SPRINKLER IRRIGATION OF CLAY SOILS IN SOUTHERN FINLAND IV. The effect of repeated applications of water and nitrogen fertili- zation on spring cereals Paavo Elonen University of Helsinki, Department of Agricultural Chemistry Osmo Kara Finnish Research Institute ofEngineering in Agriculture and Forestry, Rukkila, Helsinki Received May 15, 1972 Abstract. In 1967 and 1968, in the month of June, irrigation of silty clay soil in southern Finland by a single sprinkling, which involved the application of 30 mm of water, increased the yields of spring wheat by an average of between 880 and 970 kg per ha, or 37—51 %, and the yields of barley by 1140—1340 kg per ha, or 37—42 %. Repeating the irrigation after about one week further increased the wheat yields on the average by from 670 to 800 kg per ha and the barley yields between 810 and 860 kg per ha. The effect of the irrigation on the size of the yields was virtually of the same magnitude both years in spite of the fact that in 1967 both June and July were extremely dry months, whereas in 1968 the dry June was followed by a rainy July. The sprinkling affected the ripening of the grain, on the other hand, differently each year: slightly retarding the ripening in 1967 but considerably hastening it in 1968. In the latter year, the irrigation prevented detrimental late tillering and thereby augmented the hectoliter weight and 1000-grain weight of the crops. In response to the one-time sprinkling, the protein content of the grains decreased in the case of the wheat by an average of 1.0—1.3 and of the barley by 0.1—0.7 %-units. The effect of two sprinklings was corresponding decreases of 1.9—3.1 and 0.8—1.0 %-units. The application to the seedlings as surface dressing immediately before irrigation ofcalcium nitrate containing 60 kg/ha of nitrogen increased the protein content of the wheat on the average by 1.6 and of the barley by 1.9 %-units. The nitrogen fertilization thus prevented excessive lowering of the protein content by irrigation and, furthermore, considerably intensified the salutary effect of the irrigation in augmenting the yield. A disadvantage of abundant nitrogen fertilization was a slight retardation of ripening. The placement of basal dressing with a fertilizer drill at a depth of 9 cm proved effective, particularly in 1967, when both the wheat and the barley yields increased 22 per cent in comparison with the effect ofsurface dressing. Use of the fertilizer drill, moreover, promoted the ripening process. Sprinkling did not appear to reduce the placement effect of the ferti- lizer; rather did these two methods form an exceedingly favorable combination. In 1964 a series of investigations was started with the aim of thoroughly ascertaining the effects of sprinkler irrigation on clay soils in southern Finland. In the years 1964 https://www.c-info.fi/en/info/?token=9P_PtwX3x37yvXPz.BdDxrpJn7LhuBSAIFt1IoQ.5f6wElxXZsL61XpJ_s22oGry9VR5aYinQ2ZRiZVY3JakMTLqETvAi5E2d6lnZmKdmDqzoD45kYaFUQ21_NOVMdcagrOVJCs4wGTqUcm3y3SKRXcFBoq-LGd-hVwRK1grVDPkusISqHbW_ha_I1RKnRtz2142iWq1tUuiBbqtqdPHRURDxQ 150 66, a single sprinkling of 30 mm of water at the right time increased the yields of spring cereals between 25 and 50 per cent (Elonen, Nieminen and Kara 1967). The investigators observed that the effect of the sprinkling on the soil moisture conditions was of relatively short duration; it was therefore reasoned that more frequent sprinklings would probably have produced even better results. It was likewise surmised that the efficacy of the irrigation could have been increased by more abundant application of nitrogen fertilizer, which would at the same time have prevented the excessive reduction of the protein content of the grains caused by the irrigation. The validity of these assumptions was investigated in the following two-year period, 1967—68. The results arrived at are set forth in this publication. Field experiments Treatments and their symbols. The field experiments were laid out in a split-plot design (Steel and Torrie 1960), and they included four factors: as whole plots, four levels of irrigation (I); as subplots, two different crops; as sub-subplots, two levels of nitrogen fertilization (N); and as subsub-subplots, two fertilization depths (D). There were four replications; accordingly, the trials embraced 128 experimental plots. The experimental design was in principle similar to the one described in detail and illus- trated by a diagram in a previous publication. (Elonen, Nieminen and Kara 1967). The irrigation was performed at night by rotary