The Optimal Concentration of KH2PO4 Enhances Nutrient Uptake and Flower Production in Rose Plants via Enhanced Root Growth

Monopotassium phosphate is a widely used phosphorus and potassium fertiliser for ornamental plants, but it is not known what concentration will result in optimal flower production, root growth and nutrient uptake of rose plants. We compared potted rose plants fertilised with six different concentrations (0.0 as a water-only control, 1.0, 2.0, 3.0, 4.0 and 5.0 g·L−1) of an aqueous monopotassium phosphate solution as a combination of foliar and soil applications over two consecutive flowering cycles. Rose growth, flower production and nutrient accumulation responded differently to fertilisation with different concentrations of monopotassium phosphate. During the first flowering cycle, shoot and root dry weight, leaf chlorophyll content, flower diameter, total root length and surface area, and total fine root length significantly increased in response to increased monopotassium phosphate concentrations from 0.0 to 3.0 g·L−1 but decreased in response to fertilisation with 4.0 or 5.0 g·L−1 monopotassium phosphate. Similar trends were observed in shoot dry weight, leaf chlorophyll content, flower diameter and number, phosphorus and potassium accumulation during the second flowering cycle. According to quadratic equations derived from both flowering cycles, the optimal concentration of monopotassium phosphate, based on flower diameter and dry weight, as well as total phosphorus and potassium accumulation, was 2.6–3.0 g·L−1. Furthermore, total root length was significantly correlated with flower diameter, flower dry weight, and total phosphorus and potassium accumulation (p < 0.05). These results indicated that fertilisation with optimal concentrations of monopotassium phosphate can increase rose growth, flower productivity and nutrient uptake through enhanced root growth.

Dependence of productivity of white lupine seeds on the foliar dressing with macro- and micronutrient fertilizers

The paper presents the results of the studies on the determination of the effect of foliar dressings with macro- and micronutrient fertilizers on linear growth, the mass of air-dry matter of plants, leaf surface, the formation of a symbiotic apparatus and the yield of seeds of white lupine (Lupinualbus L.) in the conditions of black soils of the Central Black Earth region of the Russian Federation. The field experiments were carried out in 2018-2020 at the Department of Crop production, Breeding and Horticulture of Belgorod State Agrarian University. The object of the research is a high-intensity variety of white Degas lupine. The subject of the research is microfertilizer Aquamix-TV, potassium sulfate fertilizer (K2SO4), phosphate-potassium monophosphate fertilizer (KH2PO4). The weather during the years of the experiments was hot and dry. During the critical periods of the development of lupine plants, a moisture deficit was observed with the excess of heat. The soil cover of the experimental site was represented by a typical medium-thick low-humus heavy loamy black soil with a granulometric composition. The accounting area of the plot was 18 m2, the replication was fourfold and the placement was systematic. The experiment included six variants: control (without fertilizers), foliar dressing with Aquamix-TV micronutrient fertilizer, foliar dressing with potassium sulfate solution, foliar dressing with potassium monophosphate solution, foliar dressing with Aquamix-TV + potassium sulfate mixture and foliar dressing with Aquamix-TV + monophosphate mixture potassium. The analysis of the obtained data showed that the highest yield of seeds of white lupine variety Dega was obtained on variants with foliar dressing with micronutrient fertilizer Aquamix-TV in combination with potassium sulfate and monopotassium phosphate, which amounted to 3.52 and 3.51 t / ha, respectively, which is 0.52 and 0.51 t / ha or 17.3 and 17.1% more than the control variant.

Nutrient Status of Cucumber Plants Affects Powdery Mildew (Podosphaera xanthii)

We examined the effects of applications of N, P, K, Mg, and Ca through an irrigation solution and spraying K, Ca, and Mg salts on cucumber powdery mildew (CPM, Podosphaera xanthii) in potted plants and under commercial-like conditions. Spraying CaCl2 and MgCl2, or KCl and K2SO4, decreased CPM. There were significant negative correlations between the anion-related molar concentrations of the salts and disease severity. Among the sprayed treatments, NaCl provided significantly less CPM control when applied at a low (0.05 M) concentration, as compared with CaCl2 and MgCl2. When sprayed applications of Mg and K salts were analyzed separately from the untreated control, the Cl− salts were found to be more effective than the SO4−2 salts. High N and Mg concentrations in the irrigation water delivered to young, fruit-less cucumber plants reduced CPM, whereas more CPM was observed when the irrigation solution contained a medium amount of P and a high amount of K. In contrast, mature, fruit-bearing plants had less severe CPM at higher N, lower P, and higher K levels. Spraying mature plants with monopotassium phosphate, polyhalite (K2Ca2Mg(SO4)4·2H2O), and the salts mentioned above over an entire growing season suppressed CPM. CPM severity was also reduced by spray applications of Ca, Mg, and KSO4−2 and Cl− salts. Spray applications provided better CPM control than fertigation treatments. Induced resistance is probably involved in the effects of nutrients on CPM.

