Sunflower Response to Different Potassium Rates in Artificially Developed Calcareous Soils

Florida produces the most vegetables in the United States during the winter season with favorable weather conditions. However, vegetables grown on calcareous soils in Florida have no potassium (K) fertilizer recommendation. The objective of this study was to evaluate the effects of K rates on leaf tissue K concentration (LTKC), plant biomass, fruit yield, and postharvest quality of tomatoes (Solanum lycopersicum L.) grown on a calcareous soil. The experiment was conducted during the winter seasons of 2014 and 2015 in Homestead, FL. Potassium fertilizers were applied at rates of 0, 56, 93, 149, 186, and 223 kg·ha−1 of K and divided into preplant dry fertilizer and fertigation during the season. No deficiency of LTKC was found at 30 days after transplanting (DAT) in both years. Potassium rates lower than 149 kg·ha−1 resulted in deficient LTKC at 95 DAT in 2014. No significant responses to K rates were observed in plant (leaf, stem, and root combined) dry weight biomass at all the sampling dates in both years. However, at 95 DAT, fruit dry weight biomass increased with increasing K rates to 130 and 147 kg·ha−1, reaching a plateau thereafter indicated by the linear-plateau models in 2014 and 2015, respectively. Predicted from quadratic and linear-plateau models, K rates of 173 and 178 kg·ha−1 were considered as the optimum rates for total season marketable yields in 2014 and 2015, respectively. Postharvest qualities, including fruit firmness, pH, and total soluble solids (TSS) content, were not significantly affected by K rates in both years. Overall, K rate of 178 kg·ha−1 was sufficient to grow tomato during the winter season in calcareous soils with 78 to 82 mg·kg−1 of ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA)-extracted K in Florida.

Effect of sodium and magnesium on kinetics of potassium release in some calcareous soils of western Iran

Os teores de Ca, Mg e K no solo interferem no crescimento e na produção das culturas. No entanto, a relação entre esses nutrientes que proporciona o desenvolvimento adequado das plantas varia entre as espécies vegetais. O presente teve por objetivo estudar o desenvolvimento do milho em função da saturação do solo por bases e adubação potássica. O delineamento experimental foi inteiramente casualizado, com quatro repetições, em esquema fatorial 3x2x4, constituindo-se de três solos (Neossolo Quartzarênico, Latossolo Vermelho e Latossolo Bruno), dois valores de saturação por bases (40 e 70 %) e quatro doses de potássio no solo (0, 60, 120 e 240 mg kg-1). O experimento foi conduzido em casa-de-vegetação, utilizando-se o milho cv. Zêneca 8392 com uma planta por vaso de 30 L. Aos 29, 57 e 127 dias após a emergência das plântulas, efetuaram-se medidas do número de folhas por planta, altura média das plantas, diâmetro basal do colmo e comprimento médio de entrenós. Após a colheita final determinou-se a produção de grãos por planta. O desenvolvimento e a produção de grãos do milho aumentou até a adição de 60 mg kg-1 de K ao solo. O crescimento do milho foi mais rápido no solo mais arenoso, até o florescimento masculino. Solos com maior capacidade de troca catiônica proporcionaram maior comprimento de entrenós. O comprimento médio de entrenós foi inversamente relacionado ao número médio de entrenós por planta, em função do tipo de solo.

