*Recent Trends in the Yield-Nutrient-Water Nexus in Morocco DOI: http://dx.doi.org/10.5772/intechopen.112552*

*Recent Trends in the Yield-Nutrient-Water Nexus in Morocco DOI: http://dx.doi.org/10.5772/intechopen.112552*

sorghum yields can be explained by changes in phosphate fertiliser application (**Figure 6b**). Considering potash fertilisers used in sorghum cultivation, it can be observed that an R2 of 0.26 (26%) is obtained. This implies that only 26% of changes in sorghum yield can be explained by changes in potash fertiliser application (**Figure 6c**). Phosphate fertilisers outbid the other nutrients as they record a relatively higher R<sup>2</sup> of 23% and the lowest p-values of 0.009. Phosphate fertilisers tend to explain more of the changes in sorghum yield as depicted by the R2 of 23%, a statistic that is much higher than those recorded for nitrogen and potash.

The results from the scatter plots (**Figure 6a, b** and **c**) are consistent with linear regression outputs (**Table 5**). This is observed as phosphate fertilisers tend to record the lowest relative p-value of 0.009 and the highest t-value of 2.78. This is followed by nitrogen (p-value = 0.29, t-value = �1.06) and lastly potash (p-value = 0.68, t-value- = �0.40). Even though nitrogen represents higher levels of application in Moroccan agriculture, when it comes to sorghum, phosphates tend to impact maize yields more than the other fertilisers. When the linear relationship between sorghum yields as the dependent variable and agricultural water withdrawal and fertilisers as independent variables is considered, it is observed that agricultural water withdrawal records the lower p-value (0.025) and the highest t-value (�2.35) (**Table 6**). This depicts the fact that agricultural water withdrawal has a more significant relationship with sorghum yield when compared to fertiliser application.

#### **3.6 Scatter plots and linear regression outputs of the relationship between fertilisers/nutrients and wheat yields in Morocco**

In the context of nitrogen fertilisers used in wheat cultivation, it can be observed that an R2 of 0.015 (1.5%) is obtained. This implies that only 1.5% of changes in wheat yield can be explained by changes in nitrogen fertiliser application (**Figure 7a**). In terms of phosphate fertilisers used in wheat cultivation, it can be observed that an R2 of 0.03 (3%) is obtained. This implies that only 3% of changes in wheat yields can be explained by changes in phosphate fertiliser application (**Figure 7b**). Considering potash fertilisers used in wheat cultivation, it can be observed that an R2 of 0.0002 (0.02%) is obtained. This implies that only 0.02% of changes in wheat yields can be explained by changes in potash fertiliser application (**Figure 7c**). Also, though most of the relationships are weak, phosphate fertilisers seem to outbid the other nutrients as they record a relatively higher R<sup>2</sup> of 3% and the lowest p-values of 0.05. Phosphate fertilisers tend to explain more of the changes in wheat yield as depicted by the R2 of 3%, a statistic that is much higher than those recorded for nitrogen and potash.

The results from the scatter plots (**Figure 7a, b** and **c**) are consistent with linear regression outputs (**Table 7**). This is observed as phosphate fertilisers tend to record the lowest p-value of 0.05 and the highest t-value of 2.04. This is followed by nitrogen (p-value = 0.78, t-value = �0.26) and lastly potash (p-value = 0.81, t-value = �0.23). Even though nitrogen represents higher levels of application in Moroccan agriculture, when it comes to wheat, phosphates tend to impact wheat yields more than the other fertilisers. When the linear relationship between wheat yields as the dependent variable and agricultural water withdrawal and fertilisers as independent variables are considered, it is observed that agricultural water withdrawal records the lower p-value (0.17) and the highest t-value (�1.39) (**Table 8**). This depicts the fact that agricultural water withdrawal though generally weak has a relatively more significant relationship with wheat yield when compared to fertiliser application.


**Table 5.**

*Linear regression outputs of the relationship between sorghum yield and fertilisers.*


#### **Table 6.**

*Linear regression outputs of the relationship between sorghum yield, water withdrawal and fertilisers.* *Recent Trends in the Yield-Nutrient-Water Nexus in Morocco DOI: http://dx.doi.org/10.5772/intechopen.112552*


 **7.** *Linear regression outputs of the relationship between wheat yield*

 *and fertilisers.*

**Table**


**Table 8.**

*Linear regression outputs of the relationship between wheat yield, water withdrawal and fertilisers.*
