Melon Crop Response to Different Levels of Calcium in the Nutrient Solution M.C. Salas, M. Urrestarazu, A. Bretones and J.A. Sánchez-Romero Dpto. Produccion Vegetal, Universidad de Almeria La Cañada de San Urbano s/n 0420, Almeria Spain Keywords: nutrient solution, Calcium, melon crop, soilless culture, uptake water, nutrient uptake, nitrate and phosphate contamination Abstract It is well known that calcium is an important nutrient to good growth of the whole plant. Experimental trial was carried out in Southern Spain (Almeria). Two nutrient solutions were used to fertigate melon plants (Cucumis melo L. cv. Alpes RZ) in coconut peat under glasshouse. Different proportions of Ca in the nutrient solutions were adjusted to maintain the cation-anion composition of the nutrient solution at 20 mmol c L -. In this experiment two different rates of Ca were used: 9 and 7 mmol c L -. Low levels of Ca in nutrient solution started at ripening period. The effects of different levels of Ca in nutrient solution on yield and quality of fruits, nutrient and water uptake and emission were measured. Yield and nitrate, phosphate, potassium and magnesium uptake were greater with nutrient solutions containing high levels of Ca. No significant differences were observed among the nutrient solutions studied for the quality parameters of fruits measured (soluble solids, firmness, dry weight, diameter). INTRODUCTION It is well known that calcium is an important nutrient to good growth of the whole plant. Calcium is transported towards the xylem mainly by apoplastic flux and the uptake is limited to the young sections of the roots (Hanson, 982). Ca is involved in mediating many physiological processes. In the absence of calcium the membrane becomes leaky and solutes are lost from the cytoplasm (Kirby and Pilbeam, 984). This nutrient is essential for cell division and expansion (White et al., 2000) and increasing number of studies focus on Ca as a second messenger. Ca modulates different response through a change in its concentration in the cytoplasm. Roots must balance the delivery of Ca to the xylem with the Ca needed by the cytoplasm of the root cell for cell signalling (White, 998). The mobility of Ca into the plant is very low as phloem transport is negligible (Marschner, 995). This could be related to immobility of calcium in plant, resulting in no calcium in newly formed tissues or related to a direct of calcium withdrawal on disrupting root cell membranes (Kirby and Pilbeam, 984). The lack of retranslocation of calcium from leaves may involve several steps such as mobility within the sieve tubes (Marschner, 995). As in many other plants, the lack of calcium in melon has been attributed to cultivar susceptibility (Coosemans, 989); the high levels of relative humidity (Mason and Guttridge, 975); the high saline concentration in the nutrient solution or in the leaf (Mason and Guttridge, 975) and so on. The high levels of Ca in nutrient solutions increase levels of this nutrient in the leaves (De Kreij, 995). In a recent review, Mulrooney (999) suggests that uptake of water is in relationships with uptake of calcium, when the plants are exposed to water stressful the uptake of Ca, K and Mg is limited. In an attempt to find techniques to improve the quality and yield of melon crops, we wish to study the relationships between uptake of cations (Potassium, Calcium and Magnesium) with different Calcium levels in the nutrient solution, maintaining the ionic concentration to avoid the effect of saline stress, their influence on anions uptake, water uptake, quality parameters of fruits, and yield of crop. Proc. IS on Soilless Cult. and Hydroponics Ed: M. Urrestarazu Gavilán Acta Hort. 697 ISHS 2005 487
