A comparison of reciprocating flow versus constant flow in an integrated, gravel bed, aquaponic test system

Murray cod, ^{Maccullochella peelii peelii}, and Green oak lettuce, Lactuca sativa, were used to test for differences between two aquaponic flood regimes; reciprocal flow (hydroponic bed was periodically flooded) and constant flow (hydroponic bed was constantly flooded), in a freshwater aquaponic test system, where plant nutrients were supplied from fish wastes, while plants stripped nutrients from the wastewater before it was returned to the fish. The Murray cod had FCRs and biomass gains that were statistically identical in both systems. Lettuce yields were good and a significantly greater amount of both biomass and yield occurred in the constant flow treatment. Constant flow treatments exhibited greater pH buffering capacity, required fewer bicarbonate (buffer) additions to control pH and maintained lower conductivity levels than reciprocal flow controls. Water consumption in the two systems was statistically identical. Overall, results suggest that a constant flow flooding regime is as good as, or better than, a reciprocating flooding regime in the aquaponic test system used.     

粪污资源化技术研究

试验设计了由储存池、水培池两段结构组成的污水净化系统,该系统可有效净化粪污,处理后水培液中N、P浓度低,水培期间废水排放少,可用于水培黑麦草、水芹、莴苣、青菜、生菜、小葱等植物并获得高产。该粪污净化系统技术简单,投资及运行费用低,管理方便,可以满足冬季污水处理的需要,以及实现粪污的资源化回收利用,尤其适宜小城镇和农村的粪污处理。该系统目前尚存在需改进之处,主要包括储存池存储阶段的净化潜力未得到开发及水培技术有待进一步提高等。     

Potato and Human Exploration of Space: Some Observations from NASA-Sponsored Controlled Environment Studies

Future space exploration by humans will require reliable supplies of food, oxygen and clean water to sustain the expeditions. Potato is one of several crops being studied for such a “life support” role. Tests sponsored by the US National Aeronautics and Space Administration (NASA) confirmed the well-known short day tendencies for tuberisation, but also revealed that some cvs. (e.g., Norland, Denali and Russet Burbank) could tuberise well under continuous high light. Horticultural tests showed that plants grew well and tuberised readily using a nutrient film technique (NFT). CO₂ enrichment studies with potato showed typical C₃ responses in photosynthesis and yield, with maximum rates occurring near 1000 μmol mol⁻¹. The highest tuber yields from these controlled environment studies reached 19.7 kg FM m⁻² or equivalent to nearly 200 t ha⁻¹. This equated to a productivity of 38 g m⁻² DM m⁻² day⁻¹. Stand evapotranspiration (ET) rates ranged from 3.4 to 5.2 l m⁻² day⁻¹ throughout growth, while maximum ET rates for canopies could approach 10 l m⁻² day⁻¹. Harvest indices (tuber DM/total DM) typically ranged from 0.7 to 0.8, indicating that waste (inedible) biomass from potato would be less than that from many other crops. An experiment was conducted in 1995 on NASA’s Space Shuttle using excised potato leaves to study tuber formation at axillary buds during spaceflight. The results showed that tubers formed equally well in space as in the ground controls, indicating that reduced gravity should not be an impediment to tuberisation.     

Interactions Between Cadmium Uptake and Phytotoxic Levels of Zinc in Hard Red Spring Wheat

Abstract

Wheat grown on cadmium (Cd)‐uncontaminated soils can still potentially translocate unacceptable levels of Cd to grain. The effect of zinc (Zn) and Cd levels on Cd uptake and translocation in “Grandin” hard red spring wheat (HRS‐wheat) (Triticum aestivum L.) was investigated using a double chelator‐buffered nutrient solution [EGTA used to buffer Cd, Zn, copper (Cu), manganese (Mn), and nickel (Ni); and Ferrozine (FZ) used to buffer Fe²⁺]. In the Zn level series of treatments, Cd²⁺ activity was held constant at 10^?10.7 M, and the Zn²⁺ activity was varied from 10^?7.6 to 10^?5.2 M. As Zn²⁺ activity increased, the translocation of Cd to the shoots decreased. The shoot : root Cd concentration ratio decreased from 0.20 to 0.03 as pZn²⁺ went from 7.6 to 5.2, indicating that adequate to high levels of Zn are effective in reducing Cd translocation to the shoots of “Grandin” HRS‐wheat. In the Cd series, the Zn activity was at 10^?6.6 M, while Cd activity was increased from 10^?10.7 to 10^?9.2 M. High levels of Cd did not significantly affect the uptake and translocation of Zn in the roots and shoots. While at pCd²⁺ of 9.2, the root and shoot Cd concentrations significantly increased, there was not a significant increase in the shoot : root Cd ratio. This would indicate that even at high Cd²⁺ activities, Zn is effective in regulating Cd uptake and translocation in “Grandin” HRS‐wheat.     

