(2) Control less Mg (3) Control less Cu

Transcription

1 CARROT RESPONSE TO SOIL TEMPERATURE AND COPPER, MANGANESE, ZINC AND MAGNESIUM K. A. MacMILLAN and H. A. HAMILTON Resea.ch Slation, Resea.ch B,anch, Canada Depaitment of Agiiculture, St. Iean, Qttebec. Received Janua.y 4, 970, accepted Feb;uaty 22' 97.,A.BSTRACT Carrots grown under greenhouse conditions 25 and 4440 ppm of Mn, -Zn and Mg, in a medium-decomposed, acid organic soil respectively, in tissue, and soil concenffashowed a signiflcant yield and carrot length tions of 60, 80 and.300 pprn for.mn,?n response to ioil temperature and copper f!r- and Mg, respectively, were sufficient for tiliiation. Root lengfrrs at 6 C wer:e^ signifi- normal iarrot-plant development. Incre,asing cantly greater than lengths at,2 and t0 C, soil temperature significantly increased Cu which in turn were significantly greater than and Mn- concentrations in tlle leaves, and lengths at 8 C. Root ind leaf -yiilds at 8 C this occurred irrespective of whether the were significantly inferior to yields at 2, 6 source of the respective nutrient was native and 20 C. The- total native copper content or applied. In the case of Zn,.leaf concenof 0 ppm in soil, and leaf conc^e-ntrations of tratioris increased with increasing tempera- 2 ppni in the tissue, were insufficient for tures only when zinc was a.pplied to- the normal carrot development under these soil. With soil temperature above 2 C, experimental conditions. Application of cop- magnesium concentrations in tlhe leaves were per at the rate of 25 ppm in soil significantiy significantty decreased and this was so for increased yields. Leaf ioncentrations of 4j, native or applied magnesiumin the soil. INTRODUCTION Organic soils, because of their excellent water holding capacity and g,ood physical structure, are ideally suited for the commercial production of carrots. It is not surpdsing, therefore, that 3000 ha (7000 acres) of organic soils in southwestern Quebec are seeded to carrots annually for the local and export market (Quebec Bureau of Statistics, 968). These soils in general are deficient in rrlicronutrients (Campbell and Gusta, 966; MacKay et ct\.,964). Typically, they are also quite susceptible to the frost hazard, since they are slow to warm up irr the spring. Although the influence of soil temperature on plant species has been. investigated quite extensively (Nielsen and Humphries, 966), these studies have treen confined to mineral soils. There was no indication in the literature of the eftects of temperature on the growth of carrots, or of the influence of temperature on micronutrient availability to carrots. The present study, carried out in ther greenhouse, was undertaken to evaluate the interrelated influences of soil temperature and micronutrients on growth and mineral composition of carrots (Daucr^ls carota L.) grown in organic soils. MATERIALS,dND METHODS An acid, medium-decomposed virgin soil collected in ChAteauguay county, Quebec, was used in this study. The soil was limed to ph 5. with Ca(OII),. Except for lime and phosphorus, the nutrients for the various treatments wore added in solution form. The nutrients were thoroughly mixed with kg of soil (oven-dry weight) by means of a rotary mechanical mixer and placed in 9-liter clay pots. The fertilizer treatments used were: () N, P, K, Ca, Mg, Cu, Zn,Fe, Mn and B ati25,50, 25, 50, 25,25,25, 25, 25 and 4 ppm in soil, respectively (control) (2) less Mg (3) less Cu Can. J. Soil Sci. 5: (June 97) L>)

