CALCIUM NITRATE AND AMMONIUM NITRATE LIMESTONE AS SOURCES OF NITROGEN FOR OATS AND BARLEY Pentti Hänninen Agricultural Research Centre, Central Finland Agricultural Experiment Station Armi Kaila University of Helsinki, Department of Agricultural Chemistry Received April 24, 1961 The experiments, the results of which are recorded in the present paper, have been carried out in order to test several observations made in summer 1958. Ac- cording to these, spring cereals fertilized with the Finnish ammonium nitrate lime- stone, »Oulunsalpietari», seemed to be retarded in maturing as compared to the cereal stands treated with calcium nitrate. If these observations made in practice were valid, it could be supposed that there would be differences also in the effect of these fertilizers on the yields and nitrogen uptake by the plants. »Oulunsalpietari» contains 25 per cent nitrogen as ammonium nitrate and about 26 per cent dolomite which makes its magnesium content about 3 per cent. The manufacture of this product was started in 1952, and now it is the most widely used nitrogen fertilizer in our country. Since 1953 its effect has been studied in nu- merous field trials. Salonen (1) has published results of experiments from the years 1953—1956. In different groups of trials with spring cereals the effect of »Oulunsalpietari» ranged from 43 to 144 per cent of the effect of calcium nitrate. The average in 62 trials was 88 per cent. Owing to the large variation no significant difference could be demonstrated. The present authors were fully aware of the fact that this kind of problem must be studied using a method in which the experimental errors may be minimized. One of these is the split-plot technique which allows the testing of even small dif- ferences between the treatments. This technique was employed in the field trials carried out in the summers of 1959 and 1960 in order to compare the effects of calcium nitrate and ammonium nitrate limestone (Oulunsalpietari) on oats and, in one case, on barley. The development of the plants and their uptake of nitrogen were continuously followed during the growing period. https://www.c-info.fi/en/info/?token=x6oeT_U0b6R3npZM.yteSQKwZi7TcaVjIMcq3bg.ElzuiNnlP3EiBC42XGuyjl5XNrBR-aE2UqM4-S7iI7dkM-ZfNZOmfSftw9IEJ_cLELd9wqiB27eMyaYcJEz65hUCR4Fsn92zs47OBJlATJpafmCZZHRpkL72FAsiY1cW0KwVqZjlxA4F4OPJaXCnL0ssOq3xqBvbjBEGEcjR7uAGPtCzTranfOsaLq4_thVu1A 160 Experimental In 12 field trials the effects of calcium nitrate and ammonium nitrate limestone were compared as surface dressing on oats. In one trial barley was used as the experimental crop. The amounts of nitro- gen applied as these two fertilizers were 0, 25, and 50 kg/ha in 1959, in 1960 in some of the trials also 75 and 100 kg/ha were used in order to get a more distinct nitrogen effect. Since it could be supposed that the distribution of the fertilizers may have some influence on their effect, in 3 trials they were applied either as a surface dressing or worked in. The application of nitrogen was 50 kg/ha in all these experiments. The total area of an experimentalplot was 6 m X 10 m = 60 m 2. One half of each plot was treated with calcium nitrate, the other half with ammonium nitrate limestone (Oulunsalpietari). As a basal dressing 200 kg/ha of superphosphate and 100 kg/ha of 50 % potash fertilizer was worked in before sowing. The treatments were in randomized blocks replicated four times. In order to be able to get plant samples during the growing period without disturbing the stand to be harvested, an area of 0.4 m breadth was reserved for this purpose in each half of the plots. Plant samples were collected every fourteen days. Each time 20 plants were taken from one plot. The plants were air dried, weighed, and analyzed for total nitrogen by the usual Kjeldahl procedure. The field trials were carried out in five places: in Central Finland (Laukaa), on the southern coast (Viikki), in east Finland (Tohmajärvi), in southwest