Fruit Mineral Research Articles

Growth, yield, fruit mineral and Vitamin C content of Cucurbita pepo. L as affected by Organic and NPK fertilizer

Abstract The nutrients requirement for Cucurbita pepo L. (summer squash) for optimal yield and quality fruits production can be achieved through adequate nutrient supply. A field experiment was carried out during the cropping season of 2015 and 2016 at Landmark University Teaching and Research Farm, Omu-Aran, Nigeria to investigate the impact of Tithonia diversifolia, poultry manure and NPK fertilizer on the growth, yield, mineral and vitamin C content in the fruit of C. pepo. The experiment consisted of T. diversifolia at 30 tons ha−1, poultry manure at 10 tons ha−1, T. diversifolia at 30 tons ha−1 + Poultry manure 10 tons ha−1, T. diversifolia at 30 tons ha−1 + NPK (20:10:10), NPK (20:10:10) and control (no amendment of any kind) arranged in a randomized complete block design with four replications. The growth and fruit yield of C. pepo using the mean of the two years was increased by 68% and 2% respectively by T. diversifolia + poultry manure as compared to control due to an increase in nutrient availability in the soil with the amendment used. Also, Vitamin C content and Mg value of the fruit was increased by application of T. diversifolia as soil amendments as compared to the control. While the application of NPK fertilizer alone significantly increased the Ca, Mn and Fe contents of fruits. Fruit content of K was increased by 39 % by the application of T. diversifolia + NPK. Therefore, for the purpose of growing squash for the quality of fruits (vitamin C), the use of T. diversifolia at 30 tons ha−1 as organic fertilizer is sufficient for the cultivation, while for growing the crop with interest in quantity, application of T. diversifolia at 30 tons ha−1 + poultry manure at 10 tons ha−1 is recommended.

Multiple season-long sprays of ethephon or NAA combined with calcium chloride on Honeycrisp: II. Effect on fruit mineral concentrations and incidence of bitter pit

Honeycrisp apple trees are highly prone to biennial bearing and bitter pit (BP). This 3-y study tested the hypothesis that tank mix sprays of ethephon (ETH), naphthaleneacetic acid (NAA), and 1-aminocyclopropane carboxylic acid (ACC) combined with calcium chloride (CaCl2) can mitigate these production problems. Mature ‘Honeycrisp’ were treated with either three of six applications of 150 mg.L-1 ETH, 5 mg.L-1 NAA or two of five applications of 150 mg.L-1 ACC, all tank-mixed with and without CaCl2 and applied at 10-d intervals starting 21–26 June over three growing seasons. Fruit cortical tissue nutrient concentrations were influenced by applications of CaCl2, ETH, NAA, and ACC. In one year, Ca concentrations were significantly higher in fruit from trees treated with six sprays of ETH or NAA with CaCl2 compared with the untreated control. Compared with untreated trees, fruit Ca concentrations were 115% and 148% higher with three and six applications, respectively. Applications of CaCl2 significantly reduced the incidence and severity of BP post-harvest in two of three years when fruit tissue Ca levels were low. ETH alone also increased the incidence and severity of BP two-fold compared with the control, while early season sprays of NAA reduced BP incidence and severity compared with the untreated control. High and similar levels of BP incidence and severity were observed when six sprays of NAA were applied with or without Ca. Fruit tissue K levels were generally reduced with the addition of CaCl2, and within 1 year, K levels were higher in fruit treated with ACC. Fruit Mg concentrations generally decreased with the addition of Ca or NAA. Six applications of ACC resulted in a 30-fold increase in fruit Mg concentrations compared to the untreated control. Tank mixing CaCl2 with the flower-promoting bio-regulators ETH and NAA proved to effectively reduce BP and increase fruit tissue Ca levels. This approach would offer cost savings when repeat sprays of each are required on a bi-weekly basis.

