Tomato is the most important horticultural crop in the world. The yields for this crop are highest in Southeastern Spain. In this work we studied a commercial variety of tomato, with different soilless culture systems (deep flow technique, nutrient film technique, and the perlite substrate) and three levels of salinity (2.2, 6.3, and 10.2 dS·m −1 ) typical of Southeastern Spain. The irrigation management was carried out for optimizing the water use efficiency. Alterations in the water status of the plants, Cl − and Na + toxicity, and nutritional imbalances altered the vegetative growth and physiology of the plants. The marketable yield was affected by both soilless culture system and salinity. Regarding the soilles culture system, yield decreased in the order: deep flow technique > perlite > nutrient film technique. The salinity treatments improved the fruits quality by increasing the total soluble solids and titratable acidity. Plants cultivated with the nutrient film technique had the highest concentrations of Cl − and Na + and the highest Na + /K + ratio. The concentrations of Cl − and Na + in the plants were not related directly to the yield loss. Therefore, the influence of the toxicity, osmotic effect, and nutritional imbalance seems to have been responsible for the yield loss.

Saline conditions affect nitrogen (N) assimilation of higher plants. To study the effect of salinity and N source on growth and N uptake in wheat (Triticum aestivum L.), plants were grown in a growth chamber under controlled conditions. The nutrient solution contained 4 mM N, applied as either calcium nitrate [Ca(NO 3 ) 2 ] or ammonium sulfate [(NH 4 ) 2 SO 4 ], or a mixture of both, and the salinity treatments consisted in two levels of sodium chloride (NaCl) (1 and 60 mM). Salinity significantly reduced shoot and root growth and the effect of the N source was dependent on which salinity treatment was applied. Salinity decreased the net uptake rate of nitrate (NO 3 ) and NO 3 +ammonium (NH 4 ), but had little effect on NH 4 uptake when this nutrient was applied alone. Dark conditions affected NO 3 uptake to a greater extent than NH 4 uptake. The best N source for wheat growth was a mixture of NO 3 and NH 4 , especially under saline conditions or periods of low irradiance. 793

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Jatropha curcas L. has recently attracted the attention of the international research community due to its potential as a biodiesel crop. In addition, its high resistance to drought and salinity is well known. Under arid and semiarid conditions, boron (B) concentrations in irrigation water can be higher than desired when water from industry, urban areas, or desalination is used. However, the growth and physiological responses of J. curcas plants to B excess in the irrigation water are unknown. Therefore, a greenhouse experiment was conducted to study the effects of B excess in the nutrient solution (0.25, 2, 4.5, and 7 mg L–1 B, applied as H3BO3) on plant growth, mineral concentration in the different plant tissues, photosynthesis, water relations, chlorophyll fluorescence, chlorophyll concentration (as SPAD values), and composition of carbohydrates. Plant growth decreased with increasing B concentration in the nutrient solution; growth reduction was higher for roots than for leaves or stems. The B concentration increased in all plant tissues, in the following order: leaf > root > stem. These data indicate that the roots of J. curcas are more sensitive to B toxicity than the leaves and that B has restricted mobility inside these plants, accumulating mainly in the basal and middle leaves via the transpiration stream. Increasing B concentration in leaves decreased the ACO2 and the stomatal conductance, but the leaf water parameters were not affected. The data for chlorophyll concentration and chlorophyll fluorescence indicated that nonstomatal factors were involved in the ACO2 decline, whereas decreases in the parameters of PSII photochemistry due to B toxicity suggest that there was structural damage in chloroplasts. There was also a general tendency for a decrease in nonstructural carbohydrates in all plant tissues, possibly due to the decline in ACO2. With excess B, the concentrations of K and Mg increased in leaves due to a decrease in the growth, while a typical antagonistic effect between B and P was evident from the P concentration decrease in leaves. In summary, J. curcas should be considered a B‐sensitive plant, as a leaf B concentration of 1.2 mg (g dw)–1 caused a growth decline of approximately 30%.

Sufficient nutrient application is one of the most important factors in producing quality citrus fruits. One of the main guides in planning citrus fertilizer programs is by directly monitoring the plant nutrient content. However, this requires analysis of a large number of leaf samples using expensive and time-consuming chemical techniques. Over the last 5 years, it has been demonstrated that it is possible to quantitatively estimate certain nutritional elements in citrus leaves by using the spectral reflectance values, obtained by using near infrared reflectance spectroscopy (NIRS). This technique is rapid, non-destructive, cost-effective and environmentally friendly. Therefore, the estimation of macro and micronutrients in citrus leaves by this method would be beneficial in identifying the mineral status of the trees. However, to be used effectively NIRS must be evaluated against the standard techniques across different cultivars. In this study, NIRS spectral analysis, and subsequent nutrient estimations for N, K, Ca, Mg, B, Fe, Cu, Mn, and Zn concentration, were performed using 217 leaf samples from different citrus trees species. Partial least square regression and different pre-processing signal treatments were used to generate the best estimation against the current best practice techniques. It was verified a high proficiency in the estimation of N (Rv = 0.99) and Ca (Rv = 0.98) as well as achieving acceptable estimation for K, Mg, Fe, and Zn. However, no successful calibrations were obtained for the estimation of B, Cu, and Mn.

This chapter provides a review on the state of art of the use of the visible near-infrared (vis-NIR) spectroscopy technique to determine mineral nutrients, organic compounds, and other physical and chemical characteristics in samples from agricultural systemssuch as plant tissues, soils, fruits, cocomposted sewage sludge and wastes, cereals, and forage and silage. Currently, all this information is needed to be able to carry out the appropriate fertilization of crops, to handle agricultural soils, determine the organoleptic characteristics of fruit and vegetable products, discover the characteristics of the various substrates obtained in composting processes, and characterize byproducts from the industrial sector. All this needs a large number of samples that must be analyzed; this is a time-consuming work, leading to high economic costs and, obviously, having a negative environmental impact owing to the production of noxious chemicals during the analyses. Therefore, the development of a fast, environmentally friendly, and cheaper method of analysis like vis-NIR is highly desirable. Our intention here is to introduce the main fundamentals of infrared reflectance spectroscopy, and to show that procedures like calibration and validation of data from vis-NIR spectra must be performed, and describe the parameters most commonly measured in the agricultural sector.

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