EFFECT OF PLACEMENT OF FERTILIZER AND SPRINKLER IRRIGATION ON THE DEVELOPMENT OF SPRING CEREALS ON THE BASIS OF ROOT INVESTIGATIONS Jorma Kähäri and Paavo Elonen University ofHelsinki, Department ofAgricultural Chemistry Received January 25, 1969 Two effective methods have been established recently in order to diminish on the clay soils of South Finland the injuring of cereals by spring and early summer droughts; placement offertilizer and sprinkler irrigation (Pohjanheimo and Heinonen 1960, Heino- nen and Nieminen 1961, Larpes 1966, 1967, Nieminen et ai, 1967, Elonen et ai, 1967, Aura 1967). The former method is already widely adopted by farmers, but only a few of them have accepted the latter. In the sprinkler irrigation technique as well as in the technique of fertilizer placement there are, however, many unsolved problems, e. g. which is the best mutual position for fertilizer and seed under Finnish conditions. Questions of this kind cannot be solved without extending the investigations also to the underground parts of plants, towards which the irrigation and placement of fertilizer is primarily directed. The purpose of the present work was to study the development of the root system of spring cereals during the growing season, the effect of fertilizer placement and irrigation on the correlation between the yield and the root system, and on the distribution of the root system in the ploughed layer. Experimental Field trials. The root investigation was performed in the neighbourhood of Hel- sinki in connection with two large field trials, adjacent to each other. The compelete results of these trials will be published later. In trial 1, started on May 10th, the test crop was spring wheat »Svenno». Finnish com- pound fertilizer (15 —20—15) was applied according to the following plan; 1. no fertilizer, 2. 600 kg/ha as a surface dressing, 3. 600 kg/ha placed in rows at a distance of 12 cm by https://www.c-info.fi/en/info/?token=1dEaC1utNE4azqbZ.jvKNa0mXfVwdrr_2bl8wsg.kjqWsJt-Hst1YaMWEN8BJMusCm9p5LgUc6wgysEzpRZulH7L8yDncszjod7PY6hjAwmKGN5YZ2KiO-SZK1ei4xmFHoh8VRvnG8MVvZAHppBekBe2zcMLomnQzIPWuyeYkbmxKET4eYD_XOmrqz_FVRHDUYIGZ31F_35GyN5AwpFGU5kexoNK_rzujEVeuB4AU8O-wFg 90 a Finnish »MK-kombi»-fertilizer drill, 4. 600 kg/ha placed in rows at a distance of 18 cm by a Me Cormick machine. The fertilizer was placed at a depth of 8 cm. In trial 2, established on May 12th, spring wheat »Svenno» and barley »Ingrid» were used as test crops. 750 kg/ha of compound fertilizer (8 —13—9) was either applied to the soil surface or placed with a »Juko»-fertilizer drill with a row distance of 15 cm. The place- ment depth was 8 cm. The surface dressing was performed with the plastic fertilizer tubes outdrawnfrom the coulters. In the same way 400 kg/ha of calcium nitrate (15.5 % N) was applied on shoots on June 15th. The root studies were carried out on plots which were not irrigated, and on plots which were irrigated on June 15thand June 21st with 30 mm of drainage ditch water at both times. Soil and weather conditions. Certain physical and chemical char- acteristics of the experimental soil were as follows; Depth Particle size fractions % Org. C pH Exchangeable cations me/100 g Bray 1 test cm < 2 [X 2—20 (x > 20 [X % Ca ++ Mg ++ K+ Na + P ppm o—2o 52 33 15 3.7 5.4 11.1 3.9 0.88 0.23 124 25—35 77 17 6 1.1 5.6 13.6 10.5 0.76 0.38 6 The ploughed layer of the experimental area is silty clay and the subsoil is heavy clay. Both the physical and the chemical characteristics of the soil show that it represents a clay soil fairly typical of southern Finland. The average monthly temperature and precipitation during the growing season were on the experimental field the following: Temperature, °C Precipitation, mm In temperature the growing season was normal, but the precipitation was markedly lower than in normal years except in August. The root studying method. The root investigations were limited to the 20 cm deep ploughed layer, as the main part of the root system of spring cereals is usually in this zone (Salonen 1949, Wiklert 1960), and where the effect of fertilizer placement and irrigation would consequently be clearly in evidence. The sampling boards (Figure 1) were made of 50 X 50 X 1.5 cm plywood board with 4" nails at a distance of 2.5 cm on an area of 20 X 50 cm. Before a sample was taken, a cardboard sheet was pressed on the nail board. The root samples were collected from experimental