Agricultural and Food Science in Finland, Vol. 11 (2002): 301–310 301 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 11 (2002): 301–310. © Agricultural and Food Science in Finland Manuscript received April 2002 Nutritional status in commercial currant fields Raina Niskanen Department of Applied Biology, Horticulture, PO Box 27, FIN-00014 University of Helsinki, Finland, e-mail: raina.niskanen@helsinki.fi The nutritional status on commercial currant fields was elucidated by advisory analytical data of 357 pairs of soil and leaf samples from commercial black, red and white currant fields in Southern and Middle Finland. The purpose was to investigate how nutrient concentrations in soil and leaves fitted in the recommended ranges, correlated with each other and to evaluate their usefulness in diagnosis of nutritional status. Soil pH(H 2 O) and extractable nutrients (NO 3 -N, P, K, Ca, Mg, B, Cu, Mn) and leaf nutrients (N, P, K, Ca, Mg, B) were analysed. The mean soil pH, P, K and Mn were in the recommended ranges. Over 50% of soil P and 60% of Mg results and the greatest part of Ca results passed below the lower recommended limits, but soil B and Cu were frequently over the upper rec- ommended limits. The mean leaf N, P and K on all currants, Mg on black and red currants and Ca and B on black currant were within the recommended limits. The lower recommended limit of Mg was passed below in 74% of white currant leaf samples. Positive correlations were found between soil and leaf nutrient concentrations for P, Ca and Mg. The recommended lower soil analysis limits might possibly be too high for coarse soils, because low values of soil P, Mg and Ca were common. The nutrients also might not be evenly distributed in the sampled soil layer but might be accumulated in a thin surface soil layer because of repeated surface broadcasting of fertilizers. Key words: black currants, leaf analysis, macro- and micronutrients, red currants, Ribes nigrum, Ribes x pallidum, soil pH, soil testing, white currants Introduction The chemical composition of a plant changes with nutrient supply, although the change is by no means commensurate with the variation in external supplies (Asher and Loneragan 1967, Spear et al. 1978). Soil analysis alone is not al- ways a satisfactory guide to the fertilization of perennial plants like berry and fruit crops (Bould et al. 1960). Recommendations based on soil analysis assume that there is a direct relation- ship between the extractable nutrients in the soil and the uptake by plants. However, this relation- ship is affected by environmental factors like soil moisture. Therefore leaf analysis can be a more mailto:raina.niskanen@helsinki.fi 302 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Niskanen, R. Nutritional status in currant fields reliable tool in assessing the nutritional status and response to fertilizers and in giving infor- mation about the real uptake of nutrients. In Fin- land, leaf analysis has been used in the fertiliza- tion recommendations for currants since the 1970s. However, the values recommended for leaf nutrients have largely been based on the re- search done abroad. In addition, the studies have mainly concentrated on black currant (Ljones 1963, Bould 1964, 1969, Bjurman 1971, Bould and Parfitt 1972, Vang-Petersen 1973, Säkö and Laurinen 1979, Aaltonen and Dalman 1993, Nis- kanen et al. 1993, 1999, Kongsrud and Nes 1999, Aflatuni et al. 2001), and there are few studies on red and white currants (Vang-Petersen 1973, Ljones 1984, Aaltonen 1990, 1992, Aaltonen and Dalman 1993, Niskanen et al. 1993, 1994, 1999, Dierend et al. 1998, Rupp and Tränkle 2000). Therefore, recommendations for black currant (Ribes nigrum L.) have largely been applied also to red and white currants (Ribes x pallidum Otto & Dietr.). Fluctuations in berry yields are major prob- lems in commercial currant production (Voipio and Niskanen 1990, Niskanen and Matala 1991), and more knowledge is needed for solving the causes of low yields. More research is needed on the effects of fertilization on the berry yield and the applicability of soil and leaf analysis in the advisory work on fertilization (Niskanen 1989). Both environmental and economical viewpoints assume that fertilization must be as appropriate as possible. In practical cultivation, there have been problems in the interpretation and combination of soil and leaf analysis results, because they give sometimes contrary compre- hensions of the nutritional status. When nutrient concentrations in leaves are within the recom- mended range, it has been difficult to use them as a basis for optimization of fertilization, be- cause the values vary depending on the condi- tions. Because of these