Prediction method for changes in leaf number stages of paddy weeds using temperature before and after puddling and a herbicide control index
2015
Toritsuka, S. | Nakai, J. | Shibahara, F.
We analyzed the relationship between the accumulated value of the average temperature after puddling and maximum leaf number stage of Echinochloa oryzoides and Schoenoplectus juncoides each year and every puddling period. These relationships were indicated using a linear regression formula, and an extremely high correlation was recognized. However, the growth rate and emergence of E. oryzoides and S. juncoides was different each year and every puddling period. Therefore, it was necessary to clarify a method of estimating the maximum leaf number stage that corrected these differences. A multiple regression analysis that assumed the accumulated value of the average temperatures after puddling and the daily effective value of temperature before puddling was conducted for E. oryzoides and S. juncoides. In E. oryzoides, the daily effective value of temperature in April was used. In S. juncoides, the daily effective value of temperature 30 days before puddling was used. As a result, the method for determining the maximum leaf number stage was able to correct the difference in the annual and puddling period for E. oryzoides and S. juncoides. The shortest number of days from puddling to the maximum leaf number stage was established as the evaluation index using the results obtained from our multiple regression analysis. The optimum weed control effect of a herbicide is achieved when weed control is based on herbicide registration information and an evaluation index.
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