SB5J5 Qlije §. ^. ^tU pterg SB555 S00070529 N , 8061 'U Nvp •i^j jepuig NEW HAMPSHIRE COLLEGE AGRICULTURAL EXPERIMENT STATION Technical Bulletin No. ii OCTOBER, 191(> NOTES ON THE PRESENCE OF NITRATES IN ORCHARD SOILS SB366 •^i^^b'^ ■nl This BOOK may be kept out TWO WEEKS ONLY, and is subject to a fine of FIVE CENTS a day thereafter. It is due on the day indicated below: 4S^^*^ NEW HAMPSHIRE COLLEGE AGRICULTURAL EXPERIMENT STATION Technical Bclletin No. ll OCTOBER, 1916 NOTES ON THE PRESENCE OF NITRATES IN ORCHARD SOILS ::.'^ BY J. H. GOURLEY and V. D. SHUNK NEW HAMPSHIRE COLLEGE OF AGRICULTURE AND THE MECHANIC ARTS DURHAM. N. H. •W^^^ NOTES ON THE PRESENCE OF NITRATES IN ORCHARD SOILS. By J. H. GouRLEY AND V. D. Shunk. Much has been written on tlie various cultural systems used in apple orchards and considerable data have been presented to show the effect of each of the systems on the growth and yield of the trees. Some general recommendations are now considered standard and are in common use, e. g., most authorities agree that to grow trees in sod is usually not a good practice but that the grass mulch system is" a perfectly practical method of culture especially when accompanied by the use of fertilizers. There is also general agreement that tillage in the orchard is quite bene- ficial and will stimulate growth and increase production, and when the use of cover crops accompanies it the value is enhanced. Some information is also at hand to show the effects of these sys- tems on the soil but all mooted questions in this regard do not appear to be satisfactorily answered. It is the purpose of this paper to present some additional data showing the effect of sod and tillage on the presence of nitrates in the soil, and to partially correlate these with the behavior of the trees as regards yield and growth. Primarily the writers are interested in determining some of the reasons why trees behave differently under different cultural treatments and why fruit buds are formed with abundance when grown under a good system of culture and greatly reduced when grown in sod land without fertilizers or tillage. The observations here reported are made as a corollary of such a study. In Technical Bulletin No. 9, N. H. Elxperiment Station, the senior author makes the statement that the formation of nitrates is greatly reduced in a sod orchard. But the evidence presented at that time showed only that less nitrates were recovered in our soil samples during the growing season under sod than where tillage was practiced, and therefore would not show conclusively that nitrification was not active under sod, but rather raise the question whether the grass and trees together did not use up noFEimr library N. C State CoIUrp 4275^ 4 N. H. AGE. EXPERIMENT STATION. [Bulletin 11 such an excessive amount of nitrates that little accumulated as an excess or as a residual in the soil. At the outset it is well to state that the assumption is not herein made that the presence or absence of large amounts of nitrates is the sole cause of vigorous growth or the reverse, for without question other factors are of great importance. Aeration in itself has doubtless a beneficial effect other than increasing nitrification, for the oxidation processes may make available other forms of plant food materials and also encourage a beneficial soil flora. Just how much these various cultural treatments furnish additional nutritive material and how much they may be of a "sanitary" value cannot be fully stated. THE ORCHARD. The work here reported has