INFLUENCE OF IRRIGATION AND NITROGEN FERTILIZATION ON YIELD AND LEAF GREENNESS INDEX (SPAD) OF MAIZE

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1 Acta Sci. Pol., Agricultura 13(1) 2014, INFLUENCE OF IRRIGATION AND NITROGEN FERTILIZATION ON YIELD AND LEAF GREENNESS INDEX (SPAD) OF MAIZE Małgorzata Natywa, Małgorzata Pociejowska, Leszek Majchrzak, Krzysztof Pudełko Poznan University of Life Sciences 1 Abstract. Lack of water causes non-uniform development of plants during their growing season or even their drying-up. Nitrogen is one of the most important nutrients in the nutrition of higher organisms as well as microbes. Evaluation of the nitrogen nutrition status of plants and determining optimum doses of this element has a significant effect with regard to the economic aspect of production and necessity of protecting agricultural environment against nitrogen pollution. Two-factorial field experiment was carried out in the years on soil of bonitation class IVa and IVb, and according to agricultural usefulness: complex 4 (very good rye complex) and 5 (good rye complex). The aim of the research was evaluation of the effect of sprinkling irrigation and diversified nitrogen fertilization (0, 80, 160 and 240 kg ha -1 N) on chosen elements of the yield structure and on variation of SPAD index in maize leaves (cultivar Clarica, FAO 280). A considerable variation in weather conditions was observed within the years of research. The driest, and at the same time the warmest was 2008, when both in late April as well as in May and June, the amount of rainfall was small. It was observed that the amount of rainfall in May has a significant effect on the maize yield, while sprinkling irrigation applied in June and July reduced the negative effect of drought occurring in late spring. Interaction of the experimental factors indicated that the highest grain yield was obtained after application of 80 kg ha -1 N with sprinkling irrigation. However, further increase of nitrogen fertilization dose did not result in any significant increase in the yield of maize grain. The value of SPAD index determined at the stage of flowering (BBCH 67) as well as at the milk stage (BBCH 75) was the highest with nitrogen fertilization of 240 kg ha -1. Application of sprinkling irrigation significantly increased values of SPAD readings independently of the level of nitrogen fertilization. Key words: maize, chlorophyll, SPAD, nitrogen fertilization, sprinkling irrigation Corresponding author Adres do korespondencji: dr inż. Leszek Majchrzak, Department of Agronomy, Poznan University of Life Sciences, Dojazd 11, Poznań, leszmaj@up.poznan.pl

2 40 M. Natywa, M. Pociejowska, L. Majchrzak, K. Pudełko INTRODUCTION The role of maize is mainly determined by the grain production, which to a great extent is dependent on climatic conditions, mainly air temperature and rainfall [Dudek et al. 2009]. Heat deficiency causes improper technological maturity of the grain and yield decrease. However, lack of water causes non-uniform plant development in the growing season and even drying-up. Variation in air temperature and rainfall throughout the time is a feature of the Polish climate. However, rainfall deficiency in plant cultivation may be supplemented with the use of irrigation. Nitrogen is one of the most important nutrients in the nutrition of higher plants and microbes. Evaluation of the status of plant nutrition with nitrogen and determining optimum doses of this element has a significant meaning with regard to the economic aspect of production and necessity to protect agricultural environment against nitrogen pollution. A symptom of nitrogen deficiency in plants is a lighter color of older leaves and their tips turning yellow, while its excess causes, among other, decrease in the gluten content in cereal grains [Zagórda et al. 2007]. Moreover, nitrogen is one of the elements most susceptible to leaching from the soil profile, therefore application of precision agriculture practices may result in the reduction of its losses. In agricultural practice, quick and non-destructive methods are used more and more frequently to determine plant requirement for nitrogen. One of them is a test based on the close dependence between nitrogen content and the amount of chlorophyll in leaves. This method is based on determining leaf greenness with the use of an optical devices SPAD-502 (Soil and Plant Analysis Development) or Hydro N-Tester [Machul 2005]. These devices do not directly measure chlorophyll content in plant leaves, but determine their greenness index, which is a quotient of the absorption of light with two wavelengths, 650 and 940 nm. Light