Delayed harvest, fruit nutritional content and tree productivity of ‘Reed’ avocado (Persea americana)

The effects of delaying harvest on fruit mineral and proximate composition yield and fruit size of 'Reed' avocado was studied for two years. Fruit were harvested at three maturity stages (early, mid and late) at monthly intervals. Phosphorus content decreased by 40 and 23% from early to late harvest time during 2013 and 2014 seasons, respectively. Similar decrease was observed for K, Ca and Mg content. Zinc content remained constant during 2013, while, mid-season fruit had higher zinc levels during the 2014 season compared to early and late season fruit. Protein content was constant in early and mid-season fruit but decreased during the late harvest. Moisture content decreased from 74.0 to 65.0% from early to late harvest during both seasons. Starch, oil and ash content were high during late harvest time while crude fiber fluctuated throughout the season. Yield dropped from 42 to 12 kg tree-1 from early to late harvest during 2013, but there was no treatment effect during 2014. Treatments had no effect on fruit size during both seasons. Mineral content of avocado fruit decreases with fruit maturity. However, higher oil, carbohydrate and ash content late in the season increases nutritional value of the fruit.

To investigate the effect of four timings of mechanical pruning on yield and fruit quality compared to a hand pruned control in an intensive ‘Gala’ M9 orchard planted as a fruit wall

The fruit wall (le mur fruitier) has generated much interest but differing recommendations from other regions in Europe regarding the optimum timing of the mechanical pruning has led to confusion among growers in the UK. In order to determine the effects of different times of pruning and provide growers with robust guidelines, a trial was established in 2012 in a 2-year-old ‘Gala’ (clone Galaxy) orchard planted on M9 at 3.5×0.5 m in the South-East of England. The timings of mechanical pruning were determined by growth stage: pink bud and when 6, 9 or 12 new leaves emerged on the current season’s growth, and these varied by up to 38 days between the different years in the trial. The control was pruned by hand in the dormant season. Half the plots received additional pruning during the dormant season to remove very strong or very weak growth between the trees (inter-tree pruning) in order to investigate whether reducing the branch density affected yields, fruit quality or size. The trial was designed as a fully randomised block consisting of 4 replicates of each treatment. In all years the length of extension growth was related to the time of pruning with later cuts generating the least extension growth. In the first 3 years the yields were greatest in the hand pruned plots but the differences in yield decreased over time. The cumulative yield was highest in the hand pruned control. In the first 2 seasons after the mechanical cuts were imposed, fruit size and sugar content were affected especially in the treatments applied later in the season. These differences reduced in the 3rd and 4th years of the trial. The effects on fruit size, colour and sugar content from inter-tree pruning were small and varied from season to season. Some small differences in fruit mineral content were observed in some years but these were inconsistent and only significant in one or two instances. Nitrogen content of leaves was lower in trees pruned at the two later growth stages. Some modest labour savings were achieved in the mechanically pruned plots.

Mineral status of kiwiberry

Kiwiberry [Actinidia arguta (Siebold et Zucc.) Planch. ex Miq.] is – just like the green (Actinidia chinensis var. deliciosa) and yellow (A. chinensis var. chinensis) kiwifruit – a fast-growing, deciduous climbing plant that requires adequate fertilizer management for optimum orchard production. However, compared with kiwifruit, very little is known about the fertilization needs of this crop. Since kiwiberry is gaining importance worldwide, a project was started at four mature orchards in Belgium and the Netherlands with a focus on the mineral status of kiwiberry plants. During two growing seasons, visual deficiency symptoms were recorded and the mineral composition of the first basal leaves on fruiting canes was monitored for three cultivars, ‘Geneva’, ‘Weiki’ and ‘Issai’. We then assessed how these data correlated with each other and whether they were related to soil parameters. Additionally, the mineral composition of the fruits was determined and linked to fruit quality, which was evaluated by storage tests. Sufficiency ranges were set up for kiwiberry leaf composition based on hundreds of foliar analyses for three different timeframes during the growing season: pre-flowering, from flowering until 50 days after full flowering, and from 50 days after full flowering until harvest. The data showed that, in comparison with green and yellow kiwifruit, kiwiberry has a tendency to have higher B, higher Cl, and lower Zn levels in its leaves. Moreover, kiwiberry appeared to be very sensitive to Mn deficiency. Clear varietal differences were observed in the leaves for Mg and P. Sufficiency ranges are important to evaluate foliar analyses and, by consequence, the mineral status of kiwiberry orchards. Although the mineral fruit composition at harvest varied significantly depending on the location, Ca consistently played a key role in the storability of the berries. However, besides Ca, the ratios with, inter alia, K, Mg and N were also important.

