Fun on my front steps
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On February 28, I took Wana—a fine-bladed putting green type manilagrass—rhizomes and cut to a two node length. Then I planted these cut rhizomes, each with two tiny plants on them, in the center of sand-filled pots.
![The pot fertilized with N, P, and K on 7 March 2020, eight days after planting.](/media/wana_npk_7march_hu732880de8fd3a23b6050001753dbf532_158905_5f86c189471143d22b386739434558f4.webp)
The sand had a starting pH of 6.4 and Mehlich 3 extractable P and K of 17 and 20 mg/kg, respectively.
I had been applying different fertilizers to grasses during establishment at #ATC南店 to demonstrate two things.
That zoysia does respond to N fertilizer when grown from sprigs.
That zoysia grown from sprigs also responds to P and to K when the grass requirement exceeds the soil’s supply.
I used ImageJ to identify the green leaf coverage shown in the chart at the top of this post.
This is the pot fertilized with N + P + K on August 24, 178 days after planting.
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The pots I used were 13.5 cm in diameter. ImageJ starts with the images measured in pixels, and I drew a line and specified that the length was 13.5 cm, so the measurements of green leaf area could be reported in cm2.
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Then I used the color threshold settings to selectively identify the green leaf tissue, which is highlighted in red in the image below. For this set of images, I selected portions of the image with hue from 40 to 100, saturation from 80 to 255, and brightness from 45 to 255.
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After identifying the portions of the image meeting those criteria, I selected those pixels, and got a nice image of the green parts of the grass with yellow borders.
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Then I made a few more clicks to get the simple image of a white background with any of the selected pixels in black.
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This timeline sequence shows a set of nine images from the pot receiving N.
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For more about this, see: