Identification of N, K, Mg, Mn, Zn and Fe Deficiency Symptoms of Carambola, Lychee, and Papaya Grown in Sand Culture

Symptoms of nutrient deficiency in carambola {Aver rhoa carambola L.), lychee (Litchi chinensis Sonn.) and papaya (Carica papaya L.) trees have been observed periodically in south Florida, but have not been experimentally verified. Young 'Arkin' carambola, 'Mauritius' and 'Brewster' lychee and 'Cariflora' papaya were grown in 26-liter containers filled with coarse silica sand, irrigated with deionized water and fer tilized with either a modified Hoagland solution or nutrient so lutions minus N, K, Mg, Mn, Zn, or Fe. Treatments were arranged in a randomized complete block design with two to six single-tree replications per cultivar. Leaf symptoms were recorded and leaf or petiole tissues were sampled for nutrient analysis, especially with reference to tissue nutrient levels for these crops reported from their production areas. Southern Florida has long been an area of tropical and subtropical fruit production. During the past fifteen years, there has been a major increase in the area planted with spe cialty tropical fruits, including carambola, lychee and papaya (J. H. Crane, University of Florida, personal communication). However, little research has been conducted to determine nutritional requirements and to identify, describe and verify nutritional deficiency symptoms of these crops in Florida. The ability to identify and correct mineral nutrient deficien cies before they affect tree vigor and limit yields is crucial for the production of these crops. Optimal leaf nutrient levels for carambola have been re ported (Galan Sauco and Menini, 1993), but no visual de scriptions of deficiencies or toxicity's have been reported and confirmed. Several studies have been conducted to deter mine the nutritional requirements of lychee in India (Mallik and Singh, 1965). Additionally some observations from con trolled studies in Florida have been reported (Goldweber, 1959; Joiner, 1958; Young and Koo, 1964). Studies of leaf nu trient levels in papaya have been conducted in Hawaii (Awada, 1969, 1977; Awada and Long, 1969, 1971a, 1971b, 1978, 1980), Puerto Rico (Cibes and Gaxtambide, 1978; Perez-Lo pez and Childers, 1982a, 1982b) and India (Nautiyal et al., 1986). However, these studies focused on Hawaiian 'Solo' types, and little information is available on the commercial 'Cariflora' cultivar grown in Florida. The objectives of this investigation were to identify, de scribe and verify visual N, K, Mg, Mn, Zn and Fe deficiency symptoms of carambola, lychee and papaya grown in sand un der controlled conditions in a glasshouse. Materials and Methods The study was performed in a glasshouse in Gainesville, Florida, using containerized carambola, lychee and papaya plants grown in sand. The mean greenhouse temperature was 30°C (28-40°C). Plants were chosen for uniformity of size and appearance. Carambola plants were obtained from Zill's High Performance Nursery (Boyton Beach, FL) and propa gated by T-budding onto the industry standard rootstock seedlings of 'Golden Star'. Lychee plants were obtained from LNB groves, Homestead, FL and propagated by marcotting. 'Cariflora' papaya seeds were obtained from Lara Nursery & Farm, Homestead, FL and germinated in 24 cell polypropy370 Proc. Fla. State Hort. Soc. 108: 1995. lene flats filled with fine sand. Six-week old papaya seedlings were selected for uniformity of size and appearance. All trees were repotted into polypropylene pots (26 liter) containing white coarse silica sand (0.5-2.5 mm diameter). All trees were visually inspected for the presence of disease symptoms and pests to ensure that the deficiency symptoms that developed were due to nutritional anomalies. A plastic mesh screen was placed in the bottom of each pot to prevent the sand from moving through the drainage holes. Prior to potting, all polypropylene pots and the sand were washed with 10% H2SO4 and then thoroughly rinsed with de-ionized water. De-ionized water was also used for all nutrient solutions. Fresh nutrient solutions were prepared in 18 liter plastic containers prior to every application in order to minimize contamination and volatilization. A modified Hoagland nutrient solution consisting of in g I1: Ca(NO3)2,1.0; (NH2)4SO4, 0.05; KH2PO4, 0.31; and MgSO4, 0.60. In addition, 0.40 g I1 of Fe (EDDHA) and Mn (MnSO4), Cu (CuSO4) and Zn (ZnSO4) were supplied at a concentra tion of 0.04 g I1 (Hoagland and Arnon, 1938). Boron was add ed as H3BO3 at a rate of 0.004 g I1. The pH of all solutions was adjusted to 6.0 with sodium bicarbonate added to buffer the solutions immediately before they were applied to the plants. Treatments consisted of a complete modified Hoagland solu tion (control) and nutrient solutions minus N, K, Mg, Mn, Zn or Fe. One liter of nutrient solution was applied twice weekly to each plant for a period of 30 weeks (September 25,1994 Feb ruary 2,1995). Each plant was given a complete nutrient solu tion for two weeks prior to initiating the nutrient treatments. All nutrient solutions were applied to maintain moisture of the rooting media, allowing the solution to only slightly drain through each pot. On days in which nutrient solutions were not applied, each pot was irrigated with one liter of de-ion ized water, which only slightly drained through the bottom of each pot. Every two weeks, each pot was completely flushed with de-ionized water to reduce the build up of soluble salts. Plant growth and leaf coloration were observed periodically. Papaya trunk diameter (3 cm above the soil level) and plant height were measured at at the beginning and the con clusion of the study. Leaf tissue samples from each plant were collected either when deficiency symptoms appeared, or at the conclusion of the study. Sampled leaves and petioles were rinsed with deionized water, sliced into pieces and immedi ately placed into paper bags to air dry, then sealed to mini mize potential contamination. Samples were oven dried for 72 hours at 70°C then ground in a Wiley mill to pass through a 20-mesh screen and stored in plastic bottles. Chemical de termination was made on dried ground material. Analysis was determined by the Total Kjeldahl method (TKN) for N, and by inductively coupled argon plasma spectrometry for the other elements under study. There were two to six-single-plant replications arranged in a completely randomized block design for each nutrient treatment for each plant species. Data were analyzed by anal ysis of variance (SAS Institute, 1985) and where appropriate, means were separated using Dunnett's T-test at the P<0.05