Finland (Paimio), and in south Finland (Leteen- suo). The list of the trials with some information is the following: Trial Place Kind of soil pH of soil Year K 1 Laukaa silt 6.2 1959 K 2 » » 5.8 » K 3 » » 6.2 » K 4 » » 5.8 » K 5 » » 5.9 1960 K 6 » » 5.9 » V 1 Viikki silt clay 5.2 1959 V 2 » finesand clay 5.7 » V 3 » » 5.7 » V 4 » silt clay 5.2 1960 T 1 Tohmajärvi humus soil 5.6 1959 T 2 » » 5.7 1960 P 1 Paimio very heavy clay 5.5 1959 P 2 » » 5.5 1960 L 1 Leteensuo heavy silty clay 5.4 1959 L 2 t * 5.4 1960 The meteorological conditions were different in these two years and also in the various places. Summer 1959 was extremely dry in south and southwest Finland, in the eastern parts of the country the weather conditions were more favourable. In 1960 the summer was rainy in south and southwest Finland, in Central Finland, on the other hand, the growing seasons were favourable. Results In 1959 the grain yields of oats showed a distinct response to nitrogen fertili- zers in most of the trials (Table 1). Between the yields obtained when equal amounts of nitrogen as calcium nitrate or ammonium nitrate limestone were applied, no statistically significant difference at the 5 per cent level could be detected. There was, however, some tendency to a slight superiority of calcium nitrate. If the average 161 Table 1, Grain yields of oats in 1959, kg/ha N 25 kg/ha N 50 kg/ha Trial No N Ca (N0 3 ) 2 NH.NO, Ca(NO3 ) 2 NH.NO, LSD 5 % K 1 1090 1510 1420 1700 1670 160 K 2 1160 1480 1550 1660 1640 250 V 1 2890 3290 3100 3410 3390 460 V 2 3860 4200 4050 4190 4150 240 V 3 3150 3120 3100 3100 3050 340 T 1 700 1830 1650 2710 2510 320 PI 1850 2320 2210 2570 2510 350 L 1 970 1340 1220 1480 1510 290 increases in yield brought about by these fertilizers are calculated, it is found that the increase produced by 25 kg/ha of N as ammonium nitrate was 77 % of that produced by the same amount of N in calcium nitrate. The corresponding per- centage for the higher amount was 92. Table 2. Straw yields of oats in 1959, kg/ha N 25 kg/ha N 50 kg/ha Trial No N Ca(NO,), NH.NO, Ca(NO,) 2 NH 4NO, LSD 5 % K 1 1190 1880 1760 2470 2270 170 K 2 2090 3070 2720 4020 3420 580 V 1 2760 3090 3060 3340 3110 460 V 2 3270 3550 3410 3870 3560 200 V 3 3450 3770 3690 3940 3900 260 Tl 1750 2870 2650 4090 3900 660 L 1 1020 1640 1460 1790 1810 220 The straw yields of oats in 1959 are reported in Table 2. The response to nitro- gen fertilizing is distinct in most of the trials. In trials K I,K 2, and V 2 the straw yields produced by 50 kg/ha of N as calcium nitrate are slightly, but statistically significantly higher than the corresponding yields with ammonium nitrate limestone. The tendency for the superiority of calcium nitrate seems to be even more marked than in connection with the grain yields: 25 kg/ha and 50 kg/ha of N as ammonium nitrate limestone have been able to increase the yield only by 74 per cent and 80 per cent, respectively, of the increases which were obtained with the corresponding amount of calcium nitrate. The nitrogen content of grains and straw in these experiments (Table 3) is, with only a few exceptions, equal in the corresponding treatments with the two fertilizers. In trial L 1 the grains from the calcium nitrate plots are significantly 162 Table 3. Nitrogen content of grains and straw of oats in 1959 (N per cent of dry matter) N 25 kg/ha N 50 kg/ha Trial No N Ca(NO,) 2 NH.NO, Ca(NO3) 2 NH.NO, LSD 5 % Grains K 1 1.96 1.98 1.98 2.15 2.08 0.08 K 2 1.96 1.84 1.87 1.89 1.87 0.07 V 1 1.90 2.01 1.90 2.08 2.13 0.10 V 2 1.81 1.93 2.03 2.07 2.09 0.32 T 1 2.07 1.78 1.81 1.74 1.75 0.15 I. 1 1.88 2.11 1.97 2.28 2.02 0.09 Straw V 1 0.45 0.50 0.46 0.58 0.54 0.08 V 2 0.54 0.51 0.54 0.58 0.58 0.14 T 1 0.93 0.54 0.58 0.49 0.49 0.17 richer in nitrogen than those from the ammonium nitrate limestone plots. This is also true for the grains from trial V 1 treated with the lower amounts of nitrogen. In the following year also higher apphcations of