营养液pH变化对刺梨苗吸收硝态氮和铵态氮的影响

研究介质pH变化条件下刺梨(Rosa roxburghii)对不同形态氮素吸收特性的影响,能为不同pH土壤上刺梨的合理施肥提供科学依据.本研究以'贵农5号'刺梨实生苗为材料,采用营养液培养和离子耗竭法,在分别供给硝态氮和铵态氮的条件下,设置营养液分别为pH 4、5、6、7、8、9的6个处理,测定不同pH营养液培养的刺梨...     

微咸水膜下滴灌条件下南疆棉花水肥耦合规律研究

为寻求劣质水(微咸水)滴灌施肥下的水肥耦合最优模型,通过正交实验设计,从水、肥、盐三个方面分析了不同生育期棉花耗水、土壤水分、土壤盐分、硝态氮等土壤因子的变化.结果表明:棉花耗水量与灌溉定额及土壤盐分有一定的相关关系.蕾期和花铃前期各处理土壤水分变异系数较大;花铃后期土壤硝态氮的积累量则逐渐增加;矿化度2～3 g·L-1的微咸水与淡水混灌对棉田土壤盐分的积累影响较小;正交分析得出了最优水平为灌水量为600mm,咸淡配比为2∶1,尿素施入量为80 kg· 667m-2.方差分析表明灌溉定额和施肥量两个因素对产量有显著影响,并利用SPSS软件建立了两者与产量的二次回归模型.     

地表覆盖方式对辣椒水分利用效率、果实品质及氮素分布的影响

研究了地表覆盖方式对辣椒 (Capsicum anmuum L.)水分利用效率、品质、叶片硝酸还原酶活性及植株和土壤中氮素分布的影响。结果表明,覆盖可增加辣椒整个生育期土壤水分含量。覆盖地膜和覆盖秸秆+地膜比其他地表处理方式能显著增加辣椒的产量和经济收入,提高产量水分利用效率和经济水分利用效率。覆盖可显著降低耕作层（0—20 ㎝）土壤硝态氮含量,且随着土层深度的增加,硝态氮含量显著降低,但对各土壤铵态氮含量无显著影响。对品质而言,覆盖地膜处理辣椒果实pH、维生素C含量显著高于其它处理,且其电导率、阳离子交换量和硝酸盐含量显著低于其他处理。覆盖可增强叶片硝酸还原酶活性,降低叶片中的全氮含量,显著降低每百千克产量氮肥吸收量。从提高辣椒的品质、环境安全、肥料利用和经济效益各因素考虑,生产中辅以科学的水分管理,覆盖地膜和覆盖秸秆+地膜是可行的地表覆盖方式。     

Leaf Chlorophyll Readings as an Indicator for Spinach Yield and Nutritional Quality with Different Nitrogen Fertilizer Applications

The objective of this study was to investigate the possibility of predicting the concentrations of total nitrogen (N), nitrate-nitrogen, and ascorbic acid in spinach (Spinacia oleracea) leaves using the pocket chlorophyll meter SPAD-502 (Minolta, Japan) in a pot experiment in a greenhouse. Spinach plants were grown in plastic pots filled with 0.5 kg of brown soil per pot with urea as N fertilizer at 0, 30, 60, 120, and 240 mg N/kg soil. SPAD readings of the two uppermost fully expanded leaves were recorded 18, 25, and 32 d after sowing and at harvesting (34 d). Dry-matter biomass and total N concentrations in leaves and roots, and NO₃-N, and ascorbic acid concentrations in leaves, were measured after harvesting. SPAD readings showed continuous reduction with increasing growth period irrespective of N applications. SPAD readings at harvest were significantly correlated with total N, leaf dry weight (DW), and NO₃-N concentration. However, this correlation did not exist between SPAD readings and ascorbic acid concentrations in leaves. The above results suggest that it is possible to apply SPAD readings to estimate NO₃-N concentrations in spinach plants, and that they may be applied for field assessments in decision-making and operational nutrient-management programs for the plant. Furthermore, the SPAD method may also be useful for ascertaining the harvest time. The results suggest that treatment with 120 mg N/kg significantly improved both leaf yields and leaf quality (i.e., leaf nitrate-N concentration and ascorbic acid). Too little and too much N fertilizer was not good for yield or spinach quality.     

