Labeled nitrogen fertilizer research with urea in the semi-arid tropics 3. Field studies on alfisol

Field studies with bordered microplots were conducted on an Alfisol in the semiarid tropics of India to determine (1) the fate of15N-labeled urea applied to dryland sorghum in two successive rainy seasons and (2) the effect of method of application on N fertilizer efficiency. Recoveries of15N-labeled fertilizers by above-ground plant parts ranged from 46.7% to 63.6% in 1981 when the rainfall was above the average and from 54.4% to 66.9% in 1980 when the rainfall was near the average. Small (0.014 g) pellets of urea applied twice as postemergent applications in separate 5 cm deep bands were more effective than single preemergent applications either surface applied or incorporated. Both banding and the split applications contributed to overall fertilizer efficiency. Large (1.0 g) pellets of urea (supergranules) placed at a depth of 5 cm were also superior to the incorporated, small-pellet treatment in 1981. The15N-balance data for the soil (0–90 cm in depth)-plant system in 1981 showed that the unaccounted-for fertilizer N ranged from 5.1% to 20.6%. An important finding was that high grain yields, in excess of 6,000 kg/ha, with N fertilizer losses of less than 10% could be obtained through fertilizer management during a very wet season. The data from the Alfisol experiments were compared with data from similar Vertisol experiments; N fertilizer losses resulting from incorporated and surface applications were greater for Vertisols than for Alfisols in the wetter year

Effect of Water Pretreatment on Total Nitrogen Analysis of Soils by the Kjeldahl Method

Effective methods are needed for determining total N when studying the fate of N fertilizer applied to soil. This study was concerned with the pretreatment of samples of a Vertisol (calcareous Typic Pellusterts) with water, 20 and 2 mL for macro- and semimicro-Kjeldahl methods, respectively, prior to digestion. The need for such a modification with certain clay soils was originally recommended in 1925, but its requirement in conjunction with modern Kjeldahl methods is rarely reported. The macro- and semimicro-Kjeldahl methods used involved digestion of soil with a H2SO4-K2SO4-CuSO4 5H2O-Se mixture. Both techniques yielded digestion residues with dark-colored granules and low recoveries of N with soil samples ground to pass through a sieve with 0.8-mm openings (20 mesh), unless the soil was initially treated with water. For instance, N recovery from a surface Vertisol was increased by 29% as a result of a 30-min water soaking prior to a macro-Kjeldahl digestion. Extension of the digestion period up to 5 h after initial clearing did not eliminate the need for the water pretreatment. The requirement for the water pretreatment for semimicro-Kjeldahl methods was greatly reduced when the soil was ground to pass through a sieve with 0.16-mm openings (100 mesh). Increase in soil N due to water pretreatment was reduced from 35 to 6% by grinding the coarser soil to such fineness. A salicylic acid pretreatment, involving water addition after the nitration reaction, permitted satisfactory digestion. The water pretreatment effect appeared to be associated with incomplete digestion of organic N, not with the recovery of fixed NH4+, and was found with both surface and subsoils. Water pretreatment of samples from several horizons of an Alfisol (Udic Rhodustalfs) had little effect on recovery of soil N. A water pretreatment is probably not needed to obtain maximum recoveries of N if the nonmodified Kjeldahl method results in a postdigestion soil residue without dense, darkish granules. However, the water soaking was found to reduce bumping during digestion of many soils and is recommended for routine us

A high-resolution study of the X-ray emission and Sunyaev–Zel'dovich effect in the Bullet cluster (1E 0657−56)

High-resolution imaging of the Sunyaev–Zel'dovich (SZ) effect opens new possibilities for testing the presence of various high-energy particle populations in clusters of galaxies. A detailed X-ray analysis of the ‘Bullet cluster’ (1E 0657−56) with Chandra has revealed the presence of additional X-ray spectral components beyond a simple, single-temperature plasma in its X-ray spectra. X-ray methods alone are insufficient to elucidate the origins of these spectral components. We show that the morphology and magnitude of the SZ effect at high frequencies are critically dependent upon the mechanism by which the additional X-ray spectra are created. We examine the differences between the predicted SZ effect emission maps at 600 GHz assuming the X-ray spectra are composed of thermal gas with a steep power-law index component and also thermal gas with a significant contribution of strongly heated gas. A two-temperature model with a hot (kT ≃ 30–40 keV) second component is the most consistent with existing SZ data at high frequencies. However, significant morphological differences remain. High-angular-resolution SZ intensity maps at high frequencies in combination with deep X-ray data provide a new window into understanding particle energization processes in the hottest, massive merging galaxy clusters

Labeled nitrogen fertilizer research with urea in the semi-arid tropics II. Field studies on a Vertisol