sprinklers with a radius of 12 ±2 m. Drainage ditch water with apH of about 7 and electrical conductivity of < 0.1 mmho per cm was applied at a rate of smm an hour, the total single application amounting to 30 mm. It was endeavored to perform the irrigation at a time when, in the light ofprevious experience, plants were most likely to benefit from it (Fig. 1). The irrigation dates were as follows 1967 1968 I 0 = without irrigation I[ = June 15 I 0 = without irrigation I, June 9 V I 2 = June 21 Ia = June 9 and June 17 I 3 = June 9, 17 and 24I s = June 15 and June 21 The experimental plants were spring wheat (Svenno variety) and barley (Ingrid variety). The crops were cultivated in the same way under identical growing conditions side by side. The basal dressing (Nx) was applied in conjunction with the sowing May 12, 1967 and May 10, 1968. In the former year, 60 kg of N, 43 kg of P and 56 kg ofK per hectare were applied in the form of compound fertilizer. In the latter year, the corresponding figures were 75, 44 and 62. The fertilization was carried out with a fertilizer drill, the coulters being spaced 16 cm apart; on the one hand, a placement depth of 9 cm was used (D,), and on the other, the application was on the surface (D 0) with the plastic ferti- lizer tubes outdrawn from the coulters. The application of the additional nitrogen (N 2) was performed with the same machine on the surface to the sprouts immediately before the initial irrigation. Nitrogen was applied as calcium nitrate in the amount of 60 kg N per ha; thus the nitrogen levels N x and N 2 in 1967 were 60 and 120 kg N per ha, and in 1968, 75 and 135 kg N per ha. Fig. 1. The stages of development of barley on the dates of irrigation in 1967 (upper, fertilizer broadcast or placed) and 1968 (lower, fertilizer placed). 151 152 Experimental soils and their moisture conditions. The experimental plots were located in fields of silty clay on the farm maintained by the Re- search Foundation for Agricultural Machinery near Helsinki. The experimental soils were very much alike both years. The top soil contained an average of 50—52 per cent of the clay fraction (< 2 pm) and 3.4—4.0 per cent of organic carbon. The pH of the soils (in 0.01 M CaCl2 ) varied between 5.4 and 6.1, and their nutrient condition was fairly good. The subsoils were heavy clays (clay content > 60 per cent). The moisture condition of the soil was investigated by Bouyoucos’ (1954) gypsum block method. Immediately after the sowing, 48 blocks were dug to three depths in 16 barley plots. The results of the measurements are given in Table 1 as averages for five-day periods. As is well known, the method has certain drawbacks, so the results could scarcely correspond to the actual amounts of available water in the ground. The readings probably do, however, reflect fairly accurately the changes in the moisture condition of the soil and the effect of irrigation on them. In 1967 both June and July were exceptionally dry months. The amount of »available water for plants» was reduced close to zero to a depth of 10 cm as of June 21, to a depth of 20 cm about a week later and to a depth of 40 cm some three weeks later. After that, there were no measurable amounts of available water for plants until August, when fairly heavy rainfalls moistened the surface layer of the ground. The effect of a single 30-mm sprinkler irrigation was of rather short duration only about one week. By June 21 the ground had dried out to such an extent that 30 mm of water could not suffice to moisten the soil to a depth of 20 cm. Watering of the surface did appear, however, to retard the drying of the soil at a depth of 40 cm. The moisture condition in twice-irrigated soil was evidently fairly beneficial to plant growth throughout the month ofJune, but by the beginning of July the top soil dried nearly to the wilting point. In 1968 June was once more dry, and the top soil dried close to the wilting point. At the end of June and the beginning ofJuly, the total precipitation was 70 mm during a three-week period; thanks to the generous rainfall, the ground was fairly moist through- out the month ofJuly. The crops evidently utilized the first two irrigations rather com- pletely, but after the third watering, performed on June 24, dry weather continued for only two days longer. The thrice-watered experimental plots were moister than the other plots for the rest of the summer. The growth of the plants. In 1967 the grain crops emerged evenly. The beneficial effect of the placement of fertilizer could be perceived