Foliar Application Of Potassium Silicate Research Articles

Eficiência do silicato de potássio no controle do oídio e no desenvolvimento de abobrinha de moita

A medida mais utilizada para o controle de oídio em cucurbitáceas é o uso de variedades resistentes e fungicidas sistêmicos, entretanto, a nutrição silicatada tem se mostrado uma opção. O fornecimento do silício é benéfico para muitas espécies vegetais, estimulando o crescimento, a produção, a fotossíntese e a regulação da transpiração; além disso, sua deposição na epiderme evita a invasão de fungos, bactérias e insetos sugadores. O objetivo deste trabalho foi verificar a influência do silicato de potássio no controle do oídio, e no desenvolvimento e na produção de abobrinha de moita, cultivar Caserta. O experimento foi conduzido em cultivo protegido, com delineamento inteiramente casualizado, quatro repetições e cinco tratamentos: testemunha (água); tratamento químico com fenarimol (2,4 g i.a 100 L-1) e silicato de potássio, nas doses de 1,5 L ha-1; 2,0 L ha-1 e 2,5 L ha-1. Foram avaliados a severidade da doença; trocas gasosas; crescimento e produção de frutos. Os resultados mostraram que a aplicação foliar de silicato de potássio com fenarimol controlou o oídio e não teve influência no crescimento da planta. Portanto, o silicato de potássio pode ser utilizado como alternativa para o controle desse fungo e diminuição da aplicação de produtos químicos, o que proporciona uma maior sustentabilidade ambiental. No entanto, deve-se tomar cuidado com dosagens altas, pois observou-se que a dosagem de 2,5 L ha-1 foi prejudicial à produção de frutos e às trocas gasosas, apesar de ter sido eficiente no controle do oídio. Recomenda-se o uso de 2,0 L ha-1 de silicato de potássio para o controle de oídio para abobrinha de moita, podendo substituir o uso de fenarimol, sem afetar a produção e desenvolvimento das plantas.

Foliar application of potassium silicate, acibenzolar-S-methyl and fungicides on the reduction of Pestalotia leaf spot on strawberry

Pestalotia leaf spot, caused by Pestalotia longisetula, has become an important disease on strawberry, and fungicide application is the main recommended control strategy. This study evaluated the effect of foliar application of potassium silicate (PS) at the concentrations of 8 and 30 g/L, acibenzolar-S-methyl (ASM), fungicides azoxystrobin (AZO), and mancozeb (MAN) on the reduction of disease severity. Plants were inoculated at 1, 6, and 12 days after application (d.a.a.) of the products. At the 1st d.a.a., there was no difference in disease severity between PS, at the two concentrations, ASM and the control. AZO and the MAN reduced disease severity by 56.3 and 43.8%, respectively, in comparison to the control. At the 6th d.a.a., there was no difference between PS (8 g/L) and the control. PS (30 g/L) reduced disease severity by 61% compared to the control. At the 12th d.a.a., there was no difference between the treatments PS, at the two concentrations, ASM, AZO, and MAN, but these treatments differed from the control. Disease severity was different for the three inoculation times for PS (8 g/L), with the lowest value occurring at the 12th d.a.a. For treatments PS (30 g/L), ASM, AZO, and MAN, disease severity was reduced from the 1st to the 6th d.a.a., but there was no difference between the 6th and the 12th d.a.a. There was no difference between the three inoculation times for the control. Foliar application of PS was as efficient as ASM in reducing the symptoms of Pestalotia leaf spot, especially if sprayed before pathogen inoculation.

Effect of root and foliar applications of silicon on brown spot development in rice

Silicon (Si) application is a strategy to manage rice brown spot, but no studies have been conducted on Si as a foliar spray for control of this disease. The purpose of this study was to compare root and foliar Si applications on rice brown spot development, and to determine if there is a biochemical defence response. Rice plants (cv. Metica-1) were grown in a Si-deficient soil that received the following treatments: root application of calcium silicate (CS) (1.25 g/kg of soil), foliar application of potassium silicate (PS) (40 g/L), and control (leaves sprayed with distilled water). Thirty-day-old plants were inoculated with a conidial suspension of Bipolaris oryzae. Si concentration in rice tissue was markedly higher for CS compared with the other treatments. The intensity of Si deposition, as determined by X-ray microanalysis, between the adaxial and abaxial leaf blades of rice plants in the control treatment was similar. Si deposition occurred in both the adaxial and abaxial leaf blades of rice plants that received CS while this Si deposition only occurred on the adaxial leaf blades of plants that received PS. The area under brown spot progress curve (AUBSPC) was not significantly different between the PS and control treatments, but was significantly lower in plants grown in soil amended with CS. The values for the AUBSPC and the number of lesions (NL) per cm2 of leaf area decreased by 37 and 47%, respectively, with CS compared with the control. Conidial germination was not inhibited by PS. The concentration of total soluble phenolics and lignin-thioglycolic acid derivatives was not linked with the reduction observed in the AUBSPC and the NL. Although the concentration of these two biochemical variables seemed to be slightly higher in plants from the control treatment, likely due to the greater disease severity and the NL, rice tissue was not efficiently protected against colonisation by B. oryzae. The results of this study suggest that foliar-applied Si can decrease the intensity of brown spot; however, the level of control achieved was not as great as that obtained when Si was supplied to the roots.