problems, leaf analysis has not been useful enough and has not met the needs of practical cultivation (Matala 1999). Therefore, the use of commercial analysis of leaf samples has decreased radically (Alainen 1999, personal communication). The intention of this study was to elucidate the nutritional status on Finnish commercial cur- rant fields, to compare leaf nutrient levels of dif- ferent currant species, and to investigate how nutrient concentrations in soil and leaves fitted in the recommended ranges, correlated with each other and to evaluate their usefulness in diagno- sis of nutritional status. Material and methods To study the nutritional status of commercial currant fields, soil testing and leaf macronutri- ent data provided by Soil Testing Service Ltd was investigated. During 1982–1991, soil and leaf samples were taken by growers after har- vest at the end of August or at the beginning of September in commercial black, red and white currant fields located in Southern and Middle Finland. The total numbers of soil and leaf sam- ples were 287, 51 and 19 for black, red and white currant fields, respectively. The samples were sent to Soil Testing Service Ltd for analysis. The cultivars were not always reported by the grow- ers. However, ‘Red Dutch’, ‘Rondom’ and ‘White Dutch’ grew in some red and white cur- rant fields, and the main black currant cultivar was ‘Öjebyn’. According to the instructions (Soil Testing Service Ltd), soil samples should consist of 8– 10 subsamples taken from the depth of about 0– 20 cm and mixed thoroughly. The textural and humus content classes of soils were estimated by finger assessment. The pH and nitrate nitro- gen were determined in soil-water suspension (1:2.5) after 12 hours standing. An ion-specific electrode was used for the measurement of the nitrate nitrogen. Before 1989, only nitrate nitro- gen values higher than 10 mg l–1 soil were re- ported. Soil P, K, Ca and Mg were extracted by acid ammonium acetate (0.5 M acetic acid, 0.5 M ammonium acetate, pH 4.65, ratio 1:10 v/v, 1 h) (Vuorinen and Mäkitie 1955). Soil boron was extracted by hot water (Berger and Truog 1944) 303 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 11 (2002): 301–310. and copper and manganese by acid ammonium acetate-EDTA solution (Lakanen and Erviö 1971). Phosphorus was determined by a modifi- cation (Vuorinen and Mäkitie 1955) of molyb- denum blue method, potassium and calcium by flame photometry, magnesium, copper and man- ganese by atomic absorption spectrophotometry and boron by plasma emission spectroscopy. The extraction method for soil copper and manga- nese was changed in 1986 and, differing from the other elements, only the results of the period 1986–1991 were included in the present study for these two nutrients. The results of manga- nese are given as pH-corrected values. The meas- ured manganese concentrations (mg l–1 of soil) were multiplied by a coefficient which is depend- ent on soil pH (Sillanpää 1982). The leaf samples consisted of 40–100 com- pletely developed healthy leaf blades (about 100 g of fresh weight) of new shoots from all around the bushes. Air-dried leaf samples were ground and ashed at 550°C and the ash was dis- solved in 2 M HCl. P, K, Ca, Mg and B in ash extracts were determined by plasma emission spectroscopy. Leaf N was determined by the Kjeldahl method. Results The samples collected from commercial currant fields during 1982–1991 consisted mainly of coarse mineral soils (Table 1). The greatest group consisted of sandy moraines of medium humus content. The mean soil pH was in the recom- mended range, but the values were under the low- er limit in part of the soil samples (Table 2). The percentage of low pH values was highest for red currant fields. Nitrate N was below the range recommended for samples collected in autumn. The data on nitrate N was limited and included only samples from black currant fields where the Table 1. Percentage of soil samples from currant fields of different textural and humus content classes during 1982–1991. % of currant fields Black Red White (n = 287) (n = 51) (n = 19) Textural class1 Clay, silt, loam 12 00 00 Fine sand 21 10 21 Sandy moraine 60 73 79 No information 05 18 00 Humus content2 Low 06 04 16 Medium 64 57 79 Rich 21 22 05 Very rich 01 00 00 Mull 02 00 00 No information 05 18 00 1 Percentage of particle size fractions in textural classes: Diameter, mm Clay Silt Loam Coarser soils < 2 ≥ 30 < 30 < 30 < 30 2–20 > 50 < 50 < 50 > 20 < 50 > 50 2 Percentage of organic matter in humus content classes: < 3 low, 3–5.9 medium, 6–11.9 rich, 12–19.9 very rich, 20–40 mull n = number of samples 304 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Niskanen, R. Nutritional status