of a wavelength of 650 nm is absorbed by chlorophyll, while light of a wavelength of 940 nm is retained by the leaf tissue. The result is a dimensionless quantity defined as SPAD units [Hoel and Solhaug 1998]. With regard to slightly different wavelengths it is possible to calculate measurement values with N-tester meter for Minolta SPAD 502 readings [Uddling et al. 2007]. According to some researchers, there is a high correlation between the meter s readings and the extracted amount of chlorophyll, while others think that SPAD readings are different for the same amount of chlorophyll determined with in vitro method in different plant species, which is connected with the necessity to calibrate chlorophyll meter for individual species [Machul and Jadczyszyn 2005]. Chlorophyll meter is used for monitoring the nitrogen nutrition status of many plant species. It is useful in fertilization advisory service concerning rice, maize and cereals [Blackmer and Schepers 1995, Samborski and Rozbicki 2002, Zagórda et al. 2007]. The aim of the research was determining diversification in the quantity of selected structural yield components of maize, and value of leaf SPAD index depending on the analyzed experimental factors and habitat conditions. The working hypothesis assumed that irrigation and increasing doses of nitrogen fertilization cause increase in maize yield and its structural components as well as in the values of SPAD readings. Acta Sci. Pol.

3 Influence of irrigation MATERIAL AND METHODS The experiment was carried out in the years at the Research and Education Station in Złotniki (52 o 29' N; 16 o 49' E), of the University of Life Sciences in Poznań. The soil on the experimental field is included in bonitation class IVa and IVb, and according to agricultural usefulness, in complex 4 (very good rye complex) and 5 (good rye complex). The soil is classified as typical lessive soils, formed from light loamy sand and very sandy loam of the thickness of the humus horizon cm, humus content %. The soil ph is 5.7 (in 1 M KCl), and it has a high phosphorus content and an average content of potassium and magnesium. A deep level of ground water and such substrate composition make it become periodically dry. The experiment was set up in a randomized split-plot design in four replications with two experimental factors. Maize cv. Clarica (FAO 280) was sown at a rate of grains ha -1 on 13 April 2007 and 15 April in the years 2008 and 2009, intended to be harvested for grain, which was carried out in these years between 8 th and 21 st October. Sprinkling irrigation was conducted on half of the plots in the summer months (June and July). In order to do this, semi-permanent sprinkling irrigation was applied with NAAN sprinklers of a nozzle diameter of 7 mm at a working pressure from 3.5 to 4.0 atmospheres. Single water discharge amounted to 40 mm and was used when there occurred a decrease in soil moisture in the layer 0-30 cm below 70% of field water capacity. In order to avoid sprinkling non-irrigated plots, an isolating belt was created of a width of 6 m, which separated irrigated subblocks from the ones without irrigation. The second experimental factor was levels of nitrogen fertilization: 0, 80, 160 and 240 kg ha -1, applied in the form of ammonium saltpeter before sowing. Measurements of leaf greenness (SPAD index) in maize were carried out on 3 dates: at the 7-8 leaf stage (BBCH 17-18), tasselling (full flowering BBCH 67) and at the milk stage (BBCH 75) with the use of Hydro N-Tester, which is used to measure chlorophyll content in leaves. Determination was conducted three times, with 30 replications each time on every experimental plot (90 readings from each plot). With regard to the amount and distribution of rainfall, the most optimum year for maize development was 2009 (Fig. 1). May, June and July were characterized by not only the highest amount of rainfall in the experimental years, but also by its relatively uniform distribution in particular decades. The driest and at the same time the warmest was 2008, when there was a small amount of rainfall both in late April, May and June, and early July (on the level of 10 mm). Collected results were subjected to statistical analysis with the use of statistical package R [R Core Team 2013]. The results of ANOVA test were verified with LSD Tukey test from agricolae package [de Mendiburu 2013] on the confidence level of p = Agricultura 13(1) 2014

