Exchangeable potassium and potassium balances in organic crop rotations on a coarse sand

Abstract. Crops on sandy soils (<5% clay) are exposed to K deficiency due to the small release and high leaching losses of K. Reliable tools are needed to improve the K management in cropping systems with limited K input, such as organic farming where import of nutrients are restricted according to the EC regulations. We investigated K balances and exchangeable K (K_exch) changes in an organic crop rotation experiment. Potassium leaching decreased from 42 kg ha⁻¹ in 1998/99 to 21 kg ha⁻¹ in 2000/01 as an average of a crop rotation (spring barley, grass-clover, winter wheat and pea/barley) with manure application and without catch crops. In the same period, spring K_exch decreased from 5.0 to 3.0 mg K 100 g soil⁻¹ (0–20 cm). The retention of the straw K left in the field after harvest increased with decreasing levels of K_exch. The cereal crops did not respond to K application but in the pea/barley mixture the pea yield increased by 46%. The concordance between measured K balances and changes in K_exch was weak. Exchangeable K is suitable as a tool for K management on a rotational basis, and a K_exch above 3 mg 100 g soil⁻¹ in the autumn should be avoided to minimize K leaching.     

Control of ion transport by the sperm duct epithelium of brook trout (Salvelinus fontinalis)

The sperm duct epithelium of brook trout (Salvelinus fontinalis), mountedin vitro in Ussing-style epithelial chambers actively absorbs Na⁺ (measured as the short-circuit current, I_sc) and secretes K⁺ (measured using⁸⁶Rb⁺ as tracer). Dibutyryl-cyclic-adenosine monophosphate (db-cAMP) and 3-isobutyl-1-methylxanthine (IMX) produce a rapid, sustained stimulation of both ion transport processes, but the hormone connected to the response is unknown. Purified sockeye salmon CON A2 gonadotropin (GtH) produces a dose-dependent, rapid and sustained rise in Na⁺ uptake and K⁺ secretion. The time course, electrophysiological and transport characteristics are similar to those evoked by IMX. Carbohydrate-poor (chum salmon CON A1) GtH is ineffective. Pretreatment of fish with 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-P) significantly increases milt volume but is without effect on resting or stimulated (IMX + db-cAMP) levels of sperm duct ion transport. This is the first indication of a direct, rapid action of GtH on ion transport by the vertebrate blood-testis barrier. The results suggest direct involvement of GtH in control of later stages of sperm maturation.     

棉花钾肥施用的现状、效果和技术研究概况

从不同角度开展对棉花钾肥施用问题的研究,探讨棉花施钾现状和钾肥施用效果。从棉株生育、棉花产量、棉花品质、棉花生理和棉花抗逆性方面,说明钾肥在现在棉花生产上的重要性。同时,对棉花钾肥的施用技术进行探讨。     

Estimation of daily urinary potassium excretion using urinary creatinine as an index substance in prepartum dairy cows

In the present study, the daily excretion of potassium (K) in urine (urinary K(UK)) was estimated from a 6 h urine sample using urinary creatinine (UC) as the index substance. All urine was collected from six pregnant Holstein cows at 6 h intervals for 24 h on 3 days of the 4th, 2nd and final week before the expected date of parturition. In total, 72 6 h urine samples were obtained. Daily UC excretion (mg/day per kg bodyweight (BW)) was almost the same for the three sampling days. Daily UC excretion varied among cows from 22.1 to 24.3 mg/day per kg BW with a mean of 22.8 mg/day per kg BW with no significant difference. Thus, daily UC excretion was confirmed to be constant throughout the prepartum period with no differences among individuals. The concentration ratios of K to creatinine ((UK mg/dL)/(UC mg/dL) (UK/UC)) correlated strongly to the hourly K excretions (mg/h per kg BW) (r = 0.952, P < 0.01) in the 6 h urine samples. The differences in the UK/UC ratio between sampling periods were not significant within each cow. Therefore, daily UK excretion (mg/day) can be estimated using the equation: daily UK excretion (mg/day) = daily UC excretion (mg/day per kg BW) × BW (kg) × 6 h urine sample UK/UC, where daily UC excretion can be a given value.     

Comparison of whole blood and plasma potassium concentrations in dogs using the Reflovet system

Background: The Reflovet system is designed for chemical analysis of whole blood. However, plasma or serum is recommended for potassium analysis because of possible interference from RBC potassium. Because RBC potassium concentration is low in most canine erythrocytes, however, there should be little or no interference.
Objective: The objective of this study was to compare potassium results obtained in whole blood and in plasma from dogs using the Reflovet system.
Methods: Blood samples were collected from 104 dogs into lithium-heparin tubes. The potassium concentration was measured in whole blood, and subsequently the PCV was measured. Samples were centrifuged and the potassium concentration was measured in plasma. Comparisons were made using Deming's regression and Bland-Altman difference plots.
Results: There was very good correlation between results of potassium measurements in whole blood and plasma ( r = 0.93). Potassium values were moderately lower in whole blood: Potassium_blood= 0.912 × Potassium _plasma+ 0.119. Hemolysis had a negligible effect on the results, but the difference increased with the PCV value. In more than 90% of samples, the difference between the 2 measurements was ≤ 0.3 mmol/L.
Conclusion: There is only a negligible difference in most cases between potassium values in canine plasma and whole blood using the Reflovet system.     