Foliar application of potassium silicate reduces the intensity of soybean rust

This study aimed to determine if potassium silicate (KSi) sprays could reduce the intensity of soybean rust. In the field experiment 1, soybean plants were sprayed with KSi (pH 10.5) at rates of 8, 20, 40 and 60 g/L. In the field experiment 2, with the same treatments, the pH of the KSi solutions was 5.5. In experiment 3, the treatments were KSi (40 g/L, pH 10.5), potassium hydroxide (KOH) (6.5 g/L,pH10.5), epoxiconazole + pyraclostrobin, and control. In experiment 4, the treatments were the same as in experiment 3, but the pH of the KSi and KOH solutions was adjusted to 5.5. Plants sprayed with water served as a control treatment for all field experiments. Plants were artificially inoculated with Phakopsora pachyrhizi before the application of products. Even though there was no relationship between silicon (Si) concentration in leaf tissue and KSi rates, Si concentration increased by 67% and 73% respectively above the control, when averaged across all KSi rates for experiments 1 and 2. The relationship between the severity of soybean rust and KSi rates atpH10.5 and 5.5 was, respectively, linear and quadratic. Soybean rust severity at the highest KSi rate (pH 5.5) was70%less than the control. In experiments 3 and 4, the highest disease severity was observed on the control treatment which differed from other treatments. The application of KSi at pH of 10.5 (Exp. 3) and 5.5 (Exp. 4) decreased soybean rust severity by 36% and 43%, respectively, over the control. No significant difference in disease severity was found between KSi and KOH treatments, but they were significantly different, regardless of pH used, from the epoxiconazole + pyraclostrobin treatment. In greenhouse experiments, Si concentration in leaf tissue was higher with the application of KSi, regardless of the pH of the solutions, as compared with water spray. Soybean rust severity and the number of pustules were higher on leaves of plants sprayed with water, as well as on those sprayed with phosphoric acid + NaOH, and phosphoric acid + KOH, when compared with the application of KSi. There was no difference between the KSi and KOH treatments, regardless of the pH, and epoxiconazole + pyraclostrobin sprays for disease severity and number of pustules. This is the first study where field and greenhouse experiments have demonstrated a reduction of soybean rust intensity with foliar application of KSi. This information may be valuable in areas where soybean is grown as a monoculture, and where high yielding but susceptible cultivars cannot be grown because of the occurrence of frequent severe epidemics.

Controle alternativo da mancha de Ramularia do algodoeiro

A mancha de Ramularia, causada pelo fungo Ramularia gossypii (Speg.) Cif., é uma doença foliar de destaque na cotonicultura brasileira. Com a expansão da cotonicultura, existem poucos produtos avaliados para manejo da Ramularia, destacando-se os fungicidas dos grupos triazóis e estrobirulinas. Objetivou-se nesse trabalho avaliar o efeito da aplicação foliar do silicato de potássio, da calda Viçosa e de fungicidas protetores (mancozeb e clorotalonil) para o controle químico da mancha de Ramularia. O silicato de potássio não foi eficiente para o controle da doença com severidade de 15,38%, enfolhamento relativo aos 166 dias após a emergência de 38,19%, produtividade de algodão em caroço de 136,11 @ ha-1 e área abaixo da curva de progresso da mancha de Ramularia de 644, 598 e 172 nos terços inferior, médio e superior, respectivamente, com valores semelhantes à testemunha sem fungicida. A calda viçosa proporcionou satisfatório controle da doença não diferindo em termos de produtividade dos tratamentos com piraclostrobin e ou tebuconazol, sendo o incremento de produtividade em relação à testemunha de 88%. Os fungicidas mancozeb e clorotalonil em mistura com calda Viçosa ou com tebuconazole foram eficientes no controle da mancha de Ramularia, destacando-se o fungicida mancozeb em mistura com tebuconazol.

Foliar application of potassium silicate induces metabolic changes in strawberry plants

The effect of foliar silicon (Si) applications on metabolic changes in strawberry plants (Fragaria x ananassa Duch.) was studied. Silicon was used in the form of the potassium (K) salt. Foliar spray with K silicate (containing 0, 4.25, 8.50, 12.75, or 17.00 mm of Si) showed increased chlorophyll content and plant growth. Potassium silicate treatments also induced metabolic changes such as increases in citric acid and malic acid levels, and decreases in fructose, glucose, sucrose, and myo‐inositol contents. The treated tissues also had higher ratios of fatty acid unsaturation [(18:2+18:3)/18:1] in glycolipids and phospholipid and elevated amounts of membrane lipids. These results suggest that Si has beneficial effects on strawberry plant metabolism.