Core Ideas Potassium input at early growth stage should be low when initial soil K level was high. Increasing K rate reduced the proportion of K uptake distributed to tomato fruits. Efficiency of converting K fertilizer into yield decreased with increasing K rate. Potassium rate of 192 kg ha–1 was considered the sufficient total K input. Knowledge regarding K accumulation and partitioning is essential for improving potassium use efficiency (KUE). The objective of this study was to determine K uptake, distribution, and KUE in tomato (Solanum lycopersicum L.) production with multiple K rates. Field trials were conducted during the winter seasons of 2014 and 2015. Potassium was applied at 0, 56, 93, 149, 186, and 223 kg ha−1 and divided into pre‐plant dry fertilizer and weekly drip fertigation. Total potassium uptakes (TKU) at 30 d after transplanting (DAT) were not significantly affected by K rates, and averaged 5 and 14 kg ha−1 in 2014 and 2015, respectively. The response of TKU at 95 DAT was predicted by a linear‐plateau model with a critical rate of 192 kg ha−1 and a maximum uptake of 264 kg ha−1 in 2014, whereas a linear response was observed in 2015. The highest proportion of TKU at 95 DAT was accumulated in fruit, which ranged from 66 to 80% and 37 to 54% in 2014 and 2015, respectively. The ratio of fruit K uptake to TKU decreased with increasing K rate predicted by linear‐plateau models with critical rates of 187 and 218 kg ha−1 in 2014 and 2015, respectively. Results indicated the efficiency of converting K fertilizer into marketable yield also decreased with increasing K rate. Therefore, 192 kg ha−1 was considered the sufficient K fertilizer requirement for tomato production on calcareous soils with 99 to 112 mg kg−1 of Mehlich‐3 extractable K.

The rate of potassium (K) release from soils is a dynamic process, and it is important to the evaluation of soil K availability to plant. The objectives of this study were to determine K release characteristics and the correlation of these parameters with bean plant indices in surface soils of 15 calcareous soils. The kinetics of K release was determined by successive extraction with 0.01 mol/L CaCl<sub>2</sub> in a period of 2–2017 h at 25 ± 1°C. The results showed that the cumulative K‏ release ranged from 111 to 411 mg/kg. A plot of cumulative amount of K released showed a discontinuity in slope at 168 h. Thus, two equations were applied to segments of the total reaction time (2 to 168 and 168 to 2017 h). The amounts of K released during 2–168 and 168–2017 h ranged from 55 to 299 and 44 to 119 mg/kg, respectively. Release kinetics of K conformed fairly well to parabolic diffusion, simplified Elovich and power function models in two segments. Potassium released after 2–168 and 168–2017 h and K release rate constants were significantly correlated (P < 0.05) with bean plant indices, while correlation between K extracted by using 1 mol/L NH<sub>4</sub>OAc (ammonium acetate) and plant indices was not significant. The results of this research showed that information obtained from K release studies in laboratory and kinetics equation parameters can help to estimate the K supplying power of soils.  

The low cropping intensity in the southwestern coastal Bangladesh is constrained by excess wetness of soil, low fertility and scarcity of fresh irrigation water. Fallow-fallow-T. aman is the main cropping pattern in this region. In the recent years some winter (dry season) crops (wheat, sunflower, maize etc.) have been introduced. Among them sunflower is best suited as it can be established in wet soil and also having the capacity to tolerate salinity and drought to some extent. The fertility of soil of this area is low particularly nitrogen (N). There is no fertilizer recommendation for sunflower in this area. Thus it is necessary to develop a fertilizer recommendation for sunflower. To develop this, a set of field experiments were carried out during winter season (2018–19). In these experiments, the major nutrients [nitrogen (N), phosphorus (P) and potassium (K)] were varied in early (by November) and late (end of December) sown (dibbled) sunflower. Results showed that early sown sunflower produced higher seed yield with lower amount of N than that of late one. In case of P, unlike N, yield increase was not at par with the increase of P rates indicated residual P that applied to previous rice crop supported the sunflower. Potassium rates have little effect on yield increase. Based on the average yield (~3.5 t/ha) of the variety (Hysun-33) N, P and K @ 120–150, 40–50 kg/ha and 50–60 kg/ha was produced highest yield in early sown sunflower in excessively wet soil of southwestern coastal Bangladesh.

