07 April 2017 Read: 408
A three year study to investigate and quantify the advantages of growing avocados under shadenetting was recently concluded by Westfalia. Wilna Stones of Westfalia Technological Services reported on their findings at SAAGA’s research symposium.
Sunburn and wind damage are the two biggest factors leading to losses in the avocado industry. According to an industry loss factor analysis conducted in 2014, sunburn leads to 27% and wind damage 28% of all losses.
Westfalia Technological Services, based in Tzaneen, started with a study to determine the effect of shade netting on minimizing these losses and improve the quality of the fruit, in the same year these results became known.
Two shadenet structures were erected over existing orchards in the warm, dry subtropical area of Mooketsi, Limpopo and another in the cool subtropical area of Karkloof, Kwazulu-Natal. At Mooketsi, a 4 year old 1 ha orchard, planted to ‘Mendez #1’ (Carmen-Has) on Dusa with two different spacings, 3x3m and 6x3m, was covered with 20% white shade net and green sides.
At Karkloof, the 1,6ha orchard, planted to ‘3-29-5’ (Gem) on Dusa, was covered with 20% clear shade net and sides.The trees were spaced 7 x 4m apart.
Microclimate and various horticultural aspects were compared inside and outside the shade netting structures over a period of three years.
The researchers found that yields under shadenets were on average 3.8 ton/ha higher and volume packed to class 1 were on average 26% higher over the three year period.
Consequently the income of yields under shadenets were between R26 000/ha and R8 000/ha above that of openfield. (See table for more details).
According to Stone it is difficult to determine the time it will take to recoup initial and annual net costs. The benefit and potential income advantage of shadenets for the protection of fruit during adverse weather conditions, such as hail, were not taken into account during this study.
— Alita van der Walt