Table 3.
Maize Yield Response Estimation results.
| Standard Model (SM) |
Exogenous Model (EM) |
Endogenous Model (ENM) |
Full Model (FM) |
|||||
|---|---|---|---|---|---|---|---|---|
| Coef. | Std. Err. | Coef. | Std. Err. | Coef. | Std. Err. | Coef. | Std. Err. | |
| Ln_plot size (Ha) | −2.32*** | 0.338 | −0.07 | 0.0592 | −0.19** | 0.098 | −0.12* | 0.077 |
| Ln_plot size squared | −1.03*** | 0.219 | −0.06 | 0.0373 | −0.11 | 0.062 | −0.06* | 0.040 |
| Ln_Nitrogen input (N) | 2.22*** | 0.316 | 0.03 | 0.0554 | 0.17** | 0.090 | 0.15 | 0.094 |
| Ln _Nitrogen Input squared | −0.30*** | 0.053 | 0.00 | 0.0090 | −0.01 | 0.015 | 0.002 | 0.010 |
| Hybrid seeds (Yes = 1) | 1.20*** | 0.287 | 0.05 | 0.0481 | 0.04 | 0.080 | −0.08*** | 0.050 |
| Ln_Phosporous input | −0.26 | 0.303 | 0.09 | 0.0500 | 0.06 | 0.080 | 0.01 | 0.108 |
| Ln_Phosporous input sq. | 0.03 | 0.059 | −0.01 | 0.0096 | −0.02 | 0.016 | 0.00003 | 0.012 |
| Ln_Manure | 0.73*** | 0.129 | 0.05 | 0.0220 | 0.01 | 0.036 | 0.03 | 0.023 |
| Ln_Manure squared | −0.06*** | 0.015 | 0.001* | 0.0026 | 0.00 | 0.004 | −0.001 | 0.003 |
| Pop. density (Psn/Km2) | 1.15 | 1.581 | −2.65*** | 0.644 | −1.83*** | 0.903 | −1.81*** | 0.773 |
| Pop. Density squared | −0.09 | 0.122 | 0.21 | 0.050 | 0.14 | 0.069 | 0.14*** | 0.059 |
| Ln_Labour | 0.01 | 0.007 | 0.001 | 0.003 | 0.004 | 0.004 | −0.0003 | 0.003 |
| Ln_Labour squared | −0.004* | 0.002 | −0.001 | 0.001 | −0.002 | 0.001 | −0.0004 | 0.001 |
| Ln_Organic Carbon(OC) | 0.74 | 0.0594 | −0.21 | 0.205 | 1.93*** | 0.601 | ||
| Ln_Reactive Carbon(RC) | −1.33 | 0.0645 | −0.77 | 0.199 | −0.64*** | 0.243 | ||
| Ln_Soil pH | 1.92 | 0.1211 | 1.80 | 0.201 | 2.69*** | 0.129 | ||
| Ln_Plant Available P | −0.04 | 0.0309 | −0.13 | 0.051 | 0.15 | 0.135 | ||
| Ln_Land * ln N input | −0.003 | 0.035 | ||||||
| Ln_Land * P. input | 0.01 | 0.038 | ||||||
| Ln_Land * ln Manure | 0.01 | 0.007 | ||||||
| Ln Pop.Density* Ln_OC | −0.001 | 0.001 | ||||||
| Ln Pop.Density* Ln_RC | −0.001*** | 0.0004 | ||||||
| Ln Pop.Density* Ln_PAP | −0.001*** | 0.0002 | ||||||
| Ln_Nitrogen*Ln_OC | −0.21** | 0.102 | ||||||
| Ln_Phosphorous*Ln_OC | −0.01 | 0.110 | ||||||
| Ln_No. of years of fert. use | 0.0002 | 0.001 | ||||||
| Ln_Land holdings | −0.01*** | 0.004 | ||||||
| Ln_Wage rate | −0.005 | 0.012 | ||||||
| Constant | −4.79 | 5.125 | 7.53*** | 2.089 | 4.82*** | 2.932 | 4.75* | 2.540 |
| Number of Observations | 290 | 290 | 290 | 290 | ||||
| R-Squared | 0.68 | 0.74 | 0.84 | 0.89 | ||||
* Parameters are significant at the 0.1 level; *; ** parameters are significant at the 0.05 level; ***parameters are significant at the 0.01 level.