Variable rate fertilizer application for corn and soybean

Some have argued that variable rate application (VRT) of fertilizer is appropriate and profitable for the highly productive and fertile fields of the central cornbelt, but the proposition has not been tested. In this field experiment treatments of variably and uniformly applied phosphorus (P) and potassium (K) fertilizer and a control treatment with no P or K fertilizer were applied in a randomized complete block design at six locations in central Illinois in 1994. Individual experimental units were from 1,000 to 1,500 m in length and about 20 m in width. Fertilizer application rate was based upon a 100 m grid soil sampling. The variable rate treatment rate for each plot was based upon interpolated values of the soil fertility of each portion of the experimental unit. Uniform rate treatments were based upon the median soil fertility value for the entire field. Yield estimates were obtained with grain yield monitors. Neither corn nor soybean yield was significantly affected by fertilizer application treatment. We propose this lack of an effect is due to insurance built into the current fertility recommendations. A response to variable treatments will not be seen if there is no response to fertilization. Variable rate application will probably be most useful in fields with areas of very low soil tests.     

Nitrate/ammonium ratio effects on nutrient solution pH,dry matter yield,and nitrogen uptake of sorghum 1

Abstract

Sorghum [Sorghum bicolor (L.) Moench] seedlings were grown in nutrient solutions in a growth chamber to investigate the effects of different ratios of NO₃ ^– and NH₄ ⁺ on nutrient solution pH, dry matter yield, and N uptake. Nutrient solutions and plant tissues were assayed throughout the time plants grew in the nutrient solutions.

Nutrient solution pH depended on source of N. The pH rose to near 8 with NO₃ ^– as the sole source of N and decreased to near or below 4 with NH₄ ⁺ added to the solutions. Upon depletion of NH₄ ⁺ from solution, pH values rose abruptly to near 8 and remained near this value throughout the duration of the experiments. Dry matter yield was generally higher for plants grown with some NH₄ ⁺ compared to plants grown with NO₃ ^– alone. Nitrogen uptake was generally higher in plants grown with the higher proportions of NH₄ ⁺. Nitrogen concentrations remained unchanged with plant age as NO₃ ^–/ NH₄ ⁺ ratio varied. For solutions low in NH₄ ⁺, N concentrations in roots increased with plant age. Severe Fe deficiency appeared in plants when solution pH reached and remained above 7.     

多肉植物的水培试验

通过十种多肉植物的水培试验,探索不同类型的多肉植物的耐水能力,试验表明景天科伽蓝菜属、仙人掌科丝苇属、昙花属、金琥属均适合水培,光照、温度、养分影响其生根及长势,这为多肉植物水培产业化提供依据。     

不同品种苦瓜水培幼苗耐盐碱性研究初探

以翠绿、长白和绿脆3种苦瓜(Momordicacharantia L.)水培幼苗为试验材料,用Na+浓度依次为34.2 mmol/L、68.4 mmol/L、102.6 mmol/L和136.8 mmol/L的中性盐(NaCl)和碱性盐(Na2CO3)溶液进行处理,研究处理10d后苦瓜幼苗有关生理特性对2种盐胁迫的响应。结果表明:NaCl溶液处理下,苦瓜幼苗株高、茎粗、最大叶面积和叶绿素含量均随Na+浓度的增加而减少,过氧化物酶(POD)活性随Na+浓度的增加呈先下降后上升趋势,而根长和电导率则随Na+浓度的增加而增加;Na2CO3溶液处理下各形态生理指标变化与NaCl溶液处理大体相似,但Na2CO3影响程度大于NaCl。说明盐碱胁迫均对苦瓜幼苗造成不同程度的伤害,但在相同Na+浓度胁迫下,Na2CO3对苦瓜的伤害程度大于NaCl,即苦瓜对盐的忍耐程度高于碱。各品种苦瓜抗盐性大小为:翠绿>长白>绿脆。     

青菜的水培技术研究

[目的]研究青菜的水培技术,筛选青菜最适营养液配方。[方法]以上海青为试材,采用静止营养液培养方式,设置5种营养液配方,定期测定青菜的株高、根长、地上部鲜重、地上部干重、叶绿素及硝酸盐含量等指标,比较青菜在5种配方中的生长状况。[结果]5种营养液配方中,以配方4（N11.4mmol/L,P2.2mmol/L,K6.8mmol/L,Ca2.0mmol/L,Mg3.5mmol/L,S4.3mmol/L）对青菜生长的效果最好,在配方4中生长的青菜的株高、根长、地上部鲜重、地上部干重、叶绿素含量分别比平均值高1.06cm、4.60cm、8.80g/株、769.80mg/株、0.54mg/g;硝酸盐含量低于平均值8.00mg/kg。[结论]配方4由于营养液成分较均匀,更有利于青菜的生长,因此可作为水培条件下青菜高质丰产的最佳营养液配比。     

