B. M. Plaza

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.

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.

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.

Assessment of the Nitrogen and Potassium Fertilizer in Green Bean Irrigated with Disinfected Urban Wastewater

Green bean Helda in autumn cycle (118 days) was grown under greenhouse conditions in sand-mulched sandy loam soil. The crop was irrigated with disinfected urban wastewater (DUW) obtained from ozone from the Almería Purifying Plant. The average nutrient parameters of DUW were 0.4 mM of nitrate (NO3 −), 2.1 mM of ammonium (NH4 +), 0.8 mM of potassium (K+), and electrical conductivity (EC) 1.6 dS m−1. Three different treatments were established: DUW without additional fertilization (FDUW), DUW with fertilization until the recommended rate was obtained (10.0 mM of N and 3.4 mM of K) (FNK), and DUW with fertilization until 1.5 FNK rate (15.0 mM of N and 5.1 mM of K) (F1.5NK) was obtained. The dry-matter production was not conditioned by the fertilizer level. Treatments FNK and F1.5NK showed the greatest yield and uptake of N and K independent of the fertilizer level. The most nitrogen (N), calcium (Ca), and magnesium (Mg) were in the leaf, phosphorus (P) was high in fruit, and K was similar in leaf and fruit. With regard to the macronutrient absorption efficiency, the F1.5NK treatment showed the least N and K efficiency and the greatest soil salinity.

Influence of Salt Stress on the Nutritional State of Cordyline fruticosa var. Red Edge: Chloride, Nitrogen, and Phosphorus

This trial was carried out to study the nutritional and productive behavior generated by modifications in the salt concentration in the nutrient solution for Cordyline fruticosa var. Red Edge plants. The anions studied were chloride (Cl), nitrogen (N), and phosphorus (P). 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). At the end of the cultivation, leaf, petiole, shoot and root fresh and dry weights, elemental extractions, and elemental concentrations were determined. Nutrient concentrations and total plant uptake (extraction) were calculated from the dry matter. The treatment T2 induces a blade protection mechanism, which consists on the accumulation of chloride (Cl−) in root and vessels; so, leaf storage is reduced, avoiding damages. Petiole also contributes to this protection, acting as a salt pool. As NaCl concentration in the nutritive solution arises, N plant concentration increases significantly although there are no significant differences between T1 and T2. With high salinity levels, P in vessels is reduced, whereas root extraction and concentration increases. The greatest N and P extractions are observed in T2, which is due to its higher dry matter. Chloride extractions are lower in T1 than in the other treatments.

Peat Substrate Reuse in Lilium “Helvetia” Crop

The reuse of substrates for more than one growing season is an excellent alternative to reduce production costs and to improve the sustainability of the ornamental plant production system. The objectives of the present trial were to study the effects of substrate reuse on Lilium var. Helvetia plants cultivated in shipping crates in a polyethylene greenhouse, as well as possible changes in the physical and physical–chemical properties of the substrates employed. Peats used during two and three cultivation cycles and new unused peat were tested. The reused substrate reduces the particle fraction with higher diameter size, porosity, and organic matter and increases particle bulk and substrate carbon (C) / nitrogen (N) ratio, due to the substrate decomposition. However, it does not affect flowers, flower stems and leaves, and dry and fresh matter. The level of phosphorus (P) and magnesium (Mg) in leaf, as well as nitrate, potassium (K), and Mg in the substrate solution are similar among the three kinds of substrates studied. Nevertheless, the substrate used for three cultivation cycles leads to increases in organic N and K and decrease of calcium in leaves.

Improve Water and Nutrient Efficiency in Tomato Crop by a Dynamic Fertigation Management under Saline Conditions

The improvement of water and nutrient efficiency leads to a production model that is more sustainable with less water, fewer fertilizer inputs, and less environmental damages. High-technology fertigation equipment permits high precision in the nutrient solution application. Besides, the field measurement of soil water content by tensiometers and the extraction of soil solutions by suction cups allow a dynamic methodology management in agreement with real crop requirements. This trial was carried out to compare this dynamic fertigation management method (using tensiometers and suction cups) for tomato crops (Lycopersicum sculentum Mill. Forteza) under Mediterranean greenhouse conditions with other methods: the local traditional model, based only on technical consulting, and the classical model, by means of estimation of Kc and nutrient extractions references. The parameters studied were tomato yield, water, and fertilizer amounts applied during the cultivation as well as water- and fertilizer-use efficiency. The water used to prepare the nutrient solution was classified as C4-S3 following the Riverside classification system. Plants were grown from 15 August to 20 April. The results show that the supply of fertilizers during the cultivation has been significantly lower with classical and dynamic models. Dynamic method shows greater efficiencies for all the elements, except for potassium, and also decreases the water consumption, not affecting total yield.

Effects of Treated and Untreated Wastewater from Municipal Solid Waste (MSW) Leachates on the Nutritional State of Viola spp.: Sodium, Potassium, Calcium, and Magnesium

The scarcity of water for different uses has created a need for using nonconventional water resources, such as wastewater and saline water. Their use could contribute to reduced water resource consumption in arid areas and biosphere contamination. Wastewaters are normally unbalanced solutions rich in sodium (Na+), calcium (Ca2+), magnesium (Mg2+), sulfate (SO4 2−), and chloride (Cl−), which can cause damages to crops, but if they are treated, their quality can increase. The aim of this trial was to study the effects of pure, diluted, sand-filter depurated, and phytodepurated wastewater from municipal solid waste (MSW) leachates, compared with groundwater on the nutritional state of the ornamental plant Viola spp. The experimental design was unifactorial (type of irrigation water). Five treatments were tested: R9.0 [wastewater, electrical conductivity (EC) 9.0 dS m−1], R4.5 (wastewater, EC 4.5 dS m−1), D4.5 (depurated water, EC 4.5 dS m−1), FD4.5 (phytodepurated water, EC 4.5 dS m−1), and P (groundwater, EC 1.5 dS m−1). Nutrient (Na+, K+, Ca2+, and Mg2+) concentrations and partitioning per fraction (flowers, aerial vegetative fraction, including stems and leaves [called AVF], and roots) were studied. Similar total Na+ extractions were found in the 4.5 dS m−1 treatments, being greater than in the 9.0 dS m−1 treatment, all of the surpassing the control. Nevertheless, there were Na+ partitioning per fraction differences depending on Na+ concentration. Total K+ extraction was the greatest in FD4.5, related with its greater root concentration. Potassium was mainly located in AVF, followed by flowers. Calcium and Mg2+ extractions showed a similar behavior. The greatest Ca2+ extraction was noticed in control plants, which is related with Ca2+ accumulation in roots.