nitrogen were used in three of the trials. This was done because it could be supposed that the possible difference between the effects of these two fertilizers might be more distinct at the higher application levels. Table 4. Grain yields of oats in 1960, kg/ha N applied K 5 V 4 T 2 P 2 kg/ha Ca(NÜ3 ) 2 NH.NO, Ca(NO,) 2 NH 4N03 Ca(NO 3 ) 2 NH,NO3 Ca(NO,) 2 NH.NO, 0 2280 1060 840 3400 25 2760 2740 - - 2060 1820 50 3290 3410 1800 1760 2630 2620 3950 3610 75 3400 3430 1740 1760 100 3130 3020 1690 1820 - 3860 3930 LSD 5 % 220 470 990 520 The data in Table 4 show, however, that, as to the grains, even at the higher levels the difference between the effect of these two fertilizers was negligible. The same holds true also for the straw yields reported in Table 5. The nitrogen content of grains and straw and the amount of nitrogen in the yield harvested in trial K 5 (Table 6) reveal a regular increase with the increasing rate of nitrogen dressing. Yet, the differences between the corresponding values for the treatments with calcium nitrate and ammonium nitrate limestone are mostly lower than the least significant difference at the five per cent level. Only at the 163 Table 5. Straw yields of oats in 1960, kg/ha N applied K 5 V 4 T 2 kg/ha Ca(NO3 ) 2 NH.NO, Ca(NO,) 2 NH.NO, Ca(NO,) 2 NH.NO, 0 3110 4530 2340 25 4430 4150 3840 3590 60 5290 4770 5660 5490 4610 4710 75 5510 5410 5960 5670 100 6120 6250 6320 5680 - - LSD 5 ° 0 430 1070 1150 highest treatment level could a significant superiority of calcium nitrate in the nitrogen content of grains be found. The same situation may be observed in the nitrogen content of straw from the plots to which 75 kg/ha of nitrogen was applied. Also the amount of nitrogen harvested is at this rate of treatment higher when calcium nitrate is used. No differences between the effect of these fertilizers could be shown by the nitrogen analyses of samples from the other trials. Table 6. Nitrogen content of grain and straw and the amount of nitrogen in the oats yield of trial K 5. N applied N % of grain N % of straw N in yield kg/ha kg/ha Ca(NO,)2 NH.NO, Ca(NO,), NH.NO, Ca(NO,) 2 NH.NO, 0 1.67 0.39 50 25 1.72 1.71 0.42 0.44 66 65 50 1.88 1.82 0.49 0.46 88 84 75 2.09 2.01 0.60 0.50 104 96 100 2.30 2.19 0.75 0.80 118 116 LSD 5 % 0.09 0.10 8 Table 7. Yield results from trial L 2 in 1960 with barley. No N N 50 kg/ha N 100 kg/ha LSD 5 % Ca(NO3 ) 2 NH 4N0 3 Ca(NO3 ) 2 NH4N03 Grain yield, kg/ha 3750 4880 4610 5300 5080 450 Straw » » 3180 3890 3870 4190 4130 510 N % in grain 1.77 1.96 1.88 2.15 2.08 0.06 N in grain, kg/ha 66 96 87 114 106 9 164 Table 8. Comparing of calcium nitrate and ammonium nitrate limestone as a surface dressing and as worked in Worked in Surface dressing Trial No N Ca(NO,) 2 NH.NO, Ca(NO,), NH4 NO, LSD 5 % Grain yield kg/ha K 3 1130 1450 1480 1570 1560 150 K 4 1000 1540 1550 1450 1480 280 K 6 2100 3320 3150 3000 3240 440 Straw yield kg/ha K 3 1660 3070 3130 3250 3020 340 K 4 2080 3870 3730 3970 3600 800 K 6 2810 5220 5050 5200 4840 530 N % in grain K 3 1.99 2.24 2.24 2.22 2.18 0.11 K 4 1.93 1.93 1.86 1.94 1.84 0.12 K 6 1.61 1.71 1.67 1.69 1.70 0.06 N % in straw K 6 0.34 0.42 0.42 0.45 0.41 0.04 The trial in Leteensuo was in summer 1960 carried out using barley as the experimental crop. The results are recorded in Table 7. Owing to the large variation no statistically significant difference is obtained between the effect of the two fertilizers on the grain or straw yields, although some tendency for the superiority of calcium nitrate may be suspected. In the nitrogen content of the grains, however, a significant difference exists, but it is less distinct in the nitrogen of the grain yield. In both years some trials were carried out in which the effect of working in of these two fertilizers was studied. The results of these trials are collected in Table 8. Table 9. Uptake of nitrogen by oats in trial K 5, N mg per 20 plants N applied June 6 June 26 July 7 July 22 August 