Soil science
O. Toorajzadeh; H. Piri; A. Naserin; M.M. Chari
Abstract
IntroductionAppropriate and practical use of agricultural waste reduce the pressure on the environment. Recently, there has been significant promotion of biochar utilization in agricultural lands. It serves as a valuable source of organic material for enhancing plant growth and as an effective soil amendment ...
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IntroductionAppropriate and practical use of agricultural waste reduce the pressure on the environment. Recently, there has been significant promotion of biochar utilization in agricultural lands. It serves as a valuable source of organic material for enhancing plant growth and as an effective soil amendment to improve soil properties. Due to its unique chemical and physical properties, biochar can be used as a soil conditioner and has many benefits for optimal agricultural and environmental management. Studies have shown that biochar is a useful amendment for improving the physical and chemical properties of soil and effective in maintaining organic matter and soil moisture. Materials and Methods This research was conducted with the aim of investigating the effects of biochar on the physical and chemical properties of soil under conditions of water stress and irrigation using saline water. The experiment was carried out in a factorial based on a completely randomized design with three replications in greenhouse conditions. The treatments include three irrigation water treatments (60, 80, and 100 percent water requirement of the plant, respectively, I1, I2, and I3), three treatments of biochar prepared from northern forest trees at a temperature of 300 degrees Celsius (0, 2, and 4 percent by weight of potting soil, respectively, B1, B2, and B3) and three water quality treatments (with electrical conductivity 1, 4 and 7 dS/m, respectively, S1, S2 and S3). The pots were weighed every other day and at each level of biochar and salinity, the water deficit up to the agricultural moisture level was calculated based on the changes in the pot's weight. After harvesting (in the first half of April 2022), in order to investigate the effect of biochar on the amount of soil nutrients and some physical and chemical parameters of the soil under the conditions of water stress and irrigation water salinity, sampling was done from the soil of each pot. The samples were taken to the laboratory and parameters of apparent and actual specific gravity, acidity and salinity of the soil, percentage of nitrogen, phosphorus and potassium absorbable of the soil were measured in the laboratory. Referring to the yield to irrigation water ratio, water productivity is obtained by the following relation (Payero et al., 2009): WP=Y/IR, where, WP represents water productivity (kg/m3), Y denotes the yield (kg/ha), and IR shows the amount of irrigation water (m3/ha). Analysis of variance for the results obtained from different treatments was conducted using SAS software (SAS 9.1, SAS Institute, Cary, NC, USA). The mean values of the main factors and interactive effects were compared using the Duncan method at the 1% and 5% levels of significance. Results and DiscussionThe results showed that the amount of biochar, irrigation water and water salinity and their mutual effects had a significant effect on the measured parameters at the probability level of one and five percent. Adding 2 and 4 mass percent biochar to the soil increased the amount of phosphorus (35 and 60%, respectively), potassium (57% and 61%), nitrogen (83% and 91%), pH (13% and 13%) and electrical conductivity (EC) (13% and 57%) of the soil. By adding 2% and 4% of biochar to the soil, the actual specific gravity of the soil decreased by 13% and 21%, respectively, and the apparent specific gravity decreased by 11% and 22%, respectively. The actual and apparent specific gravity of the soil decreased by adding biochar to the soil. Decreasing the depth of irrigation water and increasing water salinity increased the amount of phosphorus, potassium, nitrogen, pH and EC of the soil. The amount of irrigation water had no significant effect on the apparent and actual specific gravity, however, the salinity of the irrigation water caused a significant increase in the apparent and actual specific gravity of the soil. Although the addition of biochar to the soil increased the nutrients required by plants in the soil, high amounts of biochar in the soil should be used careful, because the addition of this organic matter to the soil at high levels increased soil EC significantly. Based on the findings derived from the research, the utilization of biochar is recommended as a viable approach for enhancing both the chemical quality and productivity of nutrient-poor and sandy soils.
M.T. Pozan; M.M. Chari; P. Afrasiab
Abstract
Introduction: Infiltration is found to be the most important process that influences uniformity and efficiency of surface irrigation. Prediction of infiltration rate is a prerequisite for estimating the amount of water entering into the soil and its distribution. Since the infiltration properties are ...
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Introduction: Infiltration is found to be the most important process that influences uniformity and efficiency of surface irrigation. Prediction of infiltration rate is a prerequisite for estimating the amount of water entering into the soil and its distribution. Since the infiltration properties are a function of time and space, a relatively large number of field measurements is needed to represent an average of farm conditions (Bautista and Wallender, 1985). In recent years, researchers have proposed methods to reduce the requirement of the regional and field data in order to describe water dynamic in the soil. One of these methods is scaling which at the first was presented by Miller and Miller (1956) and developed on the similar media theory in the soil and water sciences (Miller and Miller, 1956; Sadeghi et al., 2016). According to similar media theory, soils can be similar, provided that different soils can be placed on a reference curve with ratios of a physical characteristic length, called "scaling factor". The objective of the present study was scaling the Philip infiltration equation and analyzing the spatial variability of infiltration characteristics by using minimum field measurements. In this research, a new method was presented for scaling infiltration equation and compared with previous methods scaling including: based on sorptivity (), transmissivity (), the optimum scaling factors () arithmetic, geometric and harmonic.
Materials and Methods: The basic assumption of scaling through this method was “the shape of the infiltration characteristics curve is almost constant despite the variations in the rate and depth of infiltration”. The data required for infiltration scaling were a reference infiltration curve (whose parameters are known) and the depth of water infiltrated within a specified time period in other infiltration curves. In this method, first, equation infiltration parameters are specified for one infiltration curve, called the reference infiltration curve (). If, for other infiltration equations, the depth of water infiltrated is obtained after the specified time(ts) (for example, depth of infiltration water after 4 hours), the scale factor (Fs, dimensionless) is equal to the depth of water infiltrated after ts in the reference infiltration equation to depth of infiltrated water after ts even infiltration equation is as follows:
(1)
where Ii (i=1,2, …,n) is depth of infiltrated water after a given time (ts) for each infiltration families and is depth of infiltrated water after a given time in reference, and and are parameters of reference curve.In order to assess the proposed scaling method, root mean square error (RMSE), mean bias error (MBE) and coefficient of determination (R2) were used for a totally 24 infiltration tests.
Results and Discussion: The parameters of this model (i.e. sorptivity S and transmissivity factor A) showed a wide variation among the study sites. The variation of these parameters showed no significant difference between sorptivity and transmissivity factors. In addition, Talsama et al. (1969) illustrated that there is a weak relationship between sorptivity and saturated hydraulic conductivity. Results showed that scaling achieved using αA was better than that obtained using αS. Mean curve was chosen as reference curve and scale curve was obtained by different methods. The results of statistical analysis showed that the proposed method had the best performance (RMSE=0.006, MBE=0.0019 and R2=0.9996). In order to evaluate the effect of the reference curve selection on the results, the scaled cumulative infiltration curve based on different reference curves (different infiltration equation) was evaluated. The results showed that the selection of the reference infiltration curve is optional and each cumulative infiltration families can be selected as the reference curve. For defining the relationship between and , , αS، αA ، ، ، data, a statistical analysis was performed. According to our results, had the highest correlation with .
Conclusion: In this study, a new method for penetration scaling was presented. In this method, the infiltration curve can be obtained using the minimum information including a reference curve and the depth of infiltrated water after a given time. The selection of the reference infiltration curve is optional and each cumulative infiltration equation can be selected as the reference curve. In the light of the results of this research, it can be concluded that the proposed method in this study is promising to be used for surface irrigation management.