4 42 M. Natywa, M. Pociejowska, L. Majchrzak, K. Pudełko Fig. 1. Fig. 1. Precipitation and temperature in the course of experiment Opady i temperatura w trakcie trwania doświadczenia RESULTS Sprinkling irrigation had a significant effect on an increase in the grain yield of maize in 2007 (Table 1), and a very significant effect in the dry 2008 (on average the difference regarding non-irrigated plots was above 38%). In the most optimum year regarding weather conditions, 2009, the factor of sprinkling irrigation had no significant effect on an increase in the grain yield of maize. Nitrogen fertilization caused a significant increase in the grain yield in all experimental years. In the years 2007 and 2008, a significant increase was observed after using fertilization at a dose of 80 kg ha -1, while increasing the N dose caused an over 4% increase in the grain yield of maize, which was not however statistically confirmed. In 2009, nitrogen fertilization on the level of 80 kg ha -1 had the greatest effect on the increase in the grain yield of maize. However, an interaction was found between fertilization and sprinkling irrigation. The highest yields were observed under conditions of sprinkling irrigation and nitrogen fertilization at a rate of 80 kg ha -1 (Table 2). The conducted regression analysis allowed for suggesting a model indicating an influence of the analyzed variables on the formation of maize yield: Y = W N Pv W Pv where: Y yield, Mg ha -1, W sprinkling irrigation, 0 with no irrigation and 1 with sprinkling irrigation, Acta Sci. Pol.

5 Influence of irrigation N nitrogen fertilization, kg ha -1, Pv total rainfall in May, mm. Table 1. The yield of maize grain depending on fertilization and sprinkling irrigation, Mg ha -1 Tabela 1. Plon kukurydzy w zależności od nawożenia i deszczowania, Mg ha -1 Water sprinkling* Deszczowanie Fertilization Nawożenie N kg ha -1 Yield of maize grain Plon kukurydzy a NW a ab a a W b b bc Mean Średnia NW 10.3a 5.3a 11.2 W 11.8b 9.7b a a b c b ab b bc LSD 0.05 NIR 0,05 sprinkling irrigation deszczowanie (I) ns ni fertilization nawożenie (II) 0.86 ns ni 1.55 interaction interakcja (I) x (II) 1.22 ns ni ns ni * NW no water sprinkling bez deszczowania, W water sprinkling deszczowanie ns ni non-significant differences różnice nieistotne different small case letters among treatment means indicate significant differences according to Fisher's LSD test (p < 0.05) różne małe litery występujące przy średnich z obiektów oznaczają różnice istotne według testu Fishera (p < 0,05) Table 2. Effect of fertilization and sprinkling irrigation on maize grain yield, Mg ha -1 Tabela 2. Wpływ nawożenia i deszczowania na plon kukurydzy, Mg ha -1 Level of nitrogen fertilization Poziom nawożenia azotem kg ha -1 Water sprinkling Deszczowanie* NW W mean średnia Mean Średnia LSD 0.05 NIR 0,05 sprinkling irrigation deszczowanie (I) 0.80 fertilization nawożenie (II) 0.76 interaction interakcja (I) x (II) 1.08 * explanations, see Table 1 objaśnienia tabela 1 Agricultura 13(1) 2014

6 44 M. Natywa, M. Pociejowska, L. Majchrzak, K. Pudełko The suggested model adequately describes (Fig. 2; r = ; r 2 = with p < 0.05) the significant positive effect of the applied sprinkling irrigation (p < 0.05) in relation to the amount of rainfall in May (p < 0.05) as well as of nitrogen fertilization (p < 0.1), as main factors varying maize yield. Presented results of observation and statistical modelling (Fig. 2) also indicate a possibility to reduce the negative effect of drought in late spring (May) through an application of sprinkling irrigation even in June and July. The suggested model indicates a possibility to obtain increase in the yield even by 4.5 Mg. ha -1, as a result of using sprinkling irrigation in extreme drought in May. dotted line shows regression model describing the influence of sprinkling irrigation, precipitation in May and nitrogen fertilization on maize grain yield linia przerywana przedstawia model regresji opisujący wpływ deszczowania, opadów w maju i nawożenia azotem na plon kukurydzy Fig. 2. Rys. 2. The yield of maize grain depending on sprinkling irrigation and nitrogen fertilization Plon kukurydzy w zależności od deszczowania i nawożenia azotem The number of maize cobs was significantly diversified by the analyzed experimental factors only in 2008 (Table 3). Sprinkling irrigation increased the number of cobs by 28%, and nitrogen fertilization compared with the control by over 22%. Higher N fertilization decreased the cob number per unit of area, though the difference was confirmed only with regard to the values obtained with fertilization of 160 kg ha -1. In other years, no effect of the studied factors was found on the cob number per unit of area. The conducted research did not indicate any effect of the experimental factors on the density of maize plants per unit of area (Table 4). Acta Sci. Pol.