MATERIALS AND METHODS Experimental trial was carried out in a greenhouse at Southern Spain (Almeria). Melon plants were planted on 26 February 2003 and the last harvest was on 9 June 2003. To study the effects of different concentrations of Ca 2+, a randomized completeblock design was arranged with three replications per treatments (Little and Hills, 987; Petersen, 994). Two nutrient solutions were used to fertigate melon plants (Cucumis melo L. cv. Alpes RZ) in coconut peat. In this experiment two different rates of Ca were used: 9 (T0) and 7 mmol c L - (T). Low levels of Ca in nutrient solution started at ripening period. Different proportions of Ca in the nutrient solutions were adjusted to maintain the cationanion composition of the nutrient solution at 20 mmol c L -. Throughout the experiment some fertigation parameters like uptake of ions (NO 3 -, H 2 PO 4 -, Cl -, SO 4 2-, Na +, K +, Ca 2+, Mg 2+ ) and waste of anions (NO 3 - and H 2 PO 4 ), uptake of water, EC and ph of drainage, were measured. The water uptake is the volume of water (L m -2 ) taken up in the time interval (day). Fruits were picked twice a week, weighed, early and total production and soluble solids (ºBrix), firmness (Kg), dry weight (%) and diameter (cm) were also measured. The experiment was conduced following the randomized complete block design (Little and Hills, 987; Petersen, 994). Two treatments were considered two different rates of Ca were used, and each one with three blocks. The data underwent variance analysis and the t of Student test was used to separate the averages. RESULTS AND DISCUSSION The lower yield corresponding to low levels of Ca, but not reduces early production (Fig. ). Total yield of T0 was 4.49 Kg m -2, higher than 3.57 Kg m -2 of T (7 mmol c L - ). Yield was significantly higher with high levels of Ca (p=0.05). No significant or slightly significant difference were observed among nutrient solutions studied for quality parameters measured (ºBrix, firmness, dry weight and diameter), although they improve with low levels of Ca (T) (Fig. 2). No significant difference was observed among the nutrient solution studied for water uptake and EC, ph and drainage fraction (%) (Table ). The same could be indicated for the nitrate and phosphate emissions (Table 2). The uptake of each macro-nutrient for both melon treatments (nitrate, phosphate, sulphate, calcium, potassium and magnesium) is shown in Table 3. Important differences were observed among nutrient solutions throughout the experiment, the difference were statistically significant for the data registered during some weeks and total uptake. In fact the nutrient uptake is very different at the two levels of Ca. Nutrient uptake was higher with high levels of Ca, all of cations was statistically significant (p=0.0), except Mg with p=0.05. The difference of NO 3 - and H 2 PO 4 - uptakes were statistically significant for the total uptake (p=0.0) Like another studies (Wieneke, 995) low NO 3 - uptake with low levels of Ca in nutrient solution. CONCLUSIONS The lower yield corresponding to low levels of Ca, but not reduces early production. Yield was significantly higher with high levels of Ca. No significant or slightly significant difference were observed among nutrient solutions studied for quality parameters measured (ºBrix, firmness, dry weight and diameter), although they improve with low levels of Ca. In relation ions uptake (nitrate, phosphate, sulphate, calcium, potassium and magnesium), important differences were observed among nutrient solutions throughout the experiment, the difference were statistically significant for the data registered during some weeks and total uptake. Nutrient uptake was higher with high levels of Ca. No significant difference was observed among the nutrient solution studied for water uptake. The same could be indicated for the nitrate and phosphate emission. 488