in currant fields nitrate N concentration was <10 mg l–1 soil in 83% of samples. The means of soil P and K were in the recommended ranges. However, P, Mg and Ca values commonly fell below the recommend- ed lower limits. Soil B and Cu were frequently over the upper recommendation limit. On the average, soil manganese was in the recommen- dation range. Low manganese values were most common on black currant fields. The mean values of N, P and K in currant leaves were in the recommended ranges (Ta- ble 3). In black and white currant leaves, K level was good but N was below the recommended lower limit in one-fifth of the samples. High P values were most common in red currant leaves and high K values in black currant leaves. The mean Mg concentration in leaves of black and red currants were within the recommended range, low values being most common in white currant leaves. On average, Ca and B in black currant Table 2. Soil pH(H2O), extractable P, K, Ca, Mg and B (mg l –1 soil) in 1982–1991 and NO3 – -N (mg l –1) in 1989–1991, copper (mg l–1) and pH-corrected manganese in 1986–1991 and percentage of samples with values below (low values) and above (high values) the ranges recommended for currant fields. Property1 Currant n Mean SD Range Percentage of low values high values pH Black 287 6.3 0.4 5.3–7.4 27 14 Red 051 6.2 0.4 5.2–7.0 39 14 White 019 6.4 0.5 5.7–7.2 21 37 P Black 287 22 17 001–106 59 14 Red 051 26 21 04–95 51 22 White 019 20 10 08–43 53 05 K Black 287 187 80 020–562 32 06 Red 051 195 92 040–380 35 08 White 019 164 80 055–320 53 00 Mg Black 287 198 88 040–690 61 04 Red 051 168 65 050–395 78 00 White 019 164 57 080–255 63 00 Ca Black 287 1466 461 0500–4100 91 03 Red 051 1430 451 0625–2525 86 00 White 019 2005 1577 0725–8000 74 16 B Black 287 1.0 0.4 0.3–2.5 08 48 Red 051 1.2 0.5 0.6–2.6 00 63 White 019 1.6 0.6 0.6–2.8 00 90 Cu Black 159 10.5 7.9 01.1–50.8 08 75 Red 030 6.6 4.0 2.0–6.0 00 53 White 017 11.7 6.4 01.8–25.6 06 88 Mn Black 159 37 24 006–165 38 08 Red 030 37 17 11–96 23 03 White 017 55 72 020–330 18 12 NO3 – -N Black 033 7.5 6.5 01.2–31.0 1 Ranges recommended for coarse mineral soils (Viljavuuspalvelu 1997): pH 6.1–6.5, P 20–40, K 150–350, Ca 2000– 2600, Mg 200–400, B 0.6–0.9, Cu 2.7–5.0, NO3 – -N 30–50 mg l –1 soil, Mn-value 25–75 SD = standard deviation, n = number of samples 305 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 11 (2002): 301–310. leaves were in the recommended range, although the number of analyses was low. The most re- markable distinction between nutrient levels in leaves of different currant species was a higher K level for red and white currants as compared with black currant. Mg was the only nutrient with higher values for black currant than for red and white currants. The other nutrient levels were higher for red currant than for black currant. Positive correlations between leaf and soil nutrients were rather weak for P in black and red currant fields (Fig. 1). Values of correlation coefficients were rather low also for Mg of black currant and red currant (Fig. 2). A weak nega- tive correlation was found between soil and leaf K in red currant fields (Fig. 3). Table 3. N, P, K, Mg, Ca (g kg–1 of dry matter) and B (mg kg–1 of dry matter) in currant leaves 1982–1991 and percentage of samples with nutrient values below (low values) and over (high values) the recommendation range. Nutrient1 Currant n Mean SD Range Percentage of low values high values N Black 287 24.1 5.2 10.2–54.5 18 08 Red 051 26.9 5.2 16.5–45.7 06 06 White 019 24.9 4.5 16.9–31.2 21 00 P Black 287 05.6 1.7 02.2–10.1 05 09 Red 051 06.5 3.7 02.2–15.7 12 26 White 019 05.1 1.4 3.1–8.1 00 05 K Black 287 17.2 4.5 08.7–34.6 01 26 Red 051 30.6 7.3 17.1–47.9 08 12 White 019 31.7 3.2 25.8–35.9 00 00 Mg Black 287 05.1 1.3 2.3–9.3 17 03 Red 051 03.4 0.8 1.7–4.9 28 00 White 019 02.8 0.7 1.7–4.0 74 00 Ca Black 019 20.7 3.5 12.0–25.6 Red 006 31.0 2.6 27.8–35.6 B Black 040 34.3 10.20 19.5–82.0 Red 006 37.2 2.3 35.3–41.0 1 Recommendation ranges for nutrients in August (Viljavuuspalvelu 1997): N P K Mg Ca B Currant g kg–1 of dry matter mg kg–1 of dry matter Black 20–30 3–8 10–20 4–8 20–30 20–60 Red, white 20–35 3–8 20–40 3–5 10–25 20–60 SD = standard deviation, n = number of samples Discussion The ranges recommended (Viljavuuspalvelu 1997) in Finland for macronutrient concentra- tions in currant leaves are wider and for nearly all nutrients higher than the optimum ranges for black currant leaves suggested in England (N 29– 30, P 2.5–3.0, K 10–15, Mg 1.0–1.5 g kg–1 dry matter) (Bould 1964, 1969) and values recom- mended for all currants in Norway and Sweden (N 26–29, P 1.5–2.0, K 12–16, Ca 14–17 and Mg 2.5–3.5 g kg–1 dry matter) (Larsson and Svensson 1989). In commercial