Efficacy and Selectivity of Pre- and Post-emergence Herbicides in Chia (Salvia hispanica L.) under Mediterranean Semi-arid Conditions

In the present study, the selectivity and efficacy of several post and pre-emergence herbicides in chia (Salvia hispanica L.) were examined. Field experiments were conducted at two locations with different soil types and environmental conditions. Our results showed that the pre-emergence application of pendimethalin, oxyfluorfen and linuron reduced total weed density by 71-74%, 74-82% and 53-55%, respectively. Despite their high effectiveness, the above-mentioned herbicides had a negative effect on plant density and biomass yield. In addition, herbicides bentazon and fluazifop-p-butyl which applied post-emergence did not affect significantly plant height and biomass yield. In conclusion, the herbicides linuron, pendimethalin and oyxfluorfen do not seem to be a viable option for weed control in chia crop, whereas the post-emergence applied herbicides did not affect significantly plants’ growth. Further evaluation of chia tolerance to herbicides is needed under different application rates in order to make safe suggestions for chemical control of weeds

An empirical model to estimate nutrients concentration in controlled release fertilizers aqueous solutions

Controlled release fertilizers (CRFs) insure controlled release of nutrients due to their coating. The aim of this study was to investigate the effect of nutrient solution parameters as well as time on the evolution of NO3, NH4, PO4 and K concentrations. For this reason, 0.5 g of Multicote fertilizers 14-14-14 and 15-7-15 dissolved in 100 mL and 300 mL of deionized water respectively. The solutions remained at 24oC and their pH was adjusted once during their preparation at 5.5, 6.0 and 6.5 or adjusted every three days for a 24 days period. A linear empirical mathematical model was developed for the prediction of the above mentioned nutrients concentrations (CX) in relation to the remaining (Vs) and the removed (dVs) volume of the nutrient solution, its pH and time (t) from its preparation. The model output compares favorably with data for the prediction of the concentration of these nutrients. Copyright © 2017 for this paper by its autho

Availability of iron in hydroponic nutrient solutions for rose crops

This study investigated the effect of light and agitation on the availability of iron in hydroponic nutrient solutions. In recycled hydroponic nutrient solutions used for the cultivation of roses, iron is added usually in the form of chelate fertilizers, such as Fe-EDDHA. In practice, the concentration of iron in the nutrient solution in those systems reaches low critical levels very rapidly tin less than 2 d). Fe-chelates are unstable in light and can form soluble or insoluble precipitates. Iron contained in soluble precipitates can be recovered in the solution by agitation. In contrast, iron contained in insoluble precipitates cannot be recovered. The tank of the closed-loop fertigation system used to grow a rose crop was filled with fresh nutrient solution every 10 d. Immediately after preparing each solution, four 11 plastic bottles were filled with the solution and kept in light or in the dark (two bottles of each), at the same temperature. For the next 10d the concentration of iron in the tank was measured every 2d, without any agitation before measurement, and in the bottles before and after agitation. Incident solar radiation in the greenhouse was recorded continuously. It was observed that absorption by the plants and light exposure did not affect the availability of iron in the nutrient solution. Ion concentration was not different between the samples kept in light and those kept in the dark. Agitation increased the quantity of iron available compared with the non-agitated solution. The increase was greater in the solution kept in light (+59%) than in the solution kept in the dark (+35%). The pattern of iron concentration in the recycled nutrient solution was similar to that measured without agitation in the solution exposed to light. It was concluded that in a closed hydroponics systems, agitation is very useful for keeping the concentration of available iron at acceptable levels for longer periods and thus minimizing further addition of iron, while exposure to light does not affect Fe availability

Water and fertilizers use efficiency in grafted and non grafted tomato plants on soilless culture

The improved rooting environment and the absence of pathogens in substrates used in soilless cultures, make the use of grafted plants unnecessary when grown hydroponically. The worldwide water shortages and the increased environmental pollution indicate the use of any technique that increases the production with the highest possible water and fertilizers use efficiency. In this work water use efficiency (WUE) and fertilizer use efficiency (FUE) in agronomical and biological terms (g marketable fruit and g dry matter per litre of transpired water and g of absorbed nutrients, respectively) have been determined on non grafted 'Big Red' tomato plants (Lycopersicon esculentum Mill.) as well as 'Big Red' plants grafted on 'Big Red' and 'He-mans' rootstock. Plants were grown in an open hydroponic system. Measurements of leaf area and transpiration and nutrient concentrations in shoots, leaves and fruits as well as plants fresh and dry weight were performed on grafted and non grafted plants. The results indicate that non grafted tomato plants had 25 to 44% higher leaf area (and for this reason the highest water consumption) and 30% higher shoot and leaf dry weight compared to the grafted plants. In contrast grafted plants had 31 to 39% higher fresh fruit production. Finally grafted plants had 50 and 48% higher WUE and FUE, respectively, compared to non grafted plants as the latter consume more water and nutrients on unmarketable biomass (shoots and leaves)

