The effect of nitrate and nitrous oxide on hydrogen and methane accumulation in anaerobically-incubated soils

Summary The effect of KNO₃ and N₂O on the accumulation of CH₄, H₂ and denitrification products in two North Dakota soils during anaerobic incubation at 30°C was studied by means of gas chromatography. KNO₃ and N₂O (500 ppm N) reduced the rate of accumulation of CH₄ by a Tetonka soil regardless of whether the soil was in an air-dried condition or had been pre-incubated and actively producing CH₄ prior to the treatment application. Both KNO₃ and N₂O completely suppressed H₂ accumulation by the remoistened air-dried soil; no H₂ either in the presence or absence of added KNO₃ or N₂O was accumulated by the pre-incubated Tetonka soil subsequent to the treatment application. KNO₃ (250 ppm N) reduced the rate of accumulation of CH₄ by a Cavour loam during anaerobic incubation. No H₂ was accumulated by this soil during anaerobic incubation. At equivalent K⁺ concentrations, KNO₃ suppressed CH₄ accumulation by the Tetonka and Cavour soils to a greater extent than did KCl.     

Effects of phosphorus and iron fertilizers on the growth of two soybean varieties at two soil temperatures

The influence of FeEDDHA (0, 0.2 and 2 μg Fe g⁻¹ soil) and NaH₂PO₄·H₂O (0 and 120 μg Pg⁻¹ soil) on the growth of two Fe-ineffective soybean (Glycine max L. Merr.) varieties (anoka and T203) on a calcareous soil at two soil temperatures (16 and 24°C) was compared under greenhouse conditions. The two soybean varieties differed in the following respects: (a) T203 accumulated smaller concentrations of Fe in washed tops than Anoka under comparable conditions; (b) T203 was more susceptible to Fe deficiency and its accentuation by high levels of fertilizer P than Anoka; (c) T203 accumulated lower quantities of Mn in tops than Anoka under comparable conditions; (d) T203, but not Anoka, developed Mn deficiency symptoms when treated with P and 2 μg Fe g⁻¹ at 16°C. Fe deficiency was more severe in both varieties at the higher soil temperature due apparently to: (a) greater plant concentration of P in tops at 24°C; and/or (b) an increased rate of plant growth and greater dilution of Fe in young tissue at 24°C. Foliar P concentration was increased much more than foliar Fe concentration by an increase in soil temperature. Severely Fe deficient T203 plants grown without FeEDDHA at 24°C accumulated less foliar Mn than their FeEDDHA counterparts. Comparisons of Fe effectiveness of various soybean cultivars based on relative responses to FeEDDHA can be influenced by differential effects on Mn nutrition.     

Synergistic effect of ethanol and cycloheximide on activation of freshly matured bovine oocytes

Bovine follicular oocytes were collected from ovarian antral follicles (2 to 7 mm in diameter) from slaughtered cattle. They were matured in vitro (IVM) for 23 to 24 h and then activated. In Experiment 1, 4 concentrations of ethanol were compared. The activation rates of oocytes were 4, 12, 36 and 27%, respectively, following exposure for 7 min to 0, 5, 7 and 10% ethanol. In Experiment 2, 7% ethanol was tested with exposure times of 0, 5, 7.5 and 10 min, and 6, 32, 27 and 33% of the oocytes were activated, respectively. In Experiment 3 the synergistic effect of ethanol and electric pulse was compared within 4 treatments: A) 7% ethanol alone, B) electric pulse alone, C) ethanol first and then electric pulse treatment, and D) electric pulse first followed by ethanol exposure. Of the oocytes activated, 37, 31, 28 and 51%, respectively, were from Treatments A through D. In Experiments 4 and 5 the possible synergistic effect of ethanol and a protein synthesis inhibitor, cycloheximide, was studied within 4 treatments: A) parthenogenetic control with no activation treatment, B) ethanol alone, C) cycloheximide alone, and D) ethanol treatment followed by cycloheximide. The oocyte activation rates in Experiment 4 in Treatments A through D, respectively, were 9, 44, 43 and 84%. Corresponding values for development of oocytes to the 2 to 8-cell stage after culture for 3 d (Experiment 5) were 9, 20, 14 and 45%, respectively (P<0.05). In conclusion, exposure to 7% ethanol for 5 min followed by incubation with cycloheximide was the best activation treatment for bovine IVM oocytes.     