5 0 kg/ha 15 108 130 221 289 25 kg/ha as calcium nitrate 13 178 215 349 418 » ammonium nitrate 16 178 184 284 340 50 » » calcium nitrate 17 219 243 437 535 » ammonium nitrate 17 209 276 431 483 75 » » calcium nitrate 18 254 331 533 696 » ammonium nitrate 16 228 335 559 712 100 » » calcium nitrate 16 282 376 678 934 » ammonium nitrate 16 279 335 587 949 L. S. D. at 5 % 6 33 58 123 183 165 There are no differences between these fertilizers according to the grain and straw yields and their nitrogen content. Thus, at least 50 kg/ha of nitrogen as calcium nitrate or ammonium nitrate limestone may equally well be applied as a surface dressing or worked in. According to the observations made in the field in the fairly wet summer of 1958, the maturing of the cereal stands was retarded in the areas fertilized with ammonium nitrate limestone as compared with those treated with calcium nitrate. In the present trials no difference in the ripening could be detected. Yet, in the latter part of June in southern Finland, and in the beginning of July in Central Finland, there seemed to be some difference in the colour of the stands: calcium nitrate plots were of a darker green than ammonium nitrate limestone plots. Later the differences in the colour disappeared. As an example results of the visual ana- lysis of the stands in trial K 2 are recorded. A colour scale of o—lo was used, 10 representing dark intense green, and the green’s intensity diminishing down the scale to 0 = yellow. Trial K 2 No N 5.1 Ca (N0 3 ) 2 6.8 25 kg/ha N NHiNOj 6 5 Ca (NO,), 8.5 N 50 kg/ha NHjNO3 7 4 It could be supposed that the darker colour of the calcium nitrate stands would be reflected in the nitrogen content of the plants. Actually, in some cases the per- centage of nitrogen in these samples was higher than in those collected from the ammonium nitrate limestone plots. For example on July 9th in trial K 1 the plants treated with the higher amount of calcium nitrate contained 2.80 per cent nitrogen while the plants with the corresponding ammonium nitrate limestone treatment contained only 2.52 per cent nitrogen. Samples collected at the same time from trial K 3 had an equal nitrogen content when the fertilizers were worked in, but when applied as a surface dressing, calcium nitrate produced plant material with a nitrogen content of 2.58 %, and ammonium nitrate limestone was able to increase the nitrogen content only to 2.29 %. In trial K 5 the following nitrogen content for the variously treated plants could be found on the 23rd of June: In the untreated plants the N percentage was 2.85. Calcium nitrate plants Ammonium nitrate plants N applied 25 kg/ha 3.49 % 3.55 % » 50 » 3.97 % 3.90 % » 75 I 4.60 % 4.42 % » 100 » 5.17 % 4.91 % In spite of the fairly large variation between the replicates, a statistically significant difference at the 5 per cent level exists in the nitrogen content of the plants treated with 100 kg/ha of N. The large variation in the nitrogen content of the samples from various repli- cates may be understood on the basis of the theory presented by Specht (2) of 166 the variation control mechanism. According to this theory, the variation rate between the nutrient content of plants in the same stand has a maximum within the range of the luxury consumption of the nutrients in question. It is likely that in most of the present trials the nitrogen supply was not only above the minimum but also above the »poverty adjustment» range. Owing to the fairly large variation in the nitrogen content and weight of plants from the replicate plots, only occasionally a significant difference could be detected in the amounts of nitrogen in the 20 plants regularly sampled from the corresponding halves of the plots treated with these two fertilizers. In the cases where a difference existed, calcium nitrate always gave the higher result. As an example of these stu- dies the analyses for trial K 5 are reported in Table 9. The recovery of