41 Bulgarian Journal of Agricultural Science, 1 (6), 4147 National Centre for Agrarian Sciences Comparative Study of Some Quality Parameters of Lettuce in Dependence on Way of Cultivation I. DIMITROV 1, I. STANCHEVA, I. MITOVA 1 and E. ATANASOVA 1 1 N.Poushkarov Institute of Soil Science, BG18 Sofia, Bulgaria BAS, Acad.M.Popov Institute of Plant Phisiology, BG1113 Sofia, Bulgaria Abstract DIMITROV, I., I. STANCHEVA, I. MITOVA and E. ATANASOVA, 6. Comparative study of some quality parameters of lettuce in dependence on way of cultivation. Bulg. J. Agric. Sci., 1: 4147 The influence of different way of cultivation on lettuce yield and quality was studied. Two field experiments were carried out on alluvial meadow soil in Tsalapitsa experimental station. The experiments were performed with lettuce, grown as a spring crop and winter crop with application of three fertilizer sources: mineral fertilizer, farmyard manure and foliar fertilization. Significantly higher yield values from lettuce were obtained when lettuce was grown both at spring and winter lettuce crop in the variants with mineral fertilization. The best quality parameters: high values of soluble sugars and vitamin C content, low level of cellulose and reduced nitrate content were observed in the variants with foliar fertilization. Key words: lettuce, mineral fertilization, organic fertilization, foliar fertilization, quality parameters Introduction The optimum fertilizer rates application in vegetable growing are the main factors for receiving profitable production with low nitrates content without creating conditions for pollution of different components of the ecosystem. When the lettuce was grown as a third crop in the rotation has lead to maximum inclusion of nitrogen in the nutrients cycle was observed resulted in the restoration of nitrogen content in the soil near its background values (Stoicheva, et al., ). The quality of vegetables is in close dependence on the way of cultivation. Application of different fertilizer sources influenced in a different way lettuce yield and quality which strongly depended on soil climatic conditions (Martinetti, 1996; Stancheva et al., 1997). The most favorable effect of foliar fertilization on the quality of lettuce grown during the spring was shown in our earlier work (Dimitrov et al., 5). In our previous studies with leafy vegetables the optimal fertilizer rates of mineral organic and foliar fertilizers that de
4 fined quality parameters according to Bulgarian standards were established (Stancheva and Mitova, ; Stancheva et al., 4). High nitrates accumulation in lettuce leaves is closely related to the nitrogen nutrition (Gonnella et al., ) and duration of the period of vegetation (Reinken, 199). The aim of the present study is to establish the impact of way of lettuce cultivation and respectively the vegetative period duration on the yield and quality of lettuce. Material and Methods I.Dimitrov, I.Stancheva, I.Mitova and E.Atanasova Two trials with lettuce plants (Lactuca sativa L.) cv. Paris Island cos. were grown as a spring crop with duration of vegetation 4 days (8.3. 1.5. 4) and a winter crop with duration of vegetation 184 days (4.9.4 4.5.5) at the N. Poushkarov Institute experimental field in Tzalapitca Plovdiv region on a alluvial meadow soil. Lettuce seedlings were planted at plant density 14 plants per m. All treatments were arranged in randomized complete block design with four replicates. Experimental plot area was 3 m. The following variants have been tested: B 1 control without fertilization; B mineral fertilization with N15P1K1; B 3 organic fertilization with farmyard manure,4 t/da; B 4 foliar fertilization with Agroleaf (N % P % K % ). Nitrogen fertilizer was applied as an ammonium nitrate /3 before the planting and 1/3 as a dressing. Phosphorus was applied as a triple superphosphate one time spread before the planting and