## 3 Results and Discussion
### Water Retention by Residues  
The amount of irrigation retained by harvest residues was explained significantly (\(p\leq 0.0001\)) by both the different application Ids and the amount of dry matter residue (Equation (11)). On the other hand, the analysis of the irrigation intensity of segments and the initial water content in the residue showed no significant relationship with water retention:  
\[\mathrm{PRR}=0.44+0.05\times\mathrm{DM}-0.02\times\mathrm{Id} \tag{11}\]  
where PRR: partial residue retention generated exclusively by the irrigation event (mm); DM: dry matter (ton ha\({}^{-1}\)) and Id: irrigation depth applied (mm). Each of the terms had a significance level of \(p\leq 0.0001\).  
Figure 8: Mean crop yield with confidence intervals and mean distribution uniformity (DUpa) at the different phenological stages of corn crop using two contrasting irrigation depths (40 and 6 mm) for each of the segments.  
Figure 9: Mean crop yield (ton ha\({}^{-1}\)) as a function of sprinkler spacing (m).  
Both partial and total residue retention increased with the increase in dry matter (Figure 10a,b); however, there was a greater variability in partial (PRR) than in total (TRR) for a given amount of dry matter (CV of 45% and 35%, respectively).  
Water retained in residue increased with the increase in dry matter up to a limit close to 2 mm in TRR (Figure 10b) and 1.5 mm in PRR (Figure 10a), and according to Equation (11), only 5% of the total amount of dry matter is retained. The maximum retained irrigation may represent an important loss relative to the Id applied, e.g., 25% if 6 mm is applied. These retention levels were reached with high amounts of dry matter (15 ton ha\({}^{-1}\)), a condition that can occur in no-tillage crops that are irrigated [41]. On the other hand, residue decomposition increases under high temperature and relative humidity [42]. The opposite occurs in cool climates, where residues accumulate due to the low mineralization rate [43]. The relationship between water retained in the residue and dry matter was found to respond to a quadratic equation, with the slope becoming less steep as dry matter increased [17]. The authors attributed this behavior to the overlap of residue layers and indicated that when water is applied (irrigation or rain), the droplets reaching the surface of the residue are retained by adhesion and cohesion forces until they reach a given thickness in which gravity forces act. If irrigation continues to be applied, retention in the upper residue layer will be constant since the new droplets displace those already present to lower residue layers. In corn residues, as decomposition increases, macroporosity rises, thereby increasing the water retention capacity of the residue [14]. Thus, the proportion of corn in the residue increases with increasing porosity (67.93% cobs, 86% leaves, 58.51 stalks) [44], and so does the capacity to accumulate water, which then evaporates depending on wind, temperature and radiation conditions [16], up to a maximum amount of dry matter.  
On the other hand, the behavior of PRR at the different Ids applied was opposite to that of dry matter since water retained was lower at higher depths (Figure 11a,b). Thus, the maximum PRR and TRR (1.5 and 2 mm) were recorded at the lowest depths, whereas Ids higher than 25 mm yielded PRR and TRR lower than 0.5 and 1 mm, respectively.  
Figure 11: Partial (**a**) and Total Residue Retention (**b**) (PRR and TRR, respectively) at different irrigation depths (Ids).  
Figure 10: Dry matter (DM, ton ha\({}^{-1}\)) and (**a**): partial residue retention (PRR) by the contribution of irrigation, and (**b**): total residue retention (TRR), sum of the initial residue water content plus water contributed by irrigation.  
For the 40 and 6 mm Ids, with the same dry matter present in the field, PRR accounted for different loss percentages (5% and 50%, respectively). These losses can be reduced by irrigation management by applying higher Ids.