Cadmium (Cd) and nickel (Ni) accumulation in different organs of basil plants

Basil (Ocimum basilicum) is one of the most common aromatic plants which is grown in the urban environment, due to its aesthetic, nutritional, and therapeutic value. However, in many studies, it is reported that basil accumulates high concentrations of heavy metals when irrigated with contaminated water or exposed to aerial pollution. This study aimed to investigate the heavy metals accumulation (Cd and Ni) in different plant organs (root, shoots, leaves) of basil plants grown for a short period in a greenhouse. For that reason, 33 basil potted plants were divided into three treatments groups where: a) two solutions of 250 mL contained 10 mg L-1 Cd(ΝΟ3)2 4Η2Ο and 20 mg L-1 Ni(ΝΟ3)2 6Η2Ο, respectively, were applied to nine plants per treatment every 2 weeks through irrigation, b) foliar application of 240 mg CdO and 450 mg NiO plant-1 was performed after plants transplanting in three plants per treatment, and c) nine control plants were irrigated only with tap water. The results at the end of the experiment, indicated that: a) plants irrigated with Cd contaminated water, showed high Cd concentrations in leaves (257.02 mg kg-1 dw), while those irrigated with Ni contaminated water had the highest concentration of Ni in shoots (761.52 mg kg-1 dw), b) plants treated with heavy metals foliar application, presented high Cd concentration in new leaves (3722 mg kg-1 dw) while the highest concentration in Ni was detected in shoots (5237 mg kg-1 dw), c) control plants displayed high concentrations of Ni in shoots and leaves similar to plants irrigated with Ni contaminated water. From the above, it results that basil plants can accumulate high amounts of Cd and Ni in shoots and leaves either through irrigation with contaminated water or by elements foliar deposition. © 2022 International Society for Horticultural Science. All rights reserved

Pre-symptomatic disease detection in the vine, chrysanthemum, and rose leaves with a low-cost infrared sensor

Thermography is a technique based on infrared imaging, which is used nowadays to detect plants under stress caused by biotic and abiotic factors. In many cases, temperature changes have already been correlated with pathogen attacks. In this sense, thermography offers the ability of early disease detection in plant pathology. In this work, a low-cost AMG8833 Grind-Eye infrared camera combined with a 1080P RGB web camera was used to develop an integrated infrared and RGB imaging system, to record temperature changes on vine, chrysanthemum, and rose plant leaf surfaces. Vine and chrysanthemum leaves were infected with Phomopsis viticola and Septoria ssp. respectively, respectively, whereas rose plants leaves were infected with Colletotrichum spp. as well as with Podosphaera pannosa. Measurements were performed using the integrated imaging system on infected and uninfected leaves, as well as on PDA plates with active and non-active mycelium. According to the results, vine leaf tissue infected with P. viticola and rose plants leaf tissue infected with P. pannosa had a pre-symptomatic (four days after infection) decrease in temperature up to 1.6 and 1.1◦C, respectively, compared with uninfected tissue. In contrast chrysanthemum leaf tissue infected with Septoria ssp. and rose plant leaf tissue infected with Colletotrichum spp. had a pre-symptomatic (four days after infection) increased temperature up to 1.1◦C and 1.0◦C, respectively, compared with uninfected tissue. In vitro measurements showed that the active fungi mycelium had approximately 1.1 to 2.1◦C lower temperature than the non-active mycelium. The results above show that the integrated infrared and RGB imaging system developed in this work can be used to detect early disease infection before visible symptoms appeared, facilitating the decision-making process. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Nutrient solution management recirculating soilless culture of rose in mild winter climates

