Yield and fruit characteristics of the central-leader-trained Satsuma mandarin ‘Ishiji’ multi-cultivated for 11 years after planting

For central-leader-type “Ishiji” Satsuma mandarin trees, the ground is covered with a moisture-permeable and light-reflecting sheet from the 2^nd week after blooming until the harvest time. The trees are cultivated with a multi-cultivation system using water irrigation adjusted to the growth stage. The impact on Satsuma mandarin fruit yields and quality have been studied for 11 years since planting. The results showed that the yield reached the field production target of 2.8 t/10 a in the third year after planting, in comparison with an open center trained trees, and the trees were able to stably produce fruit with equal to or more than 12 sugar-acid ratio （ratio of soluble solid to titratable acidity）, with high prices and high rate of S-M-L grading ranks. Compared to open center trained trees, the central-leader-trained trees with multi- cultivation were evaluated as having high quality and high yields with early fruiting.

Also, a period of long research presented an issue of water control limitation due to root zone expansion.

There has been an increased interest and potential demand for agricultural robots in recent years to help reduce labor and operation costs. Therefore, the performance of a robotic lawnmower for weed management in a pear (Pyrus pyrifolia) orchard was investigated at the Center for International Field Agriculture Research & Education (CIFARE) of Ibaraki University, Japan, in 2018–2019. It was found that the average weed height was lower in the robotic lawnmower-managed plot (35–87 mm) than that in the riding mower-managed plot (approximately 15–281 mm) throughout the cropping period (from flowering to harvesting). The robotic lawnmower was superior to the riding mower, brush cutter, and walk-behind mower in terms of energy consumption (6 vs. 13, 56, and 18 kWh 1000 m^–2 month^–1), costs (133 vs. 206, 1122, and 277 JPY 1000 m^–2 month^–1), CO₂ emissions (3 vs. 3.4, 14, and 4.5 kg 1000 m^–2 month^–1), and labor requirements (28 vs. 40, 604, and 62 min 1000 m^–2 month^–1). Because the robotic lawnmower can be used without manual operation, it reduces the human workload (in terms of the increased ratio of the heart rate (IRHR)) in comparison with operating a riding mower (IRHR: 1.2), brush cutter (IRHR: 1.5), and walk-behind mower (IRHR: 1.4). Therefore, given that the average age of the population is higher in Japan than elsewhere in the world and this trend is continuing to increase, the use of robotic lawnmowers can be useful for weed management in orchards.

There is an urgent need in Japan for a small mowing robot for the task of mowing steep slopes, which is hard work and unsafe. The objectives of this study were to develop such a mower and to verify its working characteristics through motion analysis. Two types of wire-towed mowers were developed: one towed by hand and one towed by electric motor. The ability of each mower to mow on steep slopes was compared with that of a commercial slope mower. Working capacity was obtained from working area could be mowed divided by working time determined through motion analysis. The working capacities were calculated from motion analysis during mowing to be 2.4 m²/min for the wire-towed mower, 1.3 m²/min for the motor-towed mower, and 5.6 m²/min for the slope mower; and the analyzed working area were 22 m², 16 m², 11 m², respectively. It was quicker to load and unload both towing mowers on the bed of a pickup truck than to load and unload the slope mower. This result shows that the two towing mowers are suited to small-scale use on steep slopes, since they can be transported easily. The wire-towed mower could be useful on long slopes with a range of length of at least 5 m on account of its 8-m-long tow wires, which would confer a high total working capacity.

As a method of collecting farm work data, the Global Navigation Satellite System （GNSS） position information can be used to record the working activities of agricultural machinery in fields. Since it is difficult to identify and quantify the detailed contents of a machine’s working activity, a combined use of GNSS and an onboard digital tachograph system or drive recorder may assist in classifying and analyzing a machine’s working activity in each field in detail. In this article, the authors present case studies on the use of the GNSS and an onboard digital tachograph system mounted on several sugarcane harvesters, and describe the detailed approaches to data collection and classification for sugarcane harvesting work.