potassium as K SO 4 1/ before the planting and 1/ as a dressing. The content of decomposed ship farmyard manure is: total N.64%, total Р О 5 1.84% and total К О.51 %. The rate of organic fertilizer is relevant to the variants with mineral fertilization. Agroleaf (Scotts Company, Ohio, USA and distributed by VLADI Company in Bulgaria) total N:P:K :: + all important microelements, was applied three times during the vegetative growth stage on 1 days interval, starting 15 days after planting. Microelements in chelated form are present in the unique Scotts M77 formula:.1% Fe,.6% Mn,.6% Cu,.6% Zn,.% B. Agroleaf was applied by spraying under high pressure at rates of.5 kg/da or.5% solution. At the lettuce harvest the following parameters were measured: yield of fresh biomass, dry weight, vitamin C content by Murry and cellulose after Kyurshner (Ermakov et al., 195), total soluble sugars (Dubois, 1956). The content of nitrates was determined by Nitrachek from Hawk Creek Laboratory Inc. USA and leaf tissue nitrate quick test was made. Nitrate reductase (NR, EC 1.6.6.1) was measured in vivo according Klepper et al., (1971). When the lettuce was harvested soil samples have been collected for determination of soil mineral nitrogen (spectrophotometrically after Kjeldal digestion), phosphorus and potassium after acetate lactate method (Ivanov, 1984). Data are expressed as means ± standard error where n=4. Comparison of means was performed by the Fisher LSD test (P<.5) after performing multifactor ANOVA analysis. The STASTICA
Comparative Study of Some Quality Parameters of Lettuce... 43 (version 6.) package was used for statistical analysis. Results and Discussion The influence of different nitrogen sources on the lettuce yield is statistically proved at LSD 5% analyzing spring lettuce crop while in the winter lettuce crop statistically significant differences at LSD 5% were established only in relation to mineral fertilization (Table 1). In relation to spring lettuce crop, the differences between mineral and organic fertilization and mineral and foliar fertilization were significant, but differences between organic and foliar fertilization were not found. The highest lettuce yield both at spring and winter lettuce crop was estimated at mineral and organic fertilization, the lowest yields were observed in the treatments with foliar fertilization (Table 1). Lettuce production was related to the nitrogen source and amounts of fertilizer applied (Stancheva et al., 1997). However some authors (Gunes et al., 1995) reported that different nitrogen sources did not cause big differences in fresh and dry weight in lettuce. The content of accessible forms of the main macronutrients N, P, K after harvest of the both lettuce trials indicated more fully uptake of these macronutrients by the plants (Table ). While in the spring lettuce nitrogen uptake was higher at foliar fertilization, in the winter lettuce crop maximal nitrogen uptake was estimated both at organic and foliar fertilization. Soil phosphorus content significantly diminished independently on different nitrogen sources. The uptake of phosphorus and potassium had maximal values in organic fertilized variants in the spring crop, but in the winter lettuce crop maximal phosphorus and potassium uptake were read in foliar and mineral fertilized plants. The changes of soil ph values were negligible at different fertilizer sources and optimal ph for lettuce growth are established in the range 6.7. which is optimal for the lettuce growth, because lettuce has been found to be sensitive to soil acidification (Arsova, 1994). Dry matter content values were the highest and almost equal in the variants with mineral and foliar fertilization (Figure 1) both in the in the spring and the winter lettuce crop. Higher percentage of dry matter in the leaves of winter lettuce Table 1 Yield of fresh biomass Variants Lettuce grown as a spring crop, kg/da Lettuce grown as a winter crop, kg/da 1. В 1 Control 77a 44.a. В Mineral fertilization 1788с 859.8b 3. В 3 Organic fertilization 1318b 774.6ab 4. В 4 Foliar fertilization 117b 587.8ab LSD 5% 34. 5 569.8 Different letters indicate significant differences assessed by Fisher LSD test (P<.5) after performing ANOVA multifactor analysis
