Effect of different macronutrient cation ratios on macronutrient and water uptake by melon (Cucumis melo) grown in recirculating nutrient solution

The aim of the present study was to determine uptake ratios between macronutrients and water for melon (Cucumis melo L. cv. Dikti) grown in a closed soilless cropping system. The obtained data can be used to establish standard nutrient solution compositions for melon crops grown in closed hydroponic systems under Mediterranean climatic conditions. Nutrient and water uptake by plants in the closed hydroponic system was compensated for by supplying replenishment nutrient solutions (RNS) differing either in the concentrations of K⁺, Ca²⁺, and Mg²⁺ or in their mutual ratio. The RNS, used as control treatment, had an electrical conductivity (EC) of 1.74 dS m^?1 and contained 6.5 mM K⁺, 2.8 mM Ca²⁺, and 1.0 mM Mg²⁺ (K⁺ : Ca²⁺ : Mg²⁺ = 0.63 : 0.27 : 0.10). Control RNS was compared with two other RNS, both with a high Ca²⁺ level (4.2 mM). The K⁺ and Mg²⁺ levels in these two RNSs were: (1) not altered (corresponding to a ratio of K⁺ : Ca²⁺ : Mg²⁺ = 0.55 : 0.36 : 0.09; EC = 2.0 dS m^?1) or (2) increased to maintain the same K⁺ : Ca²⁺ : Mg²⁺ ratio as in the control RNS (EC = 2.45 dS m^?1). Nutrient to water uptake ratios, commonly termed uptake concentrations (UCs), were assessed by two alternative methods, i.e., (1) estimating the ratio between nutrient and water removal from the system or (2) estimating the ratio between the mass of the nutrient that was recovered from plant biomass and the water consumption. Over the two methods, mean UCs for N, P, K, Ca and Mg were 15.4, 1.31, 5.47, 3.78, and 1.02 mmol L^?1, respectively, and tissue analysis resulted in a K : Ca : Mg molar ratio of = 0.55 : 0.34 : 0.11 in the whole plant. Moreover, the UCs tended to decrease as the crop aged although, in absolute values, the mass of nutrients absorbed increased following dry‐weight accumulation. Based on the obtained results, adapting the composition of the nutrient solution at least three times during the cropping period of melon is recommended. Further, the results revealed that the damage caused by the increase of the EC when attempting to maintain a target K⁺ : Ca²⁺ : Mg²⁺ ratio in the replenishment NS is higher than the benefits from the optimal cation ratio. Increasing K⁺ and Mg²⁺ concentration in addition to that of Ca²⁺ to maintain a standard K⁺ : Ca²⁺ : Mg²⁺ ratio raises the EC in the root zone (4.62 dS m^?1), due to increased accumulation of nutrients, thereby reducing the mean fruit weight and concomitantly the total fruit yield (20% decrease). Leaf gas exchange, chlorophyll parameters and fruit taste quality were not influenced by the differences in macronutrient cation concentrations or ratios in the RNS, whereas phenolics and antioxidant capacity in melon fruit were enhanced by the increased root‐zone EC.     

Blossom‐end rot and fruit cracking of tomato grown in net‐covered greenhouses in Central Thailand can partly be corrected by calcium and boron sprays

Two tomato (Lycopersicon esculentum Mill.) cultivars King Kong 2 (KK2) and FMTT 260 (FMTT) were grown in a net‐covered greenhouse in Central Thailand to investigate the influence of fruit applications of combined aqueous calcium (Ca) and boron (B) solutions amended or not with the tenside Glucopon® on fruit yield and quality. Special attention was paid on blossom‐end rot (BER) and fruit cracking (FC), two prevailing disorders in tomato and main causes for non‐marketability of tomato fruits under the conditions of protected cultivation in Central Thailand. While no effect of the additional Ca and B applications on total fruit yield was observed, the composition of the non‐marketable fraction of fruit yield differed significantly between treatments and cultivars. Cultivar KK2 proved to be highly susceptible to both BER and FC and, therefore, produced less marketable fruits than cv. FMTT. The Ca and B sprays decreased the incidence of BER but increased FC at the same time. Addition of the tenside Glucopon® to the Ca and B solutions did not yield any further advantage. The contrasting effect of the Ca and B sprays on BER and FC resulted in similar levels of non‐marketable fruit yield in the treatments with or without the sprays for both cultivars. The nutrient status in different fruit segments was surveyed during fruit development. The Ca concentration in the distal end of the fruit during the time of rapid fruit growth was correlated with the BER incidence in mature fruits. Since additional Ca and B sprays are labor‐intensive and did not significantly reduce the portion of non‐marketable fruits, the selection of cultivars insusceptible to BER and FC appears to be of highest priority when conditions favoring these disorders are to be expected. This is particularly true for protected cultivation in Central Thailand.     

