Tamotsu Funakoshi

Evaluation of water and nutrient deficiency for fertigation using NIR image

For an application of the remote sensing technique on agriculture, an image taken from an artificial satellite is used widely. The image would not be useful in a field-scale precision agriculture due to the limited power of resolution. For the purpose that remote sensing is adopted in a field-scale precision agriculture, the resolution should be increased or an image taken by another technique should be used. In this study, an image of plants was taken by using a digital camera with a band-pass filter. The image was analyzed related with soil moisture and nutrient condition. Broccoli was planted in nine pots different in soil moisture and nutrient condition. An image of plants in a pot was taken by using a digital camera with a band-pass filter (visible range [550, 650, 680, 750nm], NIR range [780, 800nm]) and captured into a personal computer. The digital images were analyzed with computer software to find the reflection characteristics of visible and near infrared rays depending on deficiencies in soil moisture and nutrient. Frequency distribution of brightness was used to evaluate an influence of soil moisture and nutrient deficit from images. The influence due to soil moisture deficit was significantly found in near infrared images (780 and 800 nm) while the difference affected by the nutrient deficit was difficult to be detected with the proposed procedure.

The desalinization effects by the cleaning crop with Na+ absorption ability

This paper includes discussions on the improvement of salinity problems at newly reclaimed fields from the sea. The object of this research is to quantify the amount of desalinization by the plant’s absorption abilities. A big reclamation project for agricultural production is going on at Isahaya Bay, Nagasaki prefecture in Japan. To improve salinity problems at initial stage of reclamation, desalinization by the plants were investigated. First, the native halophyte plants such as Shichimensou (Suaeda japonica Makno), Hamamatsuna (Suaeda maritima LINN. Dumort), Shiokugu (Carex scabrifolia Steud.) and Yoshi (Phragmites communis Trin.) living around the reclaimed land in Japan were investigated on Na+ and K+ absorption potentials. Second, the crop’s Na+ absorption abilities were investigated. Spinach, turnip, radish and some kinds of grass were grown up by some concentrations of saline irrigation water and Na+ absorptions were examined. Finally, in order to examine the effect on the Na+ cleaning, the above plants were grown in the reclaimed land soil. The desalinization by irrigation such as the leaching is effective and easy if we could use much water. But the absorption of Na+ by the crops can remove the salinity from the root area certainly though the amount of adsorption is not so much.

Effects of Plastic-Film Mulching on Discharge Rate of NO3-N from Chemical Fertilizer Inputted Fields

The lysimeter experiments were conducted to examine the effects of plastic-film mulching on the discharge rate of nitrate nitrogen (NO3-N) from the chemical fertilizer inputted fields. Two lysimeters filled with sandy loam were kept in the different mulching conditions. One of which was mulched partially only the part of ridge and another one was mulched fully including the furrow with black plastic film. Chemical fertilizer was plowed into the soil equally to the two lysimeters before the application of mulch. After transplanting broccoli, the amount of subsurface drainage discharge and the NO3-N concentrations of drainage water were measured everyday. The large rate of NO3-N discharge occurred mainly during a heavy rainfall for all treatments. The effect of mulching on the reduction of NO3-N discharge rate was higher for the sole-mulch treatment. This result showed that some types of mulching would be effective for an appropriate fertilizer management for which the amount of fertilizer applied will be reduced.

Irrigation Scheduling to Control the Capillary Saltish Water Movement at Crop Fields Newly Reclaimed from the Sea

A substantial big reclamation project for agricultural production is currently taking place at Isahaya Bay, Nagasaki prefecture located in the southwest of Japan. To improve the soil physical properties, a large amount of gypsum was added to the original heavy clay soil. Also, leaching was conducted for several months using a sprinkler. Following these treatments, crops were planted, but saltish clay soils near the drainage pipes buried below 70cm from the soil surface are still probable to damage the crop growth. In this report, some trials to control the salt damages in crop production are introduced. First, the soil’s physical improvement processes from the first stage of reclamation to the present stage are introduced. Second, experimental and numerical studies on the soil water movement and salt movement in the cropped fields are stated. Third, the optimal irrigation scheduling to suppress the upward flow of saltish water in the draught condition is discussed.