Literature Cited Coosemans, J.989. Leaf tipburn on strawberry. Acta Hort. 265: 489-496. De Kreij, C. 995. Latest insights into water and nutrient ontrol in soilless cultivation. Acta Hort. 408. Hanson, J.B. 982. The function of calcium in plant nutrition. Adv. Plant Nutrition : 49-59. Kirby, E.A. and Pilbeam, D.J. 984. Calcium as plant nutrient. Plant Cell Environmental 7: 397-405. Little,T.M. and Hills, F.J. 987. Métodos estadísticos para la investigación en la agricultura. Ed. Trillas. México Marschner, H. 995. Mineral nutrition of higher plants. 2nd. Ed. London. 889. Mason, G.F. and Guttridge, C.G. 975. The influence of relative humidity and nutrition on leaf tipburn of strawberry. Scientia Horticulturae 339-349. Mulrooney (999). Petersen, R. 994. Agricultural Field Experiments. Ed. Marcel Dekker, Inc. New York. White, P.J. 998. Calcium channels in the plasma membrane of root cells. Ann bot. New York, Academic Press, p. 73-83. White, P.J., Pneros, M., Tester, M. and Ridout, M.S. 2000. Cation permeability and selectivity of root plasma membrane calcium channel. J Memr bio. 74 :7-83. Wieneke, J. 995. Altered influx/efflux relations of nitrate in roots due to nutrient stress. Effect of calcium limitations. Journal of Plant Nutrition 8: 563-576. Tables Table. Parameters of fertigation of drainage and water consumption in a melon crop (Cucumis melo L. cv. Alpes) with two different levels of Ca 2+ in nutrient solutions: 9 mmolc L - (T0) and 7 mmolc ) L - (T). Low levels of Ca in nutrient solution started at ripening period (First week). Drainage EC (ds m - ) ph % Water uptake (L m -2 day - ) T0 T T0 T T0 T T0 T 3.42 3.47 6.29 6.03 6.0 22.76 2.74 2.53 SD 0.43 0.28 0.0 0.29.29 2.73 0.04 0.07 P 0.8933 0.4250 0.39 0.0953 489
Table 2. Nitrate and phosphate emissions (mmolc m -2 ) in a melon crop (Cucumis melo L. cv. Alpes) with two different levels of Ca 2+ in nutrient solutions: 9 mmolc L - (T0) and 7 mmolc ) L - (T). Low levels of Ca in nutrient solution started at ripening period (First week). - NO 3 - H 2 PO 4 Week T0 T T0 T 9.2 9.87 0.98 2.29 SD.38 2.55 0.07 0.76 P 0.7587 0.2452 2 5.455 5.0.0 2.2 SD 0.52 0.03 0.06 0.24 P 0.5085 0.0794 3 8.62.53.72 3.62 SD.05.9 0. 0.7 P 0.236 0.567 4 5.62 0.83 3.55 5.5 SD 0.85 0.35 0.25.2 P 0.048 0.3033 5 4.6 4.29 2.40 2.6 SD.20 4.94 0.29.5 P 0.9774 0.8405 Cycle 503.78 456.35 340.73 555.28 SD 38.84 55.44 5.0 44.80 P 0.766 0.0685 490
Table 3. Cations and anions uptake (mmolc m -2 ) in a melon crop (Cucumis melo L. cv. Alpes) with two different levels of Ca 2+ in nutrient solutions: 9 mmolc L - (T0) and 7 mmolc ) L - (T). Low levels of Ca in nutrient solution started at ripening period (First week). Cations Anions K + Na + Ca 2+ Mg 2+ Cl - - NO 3 - H 2 PO 4 2- SO 4 Week T0 T T0 T T0 T T0 T T0 T T0 T T0 T T0 T 7.8 20.76 2.58 4.26 6.46 2.54 8.07 8.7 0.80 5.22 27.08 9.67 2.90.53 6.28 4.86 SD 0.57 0.78 0.63 0.37 0.88.3 0.6 0.92 0.86.34.38 2.55 0.07 0.75 0.26.58 P 0.0420 0.087 0.087 0.8984 0.059 0.002 0.2324 0.4222 2 28.64 20.7.83 0.07 23.98 8.3 9.37 6.6 8.8 5.59 46.9 45.22.69 0.44 9.98 8.20 SD 0.74.78 0.08 0.2 0.98.20 0.62.44 0.45 0.8 0.52 0.03 0.06 0.24 0.23 3.6 P 0.066 0.0004 0.0056 0.559 0.0848 0.349 0.0728 0.627 3 26.2 8.72 3.37 2.34 28.37 8.39 2.4 8.06 9.23 3.4 42.3 33.40 4.2.4 0.95 6.99 SD 0.69 2.8 0.08 0.08 0.5.85 0.02.75 0.87 4.50.05.9 0. 0.7 0.9.72 P 0.509 0.0063 0.084 0.769 0.304 0.068 0.0968 0.858 4 9.39 7.68 4.35 0.23 26.60 5.9 0.23 5.70 6.42 2.64 40.83 2.50 4.3.2 9.67 2.53 SD 0.46.03 0.33 0.2 0.66 2.48 0.2.03 0.49.3 0.85.72 0.35 0.25.2 3.32 P 0.072 0.029 0.080 0.0972 0.0935 0.052 0.040 0.706 5 7.22 8.07 2.42 6.78 7.97.23 9.79 8.65 5.26 4.8 33.58 24.50 2.97.62 8.50 5.8 SD 0.64.68 0.0 0.35 0.54 2.36 0.6.68 0.00 0.09.20 4.94 0.29.5 0.47.94 P 0.6040 0.0355 0.399 0.50 0.0903 0.283 0.3337 0.2868 Cycle 3448 2658 509 78 3968 2298 745 286 396 758 6668 5050 556 205 588 993 SD 56 3 0 2 50 0 8 5 94 23 39 03 8 7 34 95 P 0.0092 0.0050 0.0084 0.032 0.06 0.0077 0.05 0.36 49
Figures 2,4 T0 Early production T 6 T0 T Total production,8 0.0805 4,5 0.0328,2 3 0,6,5 0,0 0 Fig.. Early and total production (kg m -2 ) in a melon crop (Cucumis melo L. cv. Alpes) with two different levels of Ca in nutrient solutions: 9 mmol c L - (T0) and 7 mmol c L - (T) T0 T T0 T 2,5,5 0,5 4,0 Soluble solids (ºBrix) Diameter (cm) 3,5 0.8664 0.4644 3,0 9,5 2,5 8,5 2,5 2,0,5,0 0,5 2,0 T0 T T0 T Firmness (kg) 2,0 Dry weight (%) 0.372 0,5 0.6623 9,0 7,5 0,0 6,0 Fig. 2. Quality parameters of fruits in a melon crop (Cucumis melo L. cv. Alpes) with two different levels of Ca in nutrient solutions: 9 mmol c L - (T0) and 7 mmol c L - (T). 492