Effects of Photoselective Netting on Root Growth and Development of Young Orange Trees

Photoselective netting is well-known for filtering the intercepted solar radiation affecting light quality. While its effects on above-ground of plants have been well investigated, the root system was neglected. We evaluated the effects of photoselective netting on root growth and plant development. Minirhizotron and ingrowth cores were applied in a field experiment, performed in a three years old orange orchard grown under four different photoselective net treatments (red, pearl, yellow and no nets control). Our observations confirmed the significant effect of photoselective nets on tree physiological performance, by increases of photosynthesis rate, vegetative growth and fruit yield. Root length density dynamics showed that root extension rate was greater in control, pearl and yellow plots compared with red plot at 50 cm distance from the trunk. Trees grown under pearl nets developed evenly distributed root system along the observation tubes while trees in control, red and yellow plots had a major part of roots concentrated at different depth ranges of 60-80, 100-120, and 120-140 cm, respectively. Photoselective nets showed strong impact on shoot-root interaction and proved equally successful in promoting rapid establishment and early high-fruit yield in young citrus trees. However, at long-term effect, yellow net might outperform because it could enable plants to develop deeper root systems, which will uptake water and nutrients more efficiently in semi-arid areas with sandy soil. Our results will help optimize the use of photoselective nets in citrus orchards and ensure an effective balance between above and below-ground plant growth.