been conducted in a mature Baldwin apple orchard of nine acres which was acquired for the purpose of experimentation in 1908. Prior to that time the orchard was in grass and the hay cut and removed each year until it was in a weakened and unproductive state. Ten plots were laid out with a division row l^etween each so that the in- fluence of one plot would not extend over to an adjoining one. The orchard is quite level and the soil fairly uniform but the plots are somewhat lighter on one end than on the other. CHARACTER OF THE SOIL. Of the ten plots in the orchard we are interested at this time in three only, Nos. 1, 4 and 5, none of which have been fertilized. The soil of these plots is practically identical and is therefore well suited to a study of the comparative amounts of nitrates and moisture present under the different systems of culture. Later in the paper, however, mention is made of Plots 11 and 12 in connection with liming. The soil of those plots is somewhat heavier and they have also been fertilized as described below. A composite sample was taken from the first series of plots mentioned and a mechanical analysis made. The following table gives this analysis: October, '16] NITRATES IN ORCHARD SOILS. Table No. 1. Mechanical Analysis of Soil. Subsoil 7 in. -3 ft. Fine gravel, 2 to 1 mm Coarse sand, 1 to 0.5 mm Medium sand, 0.5 to 0.25 mm. Fine sand, 0.25 to 0.1 mm. . . . Very fine sand, 0.1 to 0.05 mm. Silt, 0.05 to 0.005 mm Clay, 0.005 to mm Lyon, FippinandBuckman* give the average analysis of six fruit soils, and it is here cited for comparison with the soil in question: Fine gravel 1.0 Coarse sand 6.8 Fine sand 42 . Silt 23.3 Fine silt 7.3 Clay 10.9 From these analyses it will be seen that the soil under question is of a distinctly light nature, especially is the subsoil very sandy and therefore such a soil as we would expect to suffer a rapid loss of nitrates after a heavy rain, which has proven to be the case throughout. TREATMENT OF PLOTS. Plot 1. Sod. This plot has remained permanently in sod and the grass is cut once during the summer and allowed to remain where it falls. No fertilizer has been applied, and no grass mulch is included in this experiment. Plot 4. Clean cultivation. This plot is plowed every spring and cultivated every two weeks until September 1. No cover crop is sown and no fertilizer applied. Plot 5. Cultivation and cover crop. This plot is plowed in the spring and tilled every two weeks until July 10 when a cover crop of crimson clover is sown, no fertilizer is applied. *Soils, 1915. N. H. AGR. EXPERIMENT STATION. [Bulletin 11 Plot 11. The limed plot extends across one end of four fertilized plots and each tree has received an application of 20 pounds of lime* per tree for nine years.f The fertilizers on the four plots respectively are 2 pounds nitrate of soda, 4 pounds sulphate of potash, 8| pounds acid phosphate, per tree; 2 pounds nitrate of soda, 4 pounds sulphate of potash, 17pounds acid phosphate, per tree; 6 pounds nitrate of soda, 4 pounds sulphate of potash, 8| pounds acid phosphate, per tree; and 2 pounds nitrate of soda, 10 pounds sulphate of potash, 8^ pounds acid phosphate, per tree. Plot 12. For a check on the lime treatment a similar plot of trees was selected which stands parallel to the limed plot. YIELD AND GROWTH OF TREES. These plots have behaved differently as regards yield and growth since they have been under the influence of the various treatments. Therefore it should be possible to trace some of the reasons for the marked and consistent