7 Influence of irrigation Table 3. Number of maize cobs, no m -2 Tabela 3. Liczba kolb kukurydzy, szt. m -2 Water sprinkling* Deszczowanie Fertilization Nawożenie N kg ha -1 Maize cobs Liczba kolb NW W Mean Średnia NW a 8.9 W b a b a a 9.6 LSD 0.05 sprinkling irrigation deszczowanie (I) ns ni 1.10 ns ni fertilization nawożenie (II) ns ni 0.78 ns ni interaction interakcja (I) x (II) ns ni ns ni ns ni * explanations, see Table 1 objaśnienia tabela 1 Table 4. Number of maize plants, no m -2 Tabela 4. Liczba roślin kukurydzy, szt. m -2 Water sprinkling* Deszczowanie Fertilization Nawożenie N kg ha -1 Number of maize plants Liczba roślin kukurydzy NW W Mean Średnia NW W LSD 0.05 sprinkling irrigation deszczowanie (I) ns ni ns ni ns ni fertilization nawożenie (II) ns ni ns ni ns ni interaction interakcja (I) x (II) ns ni ns ni ns ni * explanations, see Table 1 objaśnienia tabela 1 Agricultura 13(1) 2014

8 46 M. Natywa, M. Pociejowska, L. Majchrzak, K. Pudełko The indirectly determined chlorophyll content in maize leaves varied depending on the time of measurement, sprinkling irrigation and nitrogen fertilization (Table 5). Table 5. Mean SPAD readings in the analyzed growth stage of maize Tabela 5. Średnie wartości SPAD w analizowanym okresie wzrostu kukurydzy Water sprinkling* Deszczowanie Fertilization Nawożenie N kg ha -1 Maize growth stage Faza wzrostu kukurydzy BBCH BBCH 67 BBCH a 501a 469a NW ab 621b 544b c 670c 578b c 711cd 623c 0 431ab 648bc 579b W b 664c 639c c 671c 640c c 680c 647c Mean NW a 554a W b 626b 0 423a 575a 524a a 642b 592b b 670bc 609b b 695c 635c LSD 0.05 sprinkling irrigation deszczowanie (I) ns ni fertilization nawożenie (II) interaction interakcja (I) x (II) * explanations, see Table 1 objaśnienia tabela 1 Only in the 7-8 leaf stage in maize (BBCH 17-18), no significant effect of sprinkling irrigation was observed on the formation of the index value of the chlorophyll content, although under conditions of sprinkling irrigation it was higher by app. 4%. An increase in the dose of nitrogen fertilization caused an increase in the values of SPAD readings, however its significance was confirmed with a dose of 160 kg ha -1 N. A similar tendency was also observed in maize at the stage of tasselling (BBCH 67) and at the milk stage (BBCH 75). Nitrogen fertilization on the level of 80 kg ha -1 N significantly varied value of this index compared with the measurement results obtained with no nitrogen fertilization, as well as after application of a nitrogen dose of 240 kg ha -1. At the stage of tasselling (BBCH 67), no differences were indicated in the quantities of SPAD readings in leaves of plants fertilized with doses of 160 and 240 kg ha -1. DISCUSSION Irrigation in longer periods with no rainfall becomes an indispensable treatment conditioning proper maize development and obtaining any grain yield. In the authors own research, an increase in the grain yield of maize was observed on irrigated plots in the years 2007 and Dudek et. al. [2009] also found that application of drip irrigation caused an increase in the grain yield and increased share of cobs in the total yield, grain share in cobs, and 1000 grain weight in maize. Rainfall affected the irrigation results Acta Sci. Pol.