Iron accumulation in seed of common bean

The effect of soil and genotype on iron concentration [Fe] in common bean (Phaseolus vulgaris L.) seed was studied in the greenhouse. Liming an acid soil increased soil pH from 6.0 to 7.3 but had no effect on seed [Fe] of three bean genotypes (Voyager, T39, UI911) from the Middle American gene pool in North Dakota. However, liming decreased seed-manganese concentration [Mn]. The influence of FeEDDHA on Fe accumulation in seed of the three bean genotypes, grown on acid (pH=6.0) and naturally calcareous (pH=8.2) soils, was also studied in North Dakota. Seed from the acid soil contained 25% higher [Fe] than seed from the calcareous soil. FeEDDHA increased seed [Fe] only on the calcareous soil, but reduced seed [Mn] on both soils. Voyager seed, characterized by a relatively low [Fe] in the seed coat, had a higher seed [Fe] than the other two genotypes. The hypothesis that high seed [Fe] is characterized by a low seed-coat [Fe] was next investigated. Voyager, T39 and 10 diverse Latin American genotypes from the Middle American gene pool were grown on a soil (pH=7.0) with Andic properties in Mexico in the presence and absence of FeEDTA. FeEDTA increased seed [Fe]. Seed of Voyager and a Mexican genotype (Bayo 400) had the highest seed [Fe]. However, Bayo 400, unlike Voyager, contained a high percentage of its seed Fe in the seed coat. Consequently, a high seed [Fe] genotype does not necessarily have a low seed-coat [Fe]. Both soil and genotype affect Fe accumulation in bean seed.     

Distribution of selected elements within flax plants as affected by FeEDDHA

Summary Flax growing on a calcareous soil in the greenhouse developed Mn toxicity symptoms. The toxicity was eliminated by application of 2 ppm FeEDDHA-Fe. FeEDDHA had major effects on distribution of Mn, Zn, Fe and P among selected plant parts. Application of the chelate reduced Mn concentration in older leaves, the tissue most susceptible to Mn toxicity, associated stem tissue, plant tops, and roots from 2295 to 133 ppm, 62 to 7 ppm, 550 to 34 ppm, and 42 to 34 ppm, respectively. Analysis of older leaves is recommended for diagnosing Mn toxicity in flax.FeEDDHA reduced Zn concentration in plant tops and this was chiefly reflected in greatly reduced leaf concentrations, especially in older leaves. FeEDDHA increased plant Fe concentration and the effect was greatest in root and older leaf tissues. The overall effect of FeEDDHA on P concentration was small but large increases occurred in younger leaf tissue due to application of the chelate. Relative distributions of K, Na, Ca, and Mg among plant parts were only slightly affected by FeEDDHA.     

Labeled nitrogen fertilizer research with urea in the semi-arid tropics

Summary 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.     

Accumulation of cadmium and selected elements in flax seed grown on a calcareous soil