In a closed hydroponic system with a rose crop, the composition of the nutrient solution in the tank was measured every two days in order to establish the dynamics of the nutrient elements in short-term periods. It was observed that the concentration of Fe decreased very fast and that the concentrations of Ca2+, Mg2+ and Cl- increased. The concentrations of K+, Ca2+ and SO4 2- did not reach critical levels. The Cl- content of commercial fertilizers was measured and it was concluded that the addition of some fertilizers (e.g, Fe-EDDHA) would lead to an accumulation of Cl- in the nutrient solution. Thus, Cl- free fertilizers should be used. The analysis of the Fe, NH4 and PO4 balance in the nutrient solution seems to be required to determine the necessary corrections to increase the life span of the nutrient solution

Electrical conductivity and pH prediction in a recirculated nutrient solution of a greenhouse soilless rose crop

The influence of nutrient solution (1) mixing rate, and (2) time of use on pH and electrical conductivity (EC) of a recirculated nutrient solution used for the irrigation of a greenhouse soilless rose crop was studied. Measurements of microclimate variables, pH, and EC of nutrient solutions and crop transpiration were conducted. The measurements of pH and EC values of nutrient solutions mixed with different mixing rates and applied for crop fertigation were used to develop and calibrate a model for pH and EC prediction in relation to nutrient-solution mixing rate and time of use. Application of the calibrated model gave satisfactory results. It was found that nutrient solutions with high mixing rates or volume equal to or double that of the total water consumed by the canopy during the conservation period had the most stable EC evolution and minimal pH changes

Calcium, magnesium and potassium concentrations prediction in a recirculated nutrient solution of a greenhouse soilless rose crop

The effects of i) biophysical processes such as crop water uptake, and elements absorption and ii) chemical processes such as fertilizers dissolution and pH changes, on Ca2+, Mg2+ and K+ concentration in a recirculated nutrient solution of a greenhouse soilless rose crop (Rosa hybrida 'First Red'), were studied. Measurements of greenhouse microclimate variables, crop water uptake as well as pH, EC and Ca2+, Mg2+ and K+ concentration in nutrient solutions kept in storage tank or applied for crop fertigation, were carried out during autumn 2001. The results showed that variations of Ca2+ concentration in the nutrient solution were highly correlated to crop water uptake, crop Ca 2+ absorption, fertilizer dissolution and pH variation of the nutrient solution. The concentration of Mg2+ in the nutrient solution was correlated to EC of the solution. Equations for Ca2+, Mg 2+ and K+ concentrations prediction in the recycled nutrient solution were developed and calibrated. Validation gave satisfactory results

Alteration of NO - 3, PO 3- 4 and SO 2- 4 Concentration on rose plants in response to greenhouse climate parameters and their concentration in the nutrient solution

The objective of this work was to quantify temporal changes of NO - 3, PO 3- 4 and SO 2- 4 concentration on leaves, shoots and roots of rose plants during a short growing period, in response to air temperature, light intensity and the concentration of the above mentioned anions in the nutrient solution. For this reason rose plants (×Rosa hybrida 'Iceberg') were placed in a glasshouse during September 2004 and grown in nutrient solution according to the Deep Flow Technique (DFT). The plants were pruned in order to develop one main flower shoot. Measurements were performed during December 2004. The concentration of NO - 3, PO 3- 4 and SO 2- 4 (mg L -1) in the nutrient solution and in different plant parts (mg kg -1) as well as the fresh (fw) and dry (dw) weight of leaves, shoots and roots were measured every day, by destructive sampling of 6 plants each time, for a period of 28 days. In addition during the same period the greenhouse air temperature and the intensity of the incoming solar radiation were continually recorded. The concentration of NO - 3 and PO 3- 4 in leaves was significantly affected by i) the intensity of the incoming solar radiation and ii) the concentration of NO - 3 and PO 3- 4 in the nutrient solution. The concentration of NO - 3 and PO 3- 4 in shoots was affected by the above mentioned parameters and by the greenhouse air temperature. Alteration of NO - 3 concentration in the nutrient solution causes an instant alteration of NO - 3 concentration in leaves and a delayed alteration of NO - 3 concentration in shoots. In contrast, alteration of PO 3- 4 concentration in the nutrient solution causes a delayed alteration of PO 3- 4 concentration in both leaves and shoots. The concentration of NO - 3 and PO 3- 4 in roots and SO 2- 4 in shoots and roots was not strongly related to the above mentioned greenhouse climate parameters and the concentration of NO - 3, PO 3- 4 and SO 2- 4 in the nutrient solution