variation in behavior to the effect of the treatments on the soil activities. The following measurements were made at the end of the grow- ing season by taking the length of new growth of twenty twigs which so far as can be determined are typical of the growth of the tree. Each tree in a plot is thus measured and the average growth for the plot then calculated. Table No. 2. Average Annual Twig Growth Per Tree. Inches. Year. Plot 1 Plot 4 Plots Sod. Tillage. Tillage and cover crop. 1909 4.59 6.29 8.31 1910 4.15 8.79 10.19 1911 3.21 8.43 8.19 1912 4.79 8.43 8.92 1913 5.76 9.03 9.03 1914 4.70 4.90 6.90 1915 6.40 7.18 10.30 Average 4.80 7.58 8.83 *65% CaCO.,. tSee Bulletin 168, N. H. Experiment Station. Octuber. '16] NITRATES IN ORCHARD SOILS. It will here be seen that Plot 1 (the sod plot) has made an average growth of less than 5 inches a year for a period of eight years, Plot 4, 7| inches and Plot 5 nearly 9 inches (8.83 in.) or nearly twice the growth of the plot in sod. It will of course be understood that the trees under cultivation produce many twigs of a greater growth as well as water sprouts and excessive growth in the tops of the trees, but such growth is eliminated from the data and only the normal growth at the ends of the permanent branches is included. Plots 4 and 5 have been of special interest as the soil on these plots is quite uniform and the outstanding difference in treatment is that Plot 5 has a cover crop plowed in annually while Plot 4 has had clean cultivation throughout. In some years there was little difference in the growth on these plots but the past two years the superior treatment of Plot 5 has been showing. At this time we wish to call attention to the greater amount of nitrates found each year in Plot 5 than in Plot 4 as shown in a later table which may explain at least to some extent the difference in growth. The moisture content is slightly superior in Plot 5 but scarcely sufficient to account for the differ- ence in growth. Table No. 3. Average Annual Yield Per Tree. Number of Apples. Year. Plot 1 Plot 4 Plot 5 Sod. Tillage. Tillage with cover crop. 1908 467 105 77 1909 95 106 80 1910 481 1859 2381 1911 795 549 99 1912 376 2105 2162 1913 734 371 99 1914 270 2859 2737 1915 No crop d lie to a freeze Average 459 1136 1091 As regards yield it will be noticed that Plot 1 remains the lowest as was true with growth, while Plot 4 shows a little higher yield 8 N. H. AGR. EXPERIMENT STATION. [Bulletin 11 than Plot 5, indicating that both plots have been receiving suffi- cient supplies of available food materials for fruit production. MOISTURE AND NITRATE DETERMINATIONS. Soil samples were taken weekly during most of the growing season for four years. The surface soil is taken from 7 to 9 inches (or a little more) depending on its depth and the subsoil is taken from that point to 3 feet. Three samples are taken from each plot and after thoroughly mixing, a pint sample is taken for analysis. Moisture is determined by oven drying a 50 gram sam- ple at close to 100° C. Nitrates are determined according to the method described in Bulletin No. 31, U. S. Dept. of Agriculture, Bureau of Soils. The following tables show the average per- centage of moisture and nitrates (parts per million of dry soil) found each week during the growing season for four years under the various treatments heretofore mentioned. Table No. 4. Summary of Moisture Determinations. Average per Plot. Percentage. Surface soil. Year. Plot 1 Sod. Plot 4 Tillage. Plot 5 Tillage with cover crops. 