Nutritional solution composition in fertigation must be designed according to crop needs. These needs are variable and depend on factors like plant growth rate, environmental conditions, and water uptake. The objective of this work is to study the influence of the N-form supply (N-NO3 – or N-NH4 +) on the potassium uptake and potassium concentration changes on the recycled solution and the development of empirical models that permit the prediction of the potassium nutritional needs of Dieffenbachia amoena, ‘Tropic Snow’. To achieve this, potassium uptake has been correlated to temperature, vapor pressure deficit, global radiation, and leaf area index. The plants were placed in a Buried Solar Greenhouse, the plants being supplied with equal amounts of nitrogen, differing in the percentage of the N-form applied (NO3 –:NH4 +): Ta (100:0), Tb (50:50), and Tc (0:100). Seasons (winter and summer) generate important differences in the potassium concentration changes in the recycled solution but are not influenced by the nitrogen form. In winter, the potassium concentration remains constant, whereas in summer conditions, there is a higher decrease. This difference in behavior should be considered in the nutritive solution formulation. The nitrogen form applied does not affect potassium uptake. The study also indicates the possibility of predicting the potassium (K) uptake using the proposed models. K uptake can be estimated with a model dependent on the leaf area index, and potassium uptake concentration can be estimated with K uptake through the model and the experimental water uptake.
Silvia Jiménez Becker, Blanca María Plaza and María Teresa Lao
Silvia Jiménez Becker, Maria Teresa Lao and Mari Luz Segura
Adjusting fertility programs according to peak demand periods will help prevent periodic nutrient disorders during crop growth, allowing enhanced use efficiency of water and fertilization. The objectives of this article were to investigate 1) the evolution of the changes in the concentration of nitrate and ammonium in the recycled solution with different N-NO3 –/N-NH4 + ratios; 2) the influence of the N form supply (N-NO3 – or N-NH4 +) on the nitrogen uptake, the nitrogen:water uptake ratio, and nitrogen use and uptake efficiency; and 3) the development of empirical models that would allow the prediction of nitrogen nutritional needs of Dieffenbachia amoena to increase the N use efficiency in a recycled system. To achieve these aims, N uptake has been correlated to climate parameters such as temperature, vapor pressure deficit and global radiation, and growth parameters such as leaf area index. The trial was carried out with Dieffenbachia amoena plants growing in a recycled system with expanded clay as substrate. The crop was placed in an INSOLE (Buried Solar Greenhouse), the plants being supplied with equal amounts of N, differing in the percentage of the N form applied (NO3 –:NH4 +): TA (100:0), TB (50:50), and TC (0:100). The nitrogen form generated important changes in the pH and nitrate and ammonium concentration in nutritive solution during the recirculating solution. In N-NO3 – treatment, pH increased and nitrate concentration showed a tendency to drop slightly. N-NH4 + treatment showed an abrupt N-NH4 + concentration decrease, and N-NO3 – concentration increased along with a pH drop. Also, the nitrogen form applied to the Dieffenbachia amoena crop affects nitrogen uptake. Nitrogen uptake rates and nitrogen uptake concentration were higher in the plants supplied with N-NH4 + or NO3 –+NH4 + than in the plants provided with N-NO3 – alone. The supply of a combination of 50:50 NO3 –+NH4 + improved the N use efficiency. The study also indicated the possibility of predicting the N uptake rate and N uptake concentration using the proposed models.