2 294 CAN{DIAN JOURNAL OF SOIL SCIENCE (4) less Zn (5) less Mn. Mo was omitted, since in an allied study no response was observed with its use for carrots (H. A. Hamilton, unpublished data). Each fertilizer treatment was replicated three times at each soil temperature. Gold Pak carrots were seeded on August 0, 968, and three weeks after germination were thinned to give four uniform plants per pot. The various fertility treatments were then subjected to water-bath temperatures of 8, 2, 6 and 20 C. The surface of the soil in each pot was covered with styrofoam beads to reduce soil temperature fluctuations and prevent moisture evaporation. Carrot plants were harvested on October 22, and roots and leaves were dried separately at 7O C. The stage of development at harvest varied between the eighth and eleventh leaf, depending on treatment. Carrot length determinations were made at the time of harvest. Leaf samples from each treatment were ground in a Wiley mill and wet ashed with perchl,oric acid. Similarly, virgin soil samples were dried at 45 C and wet ashed with perchloric acid. Determinations of Cu, Mg, Mn and Zn were made on both leaf and soil samples by means of an atomic absorption spectrophotometer. Yield and carrot length data were analyzed, taking soil temperature as main plots and fertilizer treatments as subplots. Total uptake and nutrient concentration data were analyzed, taking soil temperature as main plots and pairs of micronutrient versus no micronutrient treatments as subplots. RESULTS AND DISCUSSION The dry matter content for carrots and leaves was between lo and l2vo. Carrot lengths, root and leaf yields were significantly influenced by soil temperature (Table ). Irrespective of fertility treatment, carrots grown at 8 C produced leaf yields, root yields and root lengths inferior to those grown at the three higher soil temperatures. As temperature increased from 8 C, root and leaf yields reached a maximum at 2 C followed by a tendency toward decreased yields at 20 C. Root lengths reached a maximum ai 6 C followed by a significant decrease at 20 C. Table. The effect of increasing..tt *l?:;?,,:.""*,]d t"r,tttrer treatment on nean -r'ields and Yields (g/pot) Treatment Roots l-eaves Root length (cm) Soil ternp. (C) Fertilizer - Cu - NIn - NIg - Zn 0.4 b t.7 a z.j a.9a Ll d 0.9 b r.l a.8 a l.9a 4.7 b B.3 o 8.2 a 7.5 a 7.6a 5.+b 7.7a 7.4a l.l a 5.9 c.2.3 b 4.8 a Ll.3b.9a 8.2 b r..) o.6a 2.2 a o-c Means in each column follorved by the sane letter are not significantly different by Duncan's multiple range test

3 MACMILLAN AND HAMILTON-CARROT RESPONSE TO SOIL TEMPERATURE AND NIJTRIENTS 295 These results would indicate that root parameters were more sensitive to soil temperature than leaf parameters, probably since the roots were in the region where the various temperatures were imposed. Presumably, the metabolic processes in the leaves were influenced not only indirectly by the soil temperature but also directly by the external temperature of the atmosphere in the greenhouse. In the absence of added Cu and irrespective of soil temperature. root yields, leaf yields and carrot lengths were significantly inferior to yields and carrot lengths with other fertilizer treatments (Table ), indicating that total Cu at 0 ppm in soil (average concentration in virgin soil) was insufficient for normal carrot plant development under these experimental conditions. On the other hand, the fact that there was no significant yield response to the addition of Mn, Zn or Mg as fertrlizer treatments indicated that total soil concentrations of 60, 80 and 300 ppm in soil, respectively, (average concentration in virgin soil) were sufficient for maximum growth under the conditions of this experiment. While it is generally recognized that the determination of total elements in mineral soils is not an adequate criterion of the availability or sufficiency of a given plant nutrient, the total micronutrient content in organic soils can be a satisfactory indicator of nutrienf sufficiency because the nutrients are complexed or absorbed in the organic matter. No statistically significant yield or carrot length interaction between fertilizer treatment and soil temperature was observed, indicating that fertilizel response in all instances was independent of soil temperature. When averaged over all temperatures (Table 2), the concentratic,ns of micronutrients in carrot leaves invariably were significantly increased by the addition of the particular micronutrient. However, whereas total micronutrient uptake of Cu, Zn and Mg was significantly greater when these elements were added, this was not the case for Mn. In view of the fact that yields were not significantly increased by the addition of Zn, Mn or Mg, this would indicate that leaf concentrations of. I25,,45 and 4440 ppm (dry weight basis) observed vrhen no fertilizer was applied were sufficient for carrot development. In the case of Cu, however, significantly depressed yields where no Cu was added would indicate that 2 ppm Cu in the leaves was insufficient for normal carrot development and 6 ppm Cu in leaf tissue was sufficient. Table 2. Concentration and total tptake;tr,t.;,:ltt:,f".to, leaves as influenced bv the Treatment - Cu - Mn - Zn - Mg Concentration (ppm) in tissue 6.0 a t2.o b 757.O a 45.0 b 83.0 a 25.0 b a b Total uptake mg7'pot 0.24 a b I..JO O.ZtJ a 7.40a 0.96b.6..) a 33. b o-b Means in each column for each pair of treatments are not significantly different by Duncan's roultiple range test

