Pecans: Exciting results on an “Off Year”

Agronomist: Dirk Laubscher

Mynhardt and Riana van der Merwe are farmers in the Modderrivier district, Northern Cape. Pecans are cultivated on alluvial soils, with their first trees of 8ha planted in the early 90’s. Currently, 30+ ha of Pecan trees are being irrigated with Orange River water. Wichita, Choctaw, Pawnee and Western Schley are the main varieties grown on their farms, namely Mathabo and Lushof. The soil analyses of the two main orchards are presented in the table below:

pH P-Bray 1 K Ca Mg Na Ca Mg K Na Ca:Mg Ca+Mg/K Mg:K Na:K
KCI mg/kg mg/kg mg/kg mg/kg mg/kg % % % %
6,6 113 252 1473 360 29 66,4 26,6 5,8 1,1 2,5 16 4,6 0,19
5,7 37 207 1356 412 30 62,7 31,2 4,9 1,2 2 19,2 6,4 0,25

Mr. van der Merwe started to use Atlas Organic Fertilizers in autumn of 2015. Fertilization with Atlas products consists of four applications per year and are broadcast using a spreader in the area where water is irrigated. Pecan Mix, a balanced fertilizer for pecans, is applied twice in the season. The other two applications focus on nut filling and new growth for next season’s crop. This applications’ total plant nutrition for the last growing season of 2016/2017 is shown in the next table:

 N P K Ca Mg  S Zn B Cu Fe Mn Mo
kg/ha  kg/ha kg/ha kg/ha  kg/ha  kg/ha  kg/ha  kg/ha  kg/ha  kg/ha  kg/ha  kg/ha
 210 45 110 43 6 148 2,85 0,87 1,25 4,35 0,53 0,003


Foliar applications : 7x Zn; 2x Cu; and 1x B, are done season per season. The total fertilization cost (foliar applications included) for the last season was just short of R10 000/ha. Leaf analyses are performed every year.

The leaf analyses of all the years, size and quality of the recent crop, plus information gathered over the growing season, are used to adjust the fertilization program for the new season.

Alternate bearing of Pecans is well known and farmers refer to it as an “on-year” or an “off-year”. Meaning that the same tree will produce an above average crop the one year and a below to way-below average crop the next year. Some varieties, like Choctaw, are more prone to alternate bearing than Wichita, which is therefore a more popular cultivar among growers.

Choctaw in comparison to Witchita bear larger nuts – the demand for larger sized pecan nuts is high, thus ensuring better prices per kilogram for producers. In Mr. van der Merwe’s 20 years of experience with pecans, he has been unsuccessful to produce two consecutive average to above average harvests from his Choctaw trees. According to him, the growing season of 2015/2016, which ended with harvest in June/July 2016, was an “on year” in production for the Choctaw variety and produced approximately 3ton/ha. Due to alternate bearing the 2016/2017 season was supposed to be a “off-year”, but they finished the harvest with an exciting 2.75ton/ha production from the Choctaw trees (91.7% of “on-year” yield). The 2015/2016 season was a below average production year for his Witchita trees due to unsatisfactory pollination as well as some hail damage (between 5 – 18%) resulting in a 2ton/ha harvest. For the 2016/2017 season, the Witchita variety produced an excellent, 4ton/ha harvest.

Grades for the 2016/2017 season:
• Choctaw: 96.7% – Oversize and 3.3% – Extra-large, 58% edible kernel, 3.18% pops.
• Witchita: 14% – Oversize; 51.2% – Extra-large and 26.8% – Large, 57.4% edible kernel, 1.62% pops.

The challenge now is to produce an average to above average harvest for both varieties in the 2017/2018 season


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