María Teresa Lao

Evaluation of Nitrate Quick Tests to Improve Fertigation Management

Abstract The aim of this work was to assess rapid‐analysis equipment for nitrate nitrogen, evaluating the measurement precision, the ease of use, and the robustness of the equipment. Three kinds of samples were collected: soil solutions taken by suction cup, hydroponic drainage solutions, and nutritive solutions obtained from the emitter. The equipment used to analyze the solutions for nitrate were Handion Priva electrodes, Nanocolor photometric equipment, and test equipment for ELE hydroponic solutions. The results were as follows: all equipment was easy to use, with clear and simple instructions for use in the field for fertigation management. The electrode appeared to be the most appropriate method to determine nitrate. The Nanocolor and ELE equipment underestimated nitrate concentrations for values greater than 3 mmol L−1; to ameliorate this problem, adjustment equations can be used.

Influence of Salinity and Fertilization Level on Greenhouse Tomato Yield and Quality

The objective of this study was to evaluate the effects of two irrigation water qualities and three different levels of nitrogen–phosphorous–potassium (NPK) rates applied by fertigation on yield and quality of tomato fruit. The experiment was carried out in a polyethylene greenhouse on ‘Pitenza’ tomato grown on a sand‐mulched sandy loam soil using a trickle irrigation system. The treatment consisted of two irrigation water qualities (C2S1 and C3S2) and three fertilization levels: 50%, 100%, and 200% [7.1 mmol L−1 nitrate (NO3) N, 0.5 mmol L−1 P, and 3.1 mmol L−1 K] for each water quality category. The dry‐matter content of fruit (DMC), number of fruit, fruit weight per period (g), weight per fruit (g), number of trusses, fruits per truss, and unmarketable fruit were monitored. Quality was evaluated using fruit firmness (Kg), total soluble solids (°Brix), pH, and tritable acidity (meq citric acid L−1 of juice). The increased salinity of the irrigation water did not affect the marketable and unmarketable yield of fruit but did produce an increase in the number of fruits per truss at 127 days after transplanting (DAT) (10%) and in the DMC percentage at 127 and 179 DAT, being 9 and 6.8% respectively. High‐salinity irrigation water reduced the firmness of the fruit at 127 and 179 DAT (9% and 22%, respectively); it increased the soluble solids for all the dates analyzed as well as the fruits tritable acidity with significant differences at 127 and 206 DAT. The fertilization level increased the marketable yields, fruit number, and number of trusses during all stages. Treatment F1 produced a yield 28% lower than F2, whereas F3 was 10% higher than F2. The results show that irrigation water electrical conductivity (EC) of 2.2 dS m−1 is adequate for high yield and quality of tomato in the commercial cycle.

Physiological Stress caused by Salinity in Cordyline fruticosa and Its Indicators

Crop plants are usually nonhalophytes that tolerate only moderate saline concentrations; under salinity, they accumulate salt in their aboveground organs and, to a smaller extent, in roots. Enhanced synthesis of determined secondary metabolites (such as proline, phenolics, or malondyaldehide) under stressful conditions is believed to protect the cellular structures from oxidative damage, in addition to the osmotic advantage for the plants. The aim of this work is to study the influence of the fertigation water salinity on osmoprotectant content in Cordyline fruticosa var. ‘Red Edge.’ Four nutrient solutions with different electrical conductivity levels were applied: EC1.5 (1.5 dS m−1), EC2.5 (2.5 dS m−1), EC3.5 (3.5 dS m−1), and EC4.5 (4.5 dS m−1), obtained by the addition of different quantities of sodium chloride (NaCl) to a basic nutrient solution (EC 1.5 dS m−1), followed by stirring to dissolve the salt and make the solution homogeneous. The results show that malondialdehyde (MDA) content is not a good indicator of plant stress, as levels in EC1.5 and EC4.5 are similar, but flavonoids, phenols and sugars contents are more useful indicators, because the highest values in leaves are found with the more saline treatment. Proline plays an osmoregulatory role, increasing in roots when NaCl concentration in the nutrient solution is too high but also when it is too low.

Characterization of compost based on crop residues: changes in some chemical and physical properties of the soil after applying the compost as organic amendment.

The objectives of the present study were to make a physical, physicochemical, and biological characterization of compost obtained from crop residues of horticultural plants grown in greenhouses and to assess the physical and chemical responses of a soil tested after the applications of this organic amendment. The compost showed a high percentage of inorganic material because the source of this compost includes not only crop residues but also soil; for this reason, it had high coarseness index (CI), electrical conductivity (EC), and pH. The application of the organic amendment to a soil with reduced bulk density (BD) increased the percentage of particles with large diameters, as well as increased the nutritional status and organic matter (OM). However, nitrogen and potassium levels in soil were low. Compost addition provoked an increase in soil EC, which restricts its use to salt-tolerant plants.

