ANALYSIS OF THE EFFECT OF N FERTILISATION ON THE GROWTH DYNAMICS OF WINTER WHEAT VARIETIES USING THE HUNT PARSONS MODEL

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1 Acta Agronomica Hungarica, 9(), pp. () DOI:./AAgr.9... ANALYSIS OF THE EFFECT OF N FERTILISATION ON THE GROWTH DYNAMICS OF WINTER WHEAT VARIETIES USING THE HUNT PARSONS MODEL AGRICULTURAL RESEARCH INSTITUTE OF THE HUNGARIAN ACADEMY OF SCIENCES, MARTONVÁSÁR, HUNGARY Received: December, ; accepted: January, The effect of nitrogen (N) fertilisation on the growth of winter wheat varieties was examined in three diverse years using the functional method of growth analysis. The main plot in the two-factorial, split-plot experiment was the N treatment and the subplot the variety. The wheat varieties (extra-early), (early) and Mv (mid-early) were treated with N rates of,, and kg N ha (N, N, N, N ). The Hunt Parsons (HP) program fitted a third-degree exponential function to the dry matter and leaf area data. In 7 and dry matter accumulation continued up to the N rate and in 9 to the N rate. In all three years the highest value was recorded for (. g plant in 7,. g in and. g in 9). The highest value of maximum leaf area (7. cm ) was found for in the N treatment. The maximum values of leaf area in each N treatment, averaged over years and varieties (cm plant ), were as follows: N :.; N :.; N :.; N : 7.. The parameter AGR mean exhibited the highest value (. g day ) in the N treatment, while among the varieties had the highest mean value (7. g day ). The highest value of RGR mean was achieved by in the N treatment in 9 (.9 g g day ). The value of NAR mean increased up to fertiliser rates of N and N, with mean values (g m day ) of N :., N :., N :. and N :.7. The highest value of NAR (.9 g m day ) was obtained for in the N treatment in. On average the greatest value of LAR max was recorded in the N treatment (7. cm g ), while the highest absolute value (. cm g ) was achieved by Mv in. The unfavourable effect of the drought in 7 was clearly reflected in the values of the growth parameters. Key words: winter wheat, N fertilisation, growth analysis, Hunt Parsons model, growth parameters Introduction The basic principles and classical method of growth analysis were detailed by Evans (97), while the functional method of growth analysis was elaborated by Causton and Venus (9) and Hunt (9). The latter method involves the fitting of mathematical functions to the measurement data, which are then used to calculate the instantaneous values of various parameters. The primary /$. Akadémiai Kiadó, Budapest

2 variables used in growth analysis are dry mass and leaf area data recorded at various intervals. The functional method has numerous advantages compared with classical growth analysis, as summarised by Hunt (9). One advantage is that the functional method considers the data from all the sampling dates simultaneously, while the classical method uses various formulae to calculate the parameters from the data of only two sampling dates. A further advantage of the functional method is that it balances out small random fluctuations, making the complex process of growth easier to interpret. Hunt and Parsons (97) developed a growth analysis program which uses the stepwise method to choose the type of function that best fits the data. This growth analysis program is widely used, both in Hungary and throughout the world. Reviews of the functional method of growth analysis and of its application in Hungary were published by Berzsenyi (; ). Sugár and Berzsenyi (9) used the classical method of growth analysis to investigate the effect of N fertilisation on the growth dynamics and yield of various wheat varieties. Micskei et al. () analysed the effect of farmyard manure and mineral fertiliser on the growth of maize in a long-term experiment, using the Hunt Parsons program for plant growth analysis. Berzsenyi (99) studied the N fertiliser responses of maize hybrids with the help of growth analysis, while Árendás et al. () demonstrated the fertiliser responses of maize and winter wheat as a function of year and forecrop in a long-term experiment. The aim of the present work was to investigate the effect of nitrogen fertilisation on the growth of different winter wheat varieties in several years using the Hunt Parsons model. The first results of this work were published by Sugár and Berzsenyi (). Materials and methods Growth analysis was carried out in the /7, 7/ and /9 seasons in a long-term crop rotation experiment involving winter wheat. The experiment was set up in 9 in a two-factorial, split-plot design with four replications. The main plots included eight N treatments (in kg ha steps from kg ha ), and the subplots wheat varieties. The subplots measured. m. The growth analysis was performed on four N treatments (N, N, N, N ) and three wheat varieties with different maturity periods: (extra-early), (early) and (mid-early). When sown in early to mid-october, the mean heading dates are May th for, May th for and May nd for. Of the years included in the study, /7 was extremely dry. The rainfall sum ( mm) was around a third of that recorded in the other two years ( mm in and 7 mm in 9) and was well below the -year mean ( mm). There was no significant difference between the years in terms of daily mean temperature (7: C; and 9: C). For the purpose of growth analysis, destructive samples consisting of plants per plot were taken once a week on a total of occasions in 7, in and 7 in 9, covering the whole growing season. Sampling was begun when the wheat reached the two-leaf stage. The dry mass of the samples was determined after drying for h in a drying cabinet at C and the fresh leaf area was recorded using an AM leaf area meter. The method elaborated by Hunt and Parsons (97) was used to evaluate the data. The Hunt Parsons program fits first-, second- or third-degree exponential functions to the basic dry mass and leaf area data in a stepwise manner. The program also calculates the standard error and the values of the 9% confidence interval for the whole of the sampling period. The absolute growth rates (AGR, ALGR), relative growth rates (RGR, RLGR), net assimilation rate (NAR) and leaf area ratio (LAR) calculated by the program were characterised in terms of dynamics over time and mean and maximum values. Acta Agronomica Hungarica, 9,

