Nitrogen use efficiency and nutrient partitioning in maize as affected by blends of controlled-release and conventional urea

ABSTRACT

Blends of controlled-release urea (CRU) and conventional urea can be an alternative to conventional fertilization to improve nitrogen use efficiency (NUE) and reduce costs when applied as a single application to agricultural crops. Different indexes of NUE, grain yield, nutrient uptake and partitioning in maize (Zea mays L.) were investigated in field experiments. The treatments consisted of a single rate of 180 kg N ha^?1 with different proportions of polymer-sulfur coated urea (PSCU) and conventional urea (U) applied incorporated at sowing (0.05 m below and 0.1 m to the side of the seed row) at two tropical sites (Site 1, Typic Haplustox; Site 2, Rhodic Haplustox) in Brazil. A control treatment (without urea-N) and a treatment with conventional urea management (UCM: 20% of urea-N applied as basal fertilizer and 80% of N applied as top dressing) were also included. This study demonstrates that blends of PSCU and U are efficient in supplying N throughout the maize cycle at a Typic Haplustox site when applied in a single application incorporated at sowing, resulting in high yields and adequate macronutrient uptake. PSCU improved NUE index compared to U and UCM. There was not response for N fertilization in the Rhodic Haplustox site.     

Diurnal Macronutrients Uptake Patterns by Lettuce Roots under Various Light and Temperature Levels

In order to reduce nutrient wastes to the environment the supply should be in accordance to the demand for these. Two experiments were conducted to study and quantify the effect of temperature, irradiance, and plant age on the uptake of nitrate (NO₃^?), ammonium (NH₄⁺), dihydrogen phosphate ion (H₂PO₄^?), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), and sulfate (SO₄²). In the first experiment, various levels of temperature and irradiance were applied to plants in a growth chamber, while in the second experiment the uptake was studied along the crop season under greenhouse conditions. The uptake rates were calculated at 2-hour intervals through sampling the nutrient solution and analyzing it by inductively coupled plasma atomic emission spectrometry (ICP-AES). Increasing light and temperature enhance the uptake rates, while the rates decrease with plant age. Nitrogen absorption was similar during the day as during the night. No differences were found in the absorption of H₂PO₄^?, K⁺, Ca²⁺, Mg²⁺, and SO₄^2? between day and night. Nitrate absorption was found to have a positive correlation with the absorption of all the ions except for NH₄⁺.     

不同钾肥种类对苹果产量、 品质及耐贮性的影响

【目的】苹果需钾量高,而果农普遍忽视钾肥的施用,随近年来密植栽培的推广,苹果单产大幅提升,使得陕西苹果园土壤面临缺钾现状,故合理补充钾肥对苹果生产至关重要。本文通过比较两种钾肥(KCl与K2SO4)对树体生长、 矿质养分吸收、 果实产量品质及采后贮藏特性的影响,为苹果树钾肥的合理施用提供科学指导。【方法】以陕西凤翔8年生红富士苹果树为研究对象,连续两年(2011~2013)对果树进行3种施肥处理,分别为不施钾(CK)、 KCl和K2SO4。在果树生长期间测定新梢生长量、 新梢叶片及果实矿质元素含量、 果实产量品质并定期测定采后贮藏期果实品质的变化(包括硬度、 可溶性固形物、 可滴定酸、 腐烂率)。【结果】1)CK、 KCl、 K2SO4 3个处理的平均新梢生长量分别为18.25 cm、 17.83 cm、 19.39 cm,无显著差异。与CK相比,施KCl 和K2SO4 7月中旬新梢叶片的氮、 磷含量均有所提高,其中K2SO4处理的叶片氮、 磷含量显著高于CK,但钙、 镁含量降低。2)年均苹果产量表现为KCl K2SO4CK,且3者之间差异显著。3)CK、 KCl、 K2SO4的年均单果重分别为267.42 g、 304.72 g、 287.73 g,其中KCl处理的单果重显著高于其它处理。施用KCl和K2SO4,横径80 mm以上的果实比例分别比CK提高14.9%和11.5%; 4)与对照相比,两种钾肥均提高了果实的氮、 磷含量和累积量,且KCl处理果实氮、 磷累积量高于K2SO4。果实中的钾含量和累积量3个处理之间无显著差异。施钾与对照相比均降低了果实中的钙、 镁含量及累积量。5)施钾与否对果实采收时的硬度无显著影响,但施钾可提高果实的可滴定酸、 可溶性糖及Vc含量。在室温下贮藏,90 d内不同处理果实可滴定酸含量降低,并趋势一致; KCl和K2SO4处理可溶性固形物含量呈上升趋势,而不施钾处理的可溶性固形物逐渐降低。贮藏结束后,果实软化率CK、 KCl、 K2SO4分别为19.23%、 6.96%、 22.19%,腐烂率分别为11.11%、 9.25%、 5.55%。【结论】短期内施KCl肥在增加产量,促进果实膨大,改善采收时果实品质方面效果稍好于K2SO4; 而K2SO4在促进新梢生长、 树体养分吸收,提高果实贮藏性能方面优于KCl。     