1913 1914 1915 1916 16.02 18.87 25.63 20.48 13.69 13.39 19.29 16.45 14.20 15.03 20.82 21.31 Average 20.25 15.70 17.84 Subsoil. 1913 1914 1915 1916 10.98 14.14 14.26 14.82 9.06 9.78 14.03 12.74 8.93 10.26 13.33 13.24 Average 13.55 11.40 11.44 October, '16] NITRATES IN ORCHARD SOILS. 9 Table No. 5. Summary of Nitrate Determinations, Water Soluble Parts per Million of Dry Soil. Average per Plot. Surface soil. Year. Plot 1 Sod. Plot 4 Tillage. Plot 5 Tillage with cover cop. 1913 1914 1915 1916 2.64 4.41 2.09 3.58 18.25 14.01 21.05 16.29 38.37 37.27 18.75 41.26 Average 3.18 17.40 33.91 Subsoil. 1913 1914 1915 1916 1.55 3.56 1.51 2.18 6.90 6.62 10.76 5.05 6.87 10.81 6.88 8.05 Average 2.20 7.33 8.15 From the above data it will be seen that the amount of nitrates recovered in the soil samples under sod is considerably reduced as compared with Plots 4 and 5. The ratio of nitrates between sod, tillage and tillage with cover crops is as 1:5.4:10.6 in the surface soil and in the subsoil as 1:3.3:3.7. At no time during the experiments have we obtained a sample under sod that showed more than 14.78 parts nitrates per million and the average for the four years is 3.18 p. p.m., while for clean tillage it has gone as high as 63 p. p.m. with an average of 17.40 p. p.m., and for tillage plus a leguminous cover crop it has shown as high as 132 p.p.m. and the average is 33.91 p.p.m. for the four years. 10 N. H. AGR. EXPERIMENT STATION. [Bulletin 11 d (Si lll^[^l^F^: t: -6 5? I - I October, '16] NITRATES IN ORCHARD SOILS, 11 O ^ fni^S -9 -^ny oi SI Tt J L 12 N. H. AGR. EXPERIMENT STATION. [Bulletin 11 " -S >O(M00(Nt-O OJ f^TtH.-i^(£)C»oO'*coooO'* -ococoiooOr-Hooocncoo^cocoio 00 CO ^^.-H(M(M'*CD(MOC0C0t>O'*'*(M CO Tj^ s O 00 CT) ^ (N t^ iCi 00 '^i 00 i-H IOCS! ^ooTt^oa50(^^'*^^oooc^'-||£lco 50iCOaiCO(MGOCl'*00(M.-it^ i CO - CO ^ "* iM >* CD Tj< CD CO O 00 CO Tj< I> -■ s 1 1 1 2 lOO 00 TfH oo ^ 1-H 00 ':*< o od 0.-H(M O W^iC jT-io^-^aJocooocot^ooc^oOT-no CO CO ■* O iC (N I> CO CO (M CO CO CO 1-1 c<- CoSrHWC^S^^S^^ScoSrofo CO 00 CO 1 ^?^^^^?^^^^u^§^^^ ■^ a c^ cr O (N CDOOGOCOCOCDco^oO'*co-*t^ocoi>-05 (>, CO CO rt< rH ^ ^ rH CO(N>0<:D OiO OcO O ^ CO (N 020 GOCOCOCNCO a,00Olt^COCS|CO(M^T-HCO t^(Ma5t^CD gOOC0(Nt^C005C0t^C0 6 5 a. -HOOiOtMClCOCOOCDCOOt^COOO — 1 .-i(N .-H (N CO ^ (M <1 October, '16] NITRATES IN ORCHARD SOILS. 15 ^ ^ o Ph 1 5 (N O t^ t^ rH iXKM CO 00 (M 00 CO lO T(< O 0005CCOO^JO(N05000i^O0-H-SH-,H^Ot-C^ i i^Iz^SSSS^^^*^^^'^^^^*^ iC OcDaJC^C0(NiM(MC0OO'*O 00 i>xa>-Hoa5c»c:^oit^t^t>oiooot^ ^ O--D'^00O-«J<^Q0->*(NO;DO O-tl^C^Ot>CCiO^(N00Q0 C5 OC^Ci'-O'-OOOOOOTOOOlCOOOOJOO - 00 o Tjt CO c^ 00 •* X :oCOCOT}--HCO(N ^ iO05C000CO'#f0'-<^iOO 16 N. H. EXPERIMENT STATION. [Bulletin 11 -2 o 1 ^ CC>0(M05t^fCOcDeCO^-*t^'-(0-J(M52 »OiCC0C0iO.-lC0-*t^O5Tj<00iO<£)i0c0O eocoo>oooc^coo5t^'-i'-iOcoTt«D'^i-H^(MOCOCD.-(GOiOiCi ^'-HO(^^TJ^C0l0Tt^C0Tt^C0:0^'-(t^C0C0r}^ CO 00 o •^ 5 Tt^ C C ■JCNOIOOOCD OKNOOOJ COOOIMCOO OOOCDCO>OOfOTt05i0t^rtHi-l (Mi005Q0O'-HO(Mt^Ot>OC00i^05'-i 00!Mt^^GO-*(MiOiOOi(MiOiCOTtOOiO(MiOOOO.-H--H M^OOCOCt^(NOc000COTtH.-HC»iOO202 5(r^GO(N'-HkCTj-i— ICO-— ii>coo5t^O'* -*05C00iI>(NOt^^t> ■* ■* 3 CO iM CO lO CD lO 00 cotOTf -*,-( < s 5 5 ■* ^ 00 lo (^^ 05 c: 2COOCDCOOI^COO-*05 1 1 1 t < October, '16] NITRATES IN ORCHARD SOILS. 17 5£ P 1 1 1 ^ ss?S§§g??2:2;g^S2?ggg o C2^O00C;2.I>a5t^(NCOO5Ol^.-lO5t^r=!c0TtCC0r-iiOt--t-HCO ■*" g C^ coc So > 18 N. H. AGR. EXPERIMENT STATION. [Bulletin 11 1 1 1 0(M-*-<*r-(ioroi-H»oio =^232gg^g52?^^^?5?^^'^'^"''^^'^ d 00 CO ^ CO ^ ^ (M r-( COCO -S-3 - i-H O Cq 00002 lO i ! 1 cvi .