clearly after as short a time as two weeks after the emergence of the seedlings. Even more conspicuous was the effect of sprinkler irrigation. The watered crops were distinctly higher and denser than the unwatered ones. The barley- was gathered with a combine harvester on August 24 and the wheat on August 30. The rains that came right after the sowing in 1968 destroyed the porous structure of the soil surface and weakened the sprouting of the crops. The rains that followed in the wake of the dry month of June caused harmful late tillering of the unirrigated crops, which did not have time to ripen. The irrigated crops, by contrast, ripened evenly. The crops were harvested on September 5. 153 Table 1. ”Available soil moisture” (%) at various depths in the barley plots. Mean values during the periods offive days. Year Depth Irri- June July August gation 1— 6 11— 16—21—26 1— 6 11— 16—21 26 1— 6 11— 16—21—26 5 10 15 20 25 30 5 10 15 20 25 31 5 10 15 20 25 31 1967 10 cm I 0 0 74 45 30 10 1 0 0 0 0 0 0 0 27 76 68 71 86 I, 30 56 39 22 75 3 0 0 0 0 0 0 0 4 II 12 20 33 I, 30 61 43 18 2 84 17 1 0 0 0 0 0 27 71 54 66 97 I, 60 68 39 25 68 81 34 3 0 0 0 0 0 8 28 28 45 63 20 cm I„ 0 83 74 56 33 6 1 0 0 0 0 0 0 2 7 7 12 18 I, 30 63 56 40 79 13 2 0 0 0 0 0 0 0 0 0 0 0 I, 30 66 49 33 13 19 8 1 0 0 0 0 0 0 0 0 2 3 I, 60 79 63 53 73 58 33 7 1 0 0 0 0 0 0 0 0 0 40 cm I„ 0 100 100 100 96 81 46 13 1 0 0 0 0 0 0 0 0 0 I, 30 90 80 73 76 70 60 38 8 1 0 0 0 0 0 0 0 0 Ij 30 100 100 100 100 98 84 53 22 5 1 0 0 0 0 0 0 0 I, 60 100 100 100 100 100 95 66 19 2 0 0 0 0 0 0 0 0 1968 10 cm I„ 0 64 40 16 2 0 86 80 91 99 83 52 19 0 0 15 93 94 96 I, 30 73 74 93 11 0 86 100 99 99 81 73 35 0 0 15 93 96 99 1, 60 78 74 89 75 48 86 89 96 97 77 53 23 0 0 15 90 94 96 I, 90 70 48 61 75 42 98 93 95 97 96 76 55 23 10 15 80 71 70 20 cm 10 0 97 72 43 13 2 16 49 74 97 92 63 29 0 0 2 14 40 66 11 30 99 88 99 19 2 70 97 97 98 95 67 26 0 0 10 59 70 83 I, 60 100 87 99 72 45 86 98 98 96 94 64 32 0 0 4 25 55 79 I, 90 98 87 85 72 42 100 100 99 98 95 82 55 10 4 15 78 90 99 40 cm I„ O 100 100 100 100 98 63 55 78 100 100 85 55 26 12 0 0 5 25 I, 30 100 100 100 100 100 88 83 91 99 96 94 80 42 19 0 0 3 15 I, 60 100 100 100 100 100 91 88 90 93 100 95 73 22 9 0 0 4 14 I, 90 100 100 100 100 97 99 100 100 100 100 99 91 60 31 8 7 11 34 Precipitation mm 1967 4 3 2 0 5 0 7 1 0 0 12 4 0 31 10 9 43 18 1968 0 4 0 0 8 27 0 23 20 3 7 0 0 5 16 31 12 18 Results Grain yields (Table 2). The sprinkler irrigation on June 15, 1967, increased the wheat yields an average of 970 (1900—2870) ± 430 kg per ha, or 51 23 %, and 154 Table 2. Grain yields kgjha , moisture 15%. Year Irrigation plant mm N. N 2 D 0 Dj mean D 0 D, mean 1967 I„ O 1590 2100 1840 1730 2170 1950 wheat li 30 2320 2890 2600 2940 3330 3140 I, 30 2170 2850 2510 2830 3430 3130 I 3 60 2860 3420 3140 3680 4200 3940 1967 I0 0 2250 3110 2680 2480 3480 2980 barley I, 30 3170 3940 3550 4230 4760 4490 1 2 30 3130 4040 3590 4090 4630 4360 13 60 3840 4630 4230 5090 5800 5440 1968 I„ 0 2170 2280 2220 2640 2380 2510 wheat Ix 30 3040 3160 3100 3440 3350 3400 I 3 60 3760 3870 3810 4210 4340 4280 I3 90 3900 4130 4020 4630 4610 4620 1968 I„ 0 3570 3550 3560 3540 3890 3720 barley It 30 4730 5020 4870 5020 5170 5100 I 3 60 5610 5860 5730 5800 6080 5940 I3 90 5280 5540 5410 6030 6740 6380 Means, least significant differences (LSD), and significant interactions (*) 1967, wheat 1967, barley 1968, wheat 1968, barley I 0 1900 2830 2370 3640 I, 2870 4030 3250 4980 Ia 2820 3970 4050 5840 Ia 3540 4840 4320 5900 LSD 430 680 410 580 N, 2520 3510 3290 4890 Na 3040 4320 3700 5280 LSD 140 310 150 380 D„ 2510 3530 3470 4950 D, 3050 4300 3520 5230 LSD 80 160 110 150 I X N* the barley yields 1200 (2830—4030) 680 kg per ha, or 42 i 24 %. The effect of the sprinkling carried out six days later was approximately of the same magnitude: the wheat crop increased 920 kg per ha, or 48 %, and the barley crop 1140 kg per ha, or 40 %. Two applications ofwater caused the wheat yields to increase by no less than 1640 kg per ha, or 86 %, and the barley yields by 2010 kg per ha, or 71 %. Repetition of the sprinkler irrigation (I3—Ij) thereby augmented the wheat crops by an average of 670 kg per ha, or 35 %, and the barley crops by 810 kg per ha, or 29 %. The effect of the watering was noticeably greater in the N 2 than Nx plots. A single 155 watering of the Nx plots caused the wheat yields to increase by an average of 720 kg per ha, or 39 %, and the barley yields by 890 kg per ha, or 33 %, whereas the corresponding figures for the N 2 plots were 1190 kg