4 296 CANADIAN JOURNAL OF SOIL SCIENCE 'fable 3. Influence of irrcreasing soil temperature on mean concentration and total nutrient uptake in carrot leaf tissue Temp. (C) Nutrient Copper Manganese Zinc Nlagnesium Concentration (ppm in tissue) 8+ t2; 6+ 20i Total nutrient uptake (rng/pot) 8 t d 7.5 d TZ.J ( 7.0d 20.0a 3.7 c 23.3a 8.8 b c d 0.04 b c 0.68 o bc 0.85 a 0.4 b 97d 0 d 56 c 35 cd 67 c 5 c 279 a 22 b 0.52 d o.49 d t..)z Dt l.6c.36 bc.34 bc 2.2 a 7.8 ab 74 bc t29 c 74 b 36 c TI+ D 7t9 c 24I a 6 c 0.75 d 0.67 d.+6 b.26 bc.+6 b.04 c.93 a.87 cd. 470 c 4370 bc 6200 a 5050 b 4790 b 700 b 4740 b 360 c 2.2.J t 20.9 c 52.0 o +2.4 b 40.9 b +.t.a Means in each column follorved by the same letter are not significantly different by Dtrncan's multilrle range test Micronutrient concentration and total uptake were highly influenced by soil temperature (Table 3). For Mg, Cu and Zn,both significant soil temperaturenutrient concentration and soil temperature-total uptake interactions indicated similar trends. The soil temperature-total uptake interaction for Mn was not significant. The significant interactions in all cases can be attributed to the greater effect of temperature on the availability to plants of the applied fertilizer nutrient than the native soil nutrient. Increasing soil temperature increased both Cu and Mn concentrations and uptake. When it is considered that there were no significant differences in root and leaf yields between 72, 6 and 20 C, this suggests a considerable effect of soil temperature on the solubility and availability of these micronutrients, or else on the pump mechanism of the plant, with ultimate luxury consumption by the carrot plant at high soil temperatures. Magnesium concentration and uptake increased to a maximum at 2 C in both the native and applied treatments, and then decreased with increasing soil temperature. Zinc, on the other hand, increased with soil temperature in the applied treatment while varying slightly in the native treatment. On consideration of all the nutrients, this influence of temperature on plant absorption was in the order of Mg ) Mn ) Zn ) Cu. The findings (Tables 2 and 3) indicate soil temperature to be a factor of greater importance than added nutrients in determining total mineral uptake. This is evidenced by the variation in total nutrient uptake over the four soil temperatures, as compared with variation in total nutrient uptake between control and control minus nutrient treatment. In conclusion, results from this study indicate that under greenhouse conditions Cu is a limiting factor in carrot production for the medium-decomposed organic soils of southwestern Quebec, and soil temperatures which could commonly occur in the field can significantly affect the uptake of Cu, Mn, Zn and Mg by carrots.

5 MACMILLAN AND HAMILTON-CARROT RESPONSE TO SOIL TEMPERATURE AND NIJTRIENTS 297 ACKNOWLEDGEMENTS The authors wish to express their appreciation to Dr. E. G. Beauchannp, formerly Research Scientist at the St. Jean Research Station and now Assistant Professor, Department of Soils, University of Guelph, for his assistance in the inlstallation of the water bath system. REFERENCES CAMPBELL, J. D. and GUSTA, L. V The response of carrots and onions to micronutrients on an organic soil in Manitoba. Can. J. Plant Sci i\3. MacKAY, D. C., CHIPMAN, E. W. and LANGILLE, W. M Crop response to some micronutrients and sodium on sphagnum peat soil. Soil Sci. Soc. Amer. Proc.28: NEILSEN, K. F. and HUMPHRIES, E. C.,966. Effect of root temperature on plant grou'th. Soils and Fert. 29: 7-7. QUEBEC BUREAU OF STATISTICS, Agricultural Section Quebec City, P.Q.