^S;g:SEsSSS§;oSgSS:^g§gg 1 a t^i-icCKMiOiOOO^t^COOOOSr-iOiMCSCOC^I^ ^CD00(M(Nr-lcoioo5iocoi>.-ir-ioooi>coi> 00 COC^J-HOOi'^t^OO^COOt-iMOOCOOlOCDt^ r-HOilOCD y-f r-(--l,-l '^ coooocO'*Tt^.-HG0'*rH00lCr-(00tXM03C0-* rH ,-( (M CO --I C^ C^ ^ ^ c^i _ cvj cv) ^ M 1 1 1 1 < October, '16] NITRATES IN ORCHARD SOILS. 19 1 1 1 IS ? -2 c Oh 1 c^ o§§[^S§^5588S5J?Qf2^^§g22^ ^m050rO'*CR'OC^Tt(C^iOt^OiOCOlMiOCC ^ c.^^?2?22^SSI^^gg§g^f;?j:;;^§ CO CO ■-tOCOQO— i(MCO.-i^COC^COTtOTt 20 N. H. AGR. EXPERIMENT STATION. [Bulletin 11 o 6 ^ ^ o ^ ^^ 3 g ^ < .2 JtH ■^ O) g a •<~i s [^^ Lh ■w cri Q Pk o 1 ^ §j:gSgF:s§§28g^ s t^C Ol^ CO ^ g - ^5B^gS5?^2^2;gss 00 OOOOiO!M'*t^GOCO^O'OcOiO ^OICO'OcOCaGOiOQOI^COt^rt^ § OiO.-i»OCOC)^OCOO'*!MiO CicOCOt^'*(M'#»O^COOiMt^ ^ ^ ^ CO 05 0 CO r- CO C<1 §§^^sfej;5^^s§§;::g CO GOTt<'*>-i.-HiooO'*050coi>co .— 11— It-Ht-Ht— li— 1 C^C<)C>^CO - oot^i>coicic(N'*o CO CD CCl^ CO cow t-H 1-1 rH(N •*•*•* f 5 ^i-i00iC(NO>CO(N05CDC0OiO CO(M(M t-i i-H IM i-ilMCO II t 1 1 October, 16] NITRATES IN ORCHARD SOILS. 21 s Oh 1 3 m !M" '-DCMCviOXt^Tf-^rJ-^^OO 2 -*C002C5t^"^t^XCDiCiC:OiO '*cDMa:cviooox:CO-*05C: CO (MOCCrOiOTtHt^'MLOCOeO-^ l?5?3c^§ 1 1 - OcCC:^C:C:;r:-^XTfxt^!M ?^^?^?3?^S;^?^?jg^5^?5 ^ X^C:-*T»';000 0)OwOcO CO IS 2?:5?5^?52^g?5g2g?:3 '*C^"*XX-*^XXXO'M01 CO rMO»cr^eo-<4<(Mcox>Cfcx»o ■*x-rc-r-r3c;~u;-f — 1^ ^ 32^^c5?52S?J22i^g2 § 3 > 22 N. H. AGR. EXPERIMENT STATION. [Bulletin 11 The summer of 1915 was very wet and as a consequence the nitrates recovered in our samples were low as compared with other years. This can be well seen on Charts 3 and 8, as the heavy rains began July 6. The curves drop down at that time and remain low throughout the rainy period without much dif- ference between the plots. This is likely due to two things, first, nitrification was probably not so rapid when the soil was very high in moisture, and second, what nitrates were formed were readily leached out. Plot 5 here fell a little below Plot 4 with a difference in favor of the latter of about 2 p. p.m. This evidence seemed to warrant the position that the forma- tion of nitrates is greatly reduced in a sod orchard and from a fertility standpoint is the first limiting factor. Not only does the growth average about half as great as where a good system of culture is practiced, i.e., as 4.80:8.83, but also we find a smaller size of the leaves and a poor color, denoting an insufficient amount of available nitrogen. That the lack of vigor is due to an insuffi- cient supply of moisture cannot be advanced for it has been some- what of a surprise throughout the entire experiment that there was a higher per cent of moisture in the sod plot than in the adja- cent tilled ones. NITRIFICATION UNDER SOD. During the past season we have attempted to determine the approximate amount of nitrates formed under sod. In order to determine this a small plat 3 feet square was selected in Plot 1 (the sod plot) quite near to the point where the soil samples had been previously taken, and the sod carefully removed without stirring the soil beneath. Another plat of equal size was selected close to the first and after the sod was likewise removed the soil was spaded to the depth of the surface soil and cultivated with a hoe weekly. This gave three conditions within the original sod plot: (1) sod; (2) bare soil; (3) bare soil, stirred each week. While the bare plat would not represent the exact conditions under sod, yet it seems to be as near that condition as is practical to obtain in the field. While this phase of the work was not begun until the middle of summer the determinations seem to throw light on the question. •October, 'Ifil NITRATES IN ORCHARD SOILS. Table No. 14. Nitrates, Part.'