per ha, or 61 %, and 1450 kg per ha, or 49 %. Cor- respondingly, two irrigation rounds in the Nx plots augmented the wheat yields by an average of 1300 kg per ha, or 71 %, and the barley yields by 1550 kg per ha, or 58 %; but in the N 2 plots, the wheat yield increased as much as 1990 kg per ha, or 102 %, and the barley yield 2460 kg per ha, or 83 %. Calcium nitrate applied to the shoots increased the average wheatyield by 520 dz 140 kg per ha, or 21 dz 6 %, and the barley yields by 810 dz 310 kg per ha, or 23 dz 9 %• The effect of additional nitrogen depended significantly on the sprinkler irrigation. With- out irrigation, the additional application of nitrogen increased the wheat yields by only 110 kg per ha and the barley yields by 300 kg per ha. The corresponding figures for once- watered plots were 580 and 860 kg per ha and for twice-watered plots 800 and 1210 kg per ha. Sprinkler irrigation thus enhanced the efficacy ofnitrogen fertilization many times over. The placement of basal fertilizer to a depth of 9 cm augmented the wheat yields by an average of 540 dz 80 kg per ha, or 22 dz 3 %, and the barley yields by 770 dz 160 kg per ha, or 22 dz 5 %. The placement effect of fertilizer on the wheat yields was an increase of 470 kg per ha without irrigation, 560 kg per ha with a single watering and 540 kg per ha with two waterings. The corresponding figures for barley were 930, 690 and 750 kg per ha. Sprinkler irrigation did not therefore significantly decrease the placement effect of the fertilizer. The placement of basal fertilizer augmented the wheat yields of the N x plots by 580 kg per ha and of the N 2 plots by 490 kg per ha. The corresponding figures for barley were 830 and 700 kg per ha. The application ofadditional nitrogen to young crops thus tended to decrease the placement effect of the basal dressing, but the interaction was not statistically significant. In 1968 a single sprinkling augmented the wheat yields by an average of880 i 410 kg per ha, or 37 ± 17 %, and the barley yields by 1340 i 580 kg per ha, or 37 ± 16 %. Two waterings augmented the wheat yields, in comparison with unirrigated crops, by 1680 dz 410 kg per ha, or 71 d: 17 %, and the barley yields by 2200 dz 580 kg per ha, or 60 dz 16 %. Repetition of the sprinkler irrigation (I2—Ix) thereby augmented the wheat yields by 800 dz 410 kg per ha, or 25 d: 13 %, and the barley yields by 860 d: 580 kg per ha, orl?dzl2%. A third sprinkling tended to increase the yields further, but the effect was no longer statistically significant. The effect of dressing with additional nitrogen was noticeably slighter than the year before: the wheat crop increased an average of 410 dz 150 kg per ha, or 12 £5 %, and the barley crop 390 i 380 kg per ha, or 8 ± 8 %. The positive interaction between nitrogen dressing and sprinkler irrigation was likewise noticeable only to a very slight degree: nitrogen dressing increased the wheat yields of plots 10,I 0, T x , I 2 and I 3 by 290, 300, 470 and 600 kg per ha and the barley yields, correspondingly, by 160, 230, 210 and 970 kg per ha. The significance of the placement of the basal dressing was likewise substantially slighter than in the previous year and statistically significant only in the case of the barley plots, where the yields increased on the average by 280 i 150 kg per ha, or 6 ± 3 %. As in the previous year, sprinkler irrigation and additional nitrogen applied to the seedlings did not appear to have decreased the placement effect of the basal dressing. 156 Table 3. Moisture of grains at the harvest, %. Year Irrigation N3 N2 plant ram D0 D 3 mean D0 D 3 mean 1967 Ö 2bÄ 2eh4 284) 264) 2770 wheat I, 30 26.4 25.0 25.7 26.2 25.9 26.0 I 8 30 26.5 25.2 25.8 27.8 27.0 27.4 I 3 60 28.1 26.6 27.3 29.2 28.3 28.7 1967 I 0 0 26.2 25.1 25.7 27.8 25.2 26.5 barley I, 30 26.8 25.4 26.1 28.7 25.6 27.2 I 3 30 28.6 26.7 27.7 31.0 28.0 29.5 I 3 60 27.9 26.6 27.3 31.0 27.8 29.4 1968 I 0 0 30.5 27.9 29.2 32.3 32.1 32.2 wheat I 3 30 23.3 23.6 23.5 26.5 27.9 27.2 I 3 60 20.6 21.9 21.2 24.1 25.1 24.6 I 3 90 21.1 21.7 21.4 23.3 23.6 23.5 1968 I„ 0 35.1 35.7 35.4 39.2 37.9 38.5 barley I 3 30 25.3 24.9 25.1 27.4 28.0 27.7 I 3 60 20.2 20.5 20.4 22.7 23.5 23.1 I 3 90 20.4 19.9 20.2 21.6 20.6 21.1 Means, least significant differences (LSD), and significant interactions (*) 1967, wheat 1967, barley 1968, wheat 1968, barley I„ 26.726.1 30.737.0 I 2 25.926.6 25.326.4 I a 26.628.6 22.921.7 I, 28.128.3 22.420.6 LSD 1.50.9 3.35.5 Ni 26.326.7 23.825.3 Na 27.328.1 26.927.6 LSD 0.50.3 0.80.8 D„ 27.428.5 25.226.5 Dj 26.226.3 