Crop evapotranspiration, crop coeficiente and irrigation management for sugarcane in Nicaragua

Abstract

Sugarcane is a crop with great importance in the Nicaragua’s economy and has an important contribution to the country's GDP. The sustainability is a topic that is increasingly active on the agendas of companies and governments and agriculture is a big player in this context. In this way, it is very important to use rationally the resources destined for the crop production, in special the water. Almost 70% of the sugarcane field are irrigated in Nicaragua. However, the lack of information that supports better irrigation management towards better crop agronomical performance and water use efficiency, still a challenge to overcome in Nicaragua. Therefore, two experiments were carried out at the Casur sugarcane mill in a vertisol soil with furrow irrigation. In the first trial, using the soil water balance, the crop evapotranspiration and crop coefficient were determined and the values of Kc obtained was compared with those proposed by FAO. During the experiment, the total crop evapotranspiration (ETc) was 1346.6 mm. The Kc values for the growth phenological stage initial, tillering, grand growth and maturation were 0.37, 0.91, 1.11 and 0.71 respectively, resulting in an average of 0.9. The Kc values proposed by FAO overestimate those defined locally by 11.11%. For the second experiment, two irrigation strategies were established, one based on soil moisture content (ISw) and another with irrigation with fixed interval (IFI). The last one was watered every 31 days, which is local practice. Sugarcane yield and growth variables parameters were evaluated on a time scale and they were also measured during harvest. Irrigation and total water use efficiency was also measured. In the temporal scale, plants in the IFI treatment showed compensatory growth, recovering from water-deficit-stress due to lack of water in the soil, in almost all growth variables. Sugarcane yield was statistically different between treatments, where ISw and IFI presented 93.87 and 83.84 Mg ha-1 respectively. The irrigation and total water use efficiency were similar for both treatments. Based on the results found, the determination of local ETc and Kc, as well the irrigation management based on soil moisture are recommended for a rational use of water resources in Nicaragua. The study showed a lower crop water requirement compared to the FAO recommendation and a better sugarcane yield using the soil moisture content as irrigation strategy without compromising the water use efficiency.