fertilizer nitrogen appears to be quite distinct since the sampling at June 26. Yet, the values obtained for the treatments with equal amounts of nitro- gen in these two fertilizers do not significantly differ from each other in any case in this trial. Discussion Since the last century the problem of the value of ammonium nitrogen and nitrate nitrogen as the nutrient source of plants has been studied and discussed. Owing to the fact that in these comparisons the effect of the anion of the ammo- nium salt and the cation of the nitrate also play their role, it has not been easy to find a clear answer to this question. Even if the plants preferably would take up the nitrate ions, in most soils the rapid nitrification will convert ammonium ions to this form, and then only the secondary effects connected with the process will account for the possible differences. When such fertilizers as ammonium nitrate limestone and calcium nitrate are compared the differences in their effects cannot be very high, since the former has one half of its nitrogen as nitrate. This is likely to be enough to give a start equal to that allowed by calcium nitrate. Later on, the ammonium nitrogen is already converted to nitrate. Only in soils which are able to fix considerable amounts of ammonium ions, this process may be retarded. In spite of the fact that in the present trials the split plot technique was employed, the variation was so large that only in some cases a statistically significant diffe- rence between the effects of these fertilizers could be demonstrated. Then it always indicated the superiority of calcium nitrate. The fairly regular tendency to higher yields and nitrogen content of grains and straw in the calcium nitrate plots of most trials gives support to the few significant results obtained. In Sweden the field trials show that ammonium nitrate limestone is equal to calcium nitrate as a source of nitrogen to ley, potato, and oats, and also to other crops provided the fertilizer is worked in (Svanberg 1961, unpublished). For barley and wheat, however, calcium nitrate is considered to be the better fertilizer. In the present trial with barley, no significant difference could be shown in the yields produced by these two fertilizers. Only the nitrogen content of the grains produced by calcium nitrate was somewhat higher than those from the 167 ammonium nitrate limestone plots. In this jespect, however, the use of ammonium nitrate limestone may be more suitable, since the aim in the cultivation of barley is often the production of grains not too high in nitrogen. It should be noted that the nitrogen content of the grains of oats in the Leteensuo trial of 1959 was also higher in the plots treated with calcium nitrate. In this kind of trial weather conditions play an important role. Summer 1959 was very dry and warm in the southern parts of the country, the following summer, on the other hand, was fairly wet. In the central parts of the country the summers were more favourable, the latter being even better than the former, since enough rain fell in May and June. It may be assumed that in a very cold and wet growing period the results could have been different from those obtained in the present trials. In every case, on the basis of the results reported in this paper, the differences in the effect of calcium nitrate and ammonium nitrate limestone on oats are so low that these fertilizers may be considered equally effective as the nitrogen source for this crop. Summary Calcium nitrate and ammonium nitrate limestone (»Oulunsalpietari») were compared as the nitrogen fertilizer for oats in 15 field trials and for barley in one trial. The trials were carried out in summers 1959 and 1960 in various places in Finland. The split plot technique was employed in order to reduce the variation as much as possible. In 1959 the amounts of nitrogen applied as these two fertili- zers to the corresponding halves of the plots were 25 