VARIATION AND INTERRELATIONS AMONG NUTRIENT ELEMENTS IN WHEAT LEAVES USED FOR FORAGE

Dual purpose wheat provides valuable forage resources for cattle in the southern Great Plains during winter. In this study, 96 recombinant inbred lines (RILs) were analyzed for variation in concentrations of 11 mineral elements in leaves. The mean concentration was 133.4 mg kg^?1 for manganese (Mn) and 293 mg kg^?1 for iron (Fe), being much higher than the 30 mg kg ^?1 recommended for each of these two minor mineral elements. Mean concentrations of zinc (Zn) (24.1 mg kg^?1) and copper (Cu) (4.4 mg kg^?1) were much lower than recommended concentrations. A highly significant correlation was detected between major minerals, magnesium (Mg) and calcium (Ca) (r = 0.9272**) and between minor minerals, Fe and nickel (Ni) (r = 0.8905**). Copper had no significant correlation with any minerals except Zn (r = 0.2529*), whereas Zn had significant correlations with all of the tested minerals except Cu, Mn, and Ni. The interrelations between different minerals provided information for effective selection strategy for ideal mineral concentrations in breeding of dual purpose wheat.     

Production and Spad Reading in Marandu Palisadegrass Fertilized with Nitrogen and Magnesium

The increase in tropic grass production and its estimation by the SPAD value can be related to combined supply of nitrogen and magnesium. The objectives were to check the effect of magnesium (Mg) rates on the productive response of Marandu palisadegrass to nitrogen (N) rates; correlate the supply of N and Mg with the SPAD reading; establish the use of SPAD reading as a way of predicting the N and Mg concentrations in diagnostic leaves (DL) and shoot dry matter (SDM). The experiment was carried out in a greenhouse. Five N rates and five Mg rates were used in nutrient solutions, in a fractionated 5 × 5 factorial design with four replications. High N and Mg rates resulted in high dry mass yield and leaf area, in greater numbers of leaves and tillers. The correlations between SPAD reading and SDM, N and Mg in DL were high, high and low, respectively.     

陇东黄土丘陵区梯田土壤养分评价——以甘肃庄浪县为例

【目的】从县域尺度对陇东黄土丘陵区梯田土壤养分进行评价,为黄土丘陵区梯田土壤培肥、粮食产量增加提供科学依据。【方法】以庄浪县耕地质量评价数据为数据源,共采集3 839个样点,且采样点均匀覆盖全县农田,通过主成分分析和方差成分估计模块分析了陇东黄土区梯田土壤大量养分（有机质、全磷、全氮、缓效钾、速效磷、碱解氮、速效钾）和微量养分（有效铜、有效锌、有效锰、有效铁、有效硼）分布特征及其影响因素。【结果】1）庄浪县梯田土壤全磷和速效磷含量处于高水平,速效钾含量处于较高水平,有机质、全氮和碱解氮含量处于中等水平。土壤大量养分综合指数处于较低、中等和较高级别的样本数分别占有效样本数的14.45%,65.89%和19.66%。2）庄浪县梯田土壤有效铜、有效锰和有效铁含量为中等水平,有效锌和有效硼含量处于中下水平,且有较大面积的土壤缺硼。土壤微量养分综合指数处于较低、中等和较高级别的样本数分别占有效样本数的32.53%,63.35%和4.12%。3）土壤类型对土壤大量养分空间变异的贡献率达51.81%,海拔影响次之,其贡献率为23.60%。随着海拔的升高,土壤大量养分综合指数在较高水平样本所占比例相应增加。4）土壤微量养分空间变异性与土壤类型、土壤质地、海拔有关,土壤类型对微量养分空间变异的贡献率最高,为69.41%,土壤质地、海拔的贡献率分别为17.65%,11.76%。随着海拔的升高,土壤微量养分综合指数在中高水平所占比例总体降低。【结论】陇东黄土丘陵区梯田土壤大量养分和微量养分整体处于中等水平,有较大面积的土壤缺硼。梯田土壤养分的空间变异主要受土壤类型和海拔的影响。     