NITRATE IN LEAF PETIOLE AND BLADE OF SPINACH CULTIVARS AND ITS RELATION TO BIOMASS AND WATER IN PLANTS

A pot experiment was carried out, with 30 spinach cultivars to determine nitrate accumulation in leaf blade and petiole, and its relationship to biomass and water in plants. Results showed that the fresh weight proportion of blade to shoot was higher than that of petiole. Furthermore, a higher positive correlation was found between fresh weights of blades and shoots than that of petioles and shoots. Unlike biomass, nitrate-nitrogen (N) concentration and total amount of nitrate-N accumulated in petiole were significantly higher than those in blade, and petiole was obviously the main organ for nitrate accumulation. Differences of nitrate-N concentration in petiole and the observed positive correlation between nitrate-N concentrations in petioles and shoots were more significant than that in blades and shoots. Nitrate-N concentration in petiole was also significantly correlated with fresh and dry shoot weight and total amount of water in shoots. However, this relationship was not found for blade.     

Increased Dryland Winter Wheat Yields by Nitrogen Fertilizer Topdressing and its Relationship to Soil Moisture,Available N,P and K in Northwestern China

Winter wheat (Triticum aestivum L.) production in northwestern China as a monoculture is hampered by unfertile soil and drought. With the fast-developing Chinese chemical fertilizer industry, many farmers now use more nitrogen (N) fertilizer as topdressing for winter wheat in early spring, in addition to a basal dose of N fertilizer applied in the previous autumn at seeding time. The objective of this study was to evaluate the increase in grain yield of dryland winter wheat by early spring N fertilizer topdressing, and its relationship to soil moisture, available N, phosphorus (P) and potassium (K). Field experiments with no N fertilizer topdressing (F_b) and N fertilizer topdressing (F_b+t) treatments were carried out over two growing seasons at 54 site-years to assess the relationship between increase in winter wheat grain yield by early spring N fertilizer topdressing and soil moisture, available N, P and K in Changwu county, Shaanxi province, China. Compared to F_b treatment, the F_b+t treatment produced grain yields lower at 10 site-years, and increased by <10% at 21 site-years and by >10% at 23 site-years. The results indicated that topdressing N fertilizer could increase wheat grain yield when soil nitrate-N accumulation in the 0–20, 20–40 and 40–60 cm depths was less than 121.7, 36.4 and 24.1 kg N ha^?1, and soil moisture content in the 40–60, 60–80 and 80–100 cm depths was more than 15.7%, 16.7% and 16.9%, respectively. The findings also suggested that it is not necessary to analyze soil for ammonium-N, available P and K before topdressing N fertilizer. It is necessary to analyze 0–60 cm soil profile for nitrate-N and 40–100 cm depth for soil moisture before topdressing N fertilizer for winter wheat in dryland areas of northwestern China.     

钼对冬小麦硝态氮代谢的影响

采用全硝态氮霍格兰营养液为培养基质,在供应0(缺钼)、0.78(适钼)、2.74mol/L(高钼)3种钼浓度下培养小麦.,分期测定其体内ＮＯ3--Ｎ、NH4+-N、全Ｎ、吸氮量及硝酸还原酶活性.(ＮＲＡ).,研究钼对小麦ＮＯ3--Ｎ代谢的影响。结果表明.,ＮＲＡ受硝酸盐代谢库和贮存库之间的调节而不断变化.,但任何情况下钼对ＮＲＡ都有明显影响。培养初期适钼处理ＮＲＡ最高.,高钼次之.,缺钼最低.;培养后期由于缺钼处理的NO3--N浓度高于施钼处理.,ＮＲＡ随之增至最高。植株内NH4+-N、ＮＯ3--Ｎ浓度之和在不同测定时间大致稳定.,ＮＯ3--Ｎ浓度高时则NH4+-N浓度低.,反之亦然.,两者之间存在一定的负相关关系。稳定情况与钼供应有关.,适钼条件下培养开始时高的NH4+-N与低的ＮＯ3--Ｎ浓度明显对应.,之后两者浓度接近.;缺钼条件下与此类似.,但NO3--N浓度变化不大.,NH4+-N、ＮＯ3--Ｎ浓度之和最高.;高钼条件下NH4+-N浓度一直高于NO3--N。作物由溶液吸收的NO3--N与作物的吸氮量一致.,适钼时最多.,高钼次之.,缺钼最少。从适钼时作物体内NH4+-N、ＮＯ3--Ｎ浓度之和最低.,而吸氮量又最高可以看出.,合适的钼供应不但有利于NO3--N的吸收和向NH4+-N转化.,也有利NH4+-N向有机氮转     