Seed of flax (Linum usitatissimum L.) grown on calcareous and neutral soils sometimes accumulates relatively high concentrations of Cd. The influence of a post-flowering application of NH₄NO₃ (115 mg N kg^-1), CdSO₄ (1 mg Cd kg^-1), FeEDDHA (2 mg Fe kg^-1), NaH₂PO₄ (120 mg P kg^-1) and ZnSO₄ (8 mg Zn kg^-1) on seed accumulation of Cd, Fe, N, Mn, P and Zn by flax grown on a Calciaquoll was studied in two experiments under greenhouse conditions. Seed yields were increased by the N and Zn treatments, and the N×Zn interaction was positive. Zinc deficiency delayed flowering and boll formation by up to 20 days and reduced seed size. In the absence of added Cd, seed accumulated up to 0.33 mg Cd kg^-1. This Cd accumulation was reduced by approximately 50 and 17% by added Zn and Fe, respectively, but was little affected by P fertilizer and post-flowering N stress. In the presence of added Cd, seed Cd exceeded 3.3 mg Cd kg^-1, and the antagonistic effects of Fe and Zn on seed Cd were absent. Seed N, P, Fe and Zn concentrations were increased on average by 10, 45, 31 and 97% by the N, P, Fe and Zn fertilizer treatments, respectively. FeEDDHA reduced seed Mn concentration by approximately 58%. However, seed Mn concentration was much less than that found in vegetative tissue at flowering. Soil-applied Zn may reduce seed Cd concentration in flax under field conditions, and may increase marketability of flax for food use.     

Labeled nitrogen fertilizer research with urea in the semi-arid tropics

Summary As part of a research program to determine the fate of N fertilizers applied to dryland sorghum in the semi-arid tropics,¹⁵N balance studies were conducted with various N sources in the greenhouse. Two American soils, Houston Black clay (Udic Pellustert) and Windthorst sandy loam (Udic Paleustalf), similar in properties to the Vertisol and Alfisol in the semi-arid tropics of India, were employed. Experiments were conducted with large pots containing 20 or 60 kg of soil which was subjected to several watering regimes. The¹⁵N not accounted for in the plant and soil was presumably lost. Losses of N on calcareous Houston Black clay were greatest for broadcast urea, 16%–28%. Amendment of broadcast urea with 2% phenyl phosphorodiamidate, a urease inhibitor, reduced N losses only slightly to 15%–20%. Point placement of urea at a 6 cm soil depth reduced losses to 1%–11%. Granule size had no effect on N loss from point-placed urea. Ammonia volatilization was apparently the main N loss mechanism, since N losses from sodium nitrate were less than 7%, except when the soil surface was waterlogged. N losses on the Windthorst soil averaged 30% from urea and 11% from ammonium nitrate. Amendment of urea with urea phosphate to form a 27% N and 13% P product reduced fertilizer N losses but did not increase grain yield on Windthorst soil. N losses were also less from ammonium nitrophosphate than from urea. Band and point placement of urea 6 cm below the soil surface were equally effective in reducing N loss on Houston Black clay. The findings give credence to the recommendation of deep band placement for urea in the semi-arid tropics.     

Accumulation and within-seed distribution of iron in common bean and soybean

The influence of times of applying FeEDDHA on seed yield and Fe accumulation by four common bean (Phaseolus vulgaris L.) and two soybean (Glycine max L.) genotypes grown on a calcareous soil was studied under greenhouse conditions. The soybean genotypes, unlike the common bean genotypes, developed Fe-deficiency chlorosis and responded to application of the chelate. A preplant application of FeEDDHA was more efficacious than a flowering application in increasing seed yield of soybean. In contrast, the flowering application was much more effective than the preplant application for increasing seed Fe concentration [Fe] of both species. Percentage of seed Fe located in the seed coat of the common bean genotypes ranged from approximately 5 to 40% and was little affected by FeEDDHA. This within-seed distribution of Fe was correlated with methanol-extractable seed-coat pigments absorbing at 500 nm, presumably anthocyanins, but not with condensed tannins (proanthocyanidins). The soybean genotypes did not accumulate anthocyanins or tannins in the seed coat. Seed of Fe-deficient soybean plants without FeEDDHA had appreciably lower [Fe] and had a lower percentage of seed Fe in the seed coat than treated plants. Within-seed distribution of Fe should be considered in plant breeding because of concerns about both human nutrition and early seedling growth. Abbreviations: DTPA – diethylenetrinitrilopentaacetic acid; EDDHA – ethylenediamine di(o-hydroxyphenylacetic acid) acid; SPAD – single photon avalanche diode