Application Of KNO3 Research Articles

Response surface methodology to understand the anaerobic biodegradation of organochlorine pesticides (OCPs) in contaminated soil—significance of nitrate concentration and bioaccessibility

Problems associated with Organochlorine pesticide (OCP)-contaminated soils have received wide attention. To understand the anaerobic biodegradation process constraints, innovative mathematical analysis methods are effective. Response surface methodology (RSM) and Tenax TA extraction method combined with the first-three-compartment model were employed to systematically investigate the role of nitrate concentration and bioaccessibility enhancer (methyl-β-cyclodextrin, MCD) in the anaerobic biodegradation of OCPs in contaminated soil. The sole addition of either KNO3 or MCD could facilitate the anaerobic biodegradation of OCPs. The highest biodegradation for total OCPs, hexachlorocyclohexanes, endosulfans, and chlordanes were 71.6, 82.1, 68.3, and 55.6 %, respectively, when 20 mM KNO3 and 3.0 % (w/w) MCD were applied simultaneously. As predicted by RSM, the theoretical maximum biodegradation for total OCPs ranged from 60 to 80 % when 20 to 25 mM KNO3 and >2.5 % (w/w) MCD were applied simultaneously. Tenax TA extraction method demonstrated the enhancement of OCP bioaccessibility caused by MCD addition. Changes in the soil microbial activities also suggested the positive effects of adding suitable amounts of KNO3 as a cosubstrate to facilitate the anaerobic biodegradation of OCPs. The amount of KNO3 and MCD are crucial in influencing OCP biodegradation. RSM was demonstrated to be a powerful tool to estimate and predicting the optimal OCP biodegradation under KNO3 and MCD application simultaneously.

10.5937/ratpov51-6572 = Effect of soybean seed priming on germination and vigour depending on the seed lot and sowing date

The objective of this paper was to examine the effect of seed lot, sowing date, and priming on germination and vigour of soybean seed. Three different seed lots of an old soybean variety (Lot 1, Lot 2, Lot 3) created at the Institute of Field and Vegetable Crops in Novi Sad were used. There were three sowing dates: 10 April, 20 May and 20 June. KNO3 (1%), H2O2 (0.1%), GA3 (0.075%) and distilled water were used as primers. The results showed that soaking the seed prior to sowing, so called priming, positively affected seed germination and vigour in all three lots and with all three sowing dates. The best effect was accomplished with Lot 1 and sowing on the third date. With regards to primers, the best effect was achieved with the application of KNO3 and H2O2 solutions. Research has shown that even soaking the seed in distilled water, which is a simple, cheap, and ecological method of priming, in most cases leads to improvement of germination and vigour of soybean seed.

Response of chickpea to potassium fertilization on yield, quality, soil fertility and economic in vertisols

A field experiment was carried out to study the effect of potassium fertilization on growth, yield, quality, soil fertility and economics of chickpea during rabi 2008-09 to 2010-11. The growth and yield attributes were significantly improved by different potash levels. The application of 20 kg K2O/ha increase the seed and straw yield significantly over RDF alone and absolute control, however, could not influence significantly over foliar application of KNO3 (2%) twice at flowering and 15 days thereafter. Seed yield of chickpea increases up to 40 kg K2O/ha-1 and further decreases with 50 kg K2O/ha though the difference between them remained at par. The highest uptake of nitrogen, phosphorous and potassium was observed at 40 kg K2O ha-1 which was at par with 30 kg K2O ha-1. The seed protein content increased gradually with increase in potash level and maximum protein content were recorded with application of 40 kg K2O/ha-1 along with physical properties. Available N, P and K status of soil after harvest of chickpea were significantly influenced due to potash levels over initial status. The significantly higher net return was obtained with application of RDF+ 40 kg K2O ha-1 which in turn was found at par with lower level of RDF 30 kg K2O ha-1.