Determination of Spatial Variability of Nutrient Composition of Soil Solutions in Greenhouses by Using Suction Cups

The spatial variability of pH, EC and concentrations of K+, Ca2+, Mg2+, Na+, and Cl− in the soil solution of a fertigated soil in a greenhouse was studied using suction cups. The considered factors that modify the composition of the soil solution were: soil depth (0.10 and 0.25 m), distribution of nutrients before and after irrigation, evolution during the growth cycle, and location inside the greenhouse. Each parameter was studied separately to determine its effect on the nutrient composition of the soil solution, and consequently to standardize the soil solution sampling and design of fertilizer applications. Significantly higher levels of EC and concentrations of Mg2+, Na+, and Cl− were found at 0.25 m, whereas higher concentrations of and K+ were obtained with suction cups in the topsoil horizon (0.10 m). Irrigation with nutrient solution modified the concentrations of and significantly, and during the growth period the concentrations of pH, and Na+ varied significantly. A simple linear model to estimate the actual soil solution composition from the soil moisture and previous soil solution composition was obtained, showing a close relationship with the experimental values found by means of suction cups after irrigation. This model can be of use in the calculation of the composition of optimized nutrient solutions by means of suction cups. This procedure can also be relevant in the design of optimized nutrient solutions for fertigation, maximizing plant production and minimizing excessive use of fertilizer and pollution in intensive horticultural ecosystems.

Integral Management of Irrigation Water in Intensive Horticultural Systems of Almería

The development of intensive horticulture in Almeria, with a huge increase in greenhouse surface area, is related to three essential factors: climatic characteristics, groundwater use and mulching sandy soil. The purpose of the present paper is to draw a picture of the integral management of water irrigation in the intensive horticultural systems in the region, by identifying the most significant water resource contributions and alternative water resources. Results indicate that the use of groundwater for the irrigation of horticultural crops in the greenhouses presents a high degree of overexploitation of the aquifers, but due to the continuous search for alternative water resources, such as desalinated and reclaimed water, as well as in-depth knowledge of the integral management of water irrigation through automated fertigation and localized irrigation systems, the current status of the water resources could be sustainable. Moreover, being conscious of the pollution generated by agricultural leachates, the horticultural system of Almeria is implementing complementary sustainable systems such as recirculation, cascade cropping systems and phytodepuration for the reuse of the leachate. Considering all these factors, it can be concluded that the intensive horticultural system is on the right path towards respecting the environment and being sustainable in terms of water use.

Influence of salinity and fertilization level on the nutrient distribution in tomato plants under a polyethylene greenhouse in the Mediterranean area.

The experiment was conducted in a polyethylene greenhouse with the ‘Pitenza’ variety of tomato crop on a sand‐mulched sandy loam soil using trickle irrigation. The experimental design was two‐factorial with four randomized blocks. The treatments applied were the result of a combination of two irrigation water qualities (C2S1 and C3S2) and three fertilization levels: F1, half of the recommended rate; F2, the recommended rate [i.e., 7.1 mmol L−1 of nitrate (NO3 −)–nitrogen (N), 0.5 mmol L−1 of phosphoric acid (H2PO4 −)–phosphorus (P) and 3.1 mmol L−1 of potassium (K+)], and F3, double the recommended rate. Total content of nutrients [N, P, K, calcium (Ca), magnesium (Mg)] and sodium (Na) were determined for different plant parts (pinch rest, harvested fruit, developing fruit, leaf, and stem) for the whole season. Also, the relative sink strengths between fruit and vegetative plant parts were calculated. The main mineral constituent of the tomato plant was K, surpassing the N content, and the minor constituent was P. With the same level of fertilization, the influence of salinity was significant at F1 (half of the recommended rate) and F2 (the recommended rate) but not at the highest level. Plant nutrient distribution showed the same behavior for N, P, and K, the fruit being the nutrient sink. On the other hand, the same tendency was observed for Ca and Mg, stored mainly in the leaf. Nevertheless, Na presented low levels in young tissues, whereas the levels were higher and similar in fruit, leaf, and stem.