plots immediately outside the area to be harvested. A 30 cm deep trench was dug with a spade in the soil. The vertical wall, perpendicular to the fertilizer and seed rows, was smoothed with the spade. The nail board was forced into this vertical wall so that the topmost nail row was level with the soil surface. The sample was removed by spade and the remaining soil was cut off outside the ends of the nails. Thus, the size of the soil block was 50 X 20 X 8.5 cm. May 10.0 24 June 14.1 15 July 16.4 24 August 15.6 111 91 The soil was washed away from the sample with a soft jet of water so that the root system on the nail rows retained its original shape. The pump of the sprinkling equipment and the nozzles of a weed sprayer were used for washing. By means of these ten samples could be handled simultaneously. Since the soil was ratherheavy clay, careful and thorough washing took a long time, about 10—15 hours. At the last stage of the washing the pieces of straw and the roots of the weeds were removed with small forceps from the sample so that only the clean roots of the cereal remained. The clean plant sample was then removed on the cardboard sheet from the nail board and was air-dried in the laboratory. The three middle rows of the plants were taken for analyses. The aerial parts and the underground parts were analysed separately. The root system was divided into layers, 2.5 cm in thickness. The root mass of every zone was weighed separately. Root samples were taken at four dates, in total 56 samples June Ist, about one week after sprouting, 8 samples from trial 1, June 20th, about four weeks after sprouting, 8 samples from trial 1 and 8 samples from trial 2, July 10th, immediately after ear emergence, 16 samples from trial 2, August 21st, at harvest stage, 16 samples from trial 2. Results Weights of different parts ofplants. Figure 2 presents the air-dry weights of the aerial and underground parts in each of the 56 samples as milligrams per plant. There is a very strong positive correlation between the aerial and the underground parts of an individual plant at every sampling date, in fact during the whole growing season. Figure 2 also shows that the root system has developed strongly in the early part of the summer, while the Figure 1. Nail boards used for taking root samples. On the left, board with a sample, 92 greatest increase in weight of the aerial parts has taken place at the end of the summer when parts of the roots have already died. A strong root system is in fact needed for obtaining good aerial growth. There is a close positive correlation also between the final grain yield and the root system, as may be seen from Figure 3. The correlation coefficient for wheat is as high as 0,966***. More detailed specifications of the weights of the parts of plant are presented in Tables 1 and 2 as mean values oftwo replicates. Figure 2. Relationship between the aerial (Y) and the underground (X) parts of individual plants at different dates (June Ist: • = wheat, y = 0,45 X + 4,4, r = 0,700*, June 20th: O = wheat, /\ «■ barley, y = 1,5 x 64, r = o,BB2***, July 10th: □ = wheat, = barley, y = 3,95 x —26, r = o,BB3***, August 21st: # = wheat, X = barley, y = 9,0 x + 170, r = 0,950***). 93 The weight of the aerial parts ofwheat shoots, taken on June Ist, was, on an average, 17 mg per plant, and the mean weight of the underground parts 28 mg. Thus, the weight of the underground parts of plant one week old was nearly twice that of the aerial ones. Figure 4 shows that the root system had already by then reached the subsoil, and that it was vigorously widespread from the seed row. No effect of the fertilizing was found at that time either on the root system or on the aerial parts. On June 20th, or about three weeks later, the aerial parts of a wheat plant had an average weight of 103 mg and the underground ones 113 mg. At this stage the weight of shoots and roots was almost the same. The first stage of growth in barley was markedly faster, because the corresponding data were 227 mg and 187 mg, respectively. The effect on growth of fertilizing could be seen even visually by June 20th. Fertilizing had increased the weight of the aerial as well as the underground parts. In trial 1 there was no distinct difference between placement and surface dressing. This may be due chiefly to the fact that in trial 1 larger amounts of nutrient were applied than in trial 2. The solubility of the former fertilizer was, moreover, better so that even as surface dressing it supplied the demand during the early part of the summer. The effect of the placement therefore became visible only at the end of the summer. Further, it was found in later Figure 3. Relationship between the weight of the grains (Y) and weight of the roots (X) of wheat and barley. 