Field studies were conducted on Indian Vertisol to determine the fate of15N-labeled fertilizers applied to dryland sorghum in two successive rainy seasons. In the 1981 season, a split-band (SB) urea application of 74 kg N/ha, half amounts placed 5 cm deep and 8 cm from opposite sides of plant rows at 4 and 19 days after emergence, was superior to preemergent applications of either surface-applied (S) or incorporated (I) applications at the same rate; 907 mm of rainfall fell during the sorghum growing period. Percentages of applied N recovered in the soil-plant system after the sorghum harvest were 94%, 74%, and 72%, respectively, for the SB, I, and S application methods. Substantial quantities, 39%, 45%, and 42% of the added N for the SB, I, and S tretments, respectively, remained in the soil after the final harvest. Plant utilization of added urea-N was greater in 1980 when rainfall during the growing season was 212 mm less than in 1981. S or I applications of urea at 74 kg N/ha, with above-ground plant15N recoveries of 48.0% and 48.6%, respectively, were also equally as efficient during 1980. Residual soil N derived from fertilizer was of little value for a sorghum crop in the following rainy season and for a safflower crop in the post-rainy season in a double-cropping system

Influence of soil type and natural Zn chelates on flax response, tensile properties and soil Zn availability

A greenhouse experiment was conducted on weakly acidic and calcareous soils to evaluate the relative efficiencies of three natural Zn chelates [Zn-aminelignosulphonate (Zn-AML), Zn-polyhydroxyphenylcarboxylate (Zn-PHP) and Zn-S,S-ethylenediaminedisuccinate (Zn-S,S-EDDS)] applied to a crop textile flax (Linum ussitatisimum L.) at application rates of 0, 5 and 10 mg Zn kg−1. In the flax plant, the following parameters were determined: dry matter yield, soluble and total Zn concentrations in leaf and stem, chlorophyll, crude fibre, and tensile properties. For the different soil samples, the following parameters were determined: available Zn (DTPA-AB and Mehlich-3 extractable Zn), easily leachable Zn (BaCl2-extractable Zn), the distribution of Zn fractions, pH and redox potential. On the basis of the use of added Zn by flax, or Zn utilization, it would seem recommendable to apply Zn-S,S-EDDS at the low Zn rate in both soils. In contrast, adding the high Zn rate of this chelate to the weakly acidic soil produced an excessive Zn concentration in the plant, which caused a significant decrease in both dry matter yield and chlorophyll content. Furthermore, assessing available Zn with the DTPA-AB method proved the best way of estimating the level of excess Zn in flax plants. The soluble Zn concentration, which was established with 2-(N-morpholino)ethanesulfonic acid reagent (MES), of plant fresh and dry matter could be used as an alternative way of diagnosing the nutritional status of Zn in flax plants. In this experiment, the highest soil pHs were associated with the lowest redox potentials, which coincided with the smallest amounts of available Zn and water soluble Zn in soil, and the lowest levels of Zn uptake by flax plants

The persistent shadow of the supermassive black hole of M 87

In April 2019, the Event Horizon Telescope (EHT) Collaboration reported the first-ever event-horizon-scale images of a black hole, resolving the central compact radio source in the giant elliptical galaxy M 87. These images reveal a ring with a southerly brightness distribution and a diameter of ∼42 μas, consistent with the predicted size and shape of a shadow produced by the gravitationally lensed emission around a supermassive black hole. These results were obtained as part of the April 2017 EHT observation campaign, using a global very long baseline interferometric radio array operating at a wavelength of 1.3 mm. Here, we present results based on the second EHT observing campaign, taking place in April 2018 with an improved array, wider frequency coverage, and increased bandwidth. In particular, the additional baselines provided by the Greenland telescope improved the coverage of the array. Multiyear EHT observations provide independent snapshots of the horizon-scale emission, allowing us to confirm the persistence, size, and shape of the black hole shadow, and constrain the intrinsic structural variability of the accretion flow. We have confirmed the presence of an asymmetric ring structure, brighter in the southwest, with a median diameter of 43.3−3.1+1.5 μas. The diameter of the 2018 ring is remarkably consistent with the diameter obtained from the previous 2017 observations. On the other hand, the position angle of the brightness asymmetry in 2018 is shifted by about 30° relative to 2017. The perennial persistence of the ring and its diameter robustly support the interpretation that the ring is formed by lensed emission surrounding a Kerr black hole with a mass ∼6.5 × 109 M⊙. The significant change in the ring brightness asymmetry implies a spin axis that is more consistent with the position angle of the large-scale jet

Zinc Deficiency of Flax in North Dakota

This article address the cause of "chlorotic dieback" and the influences of zinc, phosphorus and iron fertilizers, levels of soil-extractable zinc and soil temperature on this disease

The Use of Anhydrous Ammonia in North Dakota

In 1978, the importance of anhydrous ammonia usage in the state of North Dakota exceeded the national average. Economics drove the usage of ammonia in North Dakota as it is the most highly concentrated form of nitrogen fertilizer available. It was less expensive as well. It can be incorporated in it's application while the farmer tills the land. Their was a worry at this time that foreign sources of ammonia would flood the US marketplace. The physical properties of ammonia are discussed. The equipment used to to apply ammonia rated well with North Dakota farmers in it's application of the quantity required of ammonia. Problems with lateral distribution of ammonia among injection outlets was discussed