Influence of Salt Stress on the Nutritional State of Cordyline fruticosa var. Red Edge, 2: Sodium, Potassium, Calcium, and Magnesium

The aim of this trial was to study the nutritional behavior generated by modifications in the salt concentration in the nutrient solution used for the fertigation of Cordyline fruticosa var. Red Edge plants. Four treatments were tested: T1 [control, 1.5 dS m−1, 14.3 mmol L−1 sodium chloride (NaCl)]; T2 (2.5 dS m−1, 22.2 mmol L−1 NaCl); T3 (3.5 dS m−1, 32.7 mmol L−1 NaCl); and T4 (4.5 dS m−1, 38.2 mmol L−1 NaCl). There is an accumulation of sodium (Na+) in roots, stem, and petiole when salinity increases, which avoid leaf damages. Potassium (K) concentration increases with the intermediate saline treatments in stems and leaves but decreases when plants are fertigated with T4. Calcium (Ca) accumulates in roots with T3 and T4, in stems with T4, and in petioles and leaves with T3. Magnesium (Mg) concentration is greater in stems, petioles, and leaves of T4, but is greater in roots of T3. Plants fertigated with the three saline treatments extract 1.4 times more Na+ than T1 plants. The greatest K+ extraction is observed in T2, followed by T3, and T4. T2, T3, and T4 plants extracted more Ca2+ than T1 plants. Finally, Mg2+ extractions in T3 are twice as much as they are in T1, while in T4 and T2 are much greater.

Growth and Nutritional Response of Melon to Water Quality and Nitrogen Potassium Fertigation Levels under Greenhouse Mediterranean Conditions

The Mediterranean area has been experiencing an extensive development of intensive horticulture, with a majority of that located in arid and semi-arid regions with limited water resources and poor water quality. One of the most important greenhouse vegetable crops is melon. This article studies the effects of different nitrogen–potassium (N–K) fertilizers applications and two types of irrigation water on yield and nutritional behavior of melon crop Cucumis melo L. (var. cantalupensis Naud. Alpes). The trial was conducted during two cycles under Mediterranean greenhouse conditions, on sandy mulching soil. The experimental design was bifactorial: NK fertigation and water quality, with three nutrition levels and two water qualities [MS with electrical conductivity (EC) = 0.6 dS m−1 and HS with EC = 2.3 dS m−1]. During the first cycle, the fertigation levels were F1 (50% NK), F2 (100% NK), and F3 (125% NK). In the second cycle, the fertigation levels were F2, F4 (125% N and 150% K) and F5 (180% N and 220% K). Treatment F2 was the recommended total doses (220 kg N ha−1 and 355 kg K ha−1). The increase in the NK concentration of the nutritive solution produced a rise in commercial production. The salinity of irrigation water did not affect marketable yield but had an effect on the fruit size, which was compensated for by an increase in the amount of fruit produced. Dry-matter production, N, and K uptake by plant (g m−2) were evaluated in the first and second trials. Salinity and NK nutrition levels significantly affected (P < 0.05) dry matter and N and K uptake by melon plant. Nitrogen and K uptake present interesting correlations with production and with each other, as established by mean regression analysis.

Influence of Salinity on the Nitrogen Metabolism of Cordyline fruticosa

Irrigated agriculture depends on adequate and quality water supplies. As the level of salt increases in an irrigation source, the quality of that water for plant growth decreases. Crop plants are usually nonhalophytes that tolerate only moderate salt concentrations. Under salinity, they accumulate salt in their aboveground organs and, to a smaller extent, in roots. High salinity reduces plant growth and leaf area, which prejudices quality, especially in ornamental crops. The study of the behavior of ornamental plants that are tolerant to saline waters can be an advantage in areas with poor quality waters. The aim of this work is to study the influence of the fertigation water salinity on the nitrogen metabolism of Cordyline fruticosa var. ‘Red Edge,’ known as ti plant, Hawaiian ti, cordyline, or good luck plant. Four nutrient solutions with different electrical conductivity (EC) levels were applied: T1 (1.5 dS m−1), T2 (2.5 dS m−1), T3 (3.5 dS m−1), and T4 (4.5 dS m−1), obtained with the application of different amounts of sodium chloride (NaCl) to the fertigation water. As salinity increases, nitrogen concentration in leaves does not change, but it increases in roots. In leaves, nitrate reductase (NR) in vivo activity declines when salinity increases; when a substrate [nitrate (NO3 −)] or a cofactor [molybdenum (Mo)] is added, NR activity increases. Potential NR activity (NO3 − + Mo) shows no significant differences between treatments; this indicates that NR synthesis is not affected by salinity. So, the diminution of the NR in vivo activity suggests a NO3 − and Mo level metabolic imbalance. In roots, Mo is more restrictive of the NR activity than the NO3 − substrate level. There are more amino acids in T1 than in T4, but it seems that there are no significant differences in T2 and T3. No significant differences are observed in the protein content; this indicates that amino acid diminution is due to the maintenance of the protein content. In conclusion, it can be said that the increased activity of NR in roots may constitute part of an adaptation strategy of the plant to an increasing salinity in the growing medium.