Nitrogen and phosphorus requirements of different wheat plant types under dryland and irrigated conditions 1

The wheat (Triticum aestivum L.) plant type in major producing areas of the U.S. is changing rapidly from tall cultivars to high‐yielding semidwarf cultivars. Objectives of experiments were to determine if nitrogen and phosphorus nutritional requirements differ between traditional tall cultivars and modern semidwarf cultivars under dryland and irrigated conditions. ‘Larned’, a tall cultivar; ‘Newton’, a semidwarf cultivar; and ‘Plainsman V, a high‐protein semidwarf cultivar, were grown with all combinations of three nitrogen fertilizer levels (0, 84, and 168 kg N/ha) and two phosphorus fertilizer levels (0 and 90 kg P₂O₅/ha) at Colby, Kansas for two years. Three levels of irrigation—dryland, limited irrigation, and full irrigation—were applied. Grain yields were highest with 84 kg N/ha under dryland and with 168 kg N/ha under irrigation. Phosphorus increased grain yield under dryland conditions one year, but had no effect under irrigated conditions. Cultivar X nutrition interactions from differential yield responses to fertility levels occurred under the dryland and limited irrigation regimes one year. Grain protein content was increased by nitrogen fertilization under all regimes both years and was decreased only by phosphorus fertilization under dryland conditions one year. Cultivar X nitrogen interactions for grain protein occurred under all irrigation regimes. We concluded that nutrient requirements do not differ between tall and semi dwarf wheat culti‐vars under any irrigation regime. Raising the recommended level of nutrients, particularly nitrogen, should be considered for all cultivars, both tall and semidwarf.     

The effects of apple dwarfing rootstocks on leaf nutrient element composition in stoolbed production

The nutritional status of 22 apple (Malus domestica Borkh.) dwarfing rootstocks, with varied degrees of dwarfing, was evaluated during stoolbed production in 1983 and 1984. Rootstock effects were observed for all leaf nutrient elements studied except Cu. Except for EMLA 27, leaf N levels were generally highest in dwarfing EMLA and Polish series and lowest on vigorous MAC and EMLA rootstocks. Relatively few significant differences were found in leaf P and K content among rootstocks. Foliar Ca and Mg concentrations were generally highest on Polish and Budagovski rootstocks and lowest on EMLA 111. Leaf B levels on vigorous and semi‐dwarfing EMLA rootstocks and Fe levels in MAC, Polish, and Budagovski series were considerably higher than on other rootstocks. Although significant differences were found in leaf Mn and Zn among rootstocks, no specific effect for rootstock vigor was observed for either element. Positive correlations between leaf Ca and Mg occurred in 17 rootstocks while negative correlations between N and Fe were observed in 21 rootstocks.     

Calcium uptake and concentration in bell pepper plants as influenced by nitrogen form and stages of development

Calcium uptake by bell pepper (Capsicum annuum L. cv. ‘California Wonder') varied by stage of plant development and N form supplied (NO₃ ^‐NH₄ ⁺ ratios: 1:0, 3:1, 1:1, 1:3, and 0:1) in a hydroponic study. Uptake of Ca⁺⁺ was highest at bloom and during fruit expansion, making the fruit development stage the highest demand period. Calcium uptake declined with each increasing increment of NH₄ ⁺ relative to NO₃ ^‐ supplied, although fruit yield was not significantly reduced until the ratio of NH₄ ⁺ to NO₃ ^‐ exceeded 50%. Tissue Ca⁺⁺ levels in the blossom‐end of the fruit were reduced whenever NH₄ ⁺ was included with N supplied. Vegetative yield of plants followed the same trend as that observed for total fruit dry weights. Our results indicate that pepper yields are higher when NO₃ ^‐ is the predominant form of N. Also, these results strongly suggest that Ca⁺⁺ fertilizer applications should precede the bloom period and continue during fruit development to ensure adequate Ca⁺⁺ availability for fruit development.     

Yield and quality of fennel (Foeniculum vulgare Mill.) in relation to basal and foliar application of nitrogen and phosphorus

A split‐plot field trial was conducted to study the effect of foliar application of 0 kg/ha (control), 20 kg N/ha, 2 kg P/ha or 20 kg N + 2 kg P/ha at two basal levels, viz., 90 kg N + 40 kg P/ha (optimal dose) and 60 kg N + 27 kg P/ha (sub‐optimal dose). Each group received 50 kg K/ha, which was applied uniformly on the yield and quality of fennel. Spray was applied at the flowering stage, 120 days after sowing.

