We conducted a trial using ground cover plants as a labor-saving method for managing levees between rice paddies in Tochigi Prefecture, Japan. The four ground cover species tested were phlox (Phlox subulate L.), frogfruit (Lippia nodiflora), centipede grass (Eremochloa ophiuroides), and pennyroyal (Mentha pulegium). Seedlings were prepared, planted on a levee between rice paddies, and continuously monitored for 2 years. After field planting, the growth, change in ground coverage, regrowth after overwintering, and weed suppression of the four ground cover species were compared to identify ground cover plants suitable for levee management. Frogfruit and pennyroyal, which exhibited the fastest growth in the first year after field planting, also reached full coverage in the shortest amount of time and showed superior weed suppression compared with the two other species. In the second year after overwintering, centipede grass, which grew slowly in the first year, exhibited fast growth, rapid coverage, and superior weed suppression similar to frogfruit.

The Food and Agriculture Organization of the United Nations’ Sustainability Assessment of Food and Agriculture Systems (SAFA) is a tool covering multiple fields, including the governance, the society, the economy, and the environment to assess the sustainability of agriculture. This system has an important feature, integrated evaluation with many indicators. In the present study, the evaluation of the sustainability of fields, Ibaraki University, with combined 3 types of tillage (plowing, rotary tillage, and no tillage) and 3 types of cover crop (fallow, rye, and hairy vetch) in the environmental dimension was performed using modified SAFA rating method. The objective numerical data in GHG (Greenhouse Gas) absorbance, soil properties and fuel consumption were used. Sustainability ranking was determined with SAFA method through data normalization. On comparison of the nine total combinations, no-tillage with rye as the cover crop had the highest rating and plowing with fallow had the lowest ranking. It revealed that no-tillage with use of cover crops would be the best management method to conserve the field environment.

This report examined the working properties and machine introduction conditions of the paddy iron-coated direct seeding cultivation system under conditions where the field scale and working systems were different. Two field scales; 1.5 ha and 0.3 ha, were compared by field size, and three working systems; a） included plowing, harrowing and leveling, b） excluding plowing, harrowing and leveling in direct seeding cultivation and c） the transplanting working system excluding plowing, harrowing and leveling. The operating costs of agricultural machines were calculated by measuring the effective field capacity and fuel consumption for each test plot. The effective field capacity of the whole process from soil preparation to harvesting was 2.3 ha h^–1 higher for the 1.5-ha field than for the 0.3-ha field, with the calorific value being 2241 MJ ha^–1 lower. With respect to working systems, the effective field capacity （calorific value） for the working system that included plowing, harrowing and leveling in 0.3-ha field was 0.8 ha h^–1 （3934 MJ ha^–1） higher than the working system that did not include these operations and 0.9 ha h^–1 （3722 MJ ha^–1） higher than the transplanting working system. The operating cost in the paddy direct-seeding work system in the 1.5-ha field was equivalent to the standard operation cost for conventional working systems in Shonai area. The operational cost, based on the findings if general-purpose tractors, plows, harrow, and rotary in 0.3 ha upland fields, for direct-seeding work systems and transplant work systems which exclude plowing, leveling, and leveling, can be below that of operation cost. Therefore, if plowing, harrowing, and leveling are included in the 0.3-ha field, these works should be conducted in the autumn season to increase feasible coverage.

We developed a tuber planter that planted and pushed down small sweetpotato tubers by modifying a semi-automatic vegetable transplanter. The mechanism used to plant and push down the tubers follows. The beak-shaped hopper, containing small sweetpotato tubers, descended and penetrated the ridge. When the beak-shaped hopper opened, the plastic plate in the hopper pushed down and released a tuber. We investigated the effect of planting small sweetpotato tubers using this planter on the yield, stand establishment, bird damage, planting depth, and planting angle. The variation of planting angle and the variation of planting depth were lower for the tuber planter than the vegetable transplanter. The tuber planter was able to plant tubers in a nearly horizontal state. The percentage of bird damage tended to decrease as the planting depth increased. The germination percentage （obtained by dividing the number of germinations by the total number of tubers planted minus the number of bird damage） tended to increase as the average or median of planting depth decreased. The percentage of planted tubers enlargememt tended to increase as the planting depth decreased. The yield per unit area in 2018 was the same for the tuber planter as for hand planting, and greater than for the vegetable planter; however, in 2019 it was the same for the three planting methods. The working hours of the tuber planter was about 1.9 hours per 10 ares, which was decreased about 14 hours per 10 ares compared to hand transplanting.

We conducted a serial field experiment study with row seeding cultivation (RSC) of palisade grass (a nematode-suppressive forage crop) and machine intertillage for weed and nematode control. We aimed to examine RSC of palisade grass under several inter-row spacing (IRS) conditions using intertillage with a view to the use of palisade grass in crop rotation for nematode control on cultivating farms, as well as use of the shoots as forage on regional livestock farms. In Field Experiment 1, RSC with IRSs of 60, 80, and 100 cm showed no significant differences in yield between these IRS conditions. In Field Experiment 2 and Field Experiment 3, IRSs were set at 80 and 120 cm, and plant-parasitic nematode densities were suppressed to suitably low levels in Field Experiment 2. There was no significant difference in yield between the 80 and 120 cm IRS treatments after three months of cultivation in Field Experiment 3. Comparing RSC with a 120 cm IRS with broadcast seeding cultivation (BSC) in Field Experiment 4, the yield from RSC tended to be higher than that from BSC. Weed dry weight was higher in the BSC system than in the RSC system after two rounds of intertillage in RSC until 127 days after sowing. In Field Experiment 5, an RSC treatment with a 120 cm IRS was constructed in a farmer’s field, and the root-knot nematode density was clearly suppressed on the palisade grass yield survey date. We concluded that wide-row seeding cultivation with an IRS of 120 cm is one of the practical choices for the combined utilization of palisade grass for forage production and as a nematode-suppressive crop.