Increasing water use efficiency of irrigated sugarcane production in South Africa through better agronomic practices

Abstract

In South Africa (SA) approximately 30% of sugarcane is grown under irrigation and there is increasing pressure to demonstrate efficient use of limited water resources. Agronomic practices such as the use of a crop residue layer, changed row spacing, growing suitable varieties and accurate irrigation scheduling could potentially increase water use efficiency (WUE) by saving water and/or increasing yield. The aim of the study was to investigate to what extent WUE of irrigated sugarcane production in SA can be improved by better agronomic practices, and to gain a better understanding of the mechanisms involved in crop response to these factors.An overhead irrigated field experiment was conducted near Komatipoort, South Africa on a shallow, well-drained, sandy clay loam over a four year period (one plant (P) and three ratoon crops (R1, R2 and R3)). Treatments consisted of factorial combinations of variety Page 2 (N14 and N26), row spacing (single rows spaced at 1.5 m and dual rows spaced at 1.8 m) and soil surface cover (bare soil and crop residue layer). Measurements included tiller population, interception of photosynthetically active radiation (FI PAR ), soil water content, and cane yield at harvest. Crop water use (CWU) was estimated using the water balance approach.This study showed that significant reductions in water use and irrigation requirements, and increases in WUE, are possible by using a crop residue layer to cover the soil. Water savings were largest in P1 (26% in CWU and 32% in irrigation requirement) but substantial savings were also achieved in the R crops (about 15%). It is essential to practice accurate irrigation scheduling to realize these savings, taking into account soil cover and cultivar effects, especially during the period of partial canopy. Although the residue layer caused small reductions in yield in the P, R1 and R2 crops (on average 9%) these were not statistically significant. The combined effect of large CWU reductions and small changes in cane yield resulted in increased WUE (on average 18%).These responses to a residue layer were achieved through a reduced rate of canopy development due to delayed emergence of tillers, causing less green canopy cover and reduced CWU, especially during the period of partial canopy cover when stalk growth has not yet commenced. CWU and FI PAR were affected much less during the subsequent period of stalk growth, thus affecting cane yield minimally, provided irrigation scheduling was adjusted.Variety N14 consistently developed a canopy more rapidly, intercepted more radiation and achieved a higher yield than N26. Row configuration had a significant impact on canopy development, seasonal FI PAR , final stalk population but did not affect cane yield or WUE. Page 3The study produced quantitative data for parameterizing crop models which will improve their reliability in irrigation management and yield prediction applications.

Simulated impacts of climate change on water use and yield of irrigated sugarcane in South Africa

“…Retention of crop residues has been identified by Park et al (2010) as a possible climate change adaptation to improve water management in sugarcane. Crop residue blankets have the potential to reduce non-productive soil surface evaporation losses: van den Berg and Jones (2006) reported increased soil moisture availability of 100 mm per season for rainfed crops, while Olivier and Singels (2014) recorded reductions in crop water use in irrigated sugarcane of up to 150 mm. This might, however, be a less effective farming system change in future with the shorter partial canopy period and/or if sub-surface drip irrigation is used.…”

Three-Stage Data Envelopment Analysis of Agricultural Water Use Efficiency: A Case Study of the Heihe River Basin

“…The acceleration of urbanization and population growth also brings challenges to water utilization [11,12]. Increasing water use efficiency (WUE) has become a vital step toward a more sustainable world [13]. As an important maize seed production area, the Heihe agricultural production area in Gansu Province is one of the most water-stressed parts of the country [14,15].…”

Productivity, Technological Attributes and Water Use Efficiency of Sugarcane Cultivars Under Regulated Deficit Irrigation

“…For RDI, the genotypes 'IAC5000' and 'IAC1099' were superior to the other cultivars (p < 0.01). According to Olivier & Singels et al (2015), the WUE is influenced by the cultivar, emphasizing the importance of the correct choice, since the genotype leads to a more efficient use of water and higher productivity. It is verified that irrigation depths of between 50% and 100% ETc do not affect the WUE of cultivars responsive to this system (Farias et al, 2008).…”