Effect of Inter-row Tillage on Yield and Water Productivity of Sugar Beet

Introduction: Soil compaction reduces soil porosity and thus, increases the resistance and bulk density of the soil. These changes limit water and air movement and root penetration in the soil and ultimately, they may reduce the seed germination and the crop yield. For planting sugar beets, tractors and equipment need to move several times on the ground, which is a factor in soil re-compaction and the loss of the effects of previous tillage. Therefore, if, after planting, inter-row tillage was done, it can have a positive effect on reducing the bulk density of the soil and it may even increase yield.  Materials and Methods: An experiment was conducted to determine the effect of inter-row tillage on the sugar beet yield and its quality and water use efficiency during two years cropping period (2016-2017) in Ekbatan Research Station, Hamadan with loam texture soil. A strip plot experiment with eight treatments and three replications was used. Irrigation regimes consist of 100% of sugar beet water requirement (I1) and 75% of sugar beet water requirement (I2) were considered as main plots. Inter-row tillage operations consist of  combined cultivator equipped with chisel and crescent blades to 20-25 cm soil depth (T1), a simple cultivator equipped with crescent blades (T2), crescent cultivator + inter-row subsoiling to 30-35 cm soil depth (T3), combined cultivator equipped with rotary and sweep blades to 20-25 cm soil depth were considered (T4 ) as sub-plots. During the experiment, some physical properties of soil including bulk density and soil cone index were measured. At the end of the growth season, the root yield and yield of white sugar were measured and analyzed statistically. Results and Discussion: The results showed that the effect of inter-row tillage methods on the soil bulk density and soil cone index was significant. The T3 treatment (crescent cultivator + inter-row subsoiling to 30-35 cm soil depth) had the highest effect on reducing the cone index and bulk density of soil, but the lowest root yield was obtained.  Due to the low spacing of rows (50 cm) in the sugar beet cultivation, as well as the structure of the subsoiler and its depth, it is possible that the subsoiling caused the moving of the roots and minor damage to it. The effects of irrigation and inter-row tillage and their interactions on quantitative and qualitative yield of sugar beet were not significant. The results of analysis of variance of treatment effect on the water use efficiency showed that the effect of inter-row tillage on the water use efficiency was not significant. The effect of water requirement on the water use efficiency on the basis of sugar and white sugar performance was significant at 5% probability level. The treatment of 75% of water requirement increased the efficiency of water use based on the root yield, sugar yield and white sugar yield by 4%, 14% and 7%, respectively. Therefore, with the goal of reducing water consumption and not significantly reducing the yield, after plant establishment, it can reduce water use by about 25%. Conclusions: The effect of inter-row tillage on the cone index and bulk density of soil was significant and subsoiling treatment caused a further reduction of these two indices compared to the other inter-row tillage methods. The effect of inter-row tillage and water requirement on root and sugar yields was not significant. According to the results, after planting completely establishment, the water use can be reduced by about 25% (this decrease in the total length of sugar beet growing was about 15%).