9 Influence of irrigation (total rainfall in July), which depended on its amount, the lower it was the higher was the yield increase. Żarski et al. [2004] confirm that application of drip irrigation causes increase in individual effects of production. However, a double dose of nitrogen fertilization under conditions of irrigation leads to favorable quantitative and qualitative changes [Di Pablo and Rinaldi 2008]. In 2006, Grzelak and Żarski [2009] did not obtain increase in the grain yield on plots without irrigation as a result of a severe drought in July. Being a significant factor, nitrogen fertilization caused increase in the grain yield of maize on plots without irrigation and on those with irrigation. The double dose of nitrogen increased the yield of irrigated maize by app. 11%. Nitrogen fertilization is a very important yield-producing factor in maize cultivation and affects not only quantity of the yield but also its quality [Torbert et al. 2001, Zidane et al. 2006]. Application of nitrogen fertilization at a dose of 80 kg ha -1 caused a significant increase in the grain yield in all research years: 2007, 2008 and Reports by Gołębiewska and Wróbel [2009] indicate a variation of the grain yield depending on the applied nitrogen doses. Taking into consideration means for fertilization as well as a regular yield increase, the highest increase was observed after using a dose of 30 kg ha -1 N. Moreover, an increase by 12% in the weight of grains collected from a unit of area was observed, compared with plots with no fertilization. Optimum nitrogen doses applied under maize, given in Polish literature by various authors, oscillate within the range of kg ha -1 N [Fotyma 1994, Gonet and Stadejek 1992]. Fotyma [1994] and Kruczek [1997] also state that effectiveness of fertilization decreases along with an increase in nitrogen doses. According to Fotyma [1994], effectiveness of fertilizing maize with nitrogen depends on the amount of rainfall in the growing season. In the research of Kruczek [1997], a dose of 90 kg ha -1 N was optimum for the grain yield. The cultivars tested in the experiments of Fotyma [1994] indicated significant differences in the yield under the influence of an increasing nitrogen fertilization. Different responses of the cultivars to nitrogen fertilization may indicate genetic variability in the effectiveness of using nitrogen. Jankowiak et al. [1997] state that, based on experiments, optimum nitrogen doses for the grain yield of maize are within the range of 90 to 150 kg ha -1 N. Bogucka et al. [2008] in their studies found an effect of an increasing dose of nitrogen fertilization on the quantity of grain yield in maize. A significant increase in the average grain yield occurred up to a dose of 150 kg ha -1 N, and the difference in the yield, compared with the control, was 2.6 Mg ha -1. A similar tendency was observed in the research of Księżak et al. [2012], in which increase in nitrogen fertilization from 80 to 120 kg ha -1 N in maize and sorghum in the first two years of research caused increase in the yield level. However, increasing N dose to 160 kg reduced maize yield in 2009, which was the result of lodging occurring on this plot. Machul and Księżak [2007], while increasing the dose of nitrogen fertilization from 120 to 160 kg per ha, found a significant increase in the level of maize yield and only a slight increase in the sorghum yield. Kruczek [2005] observed that method of fertilization affects among other things the level of maize yield. Row application of fertilizers significantly increased the grain yield compared with broadcast application. This pattern was observed especially in the years 2001 and 2002, in which distribution of rainfall was favorable for obtaining high yields. Chlorophyll content is dependent on rainfall, thermal conditions, measurement dates, as well as on plant supplementation with nutrients, above all with nitrogen. Based on the results of the conducted tests, Machul [2005] states that nitrogen fertilization and measurement date (number of days after emergence in maize) have the greatest effect Agricultura 13(1) 2014

