The Perfect Match: Adjusting High Tree Density to Rootstock Vigor for Improving Cropping and Land Use Efficiency of Sweet Orange

Abstract

The rise in the productivity of sweet orange in Brazil has been related to the use of superior rootstocks and higher tree density, among other factors. In order to investigate whether the cropping system and the land use efficiency would benefit from more intensive cultivation, the performance of Valencia sweet orange was evaluated over nine years on four rootstocks, which induced contrasting vigor, at 513, 696 and 1000 trees·ha−1. Agronomic Institute of Campinas (IAC) 1697 and IAC 1710 citrandarins, and diploid and allotetraploid (4×) Swingle citrumelos were classified as semi-dwarfing, super-standard, standard, and dwarfing rootstocks, respectively. The fruit yield per tree was decreased at higher tree densities, notably for more vigorous rootstocks. Conversely, the cumulative productivity was increased over the evaluation period by 27% at 1000 trees·ha−1, irrespective of the rootstock, and the most vigorous rootstock resulted in 2.5 times higher production than the dwarfing one on average. Most fruit quality parameters were seldom influenced by the tree density, while the rootstock was a decisive factor in improving the quality and the soluble solids content. Dwarfing rootstocks allowed for harvesting 17% more fruit per minute by manual pickers. Because the tree row volume per area is lower with such rootstocks, even at higher tree density, spray volume can be reduced, although appropriate equipment should be developed for better spray coverage on smaller trees. Nine years after planting under strict vector control, the cumulative incidence of huanglongbing-symptomatic trees on IAC 1710 was double that on Swingle 4×. Taken together, the results suggested that the land use efficiency in the citrus industry can be further improved by planting vigorous rootstocks at moderate to high tree densities. Nevertheless, obtaining highly productive semi-dwarfing and dwarfing rootstocks is the sine qua non for making high-density pedestrian sweet orange orchards more profitable.

Late-Season Sweet Orange Selections Under Huanglongbing and Citrus Canker Endemic Conditions in the Brazilian Humid Subtropical Region

“…Currently, the demand for small to medium-sized trees, which favors high-density plantings, have increased in commercial citrus-growing areas, particularly under endemic occurrence of HLB. It impacts the lifespan of the orchards changing the whole production system (Moreira et al, 2019;Bassanezi et al, 2020;Ferrarezi et al, 2020;Girardi et al, 2021;Carvalho et al, 2021b,c). Furthermore, high-density planting may assure higher yields at the young tree stage under the HLB pressure, favored by the increase of trees per area that optimizes the land use and improves the returns of the initial investments (Wheaton et al, 1991;Bassanezi et al, 2020).…”

“…In the last decades, advanced cultural practices in the citrus industry have been of utmost importance for Brazil to maintain the leadership in the global sweet orange production (FAO, 2019;Carvalho et al, 2019a;Bassanezi et al, 2020). These practices include irrigation, fertilization, high tree density, pest and disease controls, and planting of citrus cultivars that are more productive and adapted to a wide range of environmental conditions (Carvalho et al, 2019a;Bassanezi et al, 2020;Behlau et al, 2021;Girardi et al, 2021). The presence and progression of citrus diseases in orchards are frequent under the humid subtropical climate (Bassanezi et al, 2020;Carvalho et al, 2021a).…”

A Mini Review of Citrus Rootstocks and Their Role in High-Density Orchards

“…Hence, employing a dwarfing rootstock that grows faster and produces more fruit than scions grafted to ‘Flying Dragon’ is needed. However, the extensive use of Flying Dragon with sweet orange scion has not acquired commercial importance in the major producing areas, where farmers generally prefer more vigorous rootstocks [ 31 ]. As a result, most citrus breeding programs have developed new, alternative dwarfing rootstocks, and conventional cross-breeding has produced some promising genotypes [ 32 , 33 ] and genetic transformation [ 34 ].…”

The use of the pesticide dimethoate and cyberkill in combating the fruit fly (Ceratitis capitata) on oranges (Citrus fruits)

“…Sweet oranges [Citrus × sinensis (L.) Osbeck] are the most cultivated and consumed Citrus fruit in the world, both for juice processing and fresh fruit. Brazil, China, India, the United States, Mexico and Spain are the largest producers, representing 63.5% of global production of 78.7 million tons in 2019 (Girardi et al 2021) [11] . Rich in vitamin C and other antioxidant ingredients, Citrus fruits have enormous potential and are distributed throughout the world.…”