Evaluating the effect of irrigation water management techniques on (taro) madumbe ( Colocasia esculenta (L.) Schott) grown with anaerobic ﬁ lter (AF) ef ﬂ uent at Newlands, South Africa

This study evaluated the effects of irrigation water management techniques on the growth and yield parameters of madumbe ( Colocasia esculenta ) irrigated with anaerobic ﬁ lter (AF) ef ﬂ uent. The irrigation water management treatments considered were alternate wetting and drying (AWD), continuous ﬂ ooding irrigation (CFI) and wetting without ﬂ ooding (WWF). It was hypothesized that irrigation techniques with anaerobic baf ﬂ ed reactor (ABR) ef ﬂ uent have a signi ﬁ cant effect on the growth and yield of madumbe. The effects of the treatments were signi ﬁ cant ( P < 0.05) on the number of irrigation events, amount of irrigated water and daily water balance. The treatments had no effect on the growth parameters (plant height, leaf number and leaf area index (LAI) ( P > 0.05)). The treatments effects were, however, highly signi ﬁ cant ( P < 0.001) on the yield components (biomass, corm mass, corm number, corm size, harvest index), corm yield and water productivity (WP). AWD treatments had the highest WP. The highest average corm yields of 7.5 and 9.84 t/ha for WWF treatments for 2017 and 2018 seasons were obtained. It is concluded from this study that both AWD and CFI resulted in yield reduction compared with WWF, and as such, is not recommended to improve the productivity of madumbe. from https://iwaponline.com/jwrd/article-pdf/9/2/203/553769/jwrd0090203.pdf" /><meta name="description" content="Abstract. This study evaluated the effects of irrigation water name="description" content="Abstract. This evaluated the water


INTRODUCTION
Wastewater is the only potential source of water that will rise as the population increases and the demand for freshwater rises (Heidarpour et al. ). According to Qadir et al. (), urban and peri-urban farmers in almost all developing countries have no choice but to use wastewater.
Metropolitan population growth, predominantly in developing countries, places enormous stress on water and land resources; as a result, a growing volume of wastewater is being released and most of it untreated. The rate of wastewater usage for irrigated agriculture in urban and peri-urban and even in far rural settlements downstream of the new megacities is increasing. Sustainable techniques for wastewater disposal that enhances crop production will ease water shortages, and recycling of nutrients also necessitates the use of treated wastewater for irrigating crops (Pedrero et al. ).
The practice of periodic drying and re-flooding of fields during the lifecycle of a crop is referred to as alternate wetting and drying (AWD) irrigation management (Lampayan et al. ). The continuous flood irrigation (CFI) maintains standing water at all times (anaerobic conditions) (Yao et al. ). Well-watered conditions with 100% water holding capacity is another irrigation management technique (Ruíz-Sánchez et al. ). This is referred to as wetting without flooding (WWF).
The anaerobic baffled reactor (ABR) is made up of a series of compartments separated by discontinuous hanging baffles (Wang et al. ) that separate the compartments and force the wastewater to move through the treatment train with an upflow velocity sufficiently low to prevent biomass wash-out. The flow pattern promotes improved contact between the influent wastewater and the retained biomass.
According to Bame et al. (), ABR as a high rate digester (anaerobically) involves different hanging and vertical baffles premeditated for wastewater treatment. The ABR is an appropriate method for medium or short-term hygiene solutions in low-income societies (Foxon et al. ).
According to Musazura et al. (), the ABR effluent comprises nutrients (potassium, phosphorus and nitrogen) which are significant for growth of crops. Further treatment of the ABR effluent is undertaken by passing it through two consecutive beds of coarse stones (anaerobic filter, AF). The nutrients available in the effluent have economic value as a fertilizer when used for irrigation because the source of the wastewater is domestic households (Bame et al. ).
Madumbe (taro) (Colocasia esculenta), one of the food security crops, is a marginalized tuber food crop, with wide distribution in the tropics. The neglect of madumbe as an indigenous crop is one of the causes of food insecurity; therefore, production of indigenous crops will play a critical role in contributing to food security (Kamwendo & Kamwendo  There is no reported work on the response of madumbe to different irrigation management techniques using decentralized wastewater treatment system (DEWATS) effluent. This study, therefore, investigated the effect of irrigation water management techniques on the growth and yield parameters of madumbe. It also investigated the number, amount of irrigation, field water balance and water productivity. The (alternative) hypothesis was that irrigation water management techniques with ABR effluent have a significant effect on the growth, yield of madumbe, water balance and water productivity.  where the irrigation trials take place. Excess treated effluent is returned to the trunk sewer. The composition and characterization of the AF effluent is presented in Table 1.

