Alleviation of alternate bearing phenomenon in mango (Mangifera indica L.) trees using boron and nitrogen fertilization

Abstract

This investigation was conducted during two successive seasons (2014/2015) and (2015/2016) using 15?years old productive mango (Mangifera indica) trees cv. Zebda. The trees were grown at AlMalak Valley Farm, El-Sharkeya Governorate- Egypt (30–51° North; 32–53° East). Trees were planted 8?×?8 meter within and between rows in sandy soil under drip irrigation system using the Nile water. The objective of this study is to alleviate alternate bearing in cv. Zebda using mineral nutrients (nitrogen in the on year and boron in the off year). Treatments included three concentrations of nitrogen (1000, 1250, 1500?g/tree/year) and three concentrations of boron (0.0, 250, 500?mg L^?1). Nitrogen was applied to the soil as ammonium sulfate and boron was applied as foliar spray of boric acid. The extra amount of nitrogen fertilizer (250 and 500?g N/tree) was applied at three installments in (May, June and July). Treatment was arranged in a factorial Completely Randomized Block Design with three replicates for each treatment. Results show that the on-year nitrogen fertilization significantly increased mango tree vegetative growth (number of shoot/branch, shoot length, shoot thickness, number of leaves/meter and leaf area) and yield. The average yield in the on year is 85.5?kg/tree at 1250?g N/tree but 67.4?Kilogram/tree at 1000?g N/tree (the control treatment). While in the off year boron foliar application resulted in a significant increase in flowering, initial fruit set, final fruit set and fruit yield. The average yield in the off year is 47?kg/tree at 250?mg L^?1 boron but 9?kg/tree at 0.0?mg L^?1 boron rate (the control treatment).The interaction treatment of 250?mg L^?1 boron + 1500?g nitrogen/tree is the best treatment as it resulted in the highest values for all the tested parameters. The average yield of this treatment is 53.5?kg/tree. This treatment helps alleviate alternate bearing phenomenon by 41% and obtain the highest economic yield in the off-year, i.e. increased yield by 5.9 fold.     

Fifteen-year fallow altered the dynamics of soil phosphorus and cationic balance of a savannah Alfisol

This study was designed to evaluate changes in the dynamics of soil phosphorus and cationic balances of a savannah soil subjected to 45 years of continuous cultivation under different fertilizer management and later left fallow for 15 years. It was conducted on the experimental plots at the Institute for Agricultural Research, Ahmadu Bello University, Nigeria. Treatments consisted of nitrogen (N), phosphorus (P), potassium (K), cow dung manure (D) and their combination (DNPK). Results of P fractionation and cationic distribution were compared with previous studies on the same plot 15 years ago. Organic carbon increased from a range of 3–5 g kg^?1 in 1997 to 10.9 g kg^?1 in 2012. Similarly, the cation exchange capacity (CEC) of the soil increased from 6.40 cmol_c kg^?1 in 1997 to 16.4 cmol_c kg¹ in the present study. The degree of saturation of the CEC by Ca²⁺ was 68–79% and 10–20% for Mg²⁺, while that of K⁺ was 1.5–2%. Although there was an uneven trend in depletion and enrichment of the various P pools, however, the fallow period substantially improved the CEC and the plant available P pools of the soil by more than 200% and 6–259%, respectively.     

EFFECT OF PREVIOUS NITROGEN STARVATION ON NO3 − AND NH4 + UPTAKE AND ASSIMILATION ASSOCIATED WITH THE ENDOGENOUS SOLUBLE CARBOHYDRATE UTILIZATION IN MOROCCAN WHEAT SEEDLINGS

Uptake of the two forms of nitrogen NO₃ ^? and NH₄ ⁺ and nitrate reduction have been studied in two varieties of Moroccan wheat seedlings, cvs. Sais and Jouda, cultivated under controlled conditions in a hydroponic medium. The available form of nitrogen in the medium had a direct effect on the rate of nitrogen absorption. A brief nitrogen starvation increased the root length and stimulated accumulation of soluble carbohydrates, especially in the root tissues. A resupply of nitrogen stimulated ammonium and nitrate uptake and assimilation with higher mobilization of the soluble carbohydrates previously accumulated in root seedlings. It is suggested that root nitrogen and carbohydrate status might both regulate nitrate uptake and reduction in Moroccan wheat seedlings.

The seedlings raised with the nitrate supply accumulated nitrate in the vacuole as an osmoticum. Shoots are the preferential site for such accumulation. The accumulation of mineral nitrogen was absent in the seedlings cultivated with ammonium supply but was compensated by accumulation of soluble organic nitrogen.     