Pedro García-Caparrós, Alfonso Llanderal and María Teresa Lao
The scarcity of water in the Mediterranean area has frequently led to the use of saline water for irrigation. Container grown ornamental production has relatively high rates of water and nutrient loss from fertigation. A better understanding of water and nutrient use efficiency with water that has elevated levels of saline could reduce runoff water and its environmental impact. Fern leaf lavender (Lavandula multifida) plants were grown for 8 weeks in plastic containers with a sphagnum peatmoss and perlite substrate (80:20 by volume) to evaluate the effect of saline water [2.0 (T1 or control), 4.5 (T2), or 7.5 (T3) dS·m−1] on water and nutrient uptake efficiency. Leachate was collected to determine runoff volume and composition which included nitrate-nitrogen (NO3 −-N), phosphate-phosphorus (PO4 2−-P), and potassium (K+) concentration. Plant dry weight (DW) and nutrient content were determined in plants at the beginning and at the end of the experiment to establish the nutrient balance. Increasing salinity levels of irrigation water did not significantly reduce either the plant DW or the water use efficiency (WUE). Based on nutrient balance, the increasing salinity (2.0 to 7.5 dS·m−1) affected the plant nutrient uptake efficiency, which decreased 28% for N, increased 26% for P from the lowest to highest sodium chloride levels; whereas K did not show a clear trend. Nutrient runoff increased (28% N, 9% P, and 27% K) to the environment from the lowest to highest sodium chloride levels.
Eva María Almansa, Antonio Espín, Rosa María Chica and María Teresa Lao
In this work, we present the study of the behavior of 15 tomato cultivars under different grow lights to evaluate the quality of seedlings in the production system. The lamps used are: compact fluorescent, high-efficiency fluorescent, fluorescent, and pure blue light-emitting diodes (B-LEDs). The trial was carried out in a culture chamber with the temperature and relative humidity continuously controlled. Spectral radiation was measured at the canopy level. The following were quantified: fresh, dry biomass partitioning organs (leaves, stems, and roots), the total dry weight/total fresh weight relationship, shoot/root ratio, and indole acetic acid. We found high-efficiency fluorescent light treatment has a very interesting spectral quality for all cultivar applications as a result of it having the lowest photosynthetically active radiation (PAR):near infrared (NIR), blue:red (B:R), blue:far red (B:FR), and red:far red (R:FR) ratios; ‘Conquista’, ‘Velasco’, and ‘Lynna’ are cultivars that show sensitivity to special wavebands (ultraviolet, B, R, and FR). ‘Ikram’, ‘Saladar’, and ‘Delizia’ tolerate the lack of minimum energy and spectral quality.
Alfonso Llanderal, María Teresa Lao, Juana Isabel Contreras and María Luz Segura
The objectives of this study were to compute diagnosis and recommendation integrated system (DRIS) norms and sufficiency ranges from a survey of tomato crops grown in Mediterranean greenhouses and the verification of their variation during plant growth and development. DRIS norms were computed from 408 samples of first young mature leaves collected during different phenological stages. Using the DRIS technique, two sufficiency ranges were developed: one includes all the database regardless of the phenological stage, and the other was developed based on the phenological stage. Also, ten DRIS norm nutrient ratios and cv were computed from N, P, K, Ca, and Mg analytical results. All the ratios in flowering (FL), and only N/K, Mg/K, and Mg/N in fruit development (FD), showed low cv and therefore may play a fundamental role in crop development in accord with the DRIS norms calculated. It is also necessary to point out that a slight modification in the nutrient concentration led to a large change in the nutritional balance of the plant. Moreover, the general sufficiency ranges developed were: N (25–48), P (2.6–4.7), K (16–31), Ca (23–36), and Mg (6.7–10 g·kg−1). In conclusion, this work may signify an improvement in the nutritional diagnosis of greenhouse tomatoes in the Mediterranean area, because there is great variability when setting DRIS standards and sufficiency ranges based on phenological stages compared with general DRIS norms and sufficiency ranges. Use of DRIS norms and sufficiency ranges will allow better nutritional adjustment based on the phenological stage of the crop.