25.526.4 LSD 0.40.3 0.50.5 I X N* N X D*** I x D** Moisture of grains at harvest (Table 3). In 1967 the irrigation signifi- cantly affected the ripening of the cereal crops only in the barley plots. The moisture of the grains at threshing time was 2.5 d: 0.9 %-units higher in the twice-irrigated than in the unirrigated plots. The additionalnitrogen also slightly retarded the ripening, increasing the moisture content of the wheat by 1.0 dz 0.5 and that of the barley by 1.4 ± 0.3 %- units. Placement of the basal dressing, on the other hand, had the effect of promoting the ripening process: the moisture content of the wheat was 1.2 ± 0.4 and that of the barley grains 2.2 dz 0.3 %-units lower in the experimental plots treated with placed fertilizer than in the plots treated with surface dressing. 157 Table 4. Protein contents of grains, % of DM. Year Irrigation N x N 2 plant mm D 0 Dx mean D 0 D x mean 1967 I0 O 14.4 14.5 14.4 16.5 16.1 16.3 wheat I, 30 13.2 13.4 13.3 15.1 15.7 15.4 1 2 30 13.4 13.3 13.3 15.3 15.5 15.4 13 60 12.5 12.4 12.4 14.3 15.0 14.7 1967 I0 0 11.9 12.1 12.0 13.9 13.8 13.8 barley I, 30 11.8 11.7 11.8 13.9 13.8 13.9 I 2 30 11.9 11.5 11.7 13.9 13.8 13.8 I, 60 11.0 11.2 11.1 13.2 13.1 13.2 1968 I„ 0 16.1 16.6 16.4 17.9 18.3 18.1 wheat Ij 30 15.1 15.4 15.3 16.2 16.9 16.6 12 60 13.8 13.2 13.5 14.8 14.8 14.8 1 3 90 12.9 13.3 13.1 14.3 14.5 14.4 1968 I„ 0 14.2 14.4 14.3 15.6 15.5 15.6 barley I 3 30 13.5 12.9 13.2 15.1 15.2 15.2 12 60 13.1 12.9 13.0 14.7 14.9 14.8 13 90 11.9 11.9 11.9 13.7 13.9 13.8 Means, and least significant differences (LSD). No significant interactions. 1967, wheat 1967, barley 1968, wheat 1968, barley I„ 15.412.9 17.214.9 I, 14.412.8 15.914.2 12 14.412.8 14.113.9 13 13.512.1 13.812.8 LSD 0.70.5 1.91.2 N, 13.411.6 14.613.1 N 2 15.413.7 16.014.8 LSD 0.30.2 0.40.4 D„ 14.412.7 15.214.0 Dx 14.512.6 15.414.0 LSD 0.20.2 0.30.3 In 1968 the differences in the moisture content of the cereal crops were very great, owing to late tillering, and the sprinkler irrigation had an exceedingly beneficial effect on the ripening of the grain: once sprinkled, the wheat was 5.4 3.3 %-units, and twice sprinkled, 8.3 i 3.3 %-units drier than unirrigated wheat. With respect to the barley, the corresponding differences were even greater 10.6 5.5 and 15.3 ± 5.5 %-units. Differences in moisture content of such magnitude were partly due to the fact that the unirrigated barley crop included 4.8 %, the once-watered crop 3.0 % and the twice- watered crop only 0.8 % of green grains. Even a third application of water seemed to promote further the ripening of the crops. As in the previous year, the application of 158 Table 5. 1000-grain weights, g. Year Irrigation Nx N 2 plant mm D 0 Di mean D 0 D x mean 1967 I0 O 33.2 33.1 33.1 32.9 32.9 32.9 wheat I 30 33.5 34.1 33.8 33.2 34.1 33.6 12 30 32.9 33.6 33.2 33.2 34.5 33.9 1 3 60 33.4 34.2 33.8 34.1 35.5 34.8 1967 I„ 0 45.7 45.6 45.7 46.1 45.8 46.0 barley I3 30 45.8 45.7 45.8 46.3 45.6 46.0 12 30 46.0 46.0 46.0 45.8 45.6 45.7 1 3 60 46.4 46.6 46.5 46.5 46.1 46.3 1968 I 0 0 34.3 36.4 35.3 35.7 36.1 35.9 wheat Ij 30 37.9 37.9 37.9 38.2 38.7 38.4 1 2 60 37.2 37.9 37.5 38.2 38.0 38.1 1 3 90 36.2 36.5 36.4 37.6 37.9 37.8 1968 I„ 0 49.3 50.0 49.7 48.8 50.0 49.4 barley I 2 30 51.9 52.0 52.0 52.0 51.9 52.0 12 60 51.4 52.1 51.7 52.2 52.6 52.4 1 3 90 51.2 51.2 51.2 50.9 51.5 51.2 Means, least significant differences (LSD), and significant interactions (*) 1967, wheat 1967, barley 1968, wheat 1968, barley I 0 33.045.8 35.649.5 I, 33.745.9 38.252.0 12 33.545.8 37.852.1 13 34.346.4 37.151.2 LSD 0.90.9 1.42.4 Nj 33.546.0 36.851.1 Na 33.846.0 37.651.2 LSD 0.30.4 0.30.5 D 0 33.346.1 36.9.51.0 D x 34.045.9 37.451.4 LSD 0.30.3 0.40.5 I x N»* I x D» N x D* additional nitrogen retarded the ripening of the cereal crops: the moisture difference in the case of the wheat was 3.1 dz 0.8 and that in the case of the barley 2.3 dz 0.8 %-units. The placement of basal dressing, on the other hand, had no effect on the ripening process. Protein content of grains (Table 4). In 1967 a single sprinkling reduced the protein content of wheat (5.7 X total N) on an average by 1.0 i 0.7 and two sprink- lings by 1.9 dz 0.7 %-units. The protein content of barley (6.25 X total N) was reduced by a single sprinkling by 0.1 dz 0.5 and two sprinklings by 0.8 dz 0.5 %-units. Sprinkler irrigation carried out once did not therefore significantly cause a decrease in the protein content of barley. Additional nitrogen applied to young crops markedly increased the 159 Table 6. Hectoliter