我国农田氮肥施用现状、问题及趋势

氮素在作物产量和品质形成中起着关键作用。本文综述了什么是合理施氮,包括施氮量、施氮方法和时期,也包括与有机肥和秸秆还田措施的配合等。指出我国农田氮肥施用的主要问题是施肥过程和施肥后的严重损失。依据农户调查所获得的田块尺度施氮量,与田间试验合理施氮量对比分析表明,过量施氮田块占总调查田块的大约33%。依据区域尺度单位播种面积平均施氮量,与作物平均推荐施氮量对比分析表明,全国过量施氮面积占播种面积20%、合理面积占70%、不足面积占10%。总体而言,过量施氮现象还相当普遍,特别是在蔬菜和果树等经济作物上。本文提出了一种估算国家尺度氮肥需求量的方法,可估算出全国合理需氮量范围,称之为氮肥需求量估算法。用三种不同方法估算的我国1980~2010年间的氮肥需求量与实际氮肥使用量比较表明,如仍然依照现在的粗放施肥习惯,应该为现在的实际氮肥使用量,5年平均为N 27.9×106t左右,正好处于合理需氮量范围的中线。在改善施肥技术基础上,我国2006~2010年间5年氮肥平均使用量应该在N 19.6×106t左右;用五种方法预测的我国未来氮肥需求量表明,如果改善施肥技术,我国2020、2030、2050年合理氮肥需求量分别为N 21.0×106t、21.7×106t、23.1×106t;如施肥技术得不到实质性改善,依然粗放施氮,则氮肥需求量应处于合理使用量范围的中线,分别为N 30.4×106t、31.4×106t、33.4×106t。进一步分析了我国粮食产量和氮肥施用量与美国和西欧的差异,我国农田有机肥和碳投入对增加土壤有机碳氮库的重要性。     

黄土高原丘陵区退耕还林地土壤碳氮库的动态变化(英文)

为了揭示坡耕地退化土壤植被恢复后土壤中碳(C)、氮(N)运移规律,采用植被次生演替空间序列代替时间序列的方法,研究了黄土丘陵沟壑区纸坊沟流域不同植被恢复模式下的C、N库及其相互关系在土壤剖面的时空变化。结果表明退化农地的造林显著地促进了CO2的固存,恢复了土壤N的可获得性,进而降低了N不足对可持续的CO2固存的限制。植被恢复显著地促进了0~60 cm土壤有机碳(soil organic carbon,SOC)和总氮(total nitrogen,TN)的积累,而只有在高于一定的恢复时间阈值(如26 a)下,促进了SOC库和TN库间的线性相关性。在土壤剖面上,SOC和TN库、SOC/TN库比以及SOC-TN间的线性相关性均随着土壤深度的增加而降低。与自然恢复相比,人工林在短期内具有CO2固存的优势,但由于随着恢复时间的增加,SOC增幅越来越大于TN增幅的事实,表明造林对碳固存的可持续性需在一个较长的时段下来评估,尤其需要关注20 cm以下层土壤。研究结果为黄土高原的生态修复和减缓温室效应提供了理论依据。     

新型生物炭基氮肥对土壤一冬小麦系统氮素累积及相关生物活性的影响

通过田间试验,研究了掺混型、吸附型和反应型3种新型生物炭基硝酸铵氮肥在冬小麦生长过程中对土壤氮素累积及冬小麦对氮素的利用状况和相关生物活性的影响。试验处理包括CK（不施氮肥,不施生物炭）、硝酸铵氮肥、生物炭、掺混型生物炭基氮肥、吸附型及反应型生物炭基氮肥。研究结果表明：不同工艺制备的生物炭基氮肥对土壤铵态氮的累积具有显著影响,吸附型和反应型处理在冬小麦生长季铵态氮平均值大于对照（CK）,对于总氮、硝态氮和亚硝态氮累积量的影响不显著。除了生物炭单施处理外,其他处理均比CK显著提高冬小麦地上部的总氮累积量,但对冬小麦的氮素利用状况无显著影响,且三种炭基氮肥处理问无显著差异;施用不同类型生物炭基氮肥对土壤微生物量氮含量和硝酸还原酶活性具有提高作用,而对微生物量碳含量、亚硝酸还原酶和脲酶活性无显著影响。     

淮南矿区煤矸石风化物特性及有机碳分布特征

以淮南矿区潘一矿煤矸石山为研究对象,通过对煤矸石风化物的理化特性、电镜扫描(SEM)、能谱(EDS)和总有机碳(TOC)含量分析,初步研究了煤矸石风化物有机碳分布和释放规律,以及煤矸石山堆积淋溶作用对周边土壤溶解性有机碳(DOC)含量的影响。结果表明,从山顶、山腰到山脚煤矸石风化物中的总有机碳(TOC)含量依次减小,随着采样深度的增加总有机碳(TOC)含量逐渐变大。煤矸石风化物中总有机碳含量与煤矸石风化物粒径大小呈正相关,与煤矸石风化物的风化程度成负相关。不同粒径煤矸石风化物淋滤液中溶解性有机碳(DOC)的含量随着淋溶时间增大而减小,在96h淋滤液中溶解性有机碳含量趋于稳定,且值较为接近。距离山脚2~100m内,随着采样距离的增加土壤中溶解性有机碳含量(DOC)呈减少趋势。在距离煤矸石山80~100m处土壤溶解性有机碳含量接近正常农田土壤含量。     