94 Table 1. Mean weights of shoots (a) and the underground parts (b) as mg/wheat plant in trial 1. F 0 = unfertilized Fb = fertilizer broadcast Fpla = placement of fertilizer in rows with a distance of 12 cm Fpia placement of fertilizer in rows with a distance of 18 cm June Ist June 20th Fo Fp Fpi 2 F pi 8 f o Fp Fpi» F pi 8 a 15 14 18 19 77 111 122 93 b 29 27 29 29 86 121 116 123 a/b 0.5 0.5 0.6 0.7 0.9 0.9 1.1 0.8 Table 2. Mean weights of shoots (a) and the underground parts (b) as mg/plant in trial 2. Fb = fertilizer broadcast K 0 = unirrigated F = » placed K 2 = irrigated June 20th July 10th K„ August 21st Fb Fp wheat a b K„ K 2 K„ K 2 Fb Fp Fb Fp F b Fp F„ Fp 81 136 423 553 825 832 110 134 122 168 183 203 a/b 0.7 1.0 3.5 3.3 4.5 4.5 725 1282 1542 2095 70 138 155 190 10.4 9.3 10.0 11.0 examinations that in trial 1 the placed fertilizer had not reached the desired depth of 7—B cm. In trial 2 the placement of the fertilizer at a depth of 7—B cm had considerably in- creased the growth of both wheat and barley: that of the aerial parts by an average of 77 %, and that of the underground parts by 36 % compared with the effect of surface dressing. On July 10th, samples were taken for the third time, again about three weeks after the previous sampling. The cereals had just formed ears. The average weight of an aerial part of a wheat plant was 657 mg and that of the underground part 169 mg. Corresponding data with barley were 1445 mg and 357 mg, respectively. Thus, the aerial and the under- ground plant masses ofbarley were more than twice those ofwheat. The effect of placement was again distinct. When the fertilizer was placed, the weight of the aerial part of a plant was, on an average, 38 %, and that of the underground part 25 % higher than the corresponding figures from the plots with a surface dressing. barley a 158 296 742 1524 1618 1898 2122 1961 2572 2748 b 149 224 288 417 391 413 269 246 228 284 a/b 1.1 1.3 2.6 3.7 4.1 4.6 7.9 8.0 11.3 9.7 95 The effect of irrigation, applied on June 15th and June 21st, was on July 10th quite marked. The aerial part of an irrigated plant was 72 %, and the underground part 27 % larger than the corresponding parts ofan unirrigated plant. At the harvest stage, August 21st, the average weight of the aerial part of a wheat plant was 1286 mg, and that of the underground part 138 mg. The corresponding figures for barley were 2701 mg and 257 mg. The aerial part had grown strongly since the previous date of sampling, but the weight of the underground part had decreased by about 25 %. Obviously, a part of the storage products of the root system had been translocated to the aerial organs of the plant, and a part of the secondary root system had decomposed. The growth promoting effect of placement was still apparent at the harvest. The aerial part of a plant was, on an average, 28 %, and the underground part 34 %, heavier than Figure 4. Root sample taken on June Ist from unfertilized plot, the corresponding parts of plants which had received surface dressing. It may be pointed out that the increase in the corresponding total grain yield due to the placement, was on an average 21 % higher than that produced by surface dressing. The average weight of the aerial part of an irrigated plant was at harvest stage 59 %, and thatof the underground part 40 % more than the corresponding weights of unirrigated plants. The effect of the irrigation may have been ever greater, since the samples were taken from the outside of the harvested plots and had received less water. Irrigation increased the grain yields ofharvested plots in this trial by as much as 92 %. The average ratio between shoots (a) and the underground parts (b) of a plant (a/b in Table 2) was at different stages of development as follows: June 20th July 10th August 21st The placement had not greatly influenced the shoot/root-ratio, although it had in- creased somewhat more the growth of the aerial parts than that of the underground parts during the first and the middle stages of the growing season. Irrigation seems to