The optimal basal dose gave better results than did the sub‐optimal one. Spray of 20 kg N + 2 kg P/ha proved optimum. This spray proved more effective at sub‐optimal than at optimal basal dose. The percentage of anethole (but not of fenchone) in the essential oil was significantly higher in plants grown with the sub‐optimal basal dose. Foliar application of N, P and N + P, on the other hand, decreased the anethole content of oil and increased that of fenchone significantly. Hence, foliar feeding may be recommended if the oil is required for perfumery and confectionary industries.     

Growth and selenium uptake of range plants propagated in uranium mine soils

High soil selenium (Se) levels have been found in association with uranium deposits in Texas. A concern that high Se concentrations may be found in forages grown on reclaimed mine lands prompted this investigation. A native soil sampled near the mining area, and overburden materials sampled from two Se enriched uranium mine spoil sites were compared in a plant growth study in the greenhouse. Shoot yields and shoot Se concentration in each of ten grasses common to the region were determined from plants harvested three weeks after germination and from shoot regrowth harvested four weeks after the first harvest. Shoot weights were reduced for 5 of the 10 species growing in soils with medium and high Se status. Total shoot weights of Cynodon dactylon and Panicum coloratum from two harvests were consistently highest in all soil materials and are highly recommended for use as a stabilizing cover crop for lands disturbed from uranium mining. Generally, no correlation was observed between shoot weight and plant Se concentration or uptake in the 10 species. However, plant tissue Se concentrations in all species for at least one of the two harvest dates were above the 5 mg kg^‐1 concentration considered potentially harmful to grazing livestock. Therefore, none of these species would be a suitable forage for livestock grazing on reclaimed Se‐enriched uranium mining overburden.     

Uptake of iron,zinc, manganese,and copper by seedlings of hybrid and traditional rice cultivars from different soil types 1

In pot experiments, uptake of zinc (Zn), copper (Cu), iron (Fe), and manganese (Mn) by hybrid rice from different soil types was compared with a traditional rice (Oryza sativa L.) cultivar. The concentration and total uptake of Fe in the shoots of hybrid rice grown in Oxisol and Ultisol were lower than those of the traditional cultivar. The concentration and total uptake of Zn in the shoots of hybrid rice grown in the Inceptisol (calcareous) were significantly higher than those of the traditional cultivar. Higher ratios of Zn and Fe in upper leaves (UL) to the lower leaves (LL) were found in hybrid rice grown in the calcareous Zn‐deficiency soil. The results indicated that hybrid rice root avoided absorbing excess Fe from Fe‐toxic soils due to its higher oxidizing power, and was more efficient in absorbing Zn from calcareous Zn‐deficient soils than the traditional cultivar.     

Differentiation of chloride and sulphate salinity on the basis of ionic distribution in genetically diverse cultivars of wheat

Sulphate (SO₄) salinity, in general, was found to be more injurious than chloride (Cl) salinity in all the four genetically diverse wheat cultivars—Triticum monococcum (Cl), T. aestivum cv. Chinese spring (C2), T. turgidum cv. langdon (C3) and amphidiploid (C4) obtained by a cross between T. aestivum cv. Chinese spring x Thinopyrum bessarabicum grown in hydroponic cultures containing iso‐osmotic saline treatments T1 (90 mM NaCl), T2 (45 mM NaCl+22.5 mM Na₂SO₄), T3 (15 mM NaCl + 37.5 mM Na₂SO₄), and T4 (45 mM Na₂SO₄). Among the cultivars, C4 followed by C2 and C3 appeared to be more salt resistant and Cl the most salt sensitive as far as various observations on osmotic potential and internal ion accumulation were concerned. Salt resistance could be ascribed to more exclusion of Na and Cl ions. Sulphate injury might be due to less effective sequestration or mobility of this ion towards some innocuous centres of plant tissues. Most of the interactive effects of cultivar versus salinity were prominently higher in cultivar C4 in treatment T1.     