基于大尺度低密度样点的东北土壤全氮空间插值方法比较

基于全国第二次土壤普查东北地区土壤数据,以ArcGIS和GS⁺软件为支撑,对比分析了反距离加权法(IDW)、径向基函数(RBF)、普通克里金(OK)和回归克里金(RK)4种地统计空间插值方法在7个不同样本容量下土壤全氮含量(STNC)的空间插值效果。结果表明,由普查数据得到的东北地区STNC在0.08~21.48 g/kg之间,数据变异性较大;STNC空间结构表现出中强度空间自相关性,空间自相关范围大于同区域的小尺度采样研究;样本容量<171时,STNC空间变异性发生变化,空间结构特征和精度检验水平难以确信。4种空间插值方法对STNC空间趋势表达均呈现从东北向西南方向递减规律,空间趋势预测效果为:RK >OK >RBF >IDW。RK方法通过线性回归分析添加了阳离子交换容量(CEC)、年均温(MAT)、土层厚度(d)和pH值等辅助信息,比IDW,RBF和OK方法的插值精度分别提高了19.40%,18.50%和16.15%;在不同样本容量下RK方法的插值精度较为稳定且对无样点区STNC的空间趋势预测也体现出了更多细节信息,因此对于大尺度低密度采样的土壤属性空间插值可重点考虑RK方法。     

Influence of Rooting Media on Chrysopogon Zizanioides (L.) Roberty

The present study was carried out to find the influence of some organic materials on the optimum biomass production of Chrysopogon zizanioides (L.) Roberty (Vetiver) using soil (S), vermicompost (VC), cow dung (CD) and coir pith (CP) at different ratios. The final day results showed that the ideal combination for the growth of the Vetiver is 1:1:1:1 v/v ratio of VC/CD/CP/S. The pH, electrical conductivity (EC), nitrogen (N)- phosphorus (P)- potassium (K), organic carbon (OC), and carbon (C)/N ratio showed in 1:1:1:1 v/v ratio of (VC/CD/CP/S), on 120th day were 7.3, 0.38 dS m^?1, 1.36%, 0.11%, 8.7%, 20.5% and C/N ratio is 15:1. The root and shoot length, fresh weight, dry weight, number of culms, and total chlorophyll content of Chrysopogon zizanioides were 65cm, 197 cm, 312 g, 104.4 g, 36 culms/plant and 40.57 mg/g at 1:1:1:1 v/v ratio of (VC/CD/CP/S) treatment and compared to control sets, the increasing ratio were 6:1, 3:1, 12:1, 12:1, 3:1, 2:1 respectively.     

淹涝胁迫和氮形态对苗期玉米糖、氮代谢底物量的影响

采用砂培培养方法,比较研究淹水和不同氮形态(铵态氮、硝态氮以及铵态氮︰硝态氮为1︰1)对苗期玉米根、茎鞘和叶的糖、氮代谢底物——可溶性糖、还原糖、硝态氮和游离氨基酸等物质含量的影响。结果表明,当淹涝胁迫持续7 d时,在非淹涝胁迫条件下,铵态氮处理的根、茎鞘和叶的可溶性糖和游离氨基酸含量均显著高于硝态氮处理(P<0.05);在淹涝胁迫条件下,硝态氮处理的根、茎鞘和叶的生物量干重显著低于铵态氮处理(P<0.05),其根和叶的生物量干重也显著低于铵态氮、硝态氮混合处理(P<0.05)。与非淹涝条件相比,在淹涝胁迫条件下,硝态氮处理的根系和叶的硝态氮含量显著降低(P<0.05),降低幅度分别高达62.6%和30.0%;此外,与非淹涝条件相比,在淹涝胁迫条件下,铵态氮处理的根的可溶性糖、还原糖以及游离氨基酸含量,茎鞘的可溶性糖和还原糖含量以及叶的可溶性糖和游离氨基酸含量均显著升高(P<0.05),而硝态氮处理仅根、茎鞘和叶的还原糖含量以及叶的游离氨基酸含量显著升高(P<0.05)。因此,在本试验条件下,由于糖、氮代谢底物含量充足,铵态氮处理的苗期玉米具有相对较强的耐淹涝胁迫能力。