have in- creased both the aerial and the underground growth, the aerial growth relatively more than the underground growth, however. Root distribution. The relative distribution of the root systems in the dif- ferent zones of the ploughed layer is presented in Tables 3 and 4. It is surprising that the main part of the root system in the ploughed layer lies during the whole growing season immediately beneath the sowing depth, or at a depth of 4—locm. On the other hand parts of theroots havereached the subsoil already in the beginning of the growing season (Figure Table 3. Relative distribution (%) of the root system of wheat in different soil layers in trial 1. F 0 = unfertilized F b = fertilizer broadcast F pl2 = » placed in rows with a distance of 12 cm F plB = » » » » » 18 » Depth June Ist June 20th cm F o Fb FpU FPi» F o F b Fpl2 F pl« 0—2.5 4 3 1 12 18 15 2.5 5.0 35 53 31 44 19 32 42 44 5.0 7.5 29 25 42 23 22 22 28 18 17.5—10.0 15 10 15 11 13 12 9 11 10.0—12.5 9578 12 968 12.5—15.0 4 2 3 1 11 7 7 7 15.0—17.5 4 2 11 11 6 4 4 17.5—20.0 0 0 0 0 11 4 3 3 surface dressing 0.9 3.7 9.9 placement 1.1 4.0 9.5 unirrigated 3.3 8.9 irrigated 4.4 10.5 96 97 Table 4. Relative distribution of the root system of wheat and barley between the soil layers down to a depth of 20 cm in trial 2 F b = fertilizer broadcast Fp = » placed K 0 = unirrigated K 2 = irrigated Depth June 20th July 10th August 21st cm K„ K„ K 2 K„ K 2 FA Fp FA ¥p FA Fp Fp t'p FA Fp Wheat 0 2.5 1 0 2.5 5.0 25 21 2 7 13 6 36 28 30 20 26 33 23 32 11 13 13 18 7 5 7 II 7 5 5 5 6 5 5 4 5 4 4 4 19 15 13 31 26 24 30 22 22 26 19 22 11 10 12 13 7 8 11 5 6 5 7 3 5 6 5 2 4 6 3 2 5.0 7.5 22 35 7.5—10.0 15 20 10.0—12.5 12 7 12.5—15.0 15.0—17.5 9 6 8 6 8 517.5—20.0 Barley 0 2.5 8 3 2.5 5.0 25 26 112 2 21 19 27 31 33 37 24 38 18 19 16 12 9 8 11 6 3 5 2 10 32 11 29 24 27 20 22 30 10 24 16 18 8 16 8 7 7 9 7 4 8 9 7 4 5 6 9 3 5.0 7.5 16 21 7.5—10.0 12 18 10.0—12.5 10 10 12.5—15.0 11 7 15.0—17.5 10 8 7 6 8 5 6 6 7 3 5 4 5 317.5—20.0 8 7 4). The topmost 0—2.5 cm layer contained very few roots during the whole growing season, and in the middle and at the end of the summer the main part of these roots was buttress roots whose ability to uptake nutrients may be very slight. On the basis of the following data representing the mean percentages of root mass in various layers, the stronger root system of barley (B) seems to have penetrated somewhat deeper into the ploughed layer than that ofwheat (W): Depth June 20th July 10th August 21st cm W B W B W B o—s 24 31 35 26 45 29 s—lo 46 38 42 49 34 42 10—15 17 19 15 15 13 17 15—20 13 12 8 10 8 12 The fertilizer placement had the expected effect on the mass of the root system also in its distribution in the different zones of the ploughed layer. In trial 2 the root system was distributed, on an average, in the surface dressing (F 6) plots and placement plots as follows: 98 Per cent of root mass Depth June 20th F* F, July 10th August 21st F i F* Fpcm F * F, o—s 30 25 33 28 39 35 s—lo 32 47 41 51 35 41 10—15 21 15 15 13 15 14 15—20 17 13 Il 8 II 10 The fertilizer placement increased considerably even the relative mass of system at placement depth (5—10 cm). This is apparent also in the photographs the root (Figures Figure 5. Root sample taken on June 20th. Fertilizer is placed. 99 5—9) where dense root concentrations may be found around the fertilizer rows. Thus, roots haveclearly sought their way to thefertilizer rows. The average distribution of the root systems in the unirrigated (K 0) and irrigated (K 2) plants appears below: Per cent of root mass Depth July 10th K„ K 2 August 21st K„ K 2cm o—s 29 33 34 40 s—lo 48 44 37 38 10—15 13 14 17 13 15—20 10 9 12 9 Figure 6. Root sample taken on July 10th. Fertilizer is surface dressed. 100 It seems that irrigation had only a slight effect on the distribution of the root system. It is evident that irrigation has increased the root mass to the same extent at the different depths of the ploughed layer. Discussion The results of the study show that good aerial growth demands a vigorous development of the root system. Cultivation measures that increase root growth in the beginning and in the middle of the summer also increase the aerial growth and the grain yield. Placement offertilizer and irrigation are ways by which the growth of root systems can be increased. A stronger root system is able to give a better supply ofnutrients to theaerial parts of a plant in this way making possible a higher yield. The conclusion that the effect Figure 7. Root sample taken on July 10th. Fertilizer is placed. 