Estudios de germinación y remoción de latencia en semillas de papayuelas Vasconcellea cundinamarcensis y Vasconcellea goudotiana

Se estudió la germinación y latencia de las semillas de Vasconcellea cundinamarcensis y V. goudotiana, para desarrollar procedimientos promotores de emergencia de los embriones. La categorización de las semillas viables no germinables se realizó con el empleo del tetrazolio. La fermentación prolongada de las semillas, para remover la sarcotesta, afectó la viabilidad de éstas, en especial las de V. cundinamarcensis. Aplicaciones de KNO3 y AG3 promovieron una germinación significativamente mayor, en comparación con el testigo, en semillas fermentadas previamente durante 15 días de V. goudotiana, lo cual no ocurrió en las de V. cundinamarcensis. La aplicación de Saccharomyces cerevisiae durante 36 horas, para fermentación y liberación de la sarcotesta, indujo germinación en las dos especies, con una respuesta significativamente superior en V. goudotiana. La adición de AG3 y KNO3, luego del tratamiento anterior, promovió mayor emergencia en ambos taxa, en especial en V. goudotiana. La fermentación de las semillas con Saccharomyces cerevisiae, en combinación con AG3 y KNO3 produjo germinación en las dos especies, con énfasis en V. goudotiana al aplicar 1000 ppm de AG3 + KNO3 al 2,5% y en V. cundinamarcensis, al utilizar 600 ppm de AG3 + AG3 al 2,5%, sin diferencia significativa con la aplicación de 1000 ppm de AG3 + KNO3 al 1,5%; se logró mayor germinación en V. goudotiana en el tratamiento precitado, con el cual se obtuvo con confiabilidad estadística la máxima brotación de plántulas, en relación con el resto de tratamientos evaluados con la propia especie y en V. cundinamarcensis.

Effect of decapitation and nutrient applications on shoot branching, yield, and accumulation of secondary metabolites in leaves of Stevia rebaudiana Bertoni

The axillary buds of stevia (Stevia rebaudiana Bertoni) often remain dormant for a long time and sometimes remain dormant permanently until the plants enter into the reproductive stage. The present study was conducted to ascertain whether decapitation and foliar fertilization enhance the productivity and quality of stevia through breaking the apical dominance and increasing physiological activities. Ten treatment combinations comprising two cultural operations (non-decapitation and decapitation) and five foliar spray treatments (water spray control, KNO3 @ 5.0gL(-1), Ca(NO3)2 @ 4.06gL(-1), CuSO4·5H2O 2.0gL(-1) and (NH4)6Mo7O24 @ 1.0gL(-1)) were applied. The decapitation of apical buds of stevia increased the branches and increased dry leaf yield by 13 and 17% compared with non-decapitation during 2010 and 2011, respectively, without affecting quality. Foliar application of nutrient solutions also exerted a considerable effect on growth parameters, yield attributes and chlorophyll content, and significantly (P=0.05) higher dry leaf yield ranging from 8 to 26% over the control. Among the foliar spray treatments, KNO3 @ 5.0gL(-1) and Ca (NO3)2 4.06gL(-1) were found most effective in dry leaf yield. Thus, the decapitation of apical buds and foliar application of KNO3 and Ca (NO3)2 could enhance the productivity of stevia through improving the growth of axillary buds and physiological activities.

The Application of Rice Hull Mulch and Potassium Nitrate on Growth and Yield of Kailan (Brassica oleraceae var. Long Leaf)

Potassium (K) is absorbed by plants in larger amounts than any other mineral element except N to optimalize plant growth. Mulches may be influenced an available K at vegetative growth phase of plant. The research was conducted in Simpang Kanan Village, Gisting, Tanggamus Lampung Province. The objectives of this research were to study the application of KNO3 and rice hull mulch on growth and yield of kailan. Fields experiments were arranged by a factorial in a completely randomized block design with 10 treatments and 3 replications. A first factor was (1) dosages of KNO3 (150, 175, 200, 225, and 250 kg ha-1) and the second factor was mulch of the rice hull (with and without the rice hull). The results showed that the application of the rice hull did not significantly affected the yield of kailan, however the application of KNO3 till 250 kg ha-1 increased the level of greenness up to 6.10% and the wide of leaf up to 18,57%. In addition, the present of potassium fertilizer suspended with the rice hull significantly affected the width of kalian leaf.Keywords: Kailan, mulch, potassium nitrate, rice hull