Release rates of nonexchangeable potassium (K) were determined for 10 intensively cultivated soils of the Hamadan area in western Iran. Calcium (Ca)‐saturated soil samples were equilibrated with 0.01 M CaCl2 and 0.01 M citric acid for 2–2759 h. Plots of cumulative K+ released by different soils vs. time consisted of two parts, suggesting two different rates of K+ diffusion from soils. Four mathematical models (first‐order, parabolic diffusion, power function, and Elovich equation) were used to describe cumulative K+ release. The power function and first‐order equation described the K+ releases kinetics best as evidenced by the highest correlation coefficients and the lowest values of the standard error of the estimate (SE). The parabolic diffusion equation also described the data satisfactory, indicating diffusion‐controlled exchange.

Boron (B) deficiency hampers cotton (Gossypium hirsutum L.) growth and productivity globally, especially in calcareous soils. The crop is known as a heavy feeder of B; however, its reported plant analysis diagnostic norms for B-deficiency diagnosis vary drastically. In a 2-year field experiment on a B-deficient [hydrochloric acid (HCl)–extractable 0.47 mg B kg−1], calcareous, Typic Haplocambid, we studied the impact of soil-applied B on cotton (cv. CIM-473) growth, productivity, plant tissue B concentration, and seed oil composition. Boron was applied at 0.0, 1.0, 1.5, 2.0, 2.5, and 3.0 kg B ha−1, as borax (Na2B4O7·10H2O), in a randomized complete block design with four replications, along with recommended rates of nitrogen (N), phosphorus (P), potassium (K), and zinc (Zn). Boron use improved crop growth, decreased fruit shedding, and increased boll weight, leading to seed cotton yield increases up to 14.7% (P < 0.05). Improved B nutrition of plants also enhanced seed oil content (P < 0.05) and increased seed protein content (P < 0.05). Fiber quality was not affected. Fertilizer B use was highly cost-effective, with a value–cost ratio of 12.3:1 at 1 kg B ha−1. Fertilizer B requirement for near-maximum (95% of maximum) seed cotton yield was 1.1 kg B ha−1 and HCl-extractable soil B requirement for was 0.52 kg ha−1. Leaf tissue B requirement varied with leaf age as well as with plant age. In 30-day plants (i.e., at squaring), B-deficiency diagnosis critical level was 45.0 mg kg−1 in recently matured leaves and 38.0 mg kg−1 in youngest open leaves; at 60 days old (i.e., at flowering), critical concentration was 55.0 mg kg−1 in mature leaves and 43.0 mg kg−1 in youngest leaves. With advancement in plant age critical B concentration decreased in both leaf tissues; that is, in 90-day-old plants (i.e., at boll formation) it was 43.0 mg kg−1 in mature leaves and 35.0 mg kg−1 in the youngest leaves. As critical concentration range was narrower in youngest leaves (i.e., 35–43 mg kg−1) compared with mature leaves (i.e., 43–55 mg kg−1), B concentration in youngest leaves is considered a better indicator for deficiency diagnosis.

ABSTRACTIn order to study the effect of plant growth promoting rhizobacteria (PGPR), vermicompost and phosphate sources on the growth and nutrients uptake by lettuce, a greenhouse experiments was conducted. Treatments consisted of PGPR (Pseudomonas fluorescens) (with and without inoculation), vermicompost (0 and 1% w/w) and phosphate sources (control, rock phosphate (RP), tricalcium phosphate and triple super phosphate (TSP) at 25 mg P kg−1 level). Biological fertilizers, RP and TSP significantly increased shoot dry matter (SDM) and some measured nutrients uptake. Co-application of PGPR and RP, in non-vermicompost treatments significantly increased SDM, shoot nitrogen, phosphorus (P), potassium, zinc and manganese uptake rates. Shoot P uptake had no significant difference between TSP and RP treatments. Co-application of PGPR, vermicompost and TSP significantly decreased SDM, which may be due to the P toxic levels in the plant aerial parts and/or the inhibition of the bacterial activities in the rhizosphere soil.