Sources and doses of fertilizers affect foliar and fruit mineral composition of ‘Daiane’ apples

Excess fertilizer, whether organic or mineral, can promote several nutritional disorders in apple plants, affecting the production and fruit quality. The objective of this experiment was to evaluate the effects of sources and doses of N and of supplemental K and P on foliar and fruits mineral composition of 'Daiane' apples. Eight treatments were tested for nine years including: a control, a soil application of three levels of N as ammonium nitrate (AN1, AN2 and AN3), one level of N as poultry manure, one level of AN plus K, one level AN plus P and K, and one level of N as calcium nitrate, via annual soil applications. Macro and micronutrients were determined in leaves sampled at the eighth and ninth years after planting, and Ca, K, Mg, N and P in the fruit flesh sampled at the seventh, eighth and ninth years after planting. An annual poultry manure application increased the P, K and B content in leaves and apple fruits in comparison to the control. An annual application of 60 kg ha(-1) of K(2)O and 75 kg ha(-1) of N also increased the K content in leaves and fruits. The P and K content and the (K+Mg)/Ca ratio in the fruits increased with the annual application of 75, 20 and 40 kg ha(-1) of N, K(2)O and P(2)O(5), respectively. High doses of fertilizers, whether organic or mineral, affect the foliar and fruits mineral composition of 'Daiane' apples and can compromise the fruit quality by increasing the risk of physiological disorders.

Foliar nutrient applications to 'Wonderful' pomegranate (Punica granatum L.). I. Effects on fruit mineral nutrient concentrations and internal quality

Investigations into putative health benefits of pomegranate fruit have increased interest in its consumption and production but limited evidence exists regarding fruit mineral nutrient concentrations and other internal fruit quality characteristics, especially for Wonderful, an industry standard cultivar, and even less is known about the effects of agricultural practices such as foliar fertilizer applications on these variables. Mature ‘Wonderful’ pomegranate trees were treated during fruit set with zinc sulfate (ZnSO4), magnesium sulfate (MgSO4), potassium nitrate (KNO3), and with deionized water. Mature fruit were analyzed for mineral nutrient concentrations, antioxidant activity (AA), total phenolics (TP), total soluble solids (TSS), and titratable acidity (TA). Fruit mineral nutrient concentrations were characterized. Zinc-treated trees had greater fruit Zn concentrations. No other significant differences in fruit mineral nutrient concentrations were detected. Antioxidant activity ranged from 67.1 to 87.1 percent inhibition of 2,2′-diphenyl-1-picrylhydrazyl with no treatments resulting in AA that was significantly different from the control. Total phenolics ranged from 2091 to 3735 mg·L−1 gallic acid equivalents, with 2% KNO3 resulting in a statistically significant increase in TP at one site. Fruit TSS and TA were not affected significantly by the treatments. The results suggest that foliar ZnSO4, MgSO4, and KNO3 could be used as part of an efficient, sustainable fertilizer program for ‘Wonderful’ pomegranate while maintaining or improving fruit mineral nutrient concentrations, bioactivity, and internal quality.

