Koichiro Fukami

Growth and Yield Responses of Two Soybean Cultivars Grown under Controlled Groundwater Level in Southwestern Japan

Abstract One of the limiting factors of soybean yield in southwestern Japan is soil moisture fluctuation from flooding to drought. The Farm-Oriented Enhancing Aquatic System (FOEAS), which consists of underdrain and sub-irrigation systems and can keep groundwater levels stable, was developed in 2005 to solve this problem. To obtain basic information on soybean cultivation using the FOEAS in southwestern Japan, we examined the growth response to groundwater level by using two cultivars (cv. Fukuyutaka and Sachiyutaka) in 2008 and 2010. Plant growth, yield, yield components and seed components (protein and oil contents) were analyzed. We also studied the effect of sowing time (normal or late). The groundwater level was controlled at depths of 20 and 35 cm or not treated (NT) as a control. The groundwater level could be kept at the target depths (20 and 35 cm) by FOEAS throughout the experimental period, but that in the NT plot fluctuated greatly. The growth and yield of Sachiyutaka might be increased by FOEAS, especially in late sowing, but the yield of normal sown Sachiyutaka was decreased in the 20-cm plot in 2010. Yield of late-sown Fukuyutaka tended to be decreased in the 20-cm plot. These results suggest that (1) the optimum groundwater level for yield of Sachiyutaka is between 20 and 35 cm, regardless of sowing time and (2) the groundwater level should not be kept at 20 cm for late-sown Fukuyutaka. Further studies are needed to determine the optimum groundwater level for each cultivar.

Effects of early planting and cultivars on the yield and agronomic traits of soybeans grown in southwestern Japan

Abstract Early planting contributed to increased soybean yields in the U.S. Because a double-cropping system dominates in southwestern Japan, early planting is not performed; it is thus unclear how much the yield potential could be increased by early planting. To address this question, we planted seven U.S. and five Japanese cultivars on around 20 May (early planting), measured the agronomic traits, including yield, yield components, and oil and protein contents, and compared these traits with those of the same cultivars planted on around 20 July (normal planting). In the early planting, the yields of the U.S. cultivars were 322–453 g m−2, whereas the highest yield among the Japanese cultivars was only 315 g m−2, which is significantly lower than those of the top five U.S. cultivars, indicating the adaptability of U.S. cultivars to early planting. The increases in yield obtained with early planting were 99–199 g m−2 and −26–144 g m−2 for the U.S. and Japanese cultivars, respectively. The yield obtained by early planting was positively correlated with the pods m−2, seeds pod−1, and oil contents, but negatively correlated with the sterile pod rate, 100 seed weight and protein content. In the early planting, the U.S. cultivars had greater pods m−2, seeds pod−1 and oil content and less sterile pod rate, 100-seed weight, and protein content than the Japanese cultivars. These results suggest that early planting can increase the yield in southwestern Japan, if cultivars with agronomic traits observed in the U.S. cultivars of this study are grown.

Root Growth of Two Soybean [Glycine max (L.) Merr.] Cultivars Grown under Different Groundwater Level Conditions

Abstract Soybean yield is low in the fields with a low groundwater level during summer due to drought stress. By raising the groundwater level using Farm-Oriented Enhancing Aquatic System (FOEAS) the yield of soybean cultivar Sachiyutaka can be increased, but not that of Fukuyutaka. Here, we examined the effect of the groundwater level on root growth and its dynamics in these two cultivars. Three of the four experiments demonstrated that root elongation ceased just below groundwater level in both cultivars. However, when the groundwater level was kept at 35 cm or deeper, the root growth at an early growth stage was more vigorous at a deeper layer in Fukuyutaka than in Sachiyutaka, but at the mid-growth stage root growth in Sachiyutaka became similar to or exceeded that of Fukuyutaka. These results indicated that the optimum control technique for the groundwater level differed with the cultivar. The groundwater level for Sachiyutaka should be kept relatively high at an early growth stage. Further studies will be needed to clarify the optimum control technique for maximizing the yield of Fukuyutaka that have a fast root growth at an early growth stage.

Effect of plant density on growth and yield of new soybean genotypes grown under early planting condition in southwestern Japan

Abstract Soybeans planted in early to mid-June (early) are less affected by rainfall during rainy season than those conventionally planted in early to mid-July in southwestern Japan. Also, narrow row cultivation is expected to increase soybean yield and save labor for inter-tillage and ridging. Field experiments were performed in 2014 and 2015 to test the effect of plant density (high, middle, and low) under early planting condition on growth, yield, and several agronomical traits of Sachiyutaka A1 and three new genotypes (Sakukei 155, Kanto 127 and Shikoku 15). Early planting was performed in mid- to late June, even though rainy season started in early June. Higher plant densities produced 13% greater yield than low plant density through an increase in biomass accumulation, especially at R5. Among yield components, only pods m−2 was significantly and positively correlated with yield, indicating that an increase in pods m−2 led to a greater yield with higher plant densities. The yields of Sachiyutaka A1 were relatively stable for two years, but the lodging resistance should be further improved. Shikoku 15 had greater yield potential and lodging resistance, but its resistance to damping-off disease should be improved. Sakukei 155 with medium plant density produced relatively high and stable yield with less lodging. Although the yield of Kanto 127 fluctuated between experimental years, this genotype showed higher yield potential in higher plant densities with less lodging in 2015. Thus, Sakukei 155 and Kanto 127 with high or medium density may be suitable for early planting in this region.

Mathematical Model and Solution for Land-Use Crop Planning with Cooperative Work

Most farm work planning for land-use crops such as sugarcane belongs to flexible flow shop scheduling if neglecting cooperative work and other specific constraints. Because the conventional approaches to the flexible flow shop scheduling cannot formulate these specific constraints, we require a new approach for solving land-use crop planning problems that considers cooperative work. This paper describes a detailed mathematical model and a hybrid algorithm for solving the model, in which many practical constraints are taken into account, including cooperative work, optimum time windows, waiting time between operations, and moving time. The hybrid algorithm uses meta-heuristic simulated annealing and a mixed integer programming solver in Gurobi. In order to obtain good schedules in a reasonable time, we adopt a strategy of fixing partial work sequences in the simulated annealing procedure and optimizing the partial schedule using the solver. The results of the evaluation computation show that the proposed model is operative for the practical constraints, and that the hybrid algorithm is adaptable to scheduling computation. The strategy of fixing partial work sequences is applicable to reducing computation times for large-sized land-use crop planning problems.

Prediction of Wheel Traveling Performance Using Ground Contact Stress Models

In order to analyze the traveling performance of a wheel from the distribution of ground contact stresses, Gaussian functions were applied to the modeling of the respective normal and tangential stresses. The two functions were superposed to fit the distorted shape of the normal stress curve at a high slip ratio. The previous model over-predicted the tangential stress at low slippage and modifications in the proposed model were developed through consideration of relative slip at the contact surface. Unknown coefficients in the model can be expressed by linear and cubic functions of wheel sinkage. Based on the results, the stress model was extended to apply to arbitrary sinkage. The new model fitted very well to measured tangential and normal stresses. Drawbar pull, torque and rolling resistance could also be estimated with high accuracy.