WATER RELATIONS, PIGMENT STABILIZATION, PHOTOSYNTHETIC ABILITIES AND GROWTH IMPROVEMENT IN SALT STRESSED RICE PLANTS TREATED WITH EXOGENOUS POTASSIUM NITRATE APPLICATION

Potassium is a major nutrient which may play an important role in many processes such as ion homeostasis in plant cells and osmotic adjustment of guard cells during stomatal opening and closing. Pathumthani 1 (PT1) rice has been reported as being a salt sensitive cultivar and has been selected as a model plant in this study to investigate the possibility of improving the osmotic potential, pigment stabilization, photosynthetic efficiency and growth characteristics of this plant under salinity stress by potassium nitrate (KNO3) application. Sodium ion accumulation in root and leaves of KNO3 (11.8 mM) treated plants declined as compared to the control plants. In control plants, however, due to decline in potassium ion content, the Na + / K + ratio increased significantly. A positive relation between Na + accumulation and osmotic potential was found. Osmotic potential (Ψs) in the root and leaf tissues of PT1 rice treated with 11.8 mM KNO3 was maintained at low levels, which was accompanied with the stabilization of photosynthetic pigments, high photosynthetic performance and better growth characters under 200 mM NaCl. The photosynthetic ability in plants with KNO3 application was positively related to plant dry weight. Exogenous KNO3 application to rice crops may play a vital role as a short-gun technique for the improvement of salt tolerance.

Effects of halo and phytohormone seed priming on germination and seedling growth of maize under different duration of accelerated ageing treatment

Seed ageing is a main problem of seed storage. Unsuitable storage conditions with high moisture and temperature increases seed ageing. In fact, seed ageing results in the decrease of seed quality. Seed priming is known as a seed enhancement treatment which could improve seed germination and germination synchrony in many of crops. In this experiment we investigated effects of seed ageing, application of phytohormone and KNO3 on aged corn seeds. In order to improve germination characteristics in aged seeds phytohormone treatment using different gibberlline concentration (50, 100, 200, 400 and 800 ppm) and KNO3(0.5, 1, 2.5 and 4%) were used. Results of study showed significant difference in aged seeds. It was also observed that with higher ageing duration, more germination characteristics decreased. Gibberlline at 400 ppm increased germination characteristics in aged seeds and had a positive effect on seed germination of aged corn seeds. KNO3 also had positive effects on seed germination of aged seed. This was higher in application of 0.5% KNO3 for 8 h and 2.5% for 24 h. Based on our results, it was suggested that seed ageing for higher duration could significantly decrease seed quality. Using seed enhancement treatments like seed priming or application of phytohormone could improve aged and non-aged seed performance especially for high aged seeds. Key words: Seed, accelerated ageing, KNO3, gibberlline, seed priming, maize.

Effect of KNO<sub>3</sub> fertilization and rootstock on grapefruit response to reclaimed, salinized water

During the last 50 years world irrigation has doubled while water withdrawal has tripled, leading to a global water crisis. As a result, growers around the world are forced to utilize effluent water for irrigation. In Israel the main source for such water is SHAFDAN, i.e., tertiary-treated waste water, which is characterized by high chloride content that might increase in the future. These days about 33% of Israeli citrus orchards are irrigated with this water, yet its potential effect on citrus orchards is not clear. Citrus is one of the major fruit crops of the world and is relatively salt-sensitive. Recently it was reported that continuous application of KNO3 might reduce chloride (Cl) uptake, and thus overcome the toxic effects of salinity. We examined the effect of KNO3 fertilization and rootstock on grapefruit's response to salinized SHAFDAN reclaimed water over four years. Trees were grafted on five different rootstocks and fertigated with two KNO3 regimes (118 vs. 148 mg 1-1 NO3), and exposed to...