New insights about cadmium impacts on tomato: Plant acclimation, nutritional changes, fruit quality and yield

AbstractTomato is an important crop worldwide. Cadmium (Cd) concentrations in fruits depend on tomato genotype. This work aimed to study the relation among Cd accumulation, tolerance mechanisms, and fruit features in two tomato cultivars with contrasting tolerance to Cd stress. Tolerant (Yoshimatsu) and sensitive (Tropic Two Orders) plants were grown in control and contaminated soils (0.04 and 3.77 mg/kg Cd, respectively) from the seedling stage to fruit production. Both cultivars were able to acclimatize to Cd exposure, probably through mechanisms associated with reductions in the magnesium status. Cadmium concentrations varied according to the following descending order: roots = leaf blades > (peduncle + sepals) > stem = fruits. However, the tolerant cultivar accumulated more Cd than did the sensitive one. Although Cd reached the fruits from the first to the fourth bunches, peduncle and sepals may act as a barrier to Cd entrance in tomato pulp and peel. The Cd‐induced changes in the fruit mineral profile varied according to plant cultivar, organ, tomato tissue, and bunch position. Moreover, plant yield was not affected by the Cd stress, which was able to improve fruit size and weight in the tolerant cultivar. In conclusion, new insights about the Cd‐induced effects on tomato development and fruit attributes were provided by growing plants in soil, which is the media generally used to cultivate this crop, rather than hydroponics. It was shown that tomato cultivars with contrasting tolerance to Cd toxicity can reach sexual maturity and produce fruits with no yield losses, despite impacts on development from long‐term Cd exposure. This study also revealed the role of floral receptacle and its related structures in limiting, even partially, Cd translocation to the fruits. Furthermore, Yoshimatsu's capacity to produce bigger and heavier fruits, in plants under Cd exposure, may probably be associated with enhanced Cd accumulation.

Fruit sugar and organic acid were significantly related to fruit Mg of six citrus cultivars

The fruit quality of 6 citrus cultivars growing in the same orchard was determined at ripening stage in both 2014 and 2015. We further measured the components of sugar (sucrose, fructose and glucose), organic acid (citric, malate and quinic acid), enzymes related to Glycolysis and Krebs cycle and mineral elements at 5 stages of fruit development in the second year. The results showed that at ripening stage of both years, ‘Newhall’ cultivar had higher TSS concentration and the TSS/TA ratio but lower TA concentration, while ‘Flame’ cultivar was exactly opposite. Sucrose and citric acid were the most accumulated compounds in fruit during the fruit development of 6 citrus cultivars. Fruit sucrose concentration increased from 9.26 mg·kg−1 at 60 DAFB to 50.92 mg·kg−1 at 180 DAFB, and the citric acid concentration increased from 1.41 mg·kg−1 at 60 DAFB to 29.87 mg·kg−1 at 90 DAFB or 29.02 mg·kg−1 at 120 DAFB then decreased till ripening (5.47 mg·kg−1). We found ACO was the key enzyme resulting in the difference of citric acid accumulation, but not quite clear in sucrose metabolism. The fruit mineral nutrient concentrations of 6 cultivars during the fruit development were 0.94–1.92% of N, 0.11–0.23% of P, 1.03–1.37% of K, 0.31–1.15% of Ca, 0.11–0.29% of Mg, 3.97–72.34 mg·Fe kg−1, 1.93–10.64 mg·Mn kg−1, 1.56–10.73 mg·Cu kg−1, and 0.90–16.80 mg·Zn kg−1. We also analyzed the relationship among each sugar, organic acid component and mineral nutrient in this study by curve estimation and PCA analysis. The results indicated that only Mg was significantly correlated with both sugar and organic acid component, negative and positive respectively. It suggested that the accumulation of sugar and organic acid might be related to the dynamic changes of fruit Mg concentrations of 6 citrus cultivars.