营养液浓度和用量对醋糟基质栽培番茄生长、产量和品质的影响

以番茄‘合作906’为试材,采用醋糟基质桶栽的方法,研究了不同营养液浓度和用量对番茄植株生长和果实产量及品质的影响,并对栽培基质化学性状的变化进行了测试。实验设0、1/4、1/2、3/4倍4个Hoagland营养液浓度和600、900、1 200 mL/次3个用量,共12个处理。结果表明:在番茄营养生长期和开花期,醋糟栽培基质的pH值降低,变化范围在6.79～6.29之间;基质的EC值增大,变化范围在1.50～2.77 mS/cm之间。醋糟混配基质中只浇清水不能满足植株生长需求,1/4倍Hoagland营养液900 mL/次用量对番茄植株生长最有利,且开花期对营养液需求增大,但1/2倍浓度、900 mL/次施用量番茄果实的可溶性固形物、可溶性糖、可溶性蛋白含量都最高,又以1/2倍浓度1 200 mL/次处理产量最高。结果说明,醋糟混配基质栽培番茄的最佳水肥管理方式为:营养生长期浇灌1/4倍的Hoagland营养液可促进番茄植株的生长,并在开花期略提高营养液的用量,结果期可用1/2倍的Hoagland、900～1 200 mL/次施用量以提高果实的品质和产量。     

Effects of crop‐straw biochar on crop growth and soil fertility over a wheat‐millet rotation in soils of China

We conducted a pot experiment using a wheat‐millet rotation to examine the effects of two successive rice‐straw biochar applications on crop growth and soil properties in acidic oxisols and alkaline cambosols from China. Biochar was incorporated into soil at rates of 0, 2.25 or 22.5 Mg/ha at the beginning of each crop season with identical applications of NPK fertilizer. In the oxisols, the largest biochar treatment enhanced soil pH and cation exchange capacity, decreased soil bulk density, improved soil P, K, Ca and Mg availability and enhanced their uptake, and increased wheat and millet yields by 157 and 150% for wheat grain and straw, respectively, and 72.6% for millet straw. In the cambosols, biochar treatment decreased soil bulk density, improved P and K availability, increased N, P and K uptake by crops and increased wheat and millet straw yields by 19.6 and 60.6%, respectively. Total soil organic carbon increased in response to successive biochar applications over the rotation. No difference in water‐soluble organic carbon was recorded between biochar‐treated and control soils. Converting straw to biochar and treating soils with successive applications may be a viable option for improving soil quality, sequestering carbon and utilizing straw resources in China.     

不同供磷状况下CO2浓度升高对番茄根系生长及养分吸收的影响

采用培养试验研究了磷缺乏与正常供磷条件下,CO2浓度由350μL/L升高至800μL/L苗期番茄的生物量、根系特征和不同器官N、P、K养分含量的变化。结果表明,无论缺磷与否,CO2浓度升高均能显著增加番茄地上部及根系的干物质积累量,提高根冠比。在磷缺乏条件下,CO2浓度升高对番茄根系生长的促进主要表现为增加根系的体积和表面积;而在磷正常供应条件下主要表现为同时增加根体积和分根数,有利于形成强壮的根系。在两种供磷水平下,CO2浓度升高对番茄各器官的N、P、K含量产生不同的稀释效应,但N、P、K总积累量却随CO2浓度升高而显著增加;而且CO2浓度与供P水平对番茄植株的N、P、K积累量具有极显著的正交互效应。     