RATIO OF CALCIUM TO MAGNESIUM INFLUENCES BIOMASS,ELEMENTAL ACCUMULATIONS,AND PIGMENT CONCENTRATIONS IN KALE

Producers use elemental ratios, such as calcium (Ca): magnesium (Mg), in fertility programs to ensure sufficient nutrient uptake. Kale (Brassica oleracea L. var. acephala D.C.) accumulates high levels of carotenoids which can be beneficial for human health. Objectives were to determine the influence of Ca:Mg fertilization on 1) biomass, 2) essential nutrients, and 3) carotenoids in kale leaf tissues. ‘Redbor’ kale was greenhouse-grown in solution culture. Ca:Mg ratio treatments were 9:1, 6:1, 3:1, 1:3, 1:6, and 1:9. Ca:Mg ratio significantly affected biomass, nutrient accumulation, and carotenoids. Plant biomass decreased linearly (P ≤ 0.001) and β-carotene, lutein, neoxanthin, and antheraxanthin all increased, then decreased quadratically (P ≤ 0.001) as the ratio of Ca:Mg changed from 9:1 to 1:9. Ca:Mg ratio also affected leaf tissue Ca, Mg, potassium (K), sulfur (S), boron (B), manganese (Mn), molybdenum (Mo) and zinc (Zn). Results indicate that producers wishing to maximize elemental uptake and carotenoid content of kale need to consider the ratio of Ca:Mg in their fertility programs.     

Macronutrient Balance of Nickel-Stressed Lettuce Plants Grown under Different Sulfur Levels

This study investigated whether intensive nutrition with sulfur–sulfate (S-SO₄) (2, 6, or 9 mM S) of nickel-stressed (0, 0.0004, 0.04, or 0.08 mM Ni) butterhead lettuce cv. Justyna may improve macronutrient balance and reduce Ni bioaccumulation. Nickel exposure resulted in various unfavorable changes in the macronutrient content together with increase of Ni accumulation in the biomass. Intensive S nutrition of Ni-treated lettuce seems to have no beneficial effect on macronutrient balance. In general, it significantly reduced the root and foliar phosphorus (P), potassium (K), calcium (Ca), and S content and simultaneously did not affect the magnesium (Mg) content in the biomass. At the same time, the nitrogen (N) content was reduced in roots and elevated in shoots. Supplementation of Ni-exposed lettuce with high S doses raised in roots and reduced foliar Ni accumulation; however, Ni content in useable parts exceeded the acceptable limits established for consumption.     

Effect of top-dressed potassium fertilization on the yield and quality of cucumber

The current study aimed to evaluate the effect of top-dressed potassium (K) application on the production of hybrid cucumber “Sapphire.” The experimental design was a randomized complete block, with five blocks of 0.80 × 0.40 m² each and eight replicate plants per block. The five fertilization rates of K used were 0, 45, 90, 135, and 180 kg K₂O ha^?1. Data collection consisted of the estimation of fruit diameter, fruits length, fruit fresh and dry weights, the number of fruits per plant, and the weight of fruits per plant. The number of fruits per hectare and the fruit fresh weight per hectare were calculated. Fruit tissue was analyzed for determination of macronutrient concentrations, pH, titratable acidity, soluble solids, sugar contents, and protein content. The data were statistically analyzed using regression analysis and analysis of variance (ANOVA). There was a significant effect of the fertilization rate of K on fruit diameter, fruit fresh and dry weights, macronutrients concentrations in fruits, titratable acidity, soluble solids, and reducing sugars. A quadratic equation was adjusted for the number of fruits per plant and per hectare; fruit yield per plant and per hectare, with maximum top-dressing doses, was estimated to be between 60 and 95 kg K₂O ha^?1. A linear increase was obtained in the pH. An increase in the K fertilization rate caused a linear decrease in the fruit length.     

Growth response,body composition,plasma metabolites,digestive and antioxidant enzymes activities of Siberian sturgeon (Acipenser baerii,Brandt, 1869) fed different dietary protein and carbohydrate: lipid ratio

Knowing the effect of dietary nutrients on physiological parameters, especially oxidative stress, during fish rearing can be useful to improve fish health and optimize production in aquaculture. In this study, four iso‐energetic (2 × 2 factorial design) diets differing in nutrient composition were submitted to the Siberian sturgeon juveniles, to analyse biochemical and physiological responses. The juveniles were fed for as long as 10 weeks with the following diets: low protein–high carbohydrate (CHO): lipid ratio (LP‐St), high protein–high CHO: Lipid ratio (HP‐St), low protein‐low CHO: Lipid ratio (LP‐L) and high protein‐low CHO: Lipid ratio (HP‐L). It was shown that HP‐L diet significantly induced higher growth performance in the juveniles than LP‐L; however, there was not a significant difference between them with other treatments. HSI was increased by higher dietary CHO: L ratio. The result obviously showed the higher dietary fat led to an increase in sturgeon body fat content. In addition, dietary protein and CHO: lipid ratio significantly affected plasma metabolites (glucose, cortisol, cholesterol and triglyceride) but did not affect IGF‐1 and insulin levels. Based on enzyme activities results, incorporation of high protein (44%) in the diet induced lower amylase activity and carbohydrate digestion in the sturgeon juveniles. Moreover, antioxidant enzyme activities in this species were more influenced by lipid than other nutrients. In conclusion, using appropriate carbohydrates (~30%) in the sturgeon diet helps to spare protein. Furthermore, it is suggested to decrease the amount of lipid in high protein diet, to improve higher sturgeon fillet quality and less oxidative damage in liver.