Experimental design and treatments
The field trials were conducted at an open agricultural field for two seasons. The first season was from July 2017 (cool, dry winter) to February 2018 (hot and wet summer) and the second season was from December 2017 (hot and wet summer) to July 2018 (cool, dry winter). The trials were laid out in a randomized complete block design (RCBD) with three replications as shown in Figure 3. The slope of the field was considered to be the blocking effect. Randomization was done using Kutools for Excel software to avoid bias of both trials (Kutools ). The trials consisted of a factor, irrigation management techniques with three levels of treatments, alternate wetting and drying (AWD), conventional flooding irrigation (CFI) and continuous wetting without flooding (WWF). Treatment WWF was used as a control.
The whole field layout gave rise to nine plots of 3 m by 1.5 m each. Bunds were established between plots to isolate them from adjacent plots ( Figure 2). Bunds (300 mm wide at the base and 200 mm high) were covered with plastic sheeting (250 μm) which was buried into the soil to a depth of 0.6 m to prevent run-on, run-off, lateral-in and lateral-off flow in each plot. Inserted into each plot was a 400 mm long and 110 mm diameter PVC observation tube perforated with 5 mm diameter holes at 40 mm intervals. A measuring tape (metal) was used to measure the water level in the tube.
A water depth monitoring tube was inserted into each of the nine irrigation plots (at least 500 mm away from the bund walls, 200 mm above and 200 mm below the topsoil). It was used to determine the need for water addition and to monitor the soil water depth.

Planting material and technique
The South African madumbe landraces obtained from Umbumbulu (eddoes types) were used as planting materials.

Effect of water application
The effects of irrigation water management techniques with AF effluent were significant on the total amount of irrigation and total water used (P ¼ 0.002). The effects were highly significant (P < 0.001) on the number of irrigation events and daily water balance (Table 3). A significant (P < 0.05) of irrigation in order to ensure flooding/ponding unlike AWD treatments that received irrigation water intermittently. The WWF was similar to CFI in terms of irrigation events and amount because water application was also continuous, though not to ponding level. The higher the total number of irrigation events, the higher the amount of irrigation and water balance. Irrigation amount and/or total water use are key parameters of water balance. The values of all parameters measured in Table 3 were higher in 2018 than in 2017. This was a result of seasonal differences that produced less rainfall in 2018 compared with 2017.

Treatment effects on growth of madumbe
The results for the 2017 cropping season showed that irrigation water management techniques had no significant (P ¼

CONCLUSION
This study showed that madumbe (eddoes landraces from Umbumbulu) was susceptible to flooding (CFI). Attempts to domesticate the landrace out of its native method of irrigation (WWF) were unsuccessful as the crop failed to produce significant yield. Madumbe is a wetland crop, so it performed and produced reasonable yields under continuous wetting without flooding (WWF) conditions. The CFI treatments had the highest number of irrigation events and consumed the largest amount of irrigation water. The highest yields of 7.52 and 9.84 t/ha were obtained for the two seasons with WWF treatments. These yields were higher than the global average yield of madumbe. The eddoes landrace under flooded conditions (CFI) showed a significant reduction in corm yield compared with WWF and alternate wetting and drying (AWD) conditions. The major effect of CFI was found on the total biomass per plant. The yield obtained in this study was mainly an effect of different irrigation water management techniques using water reuse (anaerobic filter (AF) effluent) without application of additional (organic or inorganic) fertilizer. The adoption of an irrigation management technique such as WWF using AF effluent could therefore be concluded as a relatively cheaper way of enhancing food security and sanitation, especially in urban and peri-urban settlements. The hypotheses on water balance, water productivity and yield were accepted while that on growth parameters was rejected.