Use of Minolta SPAD‐502 chlorophyll meter to quantify the effectiveness of mid‐summer trunk injection of iron on chlorotic pear trees

The severity of leaf chlorosis in iron (Fe)‐deficient fruit trees is often characterized using a semi‐quantitative visual rating index that is subject to evaluator bias. Analytical instruments are now available that provide a quantitative measure of leaf green color that could substitute for visual ratings. We injected limbs of mature chlorotic pear trees (Pyrus communis L. cv. Bartlett) with distilled water or a solution of 0.1% Fe (w/v) as FeSO₄‐7H₂O on 17 July 1995. Treatments were replicated eight‐fold. On 18 August 1995, a Minolta SPAD‐502 chlorophyll meter was used to measure the green color of 30 randomly sampled leaves located above the point of injection on each injected limb. Average leaf green color was higher in the Fe‐injected tree than in the water‐injected tree of each experimental block. Leaf green color (mean±SD) averaged 34.7±3.8 SPAD units for the Fe‐injected trees and 27.3±3.8 SPAD units for the water‐injected trees. The absolute increase in mean leaf color of 7.4 SPAD units was equivalent to a relative increase of 27%. Iron injection also induced more negative skewness and increased kurtosis in the frequency distribution curve for leaf SPAD meter readings. These results suggest that the SPAD meter can provide an unbiased quantitative measure of the severity of leaf chlorosis associated with Fe deficiency, and confirm that mid‐summer trunk injection of Fe can partially ameliorate Fe‐chlorosis symptoms.     

Use of spectral radiance for correcting nitrogen deficiencies and estimating soil test variability in an established bermudagrass pasture

The use of variable rate technology has become increasingly popular for applying plant nutrient elements. The most widely used method for determining variable fertilizer rates is presently based on soil testing and yield mapping. Three field studies (Bumeyville 1995, Burneyville 1996, and Ardmore 1996) were initiated in established Midland bermudagrass [Cynodon dacrylon (L) Pers.] pastures to determine the relationship between spectral radiance at specific wavelengths with forage nitrogen (N) removal and biomass, and to determine field variability of soil test parameters. Variable N (applied to 1.5 × 2.4 m subplots within 2.4 × 45.7 m main plots), fixed N and check treatments were evaluated at each location. Spectral radiance readings were taken in the red (671±6 nm), green (570±6 nm), and near infrared (NIR) (780±6 nm) wavelengths. The normalized difference vegetation index (NDVI) was calculated as NIR‐red/NIR+red. Variable N rates were applied based on NDVI. The highest fixed variable N rate was set at 224, 336, and 672 kg N ha^‐1 for Burneyville, 1995, 1996, and Ardmore, 1996, respectively. At Bumeyville, soil samples were collected in all variable rate plots (1.5 × 2.4 m) and analyzed for various soil test characteristics. NDVI, red, green, and NIR spectral radiance readings were correlated with bermudagrass forage N removal and yield. Correlation of forage yield and N removal with red, NIR, and NDVI were best with maximum forage production, however, when forage production levels were low correlation decreased dramatically for the red wavelength compared with NIR and NDVI. Forage yield and forage N removal in variable rate treatments increased when compared to the check while being equal to the half‐fixed and fixed rates where higher N rates were applied. Also, variability about the mean in variable rate plots was significantly lower than half‐fixed and fixed rates which supports adjusting N rates based on indirect NDVI measurements. Variable N rate plots reduced fertilizer inputs by 60% and produced the same yield as fixed rate plots, while fixed and half‐fixed rates did not increase N content in the forage over that of the variable rate treatment. Soil sample data collected from small consecutive plots (<4 m²) was extremely variable indicating that intense sampling would be needed if variable fertilizer application were to be based on soil test results.     

Fate of humic acids isolated from natural humic substances

Composition of humic acids (HA) is a function of plant-derived inputs, degradation processes regulated by microorganisms, organo-mineral interactions and age. Characterization of different origin humic substances is important for evaluation of their contribution to stabile and labile carbon pool in the environment. The relative abundance of chemical components in HA isolated from soils, compost, commercial lignohumates, alginite, acadiane and lignite was studied with aim to quantify content of important biomarkers such as amino acid, lipids and polyphenols. HA were considered as a heterogeneous complex and high concentration of peptides, polyphenols and lipids was determined in acadian-HA to compare with soil-HA. Compost-HA contained much more amino acids to compare with soil-HA samples. Alginite-HA and lignite-HA were similar in biomarkers content to soil-HA. Fourier transform infrared spectroscopy confirmed that chemical composition and functional groups content differs with the origin, humification degree and the age of studied samples. Soil-HA are typically composed of a variety of ?OH, COOH?, C–O, C–H₂, (aliphatic and aromatic) groups, quinines, lignin fragments, polysaccharide, monosaccharide and proteins fragments, which are linked together by ?O?, ?NH?, ?H=, >C=O, metal ions and –S? groups. ¹³C NMR spectroscopy showed that aromatic carbon content was the highest in lignite-HA and soil-HA.