Kα X-ray sources generated from the interaction of ultra-short laser pulses with solids are compact and low-cost source of ultra-short quasi-monochromatic X-rays compared with synchrotron radiation source. Development of collimated ultra-short Kα X-ray source by the interaction of 45 fs Ti:sapphire laser pulse with Cu wire target is presented in this paper. A study of the Kα source with laser parameters such as energy and pulse duration was carried out. The observed Kα X-ray photon flux was ~2.7 × 108 photons/shot at the laser intensity of ~2.8 × 1017 W cm−2. A model was developed to analyze the observed results. The Kα radiation was coupled to a polycapillary collimator to generate a collimated low divergence (0.8 mrad) X-ray beam. Such sources are useful for time-resolved X-ray diffraction and imaging studies.

Genetic diversity and relationship of 92 bread wheat (Triticum aestivum L.) genotypes from India and exotic collections were examined using simple sequence repeat (SSR) markers and phenotypic traits to identify new sources of diversity that could accelerate the development of improved wheat varieties better suited to meet the challenges posed by heat stress in India. Genetic diversity assessed by using 82 SSR markers was compared with diversity evaluated using five physiological and six agronomic traits under the heat stress condition. A total of 248 alleles were detected, with a range of two to eight alleles per locus. The average polymorphic information content value was 0.37, with a range of 0.04 (cfd9) to 0.68 (wmc339). The heat susceptibility index was determined for grain yield per spike, and the genotypes were grouped into four categories. Two dendrograms that were constructed based on phenotypic and molecular analysis using UPGMA (unweighted pair group method with arithmetic mean) were found to be topologically different. Genotypes characterized as highly heat tolerant were distributed among all the SSR-based cluster groups. This implies that the genetic basis of heat stress tolerance in these genotypes is different, thereby enabling wheat breeders to combine these diverse sources of genetic variability to improve heat tolerance in their breeding programmes.

The present study concerns identification of the most profitable and water and nitrogen use efficient best management practice (BMP) in a rice–wheat system using a combined approach of field experimentation and simulation. In the field study, two independent experiments, (1) effect of three transplanting/sowing dates, two cultivars and two irrigation regimes and (2) effect of four nitrogen (N) levels with four irrigation regimes, were conducted for two seasons of 2008–09 and 2009–10 at Punjab Agricultural University, Ludhiana, India. Integrating the treatments of the two independent field experiments, simulations were run with the CropSyst model. The BMP demonstrated was transplanting of rice on 20 June and sowing of wheat on 5 November, irrigation to rice at 4-day drainage period and to wheat at irrigation water depth/Pan–E (open pan evaporation) ratio of 0.9, and fertilizer N of 150 kg ha−1 to each crop for medium-duration varieties. This practice gave higher profit (35%), equivalent rice yield (16%), crop water productivity (15%), irrigation water productivity (51%), economic water productivity (34%) and economic N productivity (94%) than the existing practice by the farmers. The improvement in crop water productivity by shifting the transplanting/sowing date was due to reduction in soil water evaporation and increased transpiration and fertilizer N productivity through increased N uptake.

Puddling coarse-textured soils for rice culture in the irrigated tract of the Indo-Gangetic Plains causes high soil strength in the upper layers. This may adversely affect growth and yield of following upland crops. It is possible that no-tillage (NT) in wheat (without residues of preceding rice crop) could aggravate this problem and reduce fertilizer nitrogen (N) use efficiency. In certain production scenarios, NT has been reported to be advantageous because it allows for earlier planting of wheat by eliminating delays caused by tillage. This study examined the combined effects of two crop establishment options for wheat in relation to fertilizer N and planting time following puddled rice cultivation in an irrigated environment of Punjab, northwest India. Combinations of two establishment systems, NT-direct planting and conventional-tillage (CT) with soil disruption to 0.10 m depth in main plots, with two N rates, 120 and 150 kg ha−1 in subplots, were evaluated. Variation in planting time, 31 October (D1) and 7 and 10 November (D2), was used to evaluate effect of planting-earliness. Under D1 in NT, grain yield of wheat was comparable to that under D2 in CT. However, under no advancement of wheat planting in NT, grain yield was 0.2–0.3 t ha−1 less than that in CT. This yield reduction in NT could be overcome by adding 30 kg ha−1 more fertilizer N suggesting that tillage enhanced N use efficiency. These tillage gains are ascribed to the greater extraction of profile stored and applied water and nutrients because of denser crop rooting caused by reduction in soil strength and less weed competition. Higher N use efficiency in CT suggests that farmers could achieve fertilizer N savings with this system. Comparing the tillage systems showed that NT was more cost-effective than CT even after accounting for the cost of additional fertilizer N (saving of Rs. 1685 ha−1) to overcome associated yield penalties under no advancement in planting time.

In this work, TOPO(tri-octyl phosphine oxide)/TOP(tri-octyl phosphine)-capped cadmium selenide (CdSe) quantum dots (QD's) of varied sizes (5–9 nm) prepared at different input Cd:Se precursor ratio's (1:1–2:1) using chemical route were dispersed in conducting polymer matrices viz poly[2-methoxy,5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and poly(3-hexylthiophene) (P3HT) respectively. The properties of polymer:CdSe nanocomposites are evaluated by means of photoluminescence (PL), UV-VIS absorption, Raman, Fourier transform infrared (FTIR), transmission electron microscopy (TEM) and atomic force microscopy (AFM) techniques respectively. The emission and structural properties of polymer-CdSe nanocomposites are found to be dependent on their morphology. The better quality of smallest sized CdSe QD's (size ~5 nm) in conjunction with regioregular P3HT polymer, leads to higher photostability of P3HT:CdSe QD's nanocomposites as compared to that for corresponding MEH-PPV:CdSe nanocomposites, thus making it as an attractive candidate for hybrid solar cells application.