This study was conducted to reveal the conditions and parameters which control dissolution and release of indogentic potassium in some Hammam Al-Alil soils northern Iraq, representing Aridisols order. Three pedons were selected having different soil series namely (462CCE, 453CCW and 451CCW). The study included using successive extraction with 6.25M HCl, under reflux conditions for 100 mint. to determe the amount and rates of release exchangeable and non-exchangeable potassium in some calcareous soil periphery of semictite and illite minerals according to the amount of release of mica-K. by using a kinetic diffusion parabolic equation. The results showed that amount of released potassium was reduced by increasing extraction time, and the variation in chemical, physical and mineralogical properties of the soil samples have a great effect on each amount, rate, and pathway reaction of potassium release between soil series, also the results showed that the pathway reaction of K-release consist of two segments according to the parabolic diffusion equation. The first segment represented exchangeable phase that was more than the second phase (non-exchangeable) in its amount and rate of release . Fertility evaluation of the results according to amount and rate of K-release from mica-K referred that all soils samples has a moderate reserve with low release rate, therefore the K-reserve of soils could be mapped by soil series using this method of classification such mapping would provide data on the extent availability of reserves in both short term (i.e.) the crop over a growing season and long term.

Core Ideas Water was ineffective to estimate K availability in calcareous soils in Florida. Both Mehlich‐3 and AB‐DTPA can be used to calibrate K rates in calcareous soils. High K level was above 213 and 183 mg kg –1 with Mehlich‐3 and AB‐DTPA, respectively. Potassium application rates based on a reliable soil testing method are critical for maximizing crop yields and minimizing fertilizer costs. Vegetables grown on calcareous soils, however, have no soil test potassium (STK) interpretations in Florida. Therefore, the objectives of this study were to compare Mehlich‐3, ammonium bicarbonate‐DTPA (AB‐DTPA), and water to estimate K availability and calibrate K rates for tomato ( Solanum lycopersicum L.) grown on a calcareous soil. The experiment was conducted during the winter seasons of 2014 and 2015. Potassium fertilizers were applied through preplant dry fertilizer and drip fertigation at total rate of 0, 56, 93, 149, 186, and 223 kg K ha –1 . Regression models were performed to calibrate K rates by tomato relative yield with total K input (initial STK plus full‐season K rate). Concentrations of STK were significantly correlated among the three extractants and the highest correlation occurred between Mehlich‐3 and AB‐DTPA. Due to the high variability, water was ineffective to estimate K availability. Significantly linear relationships were found between total K uptake (TKU) and total K inputs using both Mehlich‐3 extracted K (Mehlich‐3‐K) and AB‐DTPA‐K. The low STK levels were predicted from 85 to 150 and 70 to 120 mg K kg –1 and the corresponding required K rates ranged from 307 to 151 and 271 to 151 kg K ha –1 using Mehlich‐3‐K and AB‐DTPA‐K, respectively. Thus, both Mehlich‐3 and AB‐DTPA can be used to predict K availability and K rates needed to produce optimal marketable yield for tomato grown on calcareous soils in Florida.

The rate of potassium (K) release from soils can significantly influence K fertility of soils. The aim of this study was to assess the impact of different land uses on K release from calcareous soils, within agricultural areas of western Iran. The kinetics of K release in 0.01 M CaCl2 was studied in surface samples of 62 calcareous soils planted to pasture, orchard, garlic, leafy vegetables, wheat, and potato. Trend in K release kinetics was similar between land use types. We found that samples collected from pasture gave the lowest K release (245.2 mg kg−1), whereas the highest values were measured on samples from leafy vegetables (449.6 mg kg−1). Different models were used to describe K release. In general, Elovich, parabolic diffusion and power equation were found to be appropriate for modeling K release. The K release rate for the soils was estimated by parabolic equation and it was significantly different between land use types. The release rate was lower for pasture and wheat (averaged 16.1 and 25.1 mg kg−1 min−1/2, respectively) than leafy vegetables (27.4 mg kg−1 min−1/2) and potato (27.0 mg kg−1 min−1/2). When the rate of K released found from parabolic model regressed on K forms and soil properties, NH4OAc-K, CaCl2-K, pH, and EC appeared to be the most important K forms and soil properties influencing K release rates in these calcareous soils. The different K release and NH4OAc-K or CaCl2-K prior to K application both should be taken into account for potassium fertilizer application in different land uses.