10 48 M. Natywa, M. Pociejowska, L. Majchrzak, K. Pudełko on a relative chlorophyll content (SPAD values in maize leaves). Under the influence of an increase in nitrogen fertilization, SPAD readings also increase in maize leaves, and their largest increases occur with the lowest level of nitrogen fertilization (0-40 kg ha -1 N). Differences in SPAD values decrease along with an increase in the level of fertilization. An increase in SPAD readings in maize under the effect of an increased nitrogen fertilization and decreasing differences in readings with the use of higher nitrogen doses was also indicated by Costa et al. [2001], Machul [2003] as well as Machul and Jadczyszyn [2005]. The Authors think that the cultivar definitely affected variation of SPAD readings the least, while the greatest effect on their diversification in maize leaves has measurement date (number of days after emergence in maize). Machul and Jadczyszyn [2005] observed critical values for the 6-leaf stage, 10-leaf stage as well as for the stage of tasselling. CONCLUSIONS 1. An interaction was found between fertilization and sprinkling irrigation. The highest yields were observed with sprinkling irrigation and nitrogen fertilization at a dose of 80 kg ha The total rainfall in May in an interaction with irrigation applied in June and July, and also to a lesser degree with nitrogen fertilization, had a significant effect on the quantity of grain yield in maize. A negative effect of drought conditions in May on the formation of grain yield in maize may be leveled by the applied irrigation in June, and even in July. 3. Nitrogen fertilization and sprinkling irrigation had no significant effect on the density of maize plants, while both these factors affected the cob number only in the dry Value of SPAD index determined at the stage of flowering (BBCH 67) as well as at the milk stage (BBCH 75) was the highest with nitrogen fertilization at a dose of 240 kg ha -1. Application of sprinkling irrigation significantly increased values of SPAD readings independently of the level of nitrogen fertilization. REFERENCES Blackmer T.M., Schepers J.S., Use of chlorophyll meter to monitor nitrogen status and schedule fertigation for corn. J. Prod. Agric. 8, Bogucka B., Szempliński W., Wróbel E., Nawożenie azotem a plon kukurydzy uprawianej na ziarno w warunkach północno-wschodniej Polski [Effect of nitrogen fertilization on the yield of grain maize grown under climate conditions of north-eastern Poland]. Acta Sci. Pol., Agricultura 7(3), 21-30, [in Polish]. Costa C., Dwyler L.M., Dutilleul P., Stewart D.W., Ma B.L., Smith D.L., Inter-relationships of applied nitrogen, SPAD, and yield of leafy and non-leafy maize genotypes. J. Plant Nutr. 24, de Mendiburu F., agricolae: Statistical Procedures for Agricultural Research. R package version CRAN.R-project.org. Di Pablo E., Rinaldi M., Yield response of corn to irrigation and nitrogen fertilization in a Mediterranean environment. Field Crop Res. 105, Dudek S., Żarski J., Kuśmierek-Tomaszewska R., Reakcja kukurydzy na nawadnianie w świetle wyników wieloletniego eksperymentu polowego [Study of maize response to drip irrigation based on long-term field experiment]. Infrastruktura i Ekologia Obszarów Wiejskich, 3, [in Polish]. Acta Sci. Pol.