101 of placement and irrigation depends mainly on a better recovery of nutrients has been reached also by other research workers (Elonen et ai, 1967, Aura 1967). It is in fact not a question of lack of water as such, but of the roots taking up water particularly from the soil layer where nutrients are located. Judging by the present results it is important to place the fertilizer at a certain depth, but it is of no consequence whether the fertilizer row is located directly beneath the seed row or between two seed rows. Some unpublished results of field trials indicate that the fixed distance between the seed and fertilizer coulters (an inch aside and an inch downwards) has no particular effect if compared with a separate seed and fertilizer placement. The row width of fertilizer coulters may in fact vary within very wide limits, e.g. 12—18 cm, without it affecting the Figure 8. Root sample taken on August 21st. Fertilizer is placed, unirrigated. 102 yield. The results may be explained on the basis of the present root investigation. The roots of spring cereals are able to grow surprisingly rapidly around the fertilized row, although the fertilizer may lie rather far from the seed row. This is proved by the well developed root systems of sprouts one week old (Figure 4) and the strong root concentrations around fertili- zed rows, even at the harvest stage (Figures 5—9). An optimum depth ofplacement cannotbe determinedmerely on the basis of the results obtained by this study. It would be technically easiest to use as low a depth of placement as possible so as to limit friction. The chance of clogging and breaking of the fertilizer drill Figure 9. Root sample taken on August 21st. Fertilizer is placed, irrigated. 103 would likewise be slight. According to the results of root distribution, the most profitable depth would be s—lo5—10 cm. A depth lower than 5 cm may not be recommended, since a part of the roots in this layer consists of buttress roots and the layer without any roots reaches deeper between the seed rows (Figures 5—9). The right placement depth also depends on the soil and on the differences in root distribution in the ploughed layer caused by the annual variation in the moisture conditions during the spring and early summer. Summary In 1967, two large field trials were performed on clay soil in South Finland in order to obtain detailed information on the effect of fertilizer placement and sprinkler irrigation on spring cereals. In the present paper the results of the root investigations, carried out in connection with these trials, are reported. Fifty-six root samples were taken on four dates during the growing season. The roots in the soil blocks, taken perpendicularly to the fertilizer and seed rows, retained their original distributionduring washing and drying. The growth of the roots was stronger than the growth ofthe shoots of plants in the early part of the summer, but at the end of the summer, when the main yield above ground developed, the weight of the roots no longer increased, in fact it had decreased. There was a close correlation between the weights of roots and the weights of the shoots of plants during the whole growing season. A particularly high correlation was found between the root system and the grain yield. Fertilizer placement and irrigation increased both the growth of roots and the growth of shoots of plants. The relative increases produced by the placement of fertilizer were equal in the weights of roots and in the weights of aerial parts, but irrigation increased the weight ofaerial parts to a relatively greater extent than the weight ofroots. The distribution of the roots in the top soil was somewhat unexpected. A part of the roots reached the subsoil quite early in the growing season. On the other hand, the main part of the root system in the ploughed layer lay, during the whole growing season, imme- diately beneath the sowing depth, or at a depth of 4—lo cm. The topmost layer, i.e. the layer above the sowing depth, contained very few roots during the entire growing season, and the main part of these roots consisted of buttress roots, whose capacity for taking up nutrients may be very slight. Irrigation had only a slight effect on the distribution ofthe root system, while