3 EFFECT OF N FERTILISATION ON WINTER WHEAT VARIETIES 7 Results and discussion Effect of N fertilisation on the dynamics of dry matter production and leaf area of winter wheat varieties The Hunt Parsons program fitted third-degree exponential functions to the dry matter accumulation data (Figs. ), with the exception of the dry matter accumulation of and in the N treatment in 7, for which second-degree functions were fitted. These second-degree exponential functions were only plotted up to the maximum values of the data. In all cases the functions gave a good fit to the measurement data (R = %). The dynamics of dry matter accumulation was of the sigmoid type up to the maximum value and gave a good expression of the effect of the nitrogen treatments. Leaf area [cm plant - ] Leaf area [cm plant - ] Leaf area [cm plant - ] Fig.. Effect of N fertilisation and genotype on the dynamics of dry matter accumulation and leaf area in 7 Acta Agronomica Hungarica, 9,

4 Leaf area [cm plant - ] Leaf area [cm plant - ] Leaf area [cm plant - ] Fig.. Effect of N fertilisation and genotype on the dynamics of dry matter accumulation and leaf area in In response to N fertilisation, the dry matter production increased up to the N rate in 7 and and up to the N rate in 9. Averaged over the varieties and years the following values were obtained for the individual N treatments: N :., N :.9, N :. and N :. g plant. In all three years the maximum values were recorded for (7:. g, :. g, 9:. g plant ). The dynamics of dry matter production over time reflected the diverse maturity dates of the wheat varieties. Depending on the treatment and year, the number of days after sowing when the maximum values were recorded was for, 9 for and for. Acta Agronomica Hungarica, 9,

5 EFFECT OF N FERTILISATION ON WINTER WHEAT VARIETIES Leaf area [cm plant - ] Days from s ow ing 7 Leaf area [cm plant - ] Days from s ow ing Days from s ow ing 7 Fig.. Effect of N fertilisation and genotype on the dynamics of dry matter accumulation and leaf area in 9 Leaf area [cm plant - ] The HP program described the leaf area dynamics with a third-degree curve (R =.9 9.%) in all cases (Figs. ). Depending on the variety and year, the leaf area values rose up to the N or N level. The maximum values of leaf area for the individual N fertiliser rates, averaged over year and variety, were as follows (cm plant ): N :., N :., N :., N : 7.. The highest value of maximum leaf area (7. cm ) was recorded for Mv in the N treatment in. This variety also exhibited the highest value averaged over years and N treatments (.9 cm ). Averaged over varieties and N treatments, the maximum leaf area per plant in 9 (. cm ) was considerably lower than in the other two years (7:. cm, : 7. cm ). The dynamics of leaf area followed the maturity time of the varieties. Depending on the year, the maximum was achieved on the 7 7 th day by Mv, on the 9 th day by and on the 9 th day by Mv Days from s ow ing 7 Acta Agronomica Hungarica, 9,

