diverse Grain Sorghum Genotypes and Its Relationship to Nitrogen Use Efficiency

High crop N use efficiency is desirable for reducing the cost and reliance on fertilizer N, and it may help reduce ground water pollution. The objectives of this study were to (i) characterize and compare the seasonal trends in nitrate reductase activity (NRA) of seven grain sorghum [Sorghum bicolor (L.) Moench] genotypes of tropical and U.S. origin, (ii) determine how NRA is related to total plant N, dry matter, grain yield, and N use efficiency, and (iii) examine how NRA and plant N accumulation affect N use efficiency for biomass (NUE1) and grain production (NUE2). The genotypes were evaluated in field trials in 1994 and 1996 at applied N levels of 0 and 100 N kg ha−1 on a Sharpsburg silty clay loam soil (fine, smectitic, mesic Typic Argiudoll). Plant biomass, reduced N, NRA, NUE1, and NUE2 were determined at three growth stages (vegetative, anthesis, and physiological maturity). Genotypes did not differ for NRA at either N level; however, there was a definite tendency for the four tropical lines and two U.S. adapted lines to have greater NRA values at all growth stages than the one hybrid. Nitrate reductase activity decreased throughout the growing season, with the sharpest decline from anthesis to maturity. Nitrate reductase activity did not correlate with grain yield or shoot biomass, but did correlate with grain N concentration. Shoot and grain N concentration correlated with NUE1, while grain and shoot N contents and shoot N concentration were correlated with NUE2. Neither NUE1 nor NUE2 were significantly affected by the NRA level. Tropical lines had greater preanthesis N uptake accumulation (1.45 g plant−1) and greater NUE1 than the hybrid (0.90 g plant−1) and U.S. adapted lines (0.73 g plant−1). In terms of grain N use efficiency, the hybrid had a 14% greater value than U.S. adapted lines and a 17% greater value than the tropical lines. It appears that NRA is not a factor that limited N accumulation and use efficiency in grain sorghum.

High temperature poling effects on conducting barium titanate ceramics

A high temperature NTC resistivity transition (T c2) near 600°C has been found in donor modified barium titanate (BaTiO3). Thermal treatment around this temperature regime plus applied voltage (T c2-Poling) on previously developed PTCR materials significantly affects both electrical behavior and ferroelectric domain structure in samples which have not been annealed after sintering. This type poling results in alignment of the domain structure in a coherent nature in direction of the applied voltage. Samples with a highly suppressed resistivity transition have been developed within direction of the applied voltage, while typical PTCR behavior exists in the anti-poled direction. Properties are dependent on domain structure orientation and grain boundary coherency developed during T c2-poling. Annealed samples are not affected in the same fashion and do not show enhanced domain alignment due to inhomogeneous grain boundaries which pin the domain structure. Results indicate that conductivity and PTCR behavior is notably dependent on grain boundary and domain structure coherency. Conversion from typical PTCR behavior to one which exhibits minimal dependence on the phase transition and results in a highly conductive cubic state is described in terms of grain boundary/domain alignment.

Calculation of Effective Elastic Constants for Polycrystalline Materials

The average elastic properties of a polycrystalline material do not only depend on the anisotropic elastic properties of the individual grains, but also on the distribution of crystal orientations (represented by an orientation distribution function (ODF)), on the mutual misorientation of neighbouring grains, on the size of the grains and on their shape. We use a previously developed cluster model to calculate the influence of texture, anisotropy, orientation correlation and grain shape, with the latter being confined to a few idealized cases. The model consists of several hundred uniformly shaped and equally sized grains. The individual orientations of the grains are picked at random by using a random generator or an appropriate modification when simulating a given ODF. To incorporate the correlation of the grain orientation we use a method already reported elsewhere. The displacement that occurs within the grains as one subjects the cluster to external forces is expanded in terms of grain referenced basis functions. The expansion coefficients are determined by requiring these expansions and the associated stresses to match continuously at the grain boundaries. Once the displacement is known, one can calculate the stresses and strains everywhere and form their spatial averages. The effective elastic constants are defined as interconnecting these averages. It turns out that for a given ODF (e.g. for a random ODF) the effective elastic constants may vary within the entire range defined by the familiar Voigt and Reuss value if one assumes sizably different misorientation distributions functions (MODF). Our model is also suited for studying the influence of the grain shape on the elastic constants.

Cropping Intensity and Nitrogen Management Impact of Dryland No-Till Rotations in the Semi-Arid Western Great Plains

Crop N needs are not usually predicted based on cropping intensity or on tillage practice. However, N fertilizer requirements may increase dramatically as less fallow and less tillage are used in semi-arid regions of the Great Plains where summer fallow cropping is common. This long-term experiment was conducted to study the influence of N fertilizer rate, source/placement/timing (NSP), and crop rotation factors on the production of winter wheat (Triticum aestivum L.), corn (Zea mays L.), and grain sorghum (Sorghum bicolor L.), as well as their fertilizer N use efficiency (FNUE) for the initial years of conversion to no-till dryland farming. Research was conducted from 1987 through 1992 on two soils (Keith clay loam, a fine-silty, mixed, mesic Aridic Argiustoll and Weld loam, a fine-silty, mixed, mesic, Aridic Argiustoll) in eastern Colorado. Rotations included winter wheat-fallow (WF) and winter wheat-corn or grain sorghum-fallow (WCF). Wheat yields were similar between WF and WCF with adequate N application. Response to N fertilizer at lower rates was greater in WCF than WF because of its greater depletion of soil N. Corn production averaged 72 bu/acre with adequate N and required 1 Ib/acre of N uptake to produce 1 bu/acre of grain. Current N fertilizer recommendations for wheat and corn were not adequate to insure maximum production under no-till management. Fertilizer placement significantly affected average annual rotational yield (40 to 70 Ib/acre per yr difference) but application rate was more important economically. Grain biomass produced in each rotation per pound of total plant N uptake (GNUE) was 17 Ib/acre per yr in WF compared with 29 Ib/acre per yr for WCF. This 70% increase in average annual grain production of WCF over WF was accomplished with a 44% annual increase in fertilizer N application.

