The effect of mechanical bloom thinning with the Darwin 300TM, on the hand thinning time, yield, and fruit quality in 'Zephyr' nectarine
The thinning of stone fruit is important in order to produce fruit of high quality, with the appropriate fruit size. Hand thinning contributes largely to the total production cost, as hand thinning is labour intensive, and labour costs are increasing. The efficacy of the Darwin 300 mechanical thinning system at full bloom in reducing hand thinning requirements in 'Zephyr' nectarine was evaluated in consecutive seasons (2011-2012 and 2012-2013) while also determining the effect on yield and fruit quality. The Darwin 300 was used during full bloom at a constant tractor speed of 4.8 km h-1, while rotor speed varied from 200, 220 to 240 r.p.m. The time required to hand thin was consistently reduced by an average 43% in the 2011-2012 season and 33% in the 2012-2013 season. In the 2011-2012 season, a negative linear trend was observed with increasing rotor speed in the time required to hand thin. This trend was also observed in yield tree-1 in the 2011-2012 season. Yield tree-1 was consistently reduced by 21% in the 2011-2012 season and 27% in the 2012-2013 season. This reduction resulted in an increase in fruit size in both seasons. Total soluble solids were increased in both seasons. During the 2011-2012 season, no negative fruit quality effects were found, but in the 2012-2013 season the percentage of fruit cracking and split pit was significantly increased by all three machine treatments. In conclusion, mechanical thinning of nectarines with the Darwin 300 has potential to reduce hand thinning, but it is important to not over thin trees with too high rotor speeds as it can reduce yield, increase fruit size too much and lead to fruit cracking and split pit. The optimal rate of thinning needs to be determined for each cultivar individually.
Theron, K.I., De Villiers, M.H.J. and Steyn, W.J. (2016). The effect of mechanical bloom thinning with the Darwin 300TM, on the hand thinning time, yield, and fruit quality in 'Zephyr' nectarine. Acta Hortic. 1130, 631-638
split pit, fruit cracking, labour costs, crop load management