and 50 kg/ha. In 1960 also higher applications were used: 75 and 100 kg/ha of N. In three trials these fertili- zers were compared both as a surface dressing and worked in. Visual observations suggested about 5—6 weeks after sowing a darker green colour in the stands treated with calcium nitrate as compared with the other half treated with ammonium nitrate limestone. These differences later disappeared. In some trials a higher nitrogen content of the plants from the calcium nitrate stands could be demonstrated during this period. The uptake of nitrogen by plants was regularly followed throughout the growing period. Owing to the large variation, usually, no statistically significant difference between the effect of the fertilizers could be detected. In a few cases the superiority of calcium nitrate could be demonstrated. No differences in the ripening could be found. In most trials there was a fairly regular tendency to higher yields and higher nitrogen content in the grain and straw produced by calcium nitrate. Yet, only in a few cases were the differences statistically significant at the five per cent level. Thus, it was concluded that on the basis of the results of these trials ammonium nitrate limestone and calcium nitrate may be considered practically equal as nitro- gen fertilizers for oats. There was no difference in the yields of barley produced by these two fertili- zers, but the nitrogen content of grains was significantly lower with ammonium 168 nitrate limestone than with calcium nitrate. This may be worth further study in connection with the production of malting barley. Acknowledgement. The authors wish to express their gratitude to Norsk Hydro-Elektrisk Kvaelstofaktieselskab, Oslo, for providing funds for the field trials. REFERENCES (1) Salonen, M. 1958. Erilaisten typpilannoitteiden vaikutuksen vertailua. Kenttäkokeiden tuloksia vuosilta 1952—56. Referat: Vergleich der Wirkung verschiedener Stickstoffdüngemittel Staatl. Landw. Versuchstät. Veröff. Nr. 169, Helsinki, 24 S. (2) Specht, A. W. 1960. Evidence for and some implications of a variation-control mechanism in plant composition. Soil Sei. 89: 83—91. SELOSTUS; KALKKISALPIETARI JA OULUNSALPIETARI KAURAN JA OHRAN TYPPILANNOITTEINA Pentti Hänninen Maatalouden tutkimuskeskus, Keski-Suomen koeasema, Kuusa Armi Kaila Yliopiston maanviljelyskemian laitos, Helsinki Kesällä 1959 ja 1960 suoritettiin eri puolilla Suomea osaruutumenetelmää käyttäen kenttäko- keita, joissa verrattiin kalkkisalpietaria ja oulunsalpietaria kauran typpilannoitteena sekä myös yh- dessä kokeessa ohran typen lähteenä. Silmävaraisten havaintojen mukaan olivat noin 5 6 viikon ikäiset kalkkisalpietaria saaneet kasvustot tummemman vihreitä kuin vastaavat oulunsalpietarilla lannoitetut. Joissakin kokeissa oli kalkkisalpietariruutujen kasvinäytteiden typen pitoisuus tähän aikaan suurempi kuin vastaavien oulunsalpietaria saaneiden näytteiden. Värierot hävisivät myöhemmin. Tuleentumisajassa ei voitu havaita mitään eroja. Typen ottoa seurattiin koko kasvukauden ajan analysoimalla kultakin koeruudulta kahden viikon tai kymmenen päivän väliajoin otetut kasvinäytteet. Suuren hajonnan takia olivat erot har- voin tilastollisesti merkitsevät, mutta jos eroja voitiin todeta, ne osoittivat kasvien ottaneen enemmän typpeä kalkkisalpietarista kuin oulunsalpietarista. Jyvä- ja olkisatojen sekä niiden typen pitoisuuden perusteella voitiin vain muutamissa tapauk- sissa todeta eroa lannoitteiden vaikutuksessa, ja tällöin oli kalkkisalpietari aina parempi typen lähde. Näitten kokeitten perusteella kalkkisalpietari ja oulunsalpietari näyttävät olevan käytännössä jok- seenkin tasaveroisia kauran typpilannoitteena. Koska ohrakokeessa saatiin kummallakin lannoitteella yhtä suuret sadot, mutta oulunsalpietari- koejäsenten jyvien typen pitoisuus oli matalampi kuin vastaavien kalkkisalpietarilla lannoitettujen, lienee syytä tarkistaa, olisiko tällä seikalla merkitystä mallasohran viljelyssä.