6 Effect of N fertilisation on the growth rates of total dry matter (AGR, RGR) and leaf area (ALGR, RLGR) of the wheat varieties The dynamics of the absolute growth rate (AGR) was typically described by a Gauss curve. The AGR dynamics of the N treatment differed greatly from that of the fertilised treatments. In all three years the AGR dynamics was similar, with differences mainly in the maximum values. The AGR dynamics in is illustrated in Figure, and the maximum AGR values (AGR max ) in Table. The differences in AGR between N and the other N treatments were particularly evident in and 9. Averaged over varieties and years, the AGR max values were lowest (. g day ) in the N treatment, increasing in the N treatment (7. g day ) and reaching a maximum in the N treatment (. g day ), with a reduction in the N treatment (7.7 g day ). Averaged over N treatments and years, exhibited the highest absolute growth rate (7. g day ). The most favourable year for AGR was, with a maximum value of 7. g day, averaged over N treatments and varieties, while the lowest AGR max value was obtained in 7 (. g day ). The highest values of AGR max were recorded for in 7 (7. g day ), for in (9. g day ) and for in 9 (9. g day ). The AGR max values for and were highest in 9 (9. and 9. g day, respectively) and for Mv in (9. g day ). Table Effect of N fertiliser on the maximum values of absolute growth rate (AGR) and the mean values of relative growth rate (RGR) of the wheat varieties Wheat variety Year N fertiliser treatment (kg ha ) AGR max (g day ) RGR mean (g g day ) Acta Agronomica Hungarica, 9,

7 EFFECT OF N FERTILISATION ON WINTER WHEAT VARIETIES AGR [g day - ] ALGR [cm day - ] AGR [g day - ] ALGR [cm day - ] AGR [g day - ] ALGR [cm day - ] Fig.. Effect of N fertilisation and genotype on the dynamics of absolute growth rate of total dry matter (AGR) and the absolute growth rate of leaf area (ALGR) in Table shows the mean relative growth rate (RGR) of the total dry matter production per plant up to the end of dry matter accumulation, which occurred at around the end of May in all three years. The RGR values were the smallest in the N treatment, rising with the N rate up to N and declining again at N. The only exception was in 7, when the RGR values did not differ significantly in the different N treatments. The mean RGR values were lower in 7 than in the other two years. The highest values were obtained in the N treatment in 9 for and (.9 and.79 g g day ). In the case of, very similar maximum values were recorded in and 9, again in the N treatment (. and. g g day ). Overall, the highest RGR mean value was observed for in the N treatment in 9 (.9 g g day ). Acta Agronomica Hungarica, 9,

8 The dynamics of the absolute growth rate of the leaf area (ALGR) was characterised by an increase up to a maximum value, followed by a gradual decline until the end of the growth period. The rapid withering of the foliage resulted in a negative growth rate, increasing up to a negative maximum, after which the withering rate declined. The dynamics of ALGR was similar for all the experimental factors. The ALGR dynamics for is illustrated in Figure, and the maximum values, which exhibited substantial differences, in Table. Averaged over years and varieties, the maximum values of ALGR per plant in the individual N treatments were as follows: N :., N :., N :.9 and N :.9 cm day. For all three varieties the highest ALGR values were obtained in (:., :., :. cm day ). The highest value recorded in the experiment was thus found for Mv in the N treatment in (. cm day ). As can be seen in Table, the mean value of the relative leaf area growth rate per plant (RLGR) until the maximum leaf area was achieved increased with the N rate up to N. The only exception was, where the mean RLGR continued to rise in all three years up to N. In all four treatments Mv had lower RLGR values in 7 than in or 9, while the mean relative growth rate of was higher in all the treatments in than in the other two years. The RLGR values were the lowest in 7, except for in the N treatments. The highest mean values for all the varieties were recorded in 7 and 9 by in the N treatment (.7 and. cm cm day ) and in by in the N treatment (.9 cm cm day ). Table Effect of N fertiliser and the wheat variety on the maximum value of absolute growth rate (ALGR) and the mean value of relative leaf area growth rate (ALGR) Wheat variety Year N fertiliser treatment (kg ha ) ALGR max (cm day ) RLGR mean (cm cm day ) Acta Agronomica Hungarica, 9,

9 EFFECT OF N FERTILISATION ON WINTER WHEAT VARIETIES Effect of N fertilisation on the net assimilation rate (NAR) and leaf area ratio (LAR) of wheat varieties The dynamics of the net assimilation rate (NAR) was characterised by a rapid growth stage up to a relatively constant value, followed by a further rapid increase as the foliage withered. The NAR dynamics recorded in is illustrated in Figure. The value of NAR was constant for a relatively long period in 7 and, from approximately the th to the th day after sowing, i.e. until first node appearance. The mean NAR values during this period are summarised in Table. NAR [g m day - ] LAR [cm g - ] NAR [g m day - ] LAR [cm g - ] NAR [g m day - ] LAR [cm g - ] Fig.. Effect of N fertilisation and genotype on the net assimilation rate (NAR) and leaf area ratio (LAR) in Acta Agronomica Hungarica, 9,