Preparation and Performance of Structure Controllable Biochar Obtained From Cattail-Sludge Composites

Biochar obtained from cattail-sludge composites (BC/CS) was treated as a raw material, with monopotassium phosphate and ammonium chloride solution as absorbents, to find the best parameters for the preparation of structure controllable biochar (BC/SC). Slow pyrolysis and single factor experiment method were employed in the preparation of BC/CS and BC/SC, with EA, BET and SEM to illustrate the performance of BC/SC. The results showed that the best parameters for BC/CS were characterized by a ratio of cattail-sludge composites (60:40, wt%), a charring temperature of 500℃, a charring time of 0.5 hrs, KOH as an activator, an immersion ratio of 4 mL·g-1, an activation concentration of 300 g·L-1 and an immersion time of 6 hrs; the best parameters for BC/SC contained a sizing amount of 60%, a molding pressure, temperature and time of 5 N (cm2)-1, 160℃, and 95 min, respectively; compared to BC/CS, BC/SC was characterized by a higher content of H but a lower O content, leading to the increase in its hydrophobicity and stability; in addition, the addition of polyethylene enabled an increase in the pore diameter of BC/SC and a close bond with particles on the surface. Meanwhile, in BC/SC, the surface functional groups of CH3 and C—O—C were reduced in their contents, in contrast to a large amount of C crystals on its surface. Such results could provide a new process for resource recycling of cattail and sludge, as well as evidence for material selection in the treatment of eutrophication water bodies.

Effects of Phosphorus on Nitrification Process in a Fertile Soil Amended with Urea

While the effects of carbon on soil nitrogen (N) cycle have been extensively studied, it is not clearly understood how co-existing macronutrients, such as phosphorus (P), affect the N cycle in agroecosystems. In this study, P amendment effects on nitrification in a fertile agricultural soil were investigated under a typical N-P amendment rate. In a laboratory incubation study, soils were amended with urea, monopotassium phosphate and a mixture of urea and monopotassium phosphate at the same rate. In soils that received no amendments (control), P only, urea only, and urea plus P amendment, nitrification occurred within the first five days, with an average net nitrification rate of 5.30, 5.77, 16.66 and 9.00 mg N kg−1d−1, respectively. Interestingly, nitrification in urea-treated soils was retarded by P addition where a N:P ratio seemed to be a key factor impeding nitrification. This was also supported by the response of ammonia-oxidizing bacteria (AOB), which was more sensitive to P addition than ammonia-oxidizing archaea (AOA). The outcome of this study showed that application of P fertilizer suppressed the nitrification process in urea amended soil, suggesting that a synergistic aspect of N and P nutrient management should be further explored to retard N losses from agricultural systems.

Feasibility of Stabilized Zn and Pb Contaminated Soils as Roadway Subgrade Materials

The authors have developed a new binder, KMP, which is made from oxalic acid-activated phosphate rock, monopotassium phosphate (KH2PO4), and reactive magnesia (MgO). This study explores the acid neutralization capacity, strength characteristics, water-soaking durability, resilient modulus, and pore size distribution of KMP stabilized soils with individual Zn, Pb, or coexisting Zn and Pb contaminants. For comparison purpose, Portland cement (PC) is also tested. The results show that KMP stabilized soils have a higher acid buffering capacity than PC stabilized soils, regardless of the soil contamination conditions. The water stability coefficient and resilient modulus of the KMP stabilized soils are found to be higher than PC stabilized soils. The reasons for the differences in these properties between KMP and PC stabilized soils are interpreted based on the stability and dissolubility of the main hydration products of the KMP and PC stabilized soils, the soil pore distribution, and concentration of Mg or Ca leached from the KMP and PC stabilized soils obtained from the acid neutralization capacity tests. Overall, this study demonstrates that the KMP is effective in stabilizing soils that are contaminated with Zn or Pb alone and mixed Zn and Pb contaminants, and the KMP stabilized soils are better suited as roadway subgrade material.

Fixation of soluble forms of fertilizer phosphorus in salt affected soils of Ramanathapuram and Trichy districts and acid soil of Ariyalur district of Tamil Nadu

Soluble phosphorus (P) applied through phosphatic fertilizers is quickly converted into low soluble P compounds in soil. For evaluating fixation ability of P fertilizers laboratory incubation experiments were conducted with saline, sodic and acid soils. Phosphatic fertilizers selected were single super phosphate (SSP), diammonium phosphate (DAP), monoammonium phosphate (MAP), monopotassium phosphate (MPP) and 19:19:19 N, P2O5, K2O % (All-19). Fixation of P was computed based on the amount of P recovered after addition of P in the soil in increasing levels. At a typical P addition at 16 kg ha-1 the results were compared in all soils. In saline soil, high fixation of P occurred when DAP (12.18 kg ha-1) and MPP (11.28 kg ha-1) were applied. In sodic soil, high fixation of P resulted when SSP (7.10 kg ha-1) was applied. In acid soil, high fixation of P occurred when All -19 (12.64 kg ha-1), MAP (12.40 kg ha-1), SSP (12.22 kg ha-1), and DAP (11.74 kg ha-1) were applied. With all forms of phosphatic fertilizers fixation of added P occurred to the extent of 57.9 to 79.0 per cent in acid soil, 55.0 to 70.5 per cent in saline soil and 25.5 to 44.4 per cent in sodic soil. In saline soil availability of P might be higher for SSP and All-19 compared to ammonium/ potassium phosphate fertilizers. On the other hand, MPP, MAP and All-19 may be preferably applied in sodic/ acid soils alternative to SSP or DAP for realizing higher P release in soils from added fertilizers for the benefit of crop utilization.