An Investigation of Aquaponics Using Brackish Water Resources in the Negev Desert

An aquaponics system using the brackish waters of the Negev (conductivity approximately 4500 μS/cm) is described. Tilapia sp. were grown with a variety of vegetables, herbs, and other plants within three systems within an aquaculture hothouse: a brackish water floating raft system, a brackish water gravel system, and a fresh water floating raft system. Water quality remained adequate within all systems for plant growth and fish health. Growth rates for fish were low, averaging about 1.4 g/day. Standing stock of fish at harvest was 12.5 kg/m³. Plants required the addition of iron chelate to contend with chlorosis and some macro- and micronutrients seem to have been in short supply.     

温室水培甘薯树光合特性研究

【研究目的】为了准确反映水培形式下甘薯树的光合特性及对环境条件的要求,以烟薯18和烟薯20为试材,利用CIRAS-1便携式光合测定仪,对其光合特性进行了研究,结果表明：二者的光合速率日变化呈单峰曲线,两种甘薯树对光照强度、CO2浓度和温度等变化的响应可以用二次方程来描述,烟薯18和烟薯20的光饱和点为1704.721-1925.037μmol?m-2?s-1, 光补偿点为33.735-39.857μmol?m-2?s-1, 温度在25℃左右时,两种甘薯树光合速率达到最高,CO2的饱和点和补偿点为776.406-819.342μL?L-1和55.667-62.410μL?L-1之间。     

腐殖酸对水培小麦吸收硒酸态硒和亚硒酸态硒的影响

[目的]研究腐殖酸对水培小麦吸收硒酸态硒和亚硒酸态硒的影响。[方法]采用水培试验,研究小麦对10~80μg/L硒酸态硒(Se~(6+))及亚硒酸态硒(Se~(4+))的吸收和腐殖酸的影响。[结果]小麦对Se~(4+)和Se~(6+)的吸收与其在培养液中的浓度呈线性关系,小麦对Se~(6+)的吸收是Se~(4+)的6.0~10.5倍。腐殖酸促进小麦对Se~(4+)的吸收,平均增加12.1%;但腐殖酸抑制小麦对Se~(6+)的吸收,平均减少18.6%,且随Se~(6+)浓度的增加抑制作用增强。有腐殖酸存在时小麦吸收Se~(6+)是Se~(4+)的4.3~7.4倍;有腐殖酸时Se~(4+)和Se~(6+)促进小麦生长,Se~(6+)促进作用更为明显,生物量平均增加12.3%。40和80μg/L Se~(4+)培养小麦地上部分吸收的硒分别为初始加入量的3.76%和3.31%,在这2个浓度下,小麦吸收的Se~(6+)分别为初始加入量的27.2%和27.8%。施用Se~(6+)是Se~(4+)作物利用率的7.2~8.4倍。[结论]可以通过土壤溶液Se~(4+)或Se~(6+)的浓度调控农作物硒含量,应用Se~(6+)更为经济环保。     

茎段生根与幼苗水培相结合比较番茄苗期耐盐性

为了筛选出高耐盐的番茄品种,以栽培番茄品种及其野生近亲品种为材料,分别采用茎段生根和幼苗水培等方法进行盐分耐受试验,考察各番茄品种在不同盐分条件下的生长情况。结果表明:Moneymaker、PI365967和LA1310的耐盐能力较强,M82次之,LA0317最弱。     

不同供氮水平对韭菜产量和品质的影响

 采用水培法研究了不同供氮水平对‘汉中冬韭’产量、硝酸盐含量和营养品质的影响。结果表明: 2～20 mmol·L ^{- 1}氮素水平范围内, 随韭菜叶片硝酸盐含量增加硝酸还原酶活性也呈升高趋势。当氮素水平为8～12 mmol·L ^{- 1}时, 韭菜产量、维生素C、可溶性糖、蛋白质含量均处于较高水平, 而硝酸盐含量和纤维素含量处于较低水平。以产量和品质作为衡量指标, 水培韭菜以8～12 mmol·L ^{- 1}的氮素水平为宜。