weights, kg. Year Irrigation Nt N 2 plant mm D 0 Dj mean D 0 D t mean 1967 I0 O 79.9 79.3 79.6 78.5 78.8 78.6 wheat li 30 80.0 79.7 79.8 78.1 79.0 78.5 12 30 79.4 79.0 79.2 78.0 79.1 78.6 13 60 79.0 79.0 79.0 77.4 78.8 78.1 1967 I„ 0 73.4 73.8 73.6 72.6 72.4 72.5 barley I, 30 73.5 72.5 73.0 72.4 72.8 72.6 I, 30 72.6 72.8 72.7 71.8 73.1 72.4 I 3 60 71.9 72.4 72.1 72.3 71.3 71.8 1968 I„ 0 79.7 80.4 80.1 79.1 79.1 79.1 wheat 30 80.9 81.0 81.0 80.6 80.0 80.3 I 3 60 81.2 81.1 81.1 80.7 80.4 80.6 I 3 90 80.8 80.8 80.8 80.6 80.4 80.5 1968 I„ 0 69.7 68.9 69.3 67.5 68.6 68.1 barley I 3 30 70.6 70.8 70.7 70.4 70.7 70.5 12 60 71.5 71.5 71.5 71.5 71.5 71.5 13 90 71.5 71.6 71.6 71.7 72.7 72.2 Means, least significant differences (LSD), and significant interactions (*) 1967, wheat 1967, barley 1968, wheat 1968, barley I 0 79.173.1 79.668.7 I, 79.272.8 80.670.6 I, 78.9 72.5 80.9 71.5 I, 78.5 71.9 80.7 71.9 LSD 0.9 0.6 0.8 1.1 Nx 79.4 72.8 80.7 70.8 N, 78.4 72.3 80.1 70.6 LSD 0.4 0.3 0.2 0.6 D 0 78.8 72.6 80.5 70.5 D t 79.0 72.6 80.4 70.8 LSD 0.2 0.3 0.2 0.4 N x D*** I x N* N x D** protein content; that of wheat by 2.0 ± 0.3 and that of barley by 2.1 ± 0.2 %-units. The placement of basal dressing had no effect on the protein content. In 1968 a single sprinkling reduced the protein content of wheat on an average by 1,3 ± 1.9, two sprinklings by 3.1 ± 1.9, and three sprinklings by 3.4 £ 1.9 %-units. On the part of the barley, the corresponding differences were 0.7 ±1.2, 1.0 ± 1.2 and 2.1 ± 1.2. Additional nitrogen dressing raised the protein content of the wheat by 1.4 ± 0.4 and that of the barley by 1.7 ± 0.4 %-units. As in the previous year, the placement of basal dressing had no effect on the protein content of the grains. Weight of the grains (Table 5). In 1967 the effect ofirrigation on the weight 160 of the grains was slight and significant only in the case of the twice-watered wheat plots, in which the irrigation raised the weight of 1000 grains on an average by 1.3 ±0.9 g. The effect of the irrigation was most marked in the case of those wheat plots in which basal dressing had been placed and which had received additional nitrogen. Both the placement of basal dressing and the application ofadditional nitrogen tended to increase the weight of the wheat grains; but they had no effect on the weight of the barley grains. In 1968 a single sprinkling raised the weight of 1000 wheat grains on an average by 2.6 rb 1-4 and of 1000 barley grains by 2.5 rb 2.4 g. A second or third application ofwater no longer caused any increase in the weight of the grains but tended, on the contrary, to lower it. As in the year before, the placement of basal dressing and the application of additional nitrogen slightly increased the weight of the wheat grains but had no effect on the weight of the barley grains. Hectoliter weights (Table 6). In 1967 sprinkler irrigation had no significant effect on the hectoliter weight of the wheat, but that of the barley was lowered as a result of two waterings on an average by 1.2 ± 0.6 kg. The application ofadditional nitrogen reduced the hectoliter weight of wheat on an average by 1.0 rb 0.4 and that of barley by 0.5 rb 0.3 kg. The placement of basal dressing had no significant effect. In 1968 sprinkler irrigation distinctly improved the hectoliter weight of both the wheat and, in particular, the barley. The increases brought about by one, two and three sprinklings in the case of the wheat were 1.0 ± 0.8, 1.3 ± 0.8 and 1.1 ± 0.8 and, cor- respondingly, in the case of the barley, 1.9 ± 1.1, 2.8 Jr 1.1 and 3.2 ±l-1 kg. The application of additional nitrogen reduced the hectoliter weight of the wheat on an average by 0.6 ± 0.2 kg but it had no significant effect on the barley. The placement of basal dressing had no significant effect. Discussion The experimental years constitute quite an interesting pair. Common to the two years was a dry June up to the month’s 26th day. Even after that date, in 1967, the dry spell stretched out all the way to August, and the ground became parched. In 1968, how- ever, there was fairly abundant rainfall at the end ofJune and the early part ofJuly, with the effect that the ground was moist all through the middle ofthe summer. In spite of the difference between the midsummer period of the two years, the effect of the sprinkler irrigation carried out in June on the size of the harvest was highly similar both years. A single sprinkling augmented the wheat yields on an average by 880—970 kg per ha, or 37—51 %, and the barley yields by 1140—1340 kg per ha, or 37—42 %. Two