11 Influence of irrigation Fotyma E., Reakcja roślin uprawy polowej na nawożenie azotem.cz. III. Kukurydza [The response of field crops to nitrogen fertilization. III Maize]. Fragm. Agron. 4(44), [in Polish]. Gołębiewska M., Wróbel E., Wpływ nawożenia azotem na plonowanie kukurydzy [The effect of nitrogen fertilization on yielding of maize]. Biul. IHAR, [in Polish]. Gonet Z., Stadejek H., Wpływ nawożenia azotem na plon i wartość paszową kukurydzy uprawianej w dużym zagęszczeniu na zielonkę do bezpośredniego skarmiania [Effect of nitrogen fertilization on the yield and feed value of maize cultivated in large density for forage for direct feeding]. Pam. Puł. 101, [in Polish]. Grzelak B., Żarski J., Wpływ nawadniania kroplowego i nawożenia azotem na plonowanie dwóch odmian kukurydzy na glebie bardzo lekkiej [Influence of drip irrigation and nitrogen fertilization on two maize cultivars yielding on very light soil]. Infrastruktura i Ekologia Terenów Wiejskich 6, [in Polish]. Hoel B.O., Solhaug K.A., Effect of irradiance on chlorophyll estimation with the Minolta SPAD-502 Leaf Chlorophyll Meter. Ann. Bot. 82, Jankowiak J., Kruczek A., Fotyma E., Efekty nawożenia mineralnego kukurydzy na podstawie wyników badań krajowych [Effect of mineral fertilization on maize on the basis of Polish research results]. Zesz. Probl. Post. Nauk Rol. 450, [in Polish]. Kruczek A., Wpływ warunków pogodowych i nawożenia azotowego na rozwój i niektóre cechy morfologiczne kukurydzy [Effect of weather conditions and nitrogen fertilization on selected morphological traits and development of maize]. Rocz. AR Poznań, Rolnictwo 50, [in Polish]. Kruczek A., Wpływ nawożenia rzędowego różnymi rodzajami nawozów na plonowanie kukurydzy [Effect of row fertilization with different kinds of fertilizers on the maize yield]. Acta Sci. Pol., Agricultura 4(2), 37-46, [in Polish]. Księżak J., Bojarszczuk J., Staniak M., Produkcyjność kukurydzy i sorga w zależności od poziomu nawożenia azotem [The productivity of maize and sorghum yields depending on the level of nitrogen fertilization] Pol. J. Agron. 8, [in Polish]. Machul M., Wyznaczenie optymalnego zaopatrzenia kukurydzy w azot za pomocą testu SPAD [Determination of the optimum supplementation of maize with nitrogen with the use of SPAD test]. Pam. Puł. 133, [in Polish]. Machul M., Zastosowanie testu SPAD do ustalenia uzupełniającej dawki azotu dla kukurydzy [Use of the SPAD test to determine a supplementary nitrogen rate for maize]. Pam. Puł. 140, [in Polish]. Machul M., Jadczyszyn T., Przydatność wskaźnika względnej zawartości chlorofilu do oceny stanu odżywienia kukurydzy azotem [Suitability of relative chlorophyll content index to assess maize nitrogen nutrition status]. Pam. Puł. 140, [in Polish]. Machul M., Księżak J., Ocena plonowania kukurydzy w zależności od sposobu przygotowania roli i metody określenia dawki nawożenia azotem w warunkach monokultury i zmianowania [Evaluation of yielding of maize depending on pre-sowing soil cultivation and method of determining nitrogen doses under conditions of monoculture and crop rotation]. Fragm. Agron. 3(95), [in Polish]. R Core Team, R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. Samborski S., Rozbicki J., Przegląd badań nad wykorzystaniem chlorofilometru SPAD-502 do oceny stanu odżywienia roślin azotem [The review of the literature concerning the use of chlorophyll meter SPAD 502 for evaluating crop nitrogen nutritional status]. Nawozy i Nawożenie 2(11), [in Polish]. Torbert H.A., Potter K.N., Morrison J.E., Tillage system, fertilizer nitrogen rate and timing effect on corn yields in the Texas Blackland prairie. Agron. J. 93, Uddling J., Gelang-Alfredsson J., Piikki K., Pleijel H., Evaluation of the relationship between leaf chlorophyll concentration and SPAD-502 chlorophyll meter readings. Photosynth. Res. 91, Agricultura 13(1) 2014