the effect of fertilizer placement was very distinct. The roots clearly sought their way to the fertilized rows, also in cases where the distance between fertilized and sowing rows was remarkably great. On the basis of the results it was concluded that it is important to place the fertilizer at a convenient depth, s—lo5—10 cm, when spring cereals are in question. The horizontal distance between seed rows and fertilized rows appeared to be ofless importance. Acknowledgements. The authors wish to thank the Finnish Research Insti- tute of Agricultural Engineering for technical help and co-operation in the field work, as well as the Norsk Hydro-Elektrisk Kvaelstofaktieselskap for economic assistance. 104 REFERENCES Aura, E. 1967. Effect of the placement of fertilizer on the development of spring wheat. J. Sci. Agr. Soc. Finland 39: 148—155. Elonen, P. & Nieminen, L. & Kara, O. 1967. Sprinkler irrigation on clay soils in Southern Finland. Ibid 39: 67—98. Heinonen, R. & Nieminen, L. 1961. Väkilannoitteiden rivikylvö. Summary: Trials on placement of fertilizer. Maat. ja koetoim. 15: 7—14. Larpes, G. 1966. Rivilannoituksen vaikutus kevätviljoissa. Summary: The effect of fertilizer placement in spring cereals. Ibid 21: 14—20. -— »— 1967. Kevätviljojen syvälannoitus. Summary: Deep fertilization in spring cereals. Ibid 21; 20—25. Nieminen, L. & Kara, O. & Elonen, P. 1967. Kokemuksia sijoituslannoituksesta. Summary: Trials on placement of fertilizer. Ibid 21: 42 —49. Pohjanheimo, O. & Heinonen, R. 1960. The effect of irrigation on root development, water use, nitrogen uptake and yield characteristics of several barley varieties. Acta Agr. Fenn. 95,6: I—lB. Salonen, M. 1949. Tutkimuksia viljelykasvien juurten sijainnista Suomen maalajeissa. Summary: Inves- tigations of the root positions of field crops in the soils of Finland. Ibid 70,1: I—9l.1 —91. VViklert, P. 1960. Studier av rotutvecklingen hos nägra nyttoväxter med särskild hänsyn tili markstruk- turen. Grundförbättring 3: 113—148. SELOSTUS SIJOITUSLANNOITUKSEN JA SADETUKSEN VAIKUTUS KEVÄTVILJOJEN KEHITTYMISEEN JUURISTOTUTKIMUSTEN VALOSSA Jorma Kähäri ja Paavo Elonen Helsingin Yliopiston maanviljelyskemian laitos 1967 perustettiin savimaalle Espoon Pakankylään kaksi laajaa kenttäkoetta, joiden avulla pyrittiin saamaan yksityiskohtaista tietoutta sijoituslannoituksen ja sadetuksen vaikutustavoista kevätviljoihin. Tässä julkaisussa on esitetty näiden kenttäkokeiden yhteydessä suoritettujen juuristotutkimusten tulokset. Neljänä ajankohtana otettiin yhteensä 56 juuristonäytettä siten, että juurten jakautuminen kylvö-ja lannoiterivejä vastaan kohtisuoraan otetuissa maasärmiöissä säilyi luonnonmukaisena pesu- ja kuivaus- vaiheiden aikana. Juuristonkasvu oli alkukesällä voimakkaampaa kuin maanpäällisten kasvinosien kasvu, mutta loppu- kesällä, jolloin pääosa maanpäällisestä sadosta muodostui, juuriston paino ei enää lisääntynyt, vaan alkoi päinvastoin vähetä. Juuriston painon ja maanpäällisten kasvinosien painon välillä vallitsi selvä positiivinen riippuvuussuhde koko kasvukauden ajan. Erityisen selvänä korrelaatio tuli esiin juuriston ja jyväsadon välillä. Sijoituslannoitus ja sadetus lisäsivät sekä juuriston että maanpäällisten kasvinosien painoa, sijoitus- lannoitus molempia suhteellisesti yhtä paljon, sadetus suhteellisesti enemmän maanpäällistä kasvua. Juuriston sijoittuminen muokkauskerrokseen oli jossain määrin yllätyksellistä. Toisaalta viikon ikäisen oraan juuristo oli johämmästyttävän hyvin kehittynyt ulottuen jankkoon asti. Toisaalta kuitenkin pääosa juuristosta sijaitsi koko kasvukauden ajan välittömästi siemenen kylvösyvyyden alapuolella olevassa maa- kerroksessa 4 —-10 cm:n syvyydessä. Siemenen kylvösyvyyden yläpuolella oleva maan pintakerros oli käy- tännöllisesti katsoen juuretonta. Se sisälsi lähinnä vain tukijuuria, joiden merkitys ravinteiden saannin kannalta lienee vähäinen. Juuriston sijaintiin sadetus ei näyttänyt mainittavasti vaikuttaneen, mutta sijoituslannoituksen vai- kutus oli sitäkin selvempi. Pääosa muokkauskerroksen juuristosta oli hakeutunut lannoitenauhojen ympä- rille sijoitussyvyyteen, vaikka lannoiterivit olisivat sijainneet melko etäälläkin siemenriveistä. Tulosten perusteella pääteltiin, että kevätviljoille on tärkeätä sijoittaa lannoite sopivaan syvyyteen, s—lo5—10 emäin. Siemenrivien ja lannoiterivien välinen etäisyys sivusuunnassa näytti sen sijaan olevan vähem- män merkityksellistä.