MULTIFACETED POTENTIAL OF K AND GA3 ON GROWTH, PRODUCTION AND QUALITY OF F1 HYBRID Cucumis sativus L. (cv. KUK-9)

An experiment was conducted to evaluate the effect of different concentration and combination of potassium [1.0 g/l (K1), 2.5 g/l (K2) and 5.0 g/l (K3)] and gibberellic acid [0.005 g/l (G1), 0.01 g/l (G2) and 0.015 g/l (G3)] foliar application on growth characteristics, quality and yield of F1hybrid cucumber (cv. KUK-9).The results showed that the highest amounts for growth, biochemical attributes, fruit maturity, quality belonged to K2 (2.5 g/l) plus G2 (0.01 g/l) combination treatment. Plant height as well as chlorophyll content attained their greatest quantities under G2K2 treatment. Dry matter, TSS % and antioxidant activity showed significant differences compared with control, G1K1 and G2K2 treatment showed the greatest sum of data. Fruit mineral content were also significantly affected by different treatments. Higher fruit potassium was recorded with G3K3 treatment.

Reducing GHG emissions while improving diet quality: exploring the potential of reduced meat, cheese and alcoholic and soft drinks consumption at specific moments during the day

BackgroundThe typical Western diet is associated with high levels of greenhouse gas (GHG) emissions and with obesity and other diet-related diseases. This study aims to determine the impact of adjustments to the current diet at specific moments of food consumption, to lower GHG emissions and improve diet quality.MethodsFood consumption in the Netherlands was assessed by two non-consecutive 24-h recalls for adults aged 19–69 years (n = 2102). GHG emission of food consumption was evaluated with the use of life cycle assessments. The population was stratified by gender and according to tertiles of dietary GHG emission. Scenarios were developed to lower GHG emissions of people in the highest tertile of dietary GHG emission; 1) reducing red and processed meat consumed during dinner by 50% and 75%, 2) replacing 50% and 100% of alcoholic and soft drinks (including fruit and vegetable juice and mineral water) by tap water, 3) replacing cheese consumed in between meals by plant-based alternatives and 4) two combinations of these scenarios. Effects on GHG emission as well as nutrient content of the diet were assessed.ResultsThe mean habitual daily dietary GHG emission in the highest tertile of dietary GHG emission was 6.7 kg CO2-equivalents for men and 5.1 kg CO2-equivalents for women. The scenarios with reduced meat consumption and/or replacement of all alcoholic and soft drinks were most successful in reducing dietary GHG emissions (ranging from − 15% to − 34%) and also reduced saturated fatty acid intake and/or sugar intake. Both types of scenarios lead to reduced energy and iron intakes. Protein intake remained adequate.ConclusionsReducing the consumption of red and processed meat during dinner and of soft and alcoholic drinks throughout the day leads to significantly lower dietary GHG emissions of people in the Netherlands in the highest tertile of dietary GHG emissions, while also having health benefits. For subgroups of the population not meeting energy or iron requirements as a result of these dietary changes, low GHG emission and nutritious replacement foods might be needed in order to meet energy and iron requirements.

Impact of organic manure and combination of N P K S, on yield, fruit quality and fruit mineral content of Khenazi date palm (Phoenix dactylifera L.) cultivar

This study was carried out during three successive seasons 2011, 2012 and 2013 at a private orchard located in Al- Hello in Ajman Emirate (UAE). The experiment was designed to study the effect of organic manure and NPKS as soil application on yield, fruit quality, and fruit mineral nutrient content of Khenazi date palm cultivar grown in sandy soil. Fertilization treatments consisted of N1, 600g or N2, 1000g (urea 46%N), P 800g (triple superphosphate, 48% P2O5), K 1200g (potassium sulphate, 50% K2SO4) and S 700g sulphur (90% granular S), in addition to organic manure. Al experimental trees received 100g mixture of micronutrients, with the exception of the control. The results showed that combination treatments and organic manure significantly affected fruit weight, flesh weight, fruit volume, moisture content and fruit TSS. Application of different fertilization treatments significantly affected yield components of fruit, number of fruits/strand, fruit number/bunch, fruit set percent and total fruit yield / palm. The study revealed that combination of fertilizers improved fruit nutrient content of N, P, K, Ca, Mg, Fe, Zn, Mn and Cu. Moisture and TSS% content, number of fruits/strand, number of fruits/bunch, fruit nutrients content of Fe, Mn and Zn were significantly different due to the application of N1+K+S.