Continuous, alternate and double crop systems on a Vertisol in subtropical Australia

Three cropping systems using 5 crop species were compared over a 10-year period on a cracking clay soil (Vertisol) in the sub-humid subtropics of eastern Australia. The 3 cropping systems were continuous (the same crop every year), alternate (the same crop every second year) and double (a winter and summer crop in the one year). There were 2 cereal crops (sorghum and wheat) and 3 grain legumes (chickpea, green gram and black gram). The effect of cropping system was measured in terms of grain and protein yields and changes in soil organic carbon (surface 0-10 cm) and nitrogen concentrations. Summer and winter rainfall was below average in 8 and 5 years out of 10, respectively. Grain yield of cereal monocultures was about twice that of legume monocultures. The potential for double cropping, despite the generally below-average rainfall, was clearly shown with the highest grain and protein yields coming from the combination of green gram (summer) and wheat (winter). Averaged over 10 years, wheat yield (1460 kg/ha. year) was identical in the continuous and alternate cropping systems. Sorghum yields were marginally higher with alternate cropping (1340 kg/ha. year) than continuous cropping (1050 kg/ha. year). With double cropping, average wheat yields were 1081 and 698 kg/ha when combined with green and black gram, respectively. Black gram gave half the average yield of either green gram or chickpea (about 300 v. 600 kg/ha). This was attributed to the indeterminate nature of the crop in an environment with variable rainfall and to the detrimental effect of above-average rainfall during harvest time. Soil nitrogen and carbon levels, with initial values of 0.22 and 2.96%, were reduced at the end of 10 years by 16 and 27% respectively. Their rate of decline did not differ between cropping systems.

The Resistance of Grain Boundaries in BaTiO<inf>3</inf>-Based Ceramic

Evidence for grain boundary (GB) resistance in BaTiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> based capacitor ceramic exists in superohmic current voltage characteristics, in voltage-dependent activation energies, in high-voltage ohmic behavior, and in a conductivity peak at the Curie temperature. These phenomena are reviewed. Impedance-frequency measurements are reported for GB-controlled varistors and for BaTiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> -based capacitor ceramic under increasing voltage bias. The impedance plots are discussed in terms of grain and GB contributions. No contribution from contacts is evident. The resistance attributed to GB decreases faster with voltage bias than that due to grains. Schö11's model for dependence of GB barrier height on grain curvature for polycrystalline silicon is adapted to high-K ceramic. It is seen that grain curvature, along with carrier depletion in the grains, can result in significant reductions in GB barrier height and hence resistance. Variation in grain size in a given ceramic can result in GB resistance variations throughout the material.

Sulfur‐coated Urea and Urea Compared as Nitrogen Sources for Irrigated Corn

AbstractSulfur‐coated urea (SCU) was compared to urea (U) to determine their value as N fertilizers for irrigated corn (Zea mays L.) production. Two soils were studied from 1970 through 1972, Cass sandy loam (Fluventic Haplustoll) and Holder silty clay loam (Udic Arguistoll). Comparisons were made with different rates of the two fertilizers and the results interpretated in terms of yields, N uptake, and residual NO3‐‐N in the root zone.Results of the study indicated little difference between the performance of the two N fertilizers in terms of grain, forage yields, or in N uptake although N from SCU tended to be less available than from U. After 3 years of application, more NO3‐‐N was found in the root zone with SCU than U. This was especially apparent on the fine‐textured Holder soil and to a lesser extent on the sandy Cass soil. While the increased NO3‐‐N found after 3 years in the root zone did not affect fertilizer N need, data does suggest that SCU has potential for increased N efficiency by reducing leaching under moderate leaching situations.The data emphasizes the need for more accurate N recommendations that will access NO3‐‐N in the root zone, N mineralization potential of the soil, and N in the irrigation water. It was possible to grow 92 to 94% of maximum corn yields without losses of N to the groundwater.

Physiologic Maturity in Grain Sorghum1

External visualization of the apparent dark closing layer in the placental area near the sorghum [Sorghum bicolor (L.) Moench] kernel attachment point coincides closely with the cutoff of radioactive assimilate translocation to the kernel. Dark layer determination permits identification of physiologic maturity or date of maximum dry weight accumulation. This judgment is meaningful because yield is a function of both time and metabolic efficiency. Genotypes can be characterized in terms of grain filling‐period duration by noting the dates of bloom and dark layer formation. Yield data plus physiologic maturity data permit direct field quantitation of the time and metabolic efficiency components of Grain dry weight accumulation.