Quantitative and Qualitative Responses of Hydroponic Tomato Production to Different Levels of Salinity

From economic and nutritional points of view,tomato is,historically,considered one of the most important crops.Without significant yield reduction,most commercial cultivars of tomato crops are sensitive to moderate levels of salinity.However,high levels of salt stress can negatively affect the yield and quality of tomato fruits.Therefore,this study was conducted to evaluate the yield and fruit quality of three tomato cultivars(Forester,Ghandowra-F1,and Feisty-Red)cultivated hydroponically,under three different levels of nutrient solution salinity.Evaluation of tomato fruits was performed based on quantity(number and weight of fruits,and total fruit yield),physical quality(color andfirmness),and chemical quality(refractometric index“Brix”,pH,EC,K^(+),Na^(+),and NO_(3)-).Experiments were conducted using three salinity levels of the nutrient solution with electrical conductivity values(dSm^(-1))of 2.5(control),6.0,and 9.5.Results showed that the studied tomato cultivars were significantly influenced by high salinity(9.5 dSm^(-1))in comparison to the low(2.5 dSm^(-1))and medium(6.0 dSm^(-1))levels of salinity.On average,the highest fruit weight per plant of 1944.84 g and total fruit yield of 4.42 kgm^(-2) were observed at the low salinity level;however,no significant differences were obtained in the two yield factors(single fruit weight and total fruit yield)for the low and medium salinity levels.On the other hand,a significant reduction in tomato yield(31%)was associated with the high salinity level compared to the yield at low and medium salinity levels.Results of physical quality parameters showed highly significant differences among all salinity levels.On average,the maximum value of color change(1.72)was associated with the medium salinity level,and the maximum value offirmness(9.61 Ncm^(-1))was recorded at the high salinity level.Salinity levels and tomato cultivars introduced significant differences in chemical quality parameters;however,no significant differences in these parameters were attributed to the low and medium salinity levels.The maximum value of pH was recorded for the combination of medium salinity and Forester cultivar.Moreover,the maximum values of Brix,EC,K^(+),Na^(+),and NO_(3)^(-) were recorded for the Ghandowra-F1 cultivar at the high salinity level.Unlike the Feisty-Red,the performance of the Forester and Ghandowra-F1 cultivars was found to be acceptable at the tested medium salinity level(6.0 dSm^(-1)).

Impact of soil compaction on the engineering properties of potato tubers

A study on a 30 hm2 field was conducted to assess the variability in soil compaction and to investigate its effect on the engineering properties of potato tubers in terms of tuber shape and key dimensions(length,width and thickness)and resistance to penetration,rupture and shear forces.Three soil compaction levels were spatially correlated with the engineering properties of potato tubers through linear regression and ANOVA test.The three compaction levels included a low level(C1)ranging between 1.2-1.9 MPa,a medium level(C2)with compaction levels between 2.0-2.3 MPa and a high level(C3)ranging between 2.4-2.9 MPa.Results revealed that there were no significant changes in the key tuber dimensions corresponding to the variability in soil compaction.However,inverse linear relationships were observed between soil compaction and the key tuber dimensions with R2 values of 77%,97%and 96%for length,width and thickness,respectively.Similarly,the soil compaction was shown to have no effect on the tuber resistance to compression and shear force.In contrast,the tuber resistance to penetration was significantly affected by soil compaction(p>F=0.0012).

Determining soil organic carbon concentration in agricultural fields using a handheld spectroradiometer:Implication for soil fertility measurement

The soil organic carbon(SOC)plays a vital role in plant growth and development,and therefore is considered as one of the most important indicators of soil quality.This study was carried out in the central region of Saudi Arabia to explore the potential of spectroscopy in determining the SOC concentration in low-fertility soils.Spectral reflectance data were collected,under the controlled laboratory conditions on 39 air-dried 2.0 mm sieved soil samples,using a handheld spectroradiometer of a wavelength range between 350 nm and 2500 nm in the direct contact probe mode.The concentration of the SOC was determined using the Walkley and Black(W&B)and the UV-VIS spectrophotometric methods.The increase in the concentration of SOC was associated with a decrease in the corresponding spectral reflectance.Regression analysis showed linear relationships with high significant correlation between the spectral reflectance and the SOC measured by both the UV-VIS(Model-1:R^(2)=0.46,p=0.00015 and RMSE=6.6 g/kg)and the W&B(Model-2:R^(2)=0.48,p=8.92E-05 and RMSE=2.8 g/kg)methods.For these models,two wavebands with wavelengths of 2167 nm(Model-1)and 1359 nm(Model-2)were identified as the most sensitive bands to the SOC concentration.The cross-validation confirmed the validity of Model-1 with R^(2),p and RMSE values of 0.50,0.0099 and 6.6 g/kg,respectively.The validation results of the Model-2 showed values of R^(2),p and RMSE of 0.72,0.00023 and 4.0 g/kg,respectively.Results of this study revealed the possibility and the potential of using the spectral reflectance technique in predicting the concentration of SOC.