Wineries in South Africa are estimated to generate between 2 190 million and 15 330 million litres of wastewater per year.1 In a drought prone country, re-using this water for irrigation makes economic and environmental sense. However, this water has a high chemical oxygen demand (COD) with high levels of potassium (K) and sodium (Na).2 Using it for irrigation adds substantial amounts of elements such as K and Na to the soil,3,4 therefore maximising element removal by means of a catch crop is important.
In a previous study where diluted winery wastewater was used for vineyard irrigation, oats and Pearl millet removed substantial amounts of K from a sandy soil.1 However, minimal amounts of Na were taken up by these two crops. In a pot study, Fodder beet absorbed 38% of Na applied via Na-enriched irrigation water compared to soil without plants.5 Furthermore, the Fodder beet reduced exchangeable soil K by 50%, thereby indicating that it could also absorb K applied via winery wastewater. Taking above-mentioned into consideration, the aim of this study was:
- to determine whether irrigation of open land with diluted winery wastewater affected the performance and nutrient content of selected catch crops on loamy sand to sandy clay loam soils, and
- to determine the ability of the selected catch crops to intercept sufficient amounts of Na and K from the soil.
This is the second article in a series on the evaluation of selected catch crops where winery wastewater is re-used for irrigation.
Diluted winery wastewater was applied to open land on the Nietvoorbij research farm where 10 different fodder producing catch crops were compared to a control where no catch crop was cultivated in the summer. Details of the irrigation application and water quality have been given previously.6 The dry matter production (DMP) of the catch crops was estimated by sampling the above-ground vegetative growth in a 0.5 m2 sub-plot randomly chosen in each plot. Samples were oven-dried for 48 hours at 105°C. A sample was collected from the sub-plot and analysed by a commercial laboratory for macro- and micro-elements. The amounts of the different macro- and micro-elements intercepted by the cover crops were estimated by multiplying the DMP of the species with the concentration of the different elements in the samples harvested for analyses.
Results and discussion
The DMP, which is commonly used as an indication of how well a catch/cover crop grows under prescribed conditions, of the catch crops over the four years of the study is given in Table 1. These results show that the DMP of the 10 catch crops showed variability over the study period with some showing higher and lower values. However, looking globally and taking the DMP of all the years into consideration, the Vetiver grass (T8) produced the highest amount of DMP followed by Dolichos beans (T7) and Chicory (T6). Vetiver grass can be cultivated as a perennial grass and has been shown to be tolerant of elevated Na.7 Furthermore, Dolichos beans is a drought tolerant crop and tolerates a wide range of soil types from sandy soils to heavy clays.
An average of 147 bales per hectare was produced by Vetiver grass (T8) and could generate an income of as much as R11 000 when sold (R75 per bale). Expenses against this income would be the cost of the 28 kg of fertiliser N and the 10 kg per ha of P applied to promote catch crop growth. This will increase the input cost by R1 624/ha and R1 587/ha, respectively. The net income would be approximately R7 800 where 2.2 t/ha DMP of Vetiver grass is produced.
On average over the four seasons of the study, Cow peas (T5), Chicory (T6) and Dolichos beans (T7) accumulated the most N in their foliage (Figure 1). Dolichos beans (T7) and Bottle brush grass (T9) accumulated the most P and Chicory (T6) and Pearl millet (T1) accumulated the most K. Fodder radish (T3) and Chicory (T6) accumulated substantially more Na than the other catch crops.
Due to the substantially higher DMP of the Vetiver grass (T8), it extracted more P from the soil than the other catch crops (Figure 2). Dolichos beans (T7) extracted the most N and Mg from the soil. Chicory (T6) absorbed the most K, Ca and Na from the soil. In contrast, the Bottle brush grass (T9) and Weeping lovegrass (T10) catch crops extracted the least amount of elements from the soil. In general, the catch crops absorbed only a small percentage of the elements applied via the irrigation with diluted winery wastewater.6
The study showed that summer catch crops can be established using diluted winery wastewater for irrigation on open land. Dolichos beans and Chicory performed best in terms of DMP as summer catch crops. The added advantage of Vetiver grass was that it produced enough DMP to make bales which could potentially be sold. If element uptake from the soil is considered, then the Dolichos beans and Chicory were the best catch crops. However, it should be noted that unfortunately the summer catch crops only absorbed a low percentage of the elements applied via the diluted winery wastewater. This indicates that it may not be sustainable to plant catch crops and that they are probably not the only solution. However, the negative effects of using winery wastewater for irrigation is a serious concern and these effects could potentially be negated, to a certain extent, by using catch crops.
Wineries in South Africa are estimated to generate between 2 190 – 15 330 million litres of wastewater per year. Using this water for irrigation adds substantial amounts of elements to the soil. Maximising element removal by means of a catch crop is therefore important. Consequently, the objective of this study was to identify fodder producing crops that would intercept sufficient K (and Na) applied via irrigation with diluted winery wastewater on open land with loamy sand to sandy clay loam soil. Ten different fodder producing catch crops were compared to a control where no catch crop was cultivated. Vetiver grass, Dolichos beans and Chicory performed best in terms of dry matter production (DMP) as summer catch crops. Additionally, Vetiver grass produced enough DMP to make bales which could potentially be sold. If element uptake from the soil is considered, then the Dolichos beans and Chicory were the best catch crops. Unfortunately, the summer catch crops only absorbed a low percentage of the elements applied via the diluted winery wastewater. In conclusion, the study showed that catch crops can be established using winery wastewater, but they are probably not the only solution, because they did not remove substantial amounts of the salts.
Catch- and cover crop responses in the vineyard will be presented in the next article.
- The project was funded by Winetech and the Agricultural Research Council (ARC).
- ARC for infrastructure and resources.
- Staff of the Soil and Water Science division at ARC Infruitec-Nietvoorbij for technical support.
- Fourie, J.C., Theron, H. & Ochse, C.H., 2015. Effect of irrigation with diluted winery wastewater on the performance of two grass cover crops in vineyard. Afr. J. Enol. Vitic. 36, 210-222.
- Howell, C.L., Myburgh, P.A., Lategan, E.L. & Hoffman, J.E., 2016. Seasonal variation in composition of winery wastewater in the Breede River Valley with respect to classical water quality parameters. Afr. J. Enol. Vitic. 37, 31-38.
- Howell, C.L., Myburgh, P.A. & Hoogendijk, K., 2022. Use of winery wastewater as a resource for irrigation of vineyards in different environments. WRC Report No. 2651/1/22. ISBN 978-0-6392-0341-6.
- Myburgh, P.A. & Howell, C.L., 2014. The impact of wastewater irrigation by wineries on soil, crop growth and product quality. WRC Report No. 1881/1/14. ISBN 978-1-4312-0591-2.
- Myburgh, P.A. & Howell, C.L., 2014. Assessing the ability of fodder beet (Beta vulgaris ʽBrigadierʼ) to absorb sodium from a soil irrigated with sodium-enriched water. S. Afr. J. Plant Soil 31, 113-115.
- Howell, C., Freitag, K. & Sassman, L., 2023. Evaluation of selected catch crops where winery wastewater is re-used for irrigation. I. Irrigation application and water quality. Submitted to Winelands for publication.
- Fourie, J.C., Howell, C.L. & Masekwana, N., 2021. Selection of grass and broadleaf crops as catch crops where winery wastewater is used for irrigation: A review. Afr. J. Enol. Vitic. 42, 10-17.
For more information, contact Carolyn Howell at firstname.lastname@example.org.