Foliar Application of Potassium Nitrate Affects the Growth and Nitrate Reductase Activity in Sunflower and Safflower Leaves under Salinity

Effect of foliar application of KNO3 on growth and the activity of nitrate reductase were studied in the leaves of sunflower (Helianthus annuus L.) and safflower (Carthamus tinctorius L.) plants growing under different levels of salinity. The seeds were sown in pots under non saline condition and saline water irrigation was started at three leaf stage after germination. Different concentration of saline water (i.e. 0.3% and 0.6%, equivalent to an EC of 4.8 and 8.6 dS/m respectively) were made by dissolving sea salt per litre of tap water. Nutrient solution of KNO3 was sprayed at the rate of 250 ppm. The concentration of Na+ and Cl- rapidly increased in the leaves of both the plants under salinity stress. In contrast the nitrate (NO3-) and soluble protein concentration were decreased with the increasing salinity. Salinity reduced leaf area, its fresh and dry weight per plant and also inhibited the activity of Nitrate reductase (NRA) enzyme. The application of KNO3 significantly reduced the increasing tendency of Na+ and Cl- and increased leaf area, its fresh and dry weight per plant, NO3- and soluble protein concentration and NR activity in leaves irrespective to the growth of plant under non saline or saline conditions.

EFFECT OF ETHYLENE INHIBITING CHEMICALS ON YIELD AND QUALITY OF POMEGRANATE

An experiment was carried out to study the effect of ethylene inhibiting chemicals on yield and quality of pomegranate. Application of various ethylene inhibiting chemicals proved to be superior to reduce the ethylene levels in leaves of pomegranate. Spraying of cobalt chloride 2.5 ppm recorded significantly lower levels of ethylene in leaves of pomegranate. Numbers of fruits per tree, yield per tree and average fruit weight were recorded highest in plants sprayed with cobalt chloride 2.5 ppm in pomegranate. KNO 3 as an inhibitor recorded moderate results. Highest total soluble solids were recorded with cobalt chloride 2.5 ppm and KNO 3 500 ppm in pomegranate. Application of KNO 3 as foliar spray recorded the highest percentage of titratable acidity in pomegranate. Foliar application of ethylene inhibitors was most effective over soil application for all the characters.

Land Surface Evaluation Using Unit Hydrograph Methods at Way Besai Watershed, Sumberjaya, West Lampung, Indonesia

Potassium (K) is absorbed by plants in larger amounts than any other mineral element except N to optimalize plant growth. Mulches may be influenced an available K at vegetative growth phase of plant. The research was conducted in Simpang Kanan Village, Gisting, Tanggamus Lampung Province. The objectives of this research were to study the application of KNO3 and rice hull mulch on growth and yield of kailan. Fields experiments were arranged by a factorial in a completely randomized block design with 10 treatments and 3 replications. A first factor was (1) dosages of KNO3 (150, 175, 200, 225, and 250 kg ha-1) and the second factor was mulch of the rice hull (with and without the rice hull). The results showed that the application of the rice hull did not significantly affected the yield of kailan, however the application of KNO3 till 250 kg ha-1 increased the level of greenness up to 6.10% and the wide of leaf up to 18,57%. In addition, the present of potassium fertilizer suspended with the rice hull significantly affected the width of kalian leaf. Keywords: Kailan, mulch, potassium nitrate, rice hull

Study upon Seed Germination of Chrysanthemum Cinerariaefolium (Trev.) Vis.