Silvia Jiménez, Mónica Pérez, Blanca María Plaza, Roberto Salinas and María Teresa Lao
The study of models for better nutrient uptake estimation can help to improve integrated fertigation management, allowing enhanced water and fertilization use efficiency. The aim of this work was the development of empirical models that permit the prediction of the phosphorus (P) nutritional needs of Dieffenbachia amoena to increase P use efficiency in a recycled system. To achieve this, P uptake was correlated to climate parameters, such as temperature (T), vapor pressure deficit, and global radiation (Rg), and to growth parameters such as leaf area index (LAI). In addition, the influence of the N form supply (NO3 –-N or NH4 +-N) on P uptake was studied. The trial was carried out with Dieffenbachia amoena ‘Tropic Snow’ plants growing in a recycled system with expanded clay as substrate. The crop was placed in an INSOLE buried solar greenhouse, with the plants supplied with equal amounts of N, differing in the percentage of the N form applied: Ta (100 NO3 – : 0 NH4 +), Tb (50 NO3 – : 50 NH4 +) and Tc (0 NO3 – : 100 NH4 +). The N form applied to Dieffenbachia amoena ‘Tropic Snow’ plants affects P and N uptake, but it does not influence K uptake. Nitrogen and P uptake rates are higher in the plants supplied with NH4 + or NO3 – + NH4 + than in the plants provided with NO3 – alone. The supply of a combination 50 NO3 – : 50 NH4 + improves P use efficiency. The study also indicates the possibility of predicting the P uptake rate and P uptake concentration using the proposed models. Phosphorus uptake can be estimated with a model dependent on the LAI in the NO3 –-N treatments and on the LAI and Rg in the NH4 +-N treatments. The P uptake concentration can be calculated with the P uptake, estimated through the previous model, and the experimental water uptake. This parameter would permit the nutritive solutions design, decreasing nutrient losses in open systems.
Pedro García-Caparrós, Alfonso Llanderal, Ahmed El-Tarawy, John Majsztrik and María Teresa Lao
This experiment measured plant growth of a halophyte (species adapted to saline conditions) confetti tree (M aytenus senegalensis) using runoff from kneeholy plants (R uscus aculeatus). Three irrigation treatments were used, a standard nutrient solution or control (T0), runoff water collected from kneeholy plants irrigated with the standard nutrient solution blended 50:50 with tap water (T1), and 100% runoff water collected from kneeholy plants irrigated with the standard nutrient solution (T2), in which the nutrient concentrations were analyzed by high-performance liquid chromatography. Growth, photosynthetic parameters, and mineral composition were measured at the end of the experiment. Electrical conductivity and pH increased with increasing runoff application (decreased blending). Treatment 2 had significantly higher plant height, number of branches, number of leaves, leaf area index, and dry weight. Treatments 1 and 2 had significantly lower root lengths compared with the control. Chlorophyll concentration and green index color in leaves were greater in T2 and T1 than T0. The mineral composition of roots and leaves was affected by irrigation treatment, resulting in an increase of sodium and chloride concentration and a decline of nitrogen and phosphorous concentration compared with the control. The reuse of runoff water was beneficial for growing this commercially important halophytic species in Spain, a consideration that is particularly relevant in locations with water quality, quantity issues, or both.
Pedro García-Caparrós, Olga González-Salmerón, Mónica Pérez-Saiz, Raquel Calatrava, María Teresa Lao, Rosa María Chica and Gumersindo De la Cruz
The cultivation of ornamental plants under different types of shelter and covering materials which reduce light intensity, resulting in morphological and physiological changes, needs to be evaluated before any large-scale use of such types of shelter covers. Baby rubber plants were grown in pots filled with peat under four different shelters and covering materials as follows: MG (multitunnel greenhouse with thermo-reflective aluminised screen), BG (buried solar greenhouse with thermo-reflective aluminised screen), NH (net house covered only with antipest mesh) and NH-AS (net house with antipest mesh and thermo-reflective aluminised screen). At the end of the experiment, the growth parameters and color of leaves, as well as photosynthetic and nutritional parameters, were assessed for each treatment. Baby rubber plants grown under NH-AS showed the highest values for growth parameters. The absence of shading in a net house may result in photoinhibition, reducing the growth and increasing the values of red (R) and blue (B) in leaves, which may be related to the increase of anthocyanin synthesis. The low level of radiation intercepted in the multitunnel and the buried greenhouse increased chlorophyll, N and P leaf concentration, while for K concentration, there was no clear trend and Na and Cl leaf concentration were similar under the different types of shelter. We concluded that the production of baby rubber plants under net house with antipest mesh and thermo-reflective aluminised screen is the best option to maximise the market value of baby rubber plants.