10 Table Effect of N fertilisation on the mean value of net assimilation rate (NAR) and the maximum value of leaf area ratio (LAR) Wheat variety Year N fertiliser treatment (kg ha ) NAR mean (g m day ) LAR max (cm g ) As this parameter expresses the dry matter gain per unit leaf area, the value of NAR exhibits an increase as the leaf area declines. Mean NAR values rose with increasing N rates up to N or N. Averaged over varieties and years the following values were observed for the individual N treatments (g m day ): N :., N :., N :. and N :.7. In the case of the mean NAR was highest in the N treatment in and 9. This could have been due to the fact that the stand was much thinner on plots without N fertiliser, resulting in greater assimilation due to the better light conditions. The highest value of NAR (.9 g m day ) was obtained for in the N treatment in. Among the years, the lowest NAR values were obtained in 7 and the highest in and 9 (.9 g m day and.9 g m day for ). The dynamics of leaf area ratio (LAR) over time was used to characterise the leaf area per plant dry mass. The dynamics recorded in is presented in Figure. After a short initial period of growth, LAR reached its maximum value, after which it tended to decline until the end of the vegetation period. The maximum values (Table ) were obtained earlier in 7 (between days and ) than in the other two years (days 7). There were also differences in dynamics between the varieties, with exhibiting maximum LAR approximately a week earlier than the other varieties. The maximum values differed with the N rate, being lower in all cases at the N level. Averaged over varieties and years the LAR max values in the individual N treatments were Acta Agronomica Hungarica, 9,

11 EFFECT OF N FERTILISATION ON WINTER WHEAT VARIETIES (cm g ): N : 9.7, N :., N : 7. and N : 7.. The highest LAR max value (. cm g ) was obtained for in the N treatment in, with an only slightly lower value (. cm g ) for in the N treatment, again in. In conclusion it can be stated that the values of dry matter production, leaf area and growth parameters rose in most cases up to N or N. Among the varieties, had the greatest dry matter production in all three years, and also exhibited the highest values of leaf area, AGR max and ALGR max. The highest LAR was achieved by and the highest RLGR and NAR by. Of the years, 7 was extremely dry, as reflected in the growth parameters and yield. The highest values of leaf area, AGR, ALGR, RLGR, NAR and LAR were obtained in. Acknowledgements This research was funded by the AGRISAFE Project (EU-FP7-REGPOT 7- No. ). References Árendás, T., Bónis, P., Csathó, P., Molnár, D., Berzsenyi, Z. (): Fertiliser responses of maize and winter wheat as a function of year and forecrop. Acta Agron. Hung.,, 9. Berzsenyi, Z. (99): A N-műtrágyázás hatásának vizsgálata a kukorica (Zea mays L.) növekedésére Hunt Parsons modellel. (Studies on the effect of N fertilisation on maize (Zea mays L.) growth using the Hunt Parsons model.) Növénytermelés,,. Berzsenyi Z. (): Növekedésanalízis a növénytermesztésben. (Growth analysis in crop production). (Review). Növénytermelés, 9, 9. Berzsenyi Z. (): A növekedésanalízis funkcionális módszere. (Functional method of growth analysis). (Review). Növénytermelés,, 9 7. Causton, D.R., Venus, J. C. (9): The Biometry of Plant Growth. Edward Arnold, London. Evans, G. C. (97): The Quantitative Analysis of Plant Growth. Blackwell Scientific Publications, Oxford. Hunt, R. (9): Plant Growth Curves: The Functional Approach to Plant Growth Analysis. Edward Arnold, London. Hunt, R., Parsons, I. T. (97): A computer program for deriving growth-functions in plant growth analysis. J. Appl. Ecol.,, Micskei, G., Jócsák I., Berzsenyi Z. (): Studies on the effect of farmyard manure and mineral fertiliser on the growth of maize (Zea mays L.) in a long-term experiment. I. Using the classical form of plant growth analysis. Acta Agron. Hung., 9, 7. Sugár E., Berzsenyi Z. (9): Őszi búzafajták növekedésdinamikája és termésprodukciója eltérő N-tápelemszinteken. (Growth dynamics and yield of winter wheat varieties grown at diverse nitrogen levels.) Tartamkísérletek jelentősége a növénytermesztés fejlesztésében. Jubileumi tudományos konferencia, Martonvásár. pp. 9. Sugár E., Berzsenyi Z. (): Growth dynamics and yield of winter wheat varieties grown at diverse nitrogen levels. Acta Agron. Hung.,,. Corresponding author: E. Sugár Phone: sugare@mail.mgki.hu Acta Agronomica Hungarica, 9,