Chrysanthemum cinerariaefolium (Trev.) Vis is a species known for its usage in natural control of insects, inside the house and in biologic agriculture, as well as for its usage in treatment of different affections of the human and animal body. 
 Aspects regarding seed germination of this species are known as being a difficult problem, specialized literature presenting different values, generally reduced. 
 The present study establishes germination of 1, 2 and 3 years old seeds by using classical methods in blotting paper envelopes and blotting paper layer, in Linhardt dishes. 
 In order to identify solutions that would contribute to the growth of germinating values, stimulating methods were tested by exposing seeds to darkness or light or by subduing them to a KNO3 and energized water treatment. 
 Results show a low germinating percent, between 20% and 30% for all the ages of the studied seeds. Stimulating methods do not induce an appreciable germination increase, the highest percentage (31%) being obtained by using the Linhardt dish method combined with darkness exposure and application of KNO3, 0.2% solution and by using energized water (31.75%). When coming to stimulation, best results were given by energized water treatment.

The Arabidopsis vacuolar anion transporter, AtCLCc, is involved in the regulation of stomatal movements and contributes to salt tolerance

In plant cells, anion channels and transporters are essential for key functions such as nutrition, resistance to biotic or abiotic stresses, and ion homeostasis. In Arabidopsis, members of the chloride channel (CLC) family located in intracellular organelles have been shown to be required for nitrate homeostasis or pH adjustment, and previous results indicated that AtCLCc is involved in nitrate accumulation. We investigated new physiological functions of this CLC member in Arabidopsis. Here we report that AtCLCc is strongly expressed in guard cells and pollen and more weakly in roots. Use of an AtCLCc:GFP fusion revealed localization to the tonoplast. Disruption of the AtCLCc gene by a T-DNA insertion in four independent lines affected physiological responses that are directly related to the movement of chloride across the tonoplast membrane. Opening of clcc stomata was reduced in response to light, and ABA treatment failed to induce their closure, whereas application of KNO₃ but not KCl restored stomatal opening. clcc mutant plants were hypersensitive to NaCl treatment when grown on soil, and to NaCl and KCl in vitro, confirming the chloride dependence of the phenotype. These phenotypes were associated with modifications of chloride content in both guard cells and roots. These data demonstrate that AtCLCc is essential for stomatal movement and salt tolerance by regulating chloride homeostasis.

The Stem Age Required for Floral Induction of Synchronized Mango Trees in the Tropics

The quantitative floral inductive role of the age of the last vegetative flush was investigated in replicated trials of two cultivars of mango (Mangifera indica L.), Keitt and Tommy Atkins, growing in tropical conditions of Cundinamarca State in Colombia. Empirical observations have indicated that stems must be in rest for sufficient time, generally 4 to 5 months, to be induced to flower in the absence of cool temperatures. Twelve trees per cultivar were tip-pruned to stimulate a synchronous flush of vegetative growth at the beginning of the experiments. The first of four sets, each consisting of three replicate trees among the 12, were sprayed with 4% potassium nitrate on a 2-week schedule beginning 2 months after the pruning date. Biweekly sprays continued in this first set until a growth response was observed, whereupon the set was retired from further observations, and the second set of three synchronized trees began receiving biweekly spray treatments until they initiated a growth flush. The schedule continued through the four successive sets of trees until the age of stems necessary to induce a flowering response was determined. Treatment applications were quantified using a one-m-square quadrate to determine the numbers of resting stems and vegetative and /or reproductive shoots contained within. KNO3 sprays applied 3 months after the pruning date stimulated initiation of vegetatively induced shoots in both ‘Keitt’ and ‘Tommy Atkins’ trees. Synchronous generative shoot initiation in ‘Keitt’ trees occurred in ≈75% and 100% of the stems after KNO3 sprays applied 5 and 6 months after the pruning date, respectively. Tommy Atkins, a cultivar that is more difficult to induce to flower than ‘Keitt’, had 18% of shoots flowering after the 5-month application and 100% flowering after the KNO3 application 6 months after the pruning date. None of the non-treated orchard trees flowered during this time. Stem age was the key factor correlated with flowering. The experimental trees, which were naturally habituated to experience two flowering periods per year, each within separate sections of tree canopy, were stimulated to produce one annual synchronized flowering event throughout the tree canopy as a result of the treatments.

