Table 7.
Regression analysis of the effect of different nitrogen treatments on cotton seed yield over 5 years.
| Year | Regression equation | R2 | Theoretical optimal nitrogen application rate (kg/hm2) |
|---|---|---|---|
| 2017 | y = -0.0173x2 + 6.6987x + 3648.0 | 0.9437* | 193.59 |
| 2018 | y = -0.0107x2 + 5.7722x + 3770.8 | 0.8937 | 269.72 |
| 2019 | y = -0.0086x2 + 3.6869x + 3555.9 | 0.6469 | 214.35 |
| 2020 | y = -0.0096x2 + 4.4308x + 3454.4 | 0.8772 | 230.77 |
| 2021 | y = -0.0067x2 + 4.1436x + 3435.7 | 0.9724* | 309.22 |
R2, determination coefficient; *Significant at 95% confidence level.