currant fields, nutrient values below the recommended lower limits were more 306 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Niskanen, R. Nutritional status in currant fields common in soils than in leaves. The fact that soil P, Mg and Ca values commonly fell below the recommended lower limits may reflect the great proportion of coarse soils with rather small nu- trient sorption capacity. Furthermore, the pH was below the recommended lower limit in some of the soil samples. With decreasing pH the extract- ability of soil P by acid ammonium acetate de- creases (Hartikainen 1989) and the pH-depend- ent part of cation exchange capacity diminishes (Mäntylahti and Niskanen 1986). This latter fact is revealed by positive correlation between pH and extractable Ca and Mg representing prima- rily the exchangeable cation fraction (Niskanen and Jaakkola 1985). In regard to Mg, low values in soil were reflected by low values in the leaves of red and white currants. Soil and leaf analysis partially gave conflict- ing impressions of the nutritional status of cur- rant fields. Although the nutritional status was satisfactory according to the soil analysis, the leaf concentrations were low. For example, in Fig. 3. Leaf versus soil K in black and red currant fields in 1982–1991 (significance: * P = 0.05, ns = not significant; black currant, n = 287, red currant, n = 51). Fig. 1. Leaf versus soil P in black and red currant fields in 1982–1991 (significance: *** P = 0.001, * P = 0.05; black currant, n = 287, red currant, n = 51). Fig. 2. Leaf versus soil Mg in black and red currant fields in 1982–1991 (significance: *** P = 0.001, * P = 0.05; black currant, n = 287, red currant, n = 51). 307 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 11 (2002): 301–310. commercial fields K in black currant leaves tend- ed to decrease in August although the soil K was satisfactory (Niskanen 2001). In this case it was possible that high Ca decreased the uptake of K. Antagonism between the K and Ca uptakes of black currant was also found in the study of Ljones (1963). The weak negative correlation between soil and leaf K in commercial red cur- rant fields might be related to this connection. Rather weak positive correlations were found only in the cases of P and Mg. In a Norwegian field experiment on black currant, positive cor- relations between soil and leaf nutrients were found for P, K, Mg and Ca (Ljones 1963). In field experiments on black and red currants carried out by Aaltonen and Dalman (1993), the values of linear correlation coefficients between nutri- ents in the currant leaves and in the soil were mostly low. Leaf nutrient concentrations were only slightly dependent on soil nutrients also in Finnish commercial apple orchards (Dris et al. 1997, Dris and Niskanen 1998) and strawberry fields (Niskanen and Dris 2002). When the soil nutritional status is at least satisfactory, the poor correlation between nutrient concentrations in soil and in leaf dry matter is obvious and can be due to many factors affecting the availability and uptake of nutrients, e.g. weather conditions, soil moisture and nutrient levels, competition be- tween nutrients in plant uptake, efficiency of shoot growth, amount of yield and incidence of pests. Also the soil and leaf sampling, its timing and how properly it is done, has an effect on how representative the results are. The data from com- mercial currant fields included material which was analyzed during a period of ten years. Dif- ferences in field management and weather con- ditions during growing seasons could cause var- iation in the data. Additional variation might be caused by differences in leaf nutrient composi- tion between cultivars. Leaf Ca has been ana- lyzed only seldom, the data from red and white currant fields was limited and there might be variation in the sampling methods used in dif- ferent farms. As compared with the results of a single field experiment, different growth condi- tions and soil characteristics cause more varia- tion in the analysis results of a material collect- ed from many commercial fields. There seemed to be, however, no great differences in the aver- age macronutrient composition of black currant leaves between commercial cultivations and pot and field experiments (Niskanen 2001). The recommended lower soil analysis limits might be too high for coarse soils, because low values of soil P, Mg and Ca were rather com- mon. It is also possible that nutrient concentra- tions are not evenly distributed in the sampled soil layer. In order to avoid of breaking the shal- low root systems, soil tillage is lacking in per- ennial crop fields. It has been shown on black currant (Coker 1958) that under nontilled