云南烟区四个品种烤烟钾含量的研究

采集了云南烟区烤烟上、中、下3个部位的烟叶样品5 893份,采用连续流动法检测烟叶钾含量,分析了云南烟区烤烟钾含量的变化特点.结果表明:云南烤烟上、中、下3个部位烟叶钾含量的均值分别为1.6%、1.8%、2.1%,主要分布范围和样本频率分别为1.25%~2.0%、1.25%~2.25%、1.5%~2.5%和76.4%、81.9%、73.4%,各部位烟叶钾含量大于1.5%的样本频率分别为61.0%、75.8%、91.7%.各部位烟叶钾含量在年度间存在极显著差异,4个主栽品种烟叶钾含量表现为‘红大’>‘K326’>‘云烟87’>‘云烟85’;不同生态种植区域烟叶钾的含量差异极显著,其中,滇西南烟区烟叶的钾含量最高,滇东北烟区最低.     

钾镁水平对番茄苗期生长、根系形态及钾素吸收和生理利用效率的影响

采用水培方法,研究不同钾、镁水平对"天福冠露"和"毛粉802"两种番茄幼苗生长、根系特征及钾素吸收、利用效率的影响。结果表明,钾、镁水平(8 mmol/L、1 mmol/L)处理的植株鲜重、干重及钾、镁水平(4 mmol/L、4 mmol/L)处理的株高显著高于其他处理。随钾、镁水平升高,两种番茄植株的根长、"天福冠露"植株的根直径、根体积和分根数先减少后增加;番茄植株钾素吸收率显著提高,生理利用效率显著降低。钾、镁水平(8 mmol/L、1 mmol/L)处理的植株根长、根表面积、根直径及根体积显著高于缺钾处理。钾、镁水平(4 mmol/L、4 mmol/L)处理,两种番茄植株根长、根表面积、根体积和分根数均显著高于缺镁处理,"天福冠露"植株钾含量显著高于"毛粉802",而钾素生理利用效率显著低于"毛粉802"。与其它等钾处理相比,缺镁植株钾素积累量最低、生理利用效率最高,镁过量处理的植株钾素生理利用效率显著降低。     

不同施肥处理对保护地土壤非交换性钾释放能力的影响

以沈阳农业大学蔬菜保护地长期定位试验为基础,系统研究了长期定位条件下,不同施肥处理对蔬菜保护地土壤非交换性钾释放能力的影响。结果表明,不同施肥处理土壤非交换性钾的释放量和释放速率不同,有机肥和无机肥配施的土壤的释放量和释放速率大于单施化肥的各个处理;其中氮、钾肥配施处理的释放量和释放速率最高,而氮、磷肥配施处理最低。     

不同施钾量对苜蓿碳水化合物含量及抗蓟马的影响

为了明确施钾是否能有效提高苜蓿对蓟马的抗性并研究相关生理变化,本试验以感蓟马苜蓿品种甘农3号和抗蓟马苜蓿品种甘农9号为材料,设0、6、9、12、15 (K₂O) g/m²等5个钾浓度水平,在大田蓟马为害高峰期,评价和测定了不同钾水平处理下苜蓿的受害指数、叶片钾含量、产量、碳水化合物含量;在苜蓿第二茬中,随着钾水平的升高,甘农3号和甘农9号老叶和心叶的钾含量、可溶性糖、淀粉和木质素含量升高,产量显著增加(P<0.05);受害指数均显著降低,且受害指数均在K₂水平下最低,分别较K₀水平降低了47.60%和46.11%;在第三茬中,甘农3号和甘农9号的受害指数、产量、钾含量、可溶性糖、淀粉和木质素含量的变化规律与第二茬相似,受害指数在K₂水平下分别较K₀水平降低了30.78%和23.27%。第二茬和第三茬中,在低于9 (K₂O) g/m²施钾水平下,苜蓿叶片钾含量与受害指数显著负相关(P<0.05);高于12 (K₂O) g/m²水平下,苜蓿叶片钾含量与受害指数无显著相关性(P>0.05)。钾元素可通过提高苜蓿碳水化合物的合成(尤其是可溶性糖和淀粉)及生长性能来提高苜蓿对蓟马的耐害性。施钾后甘农3号的受害指数均低于未施钾甘农9号的受害指数,因此,通过施钾管理来提高苜蓿对蓟马的耐害性是一种有效的措施。9 (K₂O) g/m²是本试验中最经济有效的施肥量。     

保水剂对橡胶树专用肥氮钾淋出特性的影响

[目的]探寻减少橡胶树专用肥淋溶损失的途径,提高橡胶树专用肥利用率。[方法]采用在橡胶树专用肥中添加保水剂的方法,模拟橡胶树每年第3次施肥期(9月份)的降雨量,开展间歇性土柱淋溶试验。研究了CMC(羧甲基纤维素钠),PAM(聚丙烯酰胺)和PAA(聚丙烯酸钠)这3种保水剂对橡胶树专用肥氮素、钾素释放特征及淋溶损失的影响,筛选保水剂及合理施用比例。[结果]3种保水剂对橡胶树专用肥中氮素、钾素的淋失均有抑制作用,其中保水剂PAM用量为6%时对橡胶树专用肥中的氮素、钾素淋失抑制效果最佳。该处理对氮素、钾素首次淋失抑制率分别为44.73%,57.16%,淋溶结束时氮素、钾素累积淋出量分别较未添加保水剂的对照处理减少了20.20%,14.87%。[结论]在橡胶树专用肥中添加保水剂可有效降低橡胶树专用肥中氮素、钾素的淋溶损失。