An evaluation of MES (2(N‐Morpholino)ethanesulfonic acid) and amberlite IRC‐50 as pH buffers for nutrient solution studies ∗

All buffering agents used to stabilize pH in hydroponic research have disadvantages. Inorganic buffers are absorbed and may become phytotoxic. Solid carbonate salts temporarily mitigate decreasing pH but provide almost no protection against increasing pH, and they alter nutrient absorption. Exchange resins are more effective, but we find that they remove magnesium and manganese from solution. We have tested 2(N‐Morpholino)ethanesulfonic acid (MES) as a buffering agent at concentrations of 1 and 10 mol m^‐3 (1 and 10 mM) with beans, corn, lettuce, tomatoes, and wheat. MES appears to be biologically inert and does not interact significantly with other solution ions. Relative growth rates among controls and MES treatments were nearly identical for each species during the trial period. The pH was stabilized by 1 mol m^‐3 MES. This buffer warrants further consideration in nutrient research.     

Soil water content,absorption of nutrient elements,and responses to fertilization of sunflower: A case study

Sunflower is considered to be a drought tolerant crop due to its root system. In Argentina, water availability and mineral nutrition are the main factors determining yield. We evaluated the behavior of a sunflower hybrid subjected to fertilization in a period of drought. A trial with the hybrid Paraiso 5 was carried out on a Typic Hapludoll located in western Buenos Aires province. The six treatments were: control; 150 kg or 300 kg available nitrogen (N) ha^‐1 (Native N supplemented with fertilizer); 150 kg or 300 kg available N ha^‐1 (Native N supplemented with fertilizer) plus other macro‐ and micronutrients, and macro‐ and micronutrients without N. Leaf area, plant biomass, root biomass, and yield components were determined. Plant tops and grain were analyzed for N, phosphorus (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn). Soil water content to a 1.2 m depth was measured periodically. At sowing, soil moisture was adequate, but during the first two months, the soil water content dropped to near the wilting point. Roots were largely located in the first 10 cm and dropped abruptly at deeper depths. The highest grain yield resulted from the highest N rates, but there were no effects from other nutrient elements. The oil content was not affected by these treatments. The chemical composition of the straw showed significant differences in N, P, S, and Mn concentration. In grain, only N increased as a response to N fertilization. This hybrid absorbed most nutrient elements during the first half of the life cycle and this corresponded to a time of drought conditions. Apparently roots are able to absorb water from the deep soil depths and still absorb nutrient elements from top soil. These traits might be crop strategies to respond to fertilization under drought.     

不同氨氮浓度对水蕹菜生长特性的影响

[目的]探讨不同氨氮浓度对水蕹菜生长特性的影响。[方法]通过在营养液中设置不同氨氮浓度(0、0.1、0.5、1.0、5.0、10.0、50.0 mg/L),对优良的水面培植作物——水蕹菜扦插苗展开培养,研究其各项生长指标对氨氮浓度变化的响应及其对氨氮的吸收利用。[结果]氮素缺乏导致水蕹菜植株增高减缓,叶片黄化,分蘖受抑。当氨氮浓度超过0.5 mg/L时,植物快速增高;但超过10.0 mg/L,又会抑制植株增长,根系溃烂,叶片脱落。氨氮初始浓度为1.0 mg/L时,水蕹菜各项生长指标最优,对氨氮净化效率最大,为96.3%。氨氮浓度超过1.0 mg/L时,植株根长偏短,根重偏低,茎叶系统增重明显,总生物量增长状况优于低氨氮处理(1.0 mg/L),但净化效率却随着氨氮浓度的增加而下降。[结论]该研究为鱼虾菜生态养殖模式的推广应用提供了理论依据。     

水培生菜高产品种筛选及不同通气处理对生菜平均单株质量和品质的影响

采用简易设施水培法筛选得到适合在海南水培种植的高产生菜品种——罗马生菜,同时研究不同通气处理对生菜平均单株质量和品质的影响。结果表明：通气处理可显著降低生菜叶片的硝酸盐、纤维素含量,提高维生素C、可溶性糖和可溶性蛋白质的含量,其中以7: 00～19: 00每隔4 h通气2 h的处理对提高生菜平均单株质量和品质效果最好。     

三种柳树新品系的水插生根研究

2010年12月和2011年2月,分别对柳L0906、柳L0903、柳L0911 3种插穗在清水(CK)、NAA 10 mg/L、NAA 20mg/L、ABT10 mg/L、ABT20 mg/L5种处理下进行了水插生根试验。结果表明,在时间上2011年2月的插穗生根状况最好。插穗在ABT10 mg/L处理中形成根部愈伤组织最快,但最后在清水中长势、根的平均长度最好。这3种插穗中柳L0906的生根效果好。     

调节营养液电导率对卡罗番茄果实品质和产量的影响

以卡罗番茄为材料,采用水培法,研究营养液电导率的调节对卡罗番茄果实品质和产量的影响。结果表明,采用提高营养液浓度或添加NaCl提高营养液电导率的方法栽培番茄,可以提高番茄果实可溶性固形物、番茄红素、Vc以及可滴定总酸的含量,其中对番茄红素的提高影响最为显著,同时番茄产量有一定程度的下降。在营养液电导率相同的条件下,采用营养液添加NaCl的方法对番茄品质的影响大于提高营养液浓度的处理。变化浓度的营养液比维持恒定浓度的营养液更有利于番茄果实品质提高。