soil the level of root activity is greatest from 5–10 cm deep, if the surface soil moisture conditions are favorable. In fruit and berry fields the com- mon practice has been to broadcast fertilizers on the soil surface. Therefore, nutrients accumulat- ed in a thin surface soil layer from where the absorption of nutrients by roots has largely tak- en place. In this case, nutritional status might be satisfactory according to the leaf analysis but according to the soil analysis nutrient levels might be low because in soil sampling higher nutrient concentrations of the thin surface layer have been diluted to a larger sampled soil vol- ume. High values of soil B and Cu were common in currant fields. This can be attributable to the use of compound fertilizers including micronu- trients. The repeated surface broadcasting of these fertilizers might have caused enrichment of B and Cu in the soil surface layer at a detri- mentally high level, because these elements are liable to be tightly bound in soil. High Cu and B levels in soil have been commonly found also in strawberry fields (Kukkonen and Uosukainen 1999, Niskanen and Dris 2002). It is considered that low strawberry yields might be partially caused by high soil B concentration. In currant fields it might be also necessary to reconsider the amount of B and Cu fertilization. High soil P values were found in a part of currant fields. In nontilled soil, broadcasted P is bound to 1–2 cm thick surface layer and the sol- 308 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Niskanen, R. Nutritional status in currant fields uble P concentration of this layer increases and may lead to higher loss of P by surface runoff and drainage water (Turtola and Jaakkola 1995, Turtola and Kemppainen 1998, Turtola and Yli- Halla 1999). This risk is very possible, because currants are often cultivated on coarse mineral soils and slope fields. The recommended soil P range for currant fields is rather high as com- pared the present recommendations for cultiva- tion of cereal and other agricultural crops (Yli- Halla et al. 2001). It might be necessary to ad- just recommendations for soil P also in currant fields. Furthermore, it could be reasonable to replace surface broadcasting of fertilizers by oth- er fertilization methods like placement fertiliza- tion (Niskanen et al. 1999) and fertigation (Kongsrud and Nes 1999) for improvement of the use of nutrients and for prevention of nutri- ent losses by surface runoff and drainage water. According to the soil analysis results low Ca, Mg, K and P values were common in currant fields but leaf analysis results were mostly in recommended ranges and did not indicate fre- quent nutrient deficiences in currant fields. Be- cause the use of commercial analysis of leaf sam- ples has decreased radically, the fertilization has been based only on soil analysis results. Then low soil nutrient values have led to high fertili- zation recommendations and possibly to use of superfluous high fertilizer doses. Acknowledgements. The author wishes to thank Soil Test- ing Service Ltd. for delivering the results of berry series analysis. References Aaltonen, M. 1990. 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Aineistosta selvitettiin, oliko maan ja lehtien ravinnepitoisuuksien välillä yhteyt- tä, ja kuinka hyvin ravinnepitoisuudet vastasivat suo- situsarvoja sekä kuvasivat viljelmien ravinnetilaa. Maanäytteiden keskimääräinen pH sekä fosforin ja kaliumin pitoisuudet ja pH-korjattu mangaani oli- vat suositusten mukaisia. Suurimmassa osassa maa- näytteistä kalsiumin pitoisuus, yli 60 % näytteistä magnesiumin pitoisuus ja yli 50 % näytteistä fosfo- rin pitoisuus alitti suosituksen, mutta boorin ja ku- parin pitoisuudet ylittivät usein suosituksen. Lehtien keskimääräiset typen, fosforin ja kaliumin pitoisuu- det kaikilla herukoilla, magnesiumin pitoisuus mus- ta- ja punaherukoilla sekä kalsiumin ja boorin pitoi- suudet mustaherukalla olivat suositusten mukaisia. Valkoherukalla 74 % lehtinäytteistä magnesiumpitoi- suus alitti suosituksen. Lehtien ja maan fosforin, kal- siumin ja magnesiumin pitoisuuksien välillä oli mel- ko heikko yhteys. Vaikka ravinnetila oli lehtianalyy- sin perusteella hyvä, maan fosforin, magnesiumin ja kalsiumin pitoisuudet olivat usein pieniä. Tämä viit- taa siihen, että karkeilla kivennäismailla maa-analyy- sin ravinnesuositusten alaraja on liian korkea. Maa- analyysin pienet ravinnepitoisuudet saattavat johtua myös ravinteiden epätasaisesta jakautumisesta ja lai- menemisesta maanäytteessä, koska pintalannoituksen ja muokkaamattomuuden vuoksi ravinteet ovat ker- tyneet aivan maan pintakerrokseen. Title Introduction Material and methods Results Discussion References SELOSTUS