Dry matter and tuber yields of potato grown in a sub-tropical environment were estimated employing simple radiation-based models which require meteorological information on air temperature and solar radiation. Two versions of the MacKerron and Waister (1985) model, in which estimation of dry matter accumulation relies on a single composite parameter, radiation use efficiency (RUE), were compared with the Versteeg and Van Keulen (1986) model, which explicitly accounts for temperature and radiation effects on dry matter accumulation. In the original version of the MacKerron and Waister model, a linear change in the radiation interception factor with leaf area index is assumed; in the modified version an exponential change in the interception factor with leaf area index is considered. The accumulation of dry matter estimated from all three models was close to the measured values throughout the growing season, but estimates of tuber yield differed widely. Our analysis showed that the best agreement with measured values was obtained using the MacKerron and Waister linear model with RUE values adjusted according to the incident radiation level.

Estimatión del rendimiento del tubérculo de la patata

Extended abstract of a paper presented at MC 2007, 33rd DGE Conference in Saarbrücken, Germany, September 2 – September 7, 2007

Long-term data (20 years) on wheat (Triticum aestivum) grain yield under various fertilizer-nitrogen (N) and water conditions in rainfed and irrigated environments of sub-tropical north India were used to assess the magnitude and economics of N response in relation to amount and timing of irrigation. Treatments comprised combinations of fertilizer N rates (ranging from 0 to 150 kg ha−1) and irrigation regimes (rainfed, supplemental, limited, and adequately irrigated). Regression analysis of wheat yield against available water supply and fertilizer N showed a strong interaction between the two variables for grain yield and input use efficiency. The effect, on grain yield and returns, of increasing the N rate for a given water supply was influenced by the irrigation regimes. Economic optimization of water and N, based on constrained profit maximization technique, showed that optimum amounts of available water (or irrigation) and fertilizer N are related directly to the capital investment. Increased input prices lowered their optimum levels for a given investment. The analysis suggests an approach for resource allocation that relates to capital investment and input prices.

A study of angular distribution of X-ray line radiation emitted from a laser-produced plasma is presented. Plasma was produced by irradiating a planar magnesium target using single laser pulses of 6 J, 4.5 ns (FWHM) from an Nd:glass laser system. Angular distribution of X-ray emission in the spectral range of 7–10 Å was recorded using a single X-ray crystal spectrograph. X-ray emission intensity for different resonance lines is observed to decrease up to an angle of ∼45° with respect to target normal, followed by a significant increase at higher angles. The observed departure of angular distribution from a monotonically decreasing behavior is broadly in agreement with the calculations of the escape factor of the radiation at different angles from a thick disk-shaped plasma using a spectroscopic code RATION.

Long-term field experiments were conducted at six different sites (representing dryland and irrigated environments) with wheat (Triticum aestivum) on sandy loam soils to generate a database relating available water supply and fertilizer nitrogen (N) rate to grain yield. Step-wise multiple regression analysis showed that water supply and fertilizer N at more than 53 cm a−1 and 103 kg ha−1 a−1 were unproductive. A method, based on the principle of equi-marginal productivity of water in different periods of crop growth, has been used to estimate the optimum allocation of the variable amounts of water supply over the growing season. The optimized quantities of water in different periods of crop growth were then employed to compute fertilizer N requirement to achieve a given yield target. For medium grain yield targets (4–5 t ha−1), the range of substitution between fertilizer N and water for efficient resource use was quite wide.

An investigation of a monochromatic point X-ray source of photon energy ∼5 keV was carried out. The source was set up using a laser produced Al plasma as a cathode and a point-tip Ti anode. Optimum parameters of the diode were determined from experimental measurements of X-ray intensity dependence on laser pulse energy, applied accelerating voltage, and distance between target (cathode) and anode, using Nd:glass laser pulses (FWHM 30 ns) of 2 mJ to 4 J energy. Electron temperature characterization of the target plasma was also performed from the XUV emission spectrum (5–80 Å). Parameters of X radiation in Ti K-shells are (1) spectral brightness of ∼1020 photons/cm2-sec-sr-keV, (2) spatial size ∼300 microns, and (3) X-ray pulse duration less than 20 ns.

Water balance components under wheat were assessed by employing two simple models, differing in their structure and data requirements, namely the soil-plant–atmosphere–water (SPAW) model of Saxton (1989) and the water balance model (WBM) of Arora et al. (1987). A few modifications based on the SPAW model procedure for the estimation of green canopy were used in a modified WBM and its performance was also tested. Soil water loss (the sum of interception evaporation, soil evaporation, plant transpiration and deep drainage) from sowing to harvest, simulated with the WBM, modified WBM and the SPAW model, had a close correspondence with the measured sum of profile water depletion, rainfall and irrigation for values ranging between 18·3 and 42·7 cm. Estimates of drainage with the WBM and modified WBM using empirical coefficients were greater than those calculated using the SPAW model for situations where the upward flow of water into the root-zone was negligible. Estimates of soil water evaporation using the WBM and modified WBM were invariably smaller than those using the SPAW model. A comparison of simulated and measured soil water storage and a correlation analysis of simulated transpiration with measured biomass at harvest showed that the performance of the WBM was the most realistic of the three models. However, it requires the input of leaf area index values to infer green canopy for each water supply regime. In the absence of this information, the modified WBM and SPAW models are more useful for assessing water balance components in cropped soils.