44 I.Dimitrov, I.Stancheva, I.Mitova and E.Atanasova Table Changes of some agrochemical parameters after harvest the lettuce Variants Mineral nirtrogen, mg/1g Mobile forms, mg/1g рн (Н О) NNH 4 NNO 3 total P O 5 K O Lettuce, grown as a spring crop Initial level 1.85 6.84 8.69.3 7. 6.4 B 1 Control 3.17 4.84 8.1 6.3 16. 6.5 В Mineral fertilization 6.1 9.18 15.19 6.5. 6.3 В 3 Organic fertilization 5.51 5.1 1.5 6. 15. 6.4 В 4 Foliar fertilization 3.11 5.67 8.78 7.1 18. 6.4 Lettuce, grown as a winter crop Initial level 8.85 6.84 15.69 1. 3.5 6.6 B 1 Control 6.3 3.35 9.38 9.4 1. 6.5 В Mineral fertilization 7.71 8.38 16.9 7. 1. 6.4 В 3 Organic fertilization 7.4 3.35 1.39 9. 11. 6.5 В 4 Foliar fertilization 8.7 6.3 14.75 8. 9. 6.4 in comparison with the spring lettuce was estimated which could due to the longer vegetative period. Foliar fertilized plants in both cultivation ways contained reduced cellulose levels, which is an indicator for the good quality (Figure ). High cellulose Dry biomass content content was observed in non fertilized plants and in the plants with mineral fertilization, especially in lettuce grown in the winter. The content of vitamin C (Figure 3) and soluble sugars (Figure 4) increased in the fertilized plants, and the highest val Content of cellulose Dry weight content, % 14 1 1 8 6 4 В1 В В3 В4 Fig. 1. Dry biomass content, % Cellulose, % 1 1 8 6 4 В1 В В3 В4 Fig.. Content of cellulose, % of dry weight Legend: B 1 control; B mineral fertilization; B 3 organic fertilization; B 4 foliar fertilization; spring culture; winter culture
Comparative Study of Some Quality Parameters of Lettuce... 45 ues were found in the foliar fed plants. The trend of the higher values of quality parameters for the winter lettuce crop revealed again. Some authors (Gonella et al., ) pointed out that inappropriate fertilization resulted in quality deterioration for leafy vegetables high levels of crude protein and nitrates and reduction of carbohydrates and vitamins. Accumulation of nitrates is previously observed in the plants with mineral fertilization and higher content was measured in the leaves of spring lettuce crop (Figure 5). The content of nitrates in the leaves of the plants from spring and winter crops remained much lower than the acceptable limit concentration 1 mg/kg fresh weight (Instruction 5, 1984). Nitrate reductase activity varied among the variants of fertilization and way of cultivation (Figure 6). In the leaves of spring grown plants maximal values were found in the variants with organic and mineral fertilization, while in the winter grown Vitamin C, mg/1g fresh weight 8 6 4 Vitamin C content В1 В В3 В4 Fig. 3. Vitamin C content, mg/1g fresh weight Soluble sugars,mg/1g dry weight 14 1 1 8 6 4 Content of soluble sugars В1 В В3 В4 Fig. 4. Content of soluble sugars, mg/1g dry weight Nitrates,mg/kg fresh weigh 4 3 1 Content of nitrates В1 В В3 В4 Fig. 5. Content of nitrates, mg/kg fresh weight NRA,µg/g fresh weight 1 1 8 6 4 Nitratereductase activity В1 В В3 В4 Fig. 6. Nitratereductase activity, µg/g fresh weight Legend: B 1 control; B mineral fertilization; B 3 organic fertilization; B4 foliar fertilization; spring culture; winter culture
