Eficiência produtiva e respostas fisiológicas da limeira ácida ‘tahiti’ em função de diferentes estratégias de manejo de irrigação em clima semiárido

Abstract

Agricultural production in regions with limited water availability in Brazil is a major challenge for conomic and sustainable development. Citrus cultivation is no different, as many studies have been developed to optimize the use of various agricultural inputs and improve water use efficiency. The objective of this work was to study the water relations of 'Tahiti' [citrus latifolia (Yu. Tanaka) Tanaka] between the years 2015 and 2017 in two semiarid regions of Brazil. A study was developed in the experimental area of the Agricultural Research Company of Minas Gerais - EPAMIG in Jaíba - MG, with the rootstock HTR-069. The other study was developed in the commercial area of Fazenda Santo Antônio in Itaberaba - BA, with the 'Swingle' citrumelo (Citrus trifoliata (L.) Raf. X Citrus Paradise Macf.]. The plants were submitted to different irrigation management, with two applied slides (full irrigation and irrigation with deficit - 50% of full irrigation) and volume of irrigated soil as sources of variation. Regarding the irrigated volume, in addition to the number of irrigation lines and micro sprinkler use, irrigation strategies with partial root drying (PRD) were also evaluated. In both experiments the growth, physiological responses and production in young orchard in the EPAMIG initial stage up to three and a half years of age and in an adult orchard at the age of six years in the Fazenda Santo Antônio were evaluated. In the semi-arid region of Bahia, Swingle citrumelo rootstock, there was an impact of irrigation with deficit when the irrigation management was performed with a drip line, different from irrigation with 100% ETc replacement and two lines of drippers, which presented productivity absolute higher, but not superior to the other strategies (an irrigation line), on average 26% higher than the treatment with full irrigation and a line of drip irrigators. This result leads to the conclusion that the higher volume of irrigated soil minimizes the effects of the deficit when PRD treatment did not differ from full irrigation with one or two irrigation lines, and the greater efficiency of water use was observed in T5 PRD 50 % (10.48 kg m-3 water). This treatment promoted greater reduction of canopy volume and high productive efficiency (3.81 kg m-3 of canopy). The results of production were corroborated by the physiological studies. The highest water potential in the leaf was observed in T2 100% 2Ln (- 0.33 MPa) and lower was observed in T3 50% 1Ln (- 0.53 MPa). There was a tendency of acclimatization of the plants receiving time-deficient irrigation, corroborated by the physiological data stomatal resistance (s cm-1), leaf water potential (MPa) and foliar temperature (°C), since in the third year of study there was no statistical differences between the treatments studied. In the semiarid region of Minas Gerais, using the rootstock HTR-069, there was an impact of irrigation with deficit. The highest production at the end of 30 months of harvest was observed in the T5 treatment (22.78 kg plant-1) and T1 (11.97 kg plant-1) was the least productive. The higher efficiency of water use was observed in T5 PRD 50% (3.53 kg m-3). This treatment promoted greater reduction of canopy volume and high productive efficiency (2.38 kg m-3 of canopy). The production results were corroborated by physiological studies, and the highest water potential in the leaf was observed in T3 50% 1Ln (- 1.06 MPa) and the lowest was observed in T4 50% 2Ln (-1.78 MPa). There was good acclimatization of the plants receiving time-deficient irrigation, since they were submitted to irrigation management from the initial stages of development as can be observed by the physiological responses of the plants.