Yield and Mineral Content of Hydroponically Grown Mini-Cucumber (Cucumis sativus L.) as Affected by Reduced Nutrient Concentration and Foliar Fertilizer Application

Nutrient application is one of the major inputs required for hydroponic production of cucumbers. Reduced nutrient solution concentration with supplementary foliar fertilizer application may maintain yield and quality of mini-cucumber, while decreasing the production costs. An experiment was conducted to determine the effect of foliar fertilizer in combination with reduced nutrient concentrations on the yield and quality of hydroponically grown mini-cucumber in a plastic tunnel. Mini-cucumber plants were grown in sawdust, fertigated with nutrient solutions containing 100% (control), 75%, 50%, or 25% of the recommended nutrient concentration (NC) and two foliar fertilizer applications (no foliar and foliar application). The highest fresh and dry weight of mini-cucumber plants were obtained with 75% and 100% NC and decreased with 50% to 25% NC application. The number of marketable fruit and marketable yield on mini-cucumbers increased with 75% to 100% NC, followed by 50% NC, as compared with 25% NC. Deformed fruit were significantly lower at 25% NC than at 50%, 75%, and 100% NC. Foliar fertilizer application did not have an effect on mini-cucumber yield, but reduced the yellowing of fruit. Fruit mineral content (P, Fe, and Mn) was significantly improved by 100% NC. Improvement in yield at 75% and 100% NC was as a result of improved plant height, leaf chlorophyll content, plant fresh and dry weight, and the increase in nutrient uptake of N, P, K, and Mn, which was evident in the analysis of cucumber leaves. The reduced NC of 75% can maintain yield and quality of mini-cucumbers, whereas the application of foliar fertilizer had a limited effect.

Fruit mineral content of apricot and kiwifruit in relation to transpiration

The paper examines the relationship between fruit transpiration and the accumulation of some minerals in the fruit. Fruit transpiration determined by the main factors affecting skin conductance. Most of those factors have their largest effect early in fruit development when large amounts of phloem-immobile nutrients (e.g., Ca) are accumulated. In apricot, which has a low-transpiring fruit, Ca accumulation is about 1/5 of that accumulated in other fruits under similar vapor pressure deficit (VPD) conditions, while K and Mg (phloem-mobile nutrients) accumulate independently of VPD. Similarly in high transpiring kiwifruit, Ca may reach 40 mg fruit-1. In this paper we report an overview of the main fruit and environmental factors affecting transpiration and in turn the accumulation of minerals into apricot and kiwifruit fruit. Possible actions to increase fruit transpiration and, in turn, accumulation of certain minerals are considered.

Is fruit dry matter concentration a useful predictor of ‘Honeycrisp’ apple fruit quality after storage?

In climates such as New York State, USA, fruit quality (taste and bitter pit incidence) of Honeycrisp apple varies significantly from year to year. Our research with Honeycrisp? indicates that when crop load is too high the tree cannot supply sufficient carbon, and other nutrients to give optimum fruit quality (taste, appearance and storageability). Similarly if weather patterns are cloudy, tree carbon acquisition is reduced and carbon supply for fruit growth is limited resulting in less than adequate resources for optimum fruit quality. In an attempt to predict Honeycrisp' eating quality and bitter pit incidence post storage we began a study in 2013 where we measured fruit quality characteristics at harvest of 30 orchards in western NY and 20 orchards in northern NY and correlated them with eating quality post storage after 4.5 months in air. The dry matter concentrations at harvest among orchards ranged from 11 to 18%. Neither fruit dry matter no concentration or fruit mineral concentrations (N, Ca and Ca/N and K+Mg/Ca ratio) were predictive of post-storage fruit quality. Fruit Ca concentration was also not predictive of post storage fruit bitter pit. Fruit samples were also treated with MCP or left untreated at harvest. MCP resulted in a small but significant improvement in fruit crunchiness, reduced disagreeable flavors and increased liking score of ?Honeycrisp? fruits. Keywords: fruit mineral concentration, fruit Ca concentration, liking score, bitter pit, MCP

Biostimulants from food processing by-products: agronomic, quality and metabolic impacts on organic tomato (Solanum lycopersicum L.).

