Japanese Journal of Farm Work Research

Show abstractHide abstract

Cover crops have many benefits such as reducing chemical materials, improving soil condition, preventing soil erosion and conservation of soil water. The long-term objective of this study is to assess and estimate cover crop effectiveness such as green manure, weed depression and soil conservation. In this paper, spatial distribution of herb species and herbage mass was estimated.
A ground based hyperspectral imaging, which is useful for acquiring field information, was employed to monitor the cover crop field (bristle oat and hairy vetch). In order to generate the maps of herbage mass, first, plant portions were extracted from hyperspectral images by NDVI (normalized difference vegetation index) threshold. Next, they were classified into plant species using linear discriminant models. Finally, the herbage mass of each plant species was estimated individually using partial least squares regression model, and mapped with gradient colors depending on the estimated value.
The results show that the success rate of plant area extraction was 100% and the success rate of the plant species classification was 78.7%. With regards to the result of the herbage mass estimation, the model that used both plant pixel spectra and plant cover rate as explanatory variables had the highest and most stable accuracy than the other models. The maps of plant species and herbage mass reflected the actual spatial distribution on the field. It was demonstrated that the hyperspectral imaging system developed in this study is a useful technique for monitoring the cover crop.

View full abstract

Download PDF (1234K)

Helianthus cultivated in upland fields converted from rice paddy often suffers from excess moisture injury and is difficult to sow appropriately using sowing machines now possessed by farmers. We conducted sowing tests in the fields of farmers using a simplified ridging method to cope with excess moisture injury and a replaceable sowing roll for helianthus. Furthermore, we studied inter-tillage and topdressing techniques in order to increase the helianthus yield.
Helianthus seeds were sown at intervals of 80cm between ridges and 25cm between plants using the helianthus sowing roll in farm fields. The inter-tillage method with the ridger width reduced to about 20cm so as not to damage helianthus roots achieved a yield exceeding that where there was no weeding or where weeding was performed manually, and it was confirmed that a sufficient increase in yield could be expected if fertilization with nitrogen content of 2.1kg/10a and topdressing with 10kg/10a of nitrogen content are applied.
Furthermore, the plant separation was compared between those fields where the sowing rolls for helianthus supplied to the local farmers' union were used and that in fields where no such rolls were used. A significant difference was found : 59.6% of the plants were appropriately spaced when sowing rolls were used, but only 37.1% of the plants were appropriately spaced when the rolls were not used. Fifteen sowing rolls for helianthus were distributed to local farmers in 2009, the year after the tests.

View full abstract

Register with J-STAGE for free!