12 50 M. Natywa, M. Pociejowska, L. Majchrzak, K. Pudełko Zagórda M., Walczyk M., Kulig B., Precyzyjne nawożenie azotem pszenicy ozimej na podstawie pomiarów SPAD [Winter wheat precise nitrogen fertilization based on SPAD measurements]. Inż. Rol. 7(95), [in Polish]. Zidane M.S., Amany A., Bahr-El-Karmany M.F., Effect of nitrogen fertilizer and plant density on yield and quality of maize in sandy soil. Res. J. Agric. and Biol. Sci. 2(4), Żarski J., Dudek S., Grzelak B., Rola czynnika wodnego i termicznego w kształtowaniu plonów ziarna kukurydzy [Role of water and thermal factors in affecting maize grain yield]. Acta Agrophysica 3(1), [in Polish]. WPŁYW DESZCZOWANIA I NAWOŻENIA AZOTEM NA PLONOWANIE I WARTOŚĆ WSKAŹNIKA ZIELONOŚCI LIŚCIA (SPAD) KUKURYDZY Streszczenie. Brak wody powoduje nierównomierny rozwój roślin podczas wegetacji lub nawet ich zasychanie. Azot jest jednym z najważniejszych składników pokarmowych w żywieniu organizmów wyższych oraz drobnoustrojów. Ocena stanu odżywienia roślin azotem i wyznaczanie optymalnych dawek tego składnika ma istotne znaczenie ze względu na aspekt ekonomiczny produkcji i konieczność ochrony środowiska rolniczego przed zanieczyszczeniem azotem. Dwuczynnikowe doświadczenie polowe prowadzono w latach na glebie zaliczanej do klas bonitacyjnych IVa i IVb, a według przydatności rolniczej do kompleksu 4. (żytni bardzo dobry) i 5. (żytni dobry). Celem badań była ocena wpływu deszczowania i zróżnicowanego nawożenia azotem (0, 80, 160 i 240 kg ha -1 N) na wybrane elementy struktury plonu oraz zmienność wskaźnika SPAD liści kukurydzy (odmiana Clarica, FAO 280). W latach prowadzenia badań obserwowano duże zróżnicowanie warunków pogodowych. Najbardziej suchy, a zarazem najcieplejszy był rok 2008, gdy zarówno w ostatniej dekadzie kwietnia, ale także w maju i czerwcu ilość opadów była niewielka. Zaobserwowano, że ilość opadów w maju ma istotny wpływ na wielkość plonu kukurydzy, natomiast deszczowanie zastosowane w czerwcu i lipcu pozwala ograniczyć negatywny wpływ suszy występującej późną wiosną. Współdziałanie czynników doświadczalnych wykazało, że największy plon ziarna uzyskano po zastosowaniu 80 kg ha -1 N w warunkach deszczowania. Natomiast dalsze zwiększenie dawki nawożenia azotowego nie powodowało istotnego wzrostu plonu ziarna kukurydzy. Wartość wskaźnika SPAD określana w fazie pełni kwitnienia (BBCH 67) oraz dojrzałości mlecznej (BBCH 75) była najwyższa przy nawożeniu azotem w dawce 240 kg ha -1. Zastosowanie deszczowania istotnie zwiększało wartości odczytów SPAD niezależnie od poziomu nawożenia azotem. Słowa kluczowe: chlorofil, deszczowanie, kukurydza, nawożenie azotowe, SPAD Accepted for print Zaakceptowano do druku: For citation Do cytowania: Natywa M., Pociejowska M., Majchrzak L., Pudełko K, Influence of irrigation and nitrogen fertilization on yield and leaf greenness index (SPAD) of maize. Acta Sci. Pol., Agricultura 13(1), Acta Sci. Pol.