Responses of physiological parameters, grain yield, and grain quality to foliar application of potassium nitrate in two contrasting winter wheat cultivars under salinity stress

AbstractAn experiment was conducted to test whether foliar application of KNO3 on wheat in the heading stage could reduce salinity‐induced injuries, produce high grain yield, and improve grain quality. Salt‐resistant DK961 and salt‐sensitive JN17 wheat cultivars under 0 or 100 mM–NaCl conditions were foliarly watered with distilled water or a 10 mM–KNO3 solution. The four treatments included: T1 (CK1), 0 mM NaCl + distilled water; T2, 0 mM NaCl + 10 mM KNO3; T3 (CK2), 100 mM NaCl + distilled water; T4, 100 mM NaCl + 10 mM KNO3. The results indicate that there were no differences (p > 0.05) in plant growth, grain yield, and grain quality between T2 and T1 in both cultivars, but these response variables were significantly lower in T3 than in T1. K+ : Na+ ratio, chlorophyll content, photosynthetic capacity, grain yield, flour yield, water absorbance, ash content, dough‐development time and dough‐stability time were significantly higher in T4 than in T3, while protein concentration, wet‐gluten concentration, and antioxidant enzyme activities were lower. Although foliar application of KNO3 on JN17 enhanced plant growth, grain yield, and grain quality, these parameters were still lower in T4 than in T1. Our findings suggest that cultivating the salt‐resistant wheat cultivar combined with foliar application of KNO3 at heading stage may alleviate salinity injuries and produce higher grain yield and better grain quality under saline conditions.

Redistribution of cadmium, copper, lead, nickel, and zinc among soil fractions in a contaminated calcareous soil after application of nitrogen fertilizers

AbstractThis study was conducted to evaluate the redistribution of the heavy metals Cd, Cu, Pb, Ni, and Zn among different soil fractions by N fertilizers. In a lab experiment, soil columns were leached with distilled water, KNO3, NaNO3, NH4NO3, or Ca(NO3)2 · 4H2O. After leaching, soil samples were sequentially extracted for exchangeable (EXCH), carbonate (CARB), organic‐matter (OM), Mn oxide (MNO), Fe oxide (FEO), and residual (RES) fractions. Distilled water significantly increased the concentrations of Cd and Ni in EXCH fraction, while concentration of Cu and Zn did not change significantly. Application of KNO3, NaNO3, NH4NO3, or Ca(NO3)2 · 4H2O significantly increased the concentrations of Cd and Zn in EXCH fraction, while concentration of Pb and Ni was decreased. Application of all fertilizers caused an increase of Cu in the OM fraction. Moreover, leaching with these solutions significantly increased Cd [except in Ca(NO3)2 · 4H2O], Cu, and Zn concentrations in the CARB fraction, while Pb and Ni concentrations were decreased. With application of all leaching solutions, Zn in the EXCH, CARB, FEO, and MNO fractions was significantly increased, while Zn in the OM fraction did not change. The mobility index indicated that Ca(NO3)2 · 4H2O increased the mobility of Cd, Cu, and Zn in the soil, whereas NaNO3 decreased the mobility of Pb and Ni in the soil. The mobility index of Pb decreased by all leaching solutions. Thus, these results suggest that applying N fertilizers may change heavy‐metal fractions in contaminated calcareous soil and possibly enhance metal mobility and that N‐fertilization management therefore may need modification.

