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

Eduardo Augusto Girardi,Leandro Peña,Alécio Souza Moreira,Marcelo Da Silva Scapin,Antonio Juliano Ayres,Renato Beozzo Bassanezi,João Gabriel Panegossi Sola

doi:10.3390/agronomy11122569

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.

Highlights

IntroductionFrom 2000 to 2019, the harvested areas significantly increased in most producing countries, whereas they decreased by 31%
In order to elucidate whether citrus production in subtropical conditions may benefit from an even more intensive land use, in this work, we evaluated the association of high-tree-density orchards with rootstocks that induce contrasting vigor, including diploid and allotetraploid selections of the Swingle
The demand for better quality juice increases the need for more sustainable management practices in the field, especially to control limiting diseases such as HLB, in addition to the soaring replacement of labor by automation technologies, and environmental, economic, and climatic factors that may be partially addressed by liberating land for preservation and diversification

Summary

Introduction

From 2000 to 2019, the harvested areas significantly increased in most producing countries, whereas they decreased by 31%. 37% in Brazil and USA, respectively, the major sweet orange juice producers with. In the USA, the decrease in area was accompanied by a 1.53-fold reduction of fruit yield (FY), mainly due to the devastating spread of huanglongbing (HLB) in the state of Florida [2], resulting in a 59% decline of the total production. Brazil maintained similar production, irrespective of the decrease in the harvested area, because the average productivity increased by 1.16-fold in the same period to 28.95 t·ha−1 or a 1.53-fold increase in production compared with that in 1980 [1]

Methods

Results

Conclusion