The rate of potassium (K) release from soils can significantly influence K availability to plants. There are few studies about K-release kinetics and K availability in calcareous soils of central Iran. The objective of this study was to study the release rates in 15 different soils from Chaharmahal-Va-Bakhtiari Province through successive extractions with 10 mM citric acid over periods of 2–2016 h and the correlation of K-release characteristics with bean plant indices. The results showed that there was wide variation in the cumulative K release among soils. The cumulative K release ranged from 169 to 1199 mg kg−1. The amounts of K released after 2016 h was not significantly correlated with bean plant indices. Plots of cumulative amounts of K released show a discontinuity in slope at 168 h. Thus, two equations were applied to segments of the total period (2 to 168 and 168 to 2016 h). The amount of K released after 168 h ranged from 62 to 879 mg kg−1. The amount of K released after 168 h was significantly correlated with bean plant indices. In the segment 1 parabolic diffusion, first-order and power function equations and in the second segment parabolic diffusion, first-order, zero-order, and power function equations described K-release kinetics. Release rate constants in the segment 1 were significantly correlated with bean plant indices; however, in the segment 2 release rate constants were not significantly correlated with bean plant indices. The results of our research showed that K-release characteristics after an initial fast reaction play a role in supplying available K and dilute citric acid solution can be used for estimating of K-release kinetics in the studied soils.

A laboratory study was conducted to determine the effect of irrigation water quality on potassium desorption in some calcareous soils. It was constructed by miscible displacement technique using chlorine and sulfuric water via two different textured soils from Fadhlia and Hamdania locations in Nineveh province / northern Iraq for 240 minute with 10 minutes interval at a rate flow 1 ml.minute-1. Results showed higher values of desorbed potassium rate in sulfuric water which were 3.57, 2.128 c.mole.kg-1, while these rates referred to be much lower than that resulted by using chlorine water 2.25, 1.15 c.mole.kg-1 for both locations respectively. Also high correlation appeared between K+ desorption capacity and flow time (R2 = 0.96 , R2 = 0.79) for both water qualities in Fadhlia location , while these rates were (R2 = 0.98, R2 = 0.95) for Hamdania location respectively. Mathematical description for diffusion equation appeared to be of higher values of K+ desorption capacity rates for sulfuric water which were 0.26, 0.13 c.mole.kg-1.min.-½ for Fadhlia and Hamdania locations respectively, while these rates for chlorine water were 0.146, 0.048 c.mole.kg-1.min.-½ for both locations respectively.

High rates of potassium (K) are often applied in an attempt to increase stress tolerance of hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy] turfs. Two field-grown bermudagrass cultivars, `Tifdwarf' and `Tifway', were used to determine the influence of applied K on plant nutrient content and nutrient retention in two soils. Six rates of K ranging from 0 to 390 kg·ha-1 were applied twice per month each growing season from 1992 to 1994. The cultivars were established on both a sand-peat (9:1 by volume) and loamy sand. Potassium chloride and K2SO4 were compared as sources of K, and were applied simultaneously with N applications. Extractable soil K and leaf tissue K concentrations increased with increasing K rates. There was a critical K fertilization level (74 to 84 kg·ha-1) for each cultivar and medium combination beyond which no increase in tissue concentration was observed. Increasing K fertilization resulted in a decrease in extractable Ca and Mg in both media with corresponding decreases in tissue Ca and Mg concentrations. High K rates appear to increase the potential for Ca and Mg deficiencies in bermudagrass, indicating that rates higher than those that provide sufficient K levels for normal growth should not be used.