sprinklings increased the wheat yields on an average by 1640—1680 kg per ha, or 71— 86 %, and the barley yields by 2010—2200 kg per ha, or 60—71 %. Repetition of the watering thus further augmented the yields quite markedly, although, to be sure, the increase brought about by the second sprinkling was in the case of the wheat on an average 1 14 smaller and in the case of the barley 1/3 smaller than the crop increase obtained through the first sprinkler irrigation. The effect of the sprinkler irrigation on the protein contents of the crops was also very much the same both years. A single sprinkling lowered the protein contents of the wheat on an average by 1.0—1.3 and of the barley by 0.1—0.7 %-units. Two sprinklings reduced 161 the protein contents correspondingly by 1.9—3.1 and 0.8—1.0 %-units. It therefore looks as if sprinkler irrigation reduces the protein content of wheat more drastically than that of barley. In the drought year of 1967, the unirrigated cereal crops ripened, as if under pressure, earlier than normally; thus irrigation ostensibly delayed the ripening, though only very slightly. The following summer, the rainy midsummer season brought about detrimental late tillering of unirrigated crops and thereby delayed ripening. Under such conditions, the irrigation had the contrary effect, one of preventing belated tillering of the crops and promoting the ripening process. The findings of the investigation prove conclusively that the weather conditions pre- vailing in the month of June have a decisive effect on the development of spring cereal crops in the areas of clayey soil in southernFinland. If the month ofJune is short on rain, crops are incapable of effectively utilizing the nutrients contained in the parched earth and growth of plant life is weak. If also the middle and late summer seasons are dry, unirrigated soil is liable to have left over an abundance of unutilized plant nutrients (Kaila and Elonen 1971). If a dry June is succeeded by a rainy July, the abundant nitro- gen reserves and sparse growth stimulate belated tillering of plants which to some extent improves the harvest but at the same time delays its ripening. By sprinkler irrigation, the nutrient reserves in the ground can be made effectively available to plants as early as June (Kaila and Elonen 1970), a dense plant association develops and it ripens evenly regardless of the weather conditions prevailing during the middle and late summer seasons. It has been pointed out in previous studies that the most critical season for spring cereal crops is about three or four weeks long midway between the emergence of the plants and the appearance of the ears. The effect of irrigation at this time remains virtually unchanged provided the dry spell continues (Elonen, Nieminen and Kara 1967). The findings of the present investigation confirm, as far as they go, the results of earlier research: the irrigations carried out on June 15 and June 21, 1967, proved by and large equally beneficial. Calcium nitrate containing 60 kg N/ha, when applied to the seedlings, increased the protein content of the wheat on an average by 1.6 and of the barley by 1.9 %-units. The excessive reduction of the protein content induced by irrigation could thereby be fore- stalled, besides which the effect of the watering on the size of the harvest improved notice- ably. The amounts of nitrogen of the N2-level, 120 and 135 kg N per ha, seem to be highly suitable to the fertilization of a wheat field awaiting irrigation. The amounts of fertilizer applied to the malting barley proved to be excessive, however, for in spite of the sprinkler irrigation the protein contents exceeded 12 per cent. The placement of basal dressing to a depth of 9 cm improved its utilization by the crops quite effectively, especially in 1967. Once again, the same astonishing result was arrived at as in previously reported investigations: irrigation did not diminish the place- ment effect of fertilizer (Elonen, Nieminen and Kara 1967; Kaila and Elonen 1970). Plants grow around the rows with placed fertilizer thick root clusters, which thirstily suck the ground dry and the watering of which is probably particularly advantageous (Kähäri and Elonen 1969). After the irrigation, the ground dries up once more, first at the surface and only later at the placement depth; accordingly, irrigation is likely to im- prove for a longer time the utilization of placed nutrients than of those applied onto the 162 surface. It is known, furthermore, that in clayey soil sprinkling does not to