EFFECT OF VARIOUS FOLIAR SPRAYS ON SOME FRUIT QUALITY ATTRIBUTES AND LEAF NUTRITIONAL STATUS OF THE PEACH CULTIVAR ‘ANDROSS’

The effect of various products applied as foliar sprays on some fruit quality attributes and leaf nutritional status of the peach cultivar ‘Andross’ for a three year period is reported. Foliar application of all calcium (Ca) products plus boron (B), did not affect mean fruit weight compared to the control. Application of profical plus calcium phosphite plus power 7-B resulted in an increase of flesh firmness. Low flesh firmness was measured at the potassium nitrate (KNO3) and Chelan-K treatments. Foliar application of all Ca and K products did not alter significantly total soluble solids, total titratable acidity, and length and width of pits in comparison to the control. The highest amount of compact pits (without visual split) for the three year period was measured after foliar application of silene-K. Profical plus calcium phosphite plus power 7-B, and calcium chloride (CaCl2) plus power 7-B gave also good results for the three years. Foliar application of agriphos, chelan-K, silene-K, and KNO3 resulted in an increase of K concentration of leaves compared to the control. Foliar application of CaCl2, bcazin, power-Ca, profical and calcium phosphite plus profical resulted in an increase of Ca concentration of leaves compared to the control for all the years. The efficacy of the foliar sprays varied from year to year indicating the influence of the climatic conditions on tree nutrition.

Nitrogen transformation in acid soils subjected to pH value changes

The aim of this investigation was to determine which application of fertilizer and lime material does not form toxic quantities of nitrite nitrogen and when the losses by denitrification are the lowest in the examined acid soils. Investigations were performed on pseudogley soils of different acidity. Changes of available nitrogen forms were examined by the method of short-term incubation experiments. Experimental treatments were without the use of mineral fertilizers and with application of (NH4)2SO4 (100 ppm of NO3-N) and KNO3 (100 ppm of NO3-N); with and without addition of Ca(OH)2 (50% of full neutralization and full neutralization). When (NH4)2SO4 was used, nitrites occurred in both examined soils as a result of decelerated nitrification and when KNO3 was added as a result of chemical denitrification. Application of Ca(OH)2 caused the intensification of mineralization, nitrification and biological denitrification processes. When a higher dose of lime material was used (full neutralization), nitrites occurred in larger quantities as a result of the strengthening of nitrification and denitrification processes. Application of a lower lime dose caused nitrite occurrence in smaller quantities. Therefore, in these soils as well as in soils of similar chemical properties, application of lower doses of lime material can be recommended (<50% of full neutralization) as well as the application of ammonium fertilizer, bearing in mind that in such conditions losses of added fertilizer in the denitrification process are reduced and the occurrence of nitrites as an intermediate product of this process is prevented.

The Effect of Potassium Nitrate on the Reduction of Phytophthora Stem Rot Disease of Soybeans, the Growth Rate and Zoospore Release of Phytophthora sojae

AbstractThe effects of potassium nitrate (KNO3) application on Phytophthora stem rot disease reduction of Glycine max (L.) Merr. cvs. Chusei‐Hikarikuro and Sachiyutaka, and mycelium growth and zoospore release of a Phytophthora sojae isolate were investigated under laboratory conditions. The application of 4–30 mm KNO3 prior to inoculation greatly reduced incidence of disease in the two soybean cultivars. Although a concentration of 20–30 mm KNO3 led to a slight decrease in the growth rate of the PJ‐H30 isolate on PDA medium, no significant relationship was observed between inhibition of the growth rate and disease reduction on application of 0.4–10 mm KNO3. Disease suppression recorded in laboratory experiments using pathogen mycelium was due to the response of plant tissues rather than a direct inhibition of pathogen hyphal growth by the application of KNO3. The extent of disease reduction was related to increased potassium concentration in plants of the two cultivars (except for some cases involving cv. Sachiyutaka), suggesting that differences existed between the two cultivars in terms of the effect of KNO3 application on disease suppression. Scanning electron microscopic observation with fresh samples indicated marked accumulation of potassium at the penetration‐stopping sites of P. sojae in the cortex layer of soybean plants treated with 30 mm KNO3, compared with the non‐treated control plants. The presence of 0.4–30 mm KNO3 decreased the release of zoospores. These results suggest the possibility of applying a solution containing 20–30 mm of KNO3 to decrease the incidence of disease in agricultural fields by the response of plant tissues to KNO3.