不同供磷状况下CO2浓度升高对番茄根系生长及养分吸收的影响

采用培养试验研究了磷缺乏与正常供磷条件下,CO₂浓度由350μL/L升高至800μL/L苗期番茄的生物量、根系特征和不同器官N、P、K养分含量的变化。结果表明,无论缺磷与否,CO₂浓度升高均能显著增加番茄地上部及根系的干物质积累量,提高根冠比。在磷缺乏条件下,CO₂浓度升高对番茄根系生长的促进主要表现为增加根系的体积和表面积;而在磷正常供应条件下主要表现为同时增加根体积和分根数,有利于形成强壮的根系。在两种供磷水平下,CO₂浓度升高对番茄各器官的N、P、K含量产生不同的稀释效应,但N、P、K总积累量却随CO₂浓度升高而显著增加;而且CO₂浓度与供P水平对番茄植株的N、P、K积累量具有极显著的正交互效应。     

Short‐term response of the Ca cycle of a montane forest in Ecuador to low experimental CaCl2 additions

The tropical montane forests of the E Andean cordillera in Ecuador receive episodic Sahara‐dust inputs particularly increasing Ca deposition. We added CaCl₂ to isolate the effect of Ca deposition by Sahara dust to tropical montane forest from the simultaneously occurring pH effect. We examined components of the Ca cycle at four control plots and four plots with added Ca (2 × 5 kg ha^–1 Ca annually as CaCl₂) in a random arrangement. Between August 2007 and December 2009 (four applications of Ca), we determined Ca concentrations and fluxes in litter leachate, mineral soil solution (0.15 and 0.30 m depths), throughfall, and fine litterfall and Al concentrations and speciation in soil solutions. After 1 y of Ca addition, we assessed fine‐root biomass, leaf area, and tree growth. Only < 3% of the applied Ca leached below the acid organic layer (pH 3.5–4.8). The added CaCl₂ did not change electrical conductivity in the root zone after 2 y. In the second year of fertilization, Ca retention in the canopy of the Ca treatment tended to decrease relative to the control. After 2 y, 21% of the applied Ca was recycled to soil with throughfall and litterfall. One year after the first Ca addition, fine‐root biomass had decreased significantly. Decreasing fine‐root biomass might be attributed to a direct or an indirect beneficial effect of Ca on the soil decomposer community. Because of almost complete association of Al with dissolved organic matter and high free Ca²⁺ : Al³⁺ activity ratios in solution of all plots, Al toxicity was unlikely. We conclude that the added Ca was retained in the system and had beneficial effects on some plants.     

Effects of nitrogen addition on nitrogen mineralization and nutrient content of expanding Calamagrostis epigejos in the Podyjí National Park,Czech Republic

Effects of extra nitrogen (N) input on biomass production, the concentration of N and phosphorus (P) in plant material, and net N mineralization were studied during three growing seasons in a dry acidophilous grassland dominated by Festuca ovina and in a grassland where the tall grass Calamagrostis epigejos was aggressively expanding. In contrast to dry grassland, the Calamagrostis stand utilized more N due to higher plant and microbial demands for soil mineral N, which could prevent the N losses. Additional N supply resulted in the increased net N mineralization mainly in expanding Calamagrostis. There was no effect of N addition on biomass production of Calamagrostis, while a significant increase of total biomass was observed in Festuca in the dry grassland. This higher production was entirely accounted for by the increase in root dry weight. Concentrations of N in the aboveground biomass increased in both Calamagrostis and Festuca dry grassland as a result of N addition. However, P concentrations in Festuca were reduced, while being enhanced in Calamagrostis. The N : P ratio in aboveground biomass significantly increased in both vegetation types studied following N addition, although reaching higher values in dry grassland than in Calamagrostis. This species compensated enhanced N availability with a higher P uptake as compared to Festuca.