< per Milh'on of Dry Soil. Surface k^oil. 23 July 24. 'Si' Auk. Aug. 14. ■1?,' Aug. 28. Sept. 4. Sept. 'T Average .\ug. 7 to Sept. 23. Sod Bare TiUed 2,599 2.575 1.871 2.615 2 . 800 4.717 10.. 575 2 . (itiS 3 . 330 10.002 3.748 11.112 24 , 9(i9 3.075 10.755 51.021 4.27 7 . 856 65 . 553 .568 1 . 923 8. 332 1.464 2.380 8.820 2.656 6.010 26.469 Table No. 15. MoiMure, Percentage. Surface Soil. July 24. July 31. Aug. 7. Aug. 14. Aug. 21. ^l- Sept. 4. Sept. Sept. 23. Average Aug. 7 to Sept. 23. Sod Bare Tilled 27.0 26.4 26.8 27.4 25.0 24.4 24.6 25.2 24.4 24.6 22.0 21.2 22.2 24.9 25.7 25.8 21.8 22.8 22,8 27.0 27.0 27,5 26,5 26.5 26.5 24.6 24.6 24.8 From the tal)le it will l)e seen that there is practically no dif- ference in moisture to account for variations in nitrates. It will also be seen that the amount of nitrates formed under the sod would be approximately the amount shown on the bare soil but where this same soil is stirred nitrification progresses at a much greater rate. So it would seem to indicate that nitrates are reduced under sod to a marked degree as compared with the same soil under tillage. The ratio between the three small plats is as follows : Sod. 1 Bare. 2.2 Tilled. 10. Later in the season another sod orchard of Baldwin trees was used to duplicate the experiment. Determinations of nitrates and moisture had been made throughout the season on two un- fertilized rows under the sod and gave a weekly average for the season as follows: 24 N. H. AGR. EXPERIMENT STATION. [Bulletin II ^ ° October, '16] NITRATES IN ORCHARD SOILS. 25 Average Moisture atid Nitrates in Second Orchard, 1916. Surface Soil. Nitrates. Moisture. Row 4 3.55 3.28 22 98 Row 8 22 69 After small plats similar to the ones described in Plot 1 were made on Row 4 determinations were made which gave the fol- lowing results: Table No 16. Moisture, percentage. Nitrates, p. p.m. Aug. 21. *« Sept. ^^ ir ... 'A' •\"|- Sept. 4. "It Sept. 23. Av. Sod Bare .... Tilled. . . 22.8 26.0 i24.8 128. 23.6 26.1 124.4 27.5 21.4 20.1 23.0 28.5 29. 27. 27. 26.12 25.72 25.20 2.980! 3.838 9.046 6.5.50 11.657 13.009 4.606 6 . 382 29 . 880 .857 .901 3 . 702 1.03 1.166 3.33 2.662 4.809 12.049 No rains fell during the first few weeks of these observations and the nitrates accumulated as the weeks progressed and formed a rapidly ascending curve where the soil was stirred, but on Sept. 15, 1.42 inches and Sept. 18 1.10 inches of rain fell and the curve drops down again as the nitrates had washed out. These results do not extend over as long a period as might be desirable but from our experience over four years in the orchard they seem to duplicate the results obtained there. EFFECT OF LIME ON NITRIFICATION. It has been shown a number of times that when lime is applied to soil it will increase nitrification. Four years' results on a cultivated orchard show a greater average amount of nitrates recovered in the samples where the lime was applied. However, nitrates are quite variable and seem to be readily affected by weather conditions. Especially where fertilizers have been ap- plied do we find irregularities apparently due to obtaining some of the fertilizers in the sample occasionally. So that any par- 26 N. II. a(;r. experiment station. [Bulletin ir CO e ^ 2 ^ !liliMiiMrSI^#lJ vz tz 79 -any -z Mp-z 1>z i rtif! ■ft ■^4^. tiH 1^ s w i ^i )tf il J \ I I iilis October, 'Ifi] NITRATES IN ORCHARD SOILS. 27 |ie^y,h:[iM:|Tfi^ :::h^a::::!::-: !:