Biostimulants have recently gained increased attention due to their multiple benefits for sustainable agriculture. In this study, three food processing by-products-fennel processing residues (FPR), lemon processing residues (LPR) and brewer's spent grain (BSG)-were investigated as potential sources of biostimulants. Their aqueous extracts as individual and associated applications were assessed for their effects on agronomic, quality and metabolic performance of organic tomato in comparison to extract of humic substances (HS) and untreated control (CTRL). Only FPR extracts stimulated shoot growth and tomato dry matter content, whereas all candidates improved tomato yield. FPR and BSG increased fruit mineral content and BSG-FPR-LPR in combination enhanced titratable acidity. FPR-treated fruits had also 20% more vitamin C than CTRL, and higher phenol content was obtained in those of BSG-LPR. Fruit metabolomic profile showed the tendency of all extracts, except BSG-LPR, to increase tomato citric acid and to decrease β-glucose and methanol concentrations. The analysis revealed accordingly the indispensable role of FPR in combined applications for inducing an HS-like response in fruits. The results were indicative of the biostimulant activity of these extracts and demonstrated them, particularly FPR, as promising candidates for enhancing plant productivity and fruit quality. © 2017 Society of Chemical Industry.

Effects of different irrigation practices using treated wastewater on tomato yields, quality, water productivity, and soil and fruit mineral contents

Wastewater use in agricultural irrigation is becoming a common practice in order to meet the rising water demands in arid and semi-arid regions. The study was conducted to determine the effects of the full (FI), deficit (DI), and partial root-zone drying (PRD) irrigation practices using treated municipal wastewater (TWW) and freshwater (FW) on tomato yield, water use, fruit quality, and soil and fruit heavy metal concentrations. The TWW significantly increased marketable yield compared to the FW, as well as decreased water consumption. Therefore, water use efficiency (WUE) in the TWW was significantly higher than in the FW. Although the DI and the PRD practices caused less yields, these practices significantly increased WUE values due to less irrigation water applied. The water-yield linear relationships were statistically significant. TWW significantly increased titratable acidity and vitamin C contents. Reduced irrigation provided significantly lower titratable acidity, vitamin C, and lycopene contents. TWW increased the surface soil and fruit mineral contents in response to FW. Greater increases were observed under FI, and mineral contents declined with reduction in irrigation water. Heavy metal accumulation in soils was within safe limits. However, Cd and Pb contents in fruits exceeded standard limits given by FAO/WHO. Higher metal pollution index values determined for fruits also indicated that TWW application, especially under FI, might cause health risks in long term.

Prediction of kiwifruit firmness using fruit mineral nutrient concentration by artificial neural network (ANN) and multiple linear regressions (MLR)

Many properties of fruit are influenced by plant nutrition. Fruit firmness is one of the most important fruit characteristics and determines post-harvest life of the fruit. In recent decades, artificial intelligence systems were employed for developing predictive models to estimate and predict many agriculture processes. In the present study, the predictive capabilities of multiple linear regressions (MLR) and artificial neural networks (ANNs) are evaluated to estimate fruit firmness in six months, including each of nutrients concentrations (nitrogen (N), potassium (K), calcium (Ca) and magnesium (Mg)) alone (P1), combination of nutrients concentrations (P2), nutrient concentration ratios alone (P3), and combination of nutrient concentrations and nutrient concentration ratios (P4). The results showed that MLR model estimated fruit firmness more accuracy than ANN model in three datasets (P1, P2 and P4). However, the application of P3 (N/Ca ratio) as the input dataset in ANN model improved the prediction of fruit firmness than the MLR model. Correlation coefficient and root mean squared error (RMSE) were 0.850 and 0.539 between the measured and the estimated data by the ANN model, respectively. Generally, the ANN model showed greater potential in determining the relationship between 6-mon-fruit firmness and nutrients concentration.