菠菜叶片硝态氮还原对叶柄硝态氮含量的影响

选用3个菠菜品种,设置N.0.1和0.3.g/kg2个施氮水平进行盆栽试验。在不同时期采样测定叶片内、外源硝酸还原酶活性、硝态氮代谢/贮存库大小,以及加入外源硝态氮培养后叶片硝酸还原酶活性的变化,探讨菠菜叶片的硝态氮还原与叶柄硝态氮含量的关系。结果表明,叶片内源硝酸还原酶活性、内源/外源硝酸还原酶活性比值、叶片的硝态氮代谢库大小及代谢/贮存库比值与叶柄硝态氮含量呈相反趋势。加入外源硝态氮培养后叶片硝酸还原酶活性的增加程度与叶柄硝态氮含量相一致。叶片内源硝酸还原酶活性高低及其发挥程度,叶片硝态氮代谢库大小及硝态氮在代谢、贮存库中的分配是造成品种间叶柄硝态氮含量高低差异的重要原因。     

沼液不同氮素水平对狼尾草产量、质量氮素利用率和土壤剖面硝态氮分布的影响

采用田间试验,研究了不同氮素水平的沼液(设N0~N6共7个氮素水平,即每次浇灌折纯氮0、5、10、20、40、80、160kg·hm-2,每45d刈割周期浇灌3次)对"闽牧6号"狼尾草产量、质量、氮素利用效率和土壤剖面全氮及硝态氮含量的影响。结果表明,"闽牧6号"狼尾草3个刈割期和全年干草产量均随着沼液氮素浓度的增加而增加,其中N6处理全年干草总产量达27.51 t·hm-2,显著高于N0~N5处理(P0.05)。植株硝酸盐含量、全氮含量和牧草粗蛋白产量也随着沼液氮素水平的提高呈上升的趋势,牧草刈割期的硝酸盐含量为355.1~572.5 mg·kg-1,均低于牧草畜牧利用的有毒限量指标0.25%,牧草粗蛋白产量最高达2459 kg·hm-2(N6处理)。对全年牧草生产的氮素利用率、氮素生理利用率、粗蛋白生产效率、氮素农学生产效率、氮素偏生产力等5个氮素利用效率指标分析可知,随着沼液中氮素水平的提高,氮素利用效率逐渐降低。牧草地全氮含量和硝态氮含量随着沼液氮素水平的增加而增加,不同土层间(0~60cm)随着土层深度的增加而降低。土壤硝态氮含量的增加,表明高氮量的沼液可能增加土壤硝态氮淋失的风险。     

滴灌灌水量对风沙土大豆根区硝态氮及水分分布的影响

为合理进行风沙土地区灌溉管理,将水肥控制在根区范围内并满足大豆生长需求,以灌水量为试验因素,基于作物冠层蒸发皿蒸发量设置0.4（W1）、0.6（W2）、0.8（W3）、1.0 E_pan（W4）和1.2 E_pan（W5）5个灌溉水平,研究不同灌水量对大豆根区硝态氮和水分分布的影响。结果表明：增加灌水量会使土壤水分入渗深度增加10~30 cm,增大根区土壤水分分布的不均匀性,苗期W5处理剖面水分平均值较W1处理增大40.22%,W4、W5处理能够维持大豆根区6%~7%的土壤含水率。硝态氮有明显表聚现象,随着灌水量的增大,淋洗深度增加且不均匀性增大,根区土壤硝态氮平均含量降低,当灌水量高于1.0 E_pan时,硝态氮含量低于10 mg·kg^-1。W2、W3和W4处理能保证大豆根区在生育前、中、后期处于15~22 mg·kg^-1的硝态氮浓度区间,垂直方向上灌水量与硝态氮呈负相关关系。风沙土土壤剖面含水率均在4%~10%之间,灌水量是影响风沙土硝态氮含量和分布的主要因素之一;各处理硝态氮含量在10~30 mg·kg^-1之间。综合考虑作物对根区土壤水分和硝态氮含量的需求,以及土壤水分和硝态氮在根层的分布特征,推荐灌溉水量为1.0 E_pan。