any noteworthy extent carry downward other macronutrients than nitrate (Aura 1967). This also em- phasizes the importance of fertilization by placement. Quite favorable results have been obtained with the placement of fertilizer in Finland (Larpes 1967, Nieminen, Kara and Elonen 1967, Kivi and Hovinen 1969, Pessi et ai. 1970, Paulamäki and Luostarinen 1971). It seems clear that this method could be profitably applied also in irrigated fields. It is possible that also additional nitrogen, which in the present investigation was given to seedlings, could be advantageously applied in immediate conjunction with sowing by the placement technique. REFERENCES Aura, E. 1967. Effect of the placement of fertilizer on the development of spring wheat. J. scient. agric. Soc. Finl. 39:148—155. Bouyoucos, G. J. 1954. New type electrode for plaster of paris moisture blocks. Soil Sci. 78: 339—342. Elonen, P., Nieminen, L. & Kara, O. 1967. Sprinkler irrigation on clay soils in southern Finland I—-111. J. scient. agric. Soc. Finl. 39: 67—98. Kaila, A. & Elonen, P. 1970. Influence of irrigation and placement of nitrogen fertilizers on the uptake of nitrogen by spring wheat. J. scient. agric. Soc. Finl. 42; 123—130. Kaila, A. & Elonen, P. 1971. Effect of irrigation on fertilizer nitrogen in arable clay soil. Acta Agr. Fenn. 123: 126—135. Kivi, E. I. & Hovinen, S. 1969. Lajikkeen ja lannoitustavan vaikutus kevätvehnän viljelyarvoon. Sum- mary: Influence of variety and fertilizing on the properties of spring wheat. J. scient. agric. Soc. Finl. 41: 258—276. Kähäri, J. & Elonen, P. 1969. Effect of placement of fertilizer and sprinkler irrigation on the develop- ment of spring cereals on the basis of root investigations. J. scient. agric. Soc. Finl. 41: 89—104. Larpes, G. 1967. Rivilannoituksen vaikutus kevätviljoissa. Summary: The effect of fertilizer placement in spring cereals. Maatal. ja Koetoim. 21: 14—20. Nieminen, L., Kara, O. & Elonen, P. 1967. Kokemuksia sijoituslannoituksesta. Summary: Trials on placement of fertilizer. Maatal. jaKoetoim. 21: 42 —49. Paulamäki, E. & Luostarinen, H. 1971. Fertilizer drilling on peat soils. Acta Agr. Fenn. 123: 167—172. Pessi, Y., Ylänen, M., Leskelä, A. & Syvälahti, J. 1970. Results of tests made with placement ferti- lization on the Kotkaniemi Experimental Farm. J. scient. agric. Soc. Finl. 42: 193—202. Steel, G. D. & Torrie, J. H. 1960. Principles and procedures of statistics. 481 p. New York. SELOSTUS KEVÄTVILJOJEN SADETUKSESTA ETELÄ-SUOMEN SAVIMAILLA. IV. SADETUKSEN UUSIMISEN JA TYPPILANNOITUKSEN VAIKUTUS. Paavo Elonen Helsingin yliopiston maanviljelyskemian laitos, Viikki Osmo Kara Valtion maatalouskoneiden tutkimuslaitos, Rukkiin Vuosina 1967 ja 1968 yksi kesäkuussa suoritettu 30 mtn;n sadetus hiesusavimailla Espoossa lisäsi, keski- määrin kevätvehnäsatoja 880—970 kg/ha eli 37—-51 %ja ohrasatoja 1140—1340 kg/ha eli 37-—42 %. 163 Sadetuksen uusiminen noin viikon kuluttua lisäsi edelleen vehnäsatoja keskimäärin 670—800 kg/ha ja ohrasatoja 810—860 kg/ha. Sadetuksen vaikutus sadon määrään oli kumpanakin vuonna likimain samansuuruinen huolimatta siitä, että vuonna 1967 sekä kesäkuu että heinäkuu olivat erittäin kuivia mutta vuonna 1968 kuivaa kesä- kuuta seurasi sateinen heinäkuu. Viljan tuleentumiseen sadetus sensijaan vaikutti eri vuosina eri tavalla: vuonna 1967 lievästi tuleentumista hidastaen mutta vuonna 1968 sitä suuresti edistäen. Jälkimmäisenä vuonna sadetus esti haitallisen myöhäisversonnan ja samalla lisäsi viljojen hehtolitran painoa ja 1000- jyvän painoa. Jyvien valkuaispitoisuus aleni kertasadetuksen vaikutuksesta keskimäärin vehnällä11.1.30 —1.3 ja ohralla 0.1 —0.7 %-yksikköä sekä kahden sadetuksen vaikutuksesta vastaavasti11.3.19—3.1 ja00.1.0 %-yksikköä. Oraille välittömästi ennen ensimmäistä sadetusta pintalannoituksena annettu kalkkisalpietari, joka sisälsi typpeä 60 kg/ha, kohotti valkuaispitoisuutta vehnällä keskimäärin 1.6 ja ohralla 1.9 %-yksikköä. Typpi- lannoitus esti siten sadetuksen aiheuttaman valkuaispitoisuuden liiallisen alenemisen ja samalla tehosti huomattavasti sadetuksen satoa lisäävää vaikutusta. Runsaan typpilannoituksen epäkohtana oli lievä tuleentumisen viivästyminen. Aluslannoituksen sijoittaminen rivilannoittimella 9 cm:n syvyyteen vaikutti tehokkaasti erityisesti vuonna 1967, jolloin sekä vehnä- että ohrasato lisääntyivät 22 % pintalannoitukseen verrattuna. Lisäksi rivilannoitus edisti tuleentumista. Sadetus ei näyttänyt vähentävän lannoitteen sijoitusvaikutusta, vaan nämä kaksi menetelmää muodostivat erittäin edullisen yhdistelmän.