46 plants nitrate reductase activity was the highest in the variants with mineral and foliar fertilization. Nitrate reductase enzyme activity is higher in the winter lettuce compared to the spring lettuce crop. The values of quality parameters (dry weight, percentage of the cellulose, content of vitamin C, soluble sugars and nitrates) both in the spring and winter lettuce crop changed in a similar way in dependence of fertilizer sources. In general the values of quality parameters (percentage of dry biomass, content of soluble sugars, vitamin C, cellulose and nitrate accumulation) obtained for the winter lettuce crop are higher in comparison with the parameters obtained for the spring lettuce crop with the exception of the content of nitrates in the variants with mineral fertilization of the spring lettuce. Conclusions The highest yields of lettuce, grown as a spring and winter crop were obtained after application of mineral and organic fertilizers. Significantly higher yields were observed during the winter lettuce cultivation. Fresh lettuce produce with best quality parameters was obtained as a result of foliar fertilization both in the spring and the winter lettuce cultivation. The better lettuce quality was estimated in the winter crop. Acknowledgements The study was conducted with a financial support of a National Science Fund at Ministry of Education and Science, Bulgaria. I.Dimitrov, I.Stancheva, I.Mitova and E.Atanasova References Arsova, A., 1994. Effects of soil acidity neutralization and mineral nutrition on yield and cation in biomass of parsley, lettuce and perko. Bulg. J. Pl. Phys., (14): 4653 Dimitrov, I., I. Stancheva, I. Mitova, E. Atanasova, 5. Quality and yield of lettuce in dependence on different fertilizer sources. Bulg. J. Agric. Sci., 11: 589594. Dubois, M., K. A. Giles, J. K. Hamilton, P. A Rebers and F. Smith, 1956. Colorimetric method for determination of sugars and related substances. Anal. Chem., 8: 35356. Ermakov, A.I., V.V. Arasimovich, M.I. SmirnovaIkonnikova and I. K. Murry, 195. Metody biokhimicheskogo issledovaniya rastenij, GISL, Moscow, 34 pp. (Ru). Gonnella, M., G.Gonversa and A. Elia,. Nitrogen level yields and nitrate accumulation in soilless grown lettuce (Lactica sativa L.). In: Proceeding of Scientific meeting of Italian Horticultre society., 83 May, Sirmone, Brescia, Italy. Gunes, A., W. H. K. Post and M. Aktas, 1995. Effect of partial replacement of NH4+N urean and amino acidn in nutrient solution on nitrate accumulation in lettuce (Lactuca sativa L.). Agrochimica, 39 (5 6): 36333. Instruction No5. 1984. Selected Passages from Instruction No5 of the Ministry of Health about Sanitary Standards and Acceptable Limit Concentrations for Chemical and Biological Pollutions in Foods. State Newspa
Comparative Study of Some Quality Parameters of Lettuce... 47 per, No39/1984,add. No5/1986, add. No15/1987. Ivanov, P., 1984. Nov acetatnolaktaten metod za opredelyane na usvoimite phosphor i kalij v pochvata. Soil Science and Agrochemistry, 19: 8896 (Bg). Klepper, L.A., D. E. Flesher and R. H. Hageman, 1971. Generation of reduced nicotinamide adenine dinucleotide for nitrate reduction in green leaves. Plant Physiology, 48: 5859. Martinetti, L., 1996. Nitrate and nitrite content of lettuce (Lactuca sativa L.) with different nitrogen fertilizer rates, Rivista di Agronomia, 3 (1): 996. Reinken, G., 199. Nitrat in Gemnfordet oder hemmt es die Gesundheit. Gemuse, 7: 36137. Stancheva, I., A. Arsova and N. Dinev, 1997. Received February, 14, 6; accepted April, 1, 6. Lettuce growth in relation to nitrogen source, fertilizer rate and soil acidity.i. Yield and plant mineral composition. Bulg. J. Agric.Sci., 3: 14315. Stancheva, I. and I. Mitova,. Effects of different sources and fertilizer rates on the lettuce yield and quality under controlled conditions, Bulg. J. Agric. Sci., 8: 15716. Stancheva, I., I. Mitova, E. Atanasova and R. Toncheva, 4. Effect of nitrogen fertilizer sources and rates on the lettuce yield and quality. Ecologia i industria, 6 (1): 883 (Bg). Stoicheva, D., P. Alexsandrova, D. Donov, D. Stoichev, G. Angelov and L. Raikova,. Ecological Assessment of Different Nitrogen Fertilizer Rates in a Vegetable Crop Rotation. Bulg. J. Agric. Sci., 8: 14115.