JWSS - Journal of Water and Soil Science

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The present research was intended to alleviate the problems and costs of deep tilling in sugarcane production in Mian-Ab sugarcane farms located in Khuzestan province, Iran. The main objective was to investigate the feasibility of subsoiling operations with bentleg subsoiler (BLS) equipped with shallow tines, a combination expected to increase the critical depth resulting in less power consumption and improved soil physical conditions. Six treatments arranged in a completely randomized block design were used to measure the draft force (except for the bulldozer mounted rippers), disturbed soil cross-sectional area and penetration resistance. The treatments included (1) subsoiling with rippers mounted on bulldozer, (2) BLS without attachment, (3), and (4) BLS equipped with single tine at working depths of ½ and ⅓ of target depth, (5) and (6) BLS equipped with two tines at ½ and ⅓ target depth. The experiment was replicated three times. The results indicated that BLS without attachment had the highest draft requirement as compared with other BLS treatments with shallow tines. In general, tine attachment resulted in less draft mainly due to displacement of critical depth to lower soil zones. Increasing the number and depth of shallow tines resulted in less draft force. The BLS equipped with two tines working at ½ target depth exhibited minimum drawbar power. The inclusion of shallow tines resulted in 21% reduction in drawbar power requirement as compared to BLS without tine attachment. The cross-sectional area of the soil tilled by ripper was minimum. Furthermore, the tilled area was not uniform and subsequent subsoiling operations were needed. The average soil cross-sectional area per unit width was improved by BLS treatments by a factor of 2.3 as compared with that of ripper. The highest cone index was obtained in plots tilled by ripper the BLS reduced this index in a significant manner. The soil worked with subsoiler equipped with tines exhibited the least resistance. The range of wheel slippage for BLS treatments was 12-16% which lies in the upper end of the recommended range for optimum traction efficiency. The proposed idea proved prominent in subsoiling fine textured compact soils.

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In the present study Hydrus-1D software was used to simulate electrical conductivity, pH and sodium, potassium, calcium, magnesium, chloride and sulfate ions. Field experiments were performed at the Sugarcane Research Center located in south of Ahvaz on sugarcane varieties CP48-103 with four water treatments (one treatment was Karun river water and three treatments were diluted drainage water) and three replications. The samples were collected from 0-30, 30-60 and 60-90 cm soil depth before irrigation and electrical conductivity and anions and cations of soil were measured in the laboratory. Sensitivity analysis and calibration were first performed with the aim of verifying the Hydrus-1D software. The sensitivity analysis indicated that the software had maximum sensitivity to the saturated volumetric water content. Minimum sensitivity was for the inverse of the air-entry suction, tortuosity parameter, residual volumetric water contents and moderate sensitivity was for hydraulic conductivity at natural saturation. Also, the software did not show any sensitivity to empirical parameter related to the pore size distribution that is reflected in the slope of water retention curve. In calibration stage the amount of hydraulic conductivity at natural saturation, residual volumetric water contents, saturation volumetric water contents, the inverse of the air-entry suction, empirical parameter related to the pore size distribution and tortuosity were obtained as 18 (cm/day), 0.04 (cm³/cm³), 0.63(cm³/cm³), 0.012 (cm^-1), 1.2 and 0.6 respectively. The results showed that the coefficient of determination of all parameters was more than 0.85 which confirms the appropriate capabilities of the model in simulation of electrical conductivity, pH, anions and cations. In the modeling carried out the amount of NRMSE was between 11 and 18 percent which indicates good performance of the model. The Nash-Sutcliffe efficiency criterion was obtained 0.72 to 0.8 that indicates a good match of the model with reality. The coefficient of residual mass in this paper was positive for electrical conductivity, pH and sodium, potassium, calcium, magnesium and negative for chloride and sulfate. The positive and negative coefficient of the residual mass shows less and over estimation of the model.