Calcium and Potassium Foliar Sprays Affect Fruit Skin Color, Quality Attributes, and Mineral Nutrient Concentrations of ‘Red Delicious’ Apples

ABSTRACTThis study was conducted to evaluate the influences of foliar spray of potassium (K), calcium (Ca), and their combination on the fruit red skin color and quality attributes of ‘Red Delicious’ apple under conditions of south central Iran with warm and dry summer, where low and high temperature differences are low. The trees were sprayed five times using 5 g L–1 calcium chloride (CaCl2) at 3-week intervals starting from 3 weeks after full bloom and three times (at 9, 12, and 15 weeks after full bloom) using 2.5 g L–1 K sources [potassium chloride (KCl), potassium sulfate (K2SO4), and potassium nitrate (KNO3)] during two growing seasons in 2013 and 2014. Anthocyanin, some physicochemical attributes, and fruit mineral concentrations were measured at harvest. Results showed that spraying with K, CaCl2, and their combinations significantly increased fruit weight, sugar and anthocyanin concentrations, firmness, and K uptake. A combined foliar application of CaCl2 and each of the K sources was more effective on the improvement of fruit color, firmness, fruit K and Ca uptake, and K/Ca ratio as compared to the case when either K or Ca was applied alone.

Response of Hydroponically Grown Cherry and Fresh Market Tomatoes to Reduced Nutrient Concentration and Foliar Fertilizer Application under Shadenet Conditions

Reduced nutrient concentration (NC) through fertigation in an open-bag hydroponic system with additional foliar fertilizer application may reduce nutrient wastage and thus decrease the production costs. A study was conducted to determine the effect of foliar fertilizer in combination with reduced NCs on the yield and quality of hydroponically grown cherry and fresh market (FM) tomatoes in a shadenet structure. In the first experiment, FM tomato plants were grown in sawdust fertigated with nutrient solutions containing 100% (control), 75%, 50%, or 25% of the recommended NC. Marketable yield and fruit mineral content were unaffected by NC, whereas the total yield decreased with a decrease in NC. The second and third experiments were on FM and cherry tomatoes, respectively, subjected to four NCs (100%, 75%, 50%, or 25%) and two foliar fertilizer applications (no foliar and foliar application). Fresh and dry weight of FM and cherry tomato plants decreased with a decrease in NC application. Marketable yield on FM tomatoes increased with 50% to 100% NC, whereas the total yield increased with 75% and 100% NC, as compared with 25% NC. Cherry tomatoes produced lower marketable yield at 25% and 50% NC, as compared with 75% and 100% NC. Foliar fertilizer application did not have an effect on FM and cherry tomato yield, but improved the plant dry weight of cherry tomatoes. Fruit and leaf Ca content of FM tomatoes were improved by the decrease in the NC. Fruit mineral content (K, P, Ca, Mg, and Zn) of cherry tomatoes increased with an increase in NC. The improvement in yield was primarily due to nutrient uptake, especially, N, P, and K, as determined in tomato leaves. Reduced NC of 50% can maintain yield and quality of FM tomatoes, whereas application of foliar fertilizer had a limited effect. In cherry tomatoes, yield and fruit mineral content were maintained at 75% NC combined with foliar fertilizer application. The findings of this research may reduce nutrient wastage and result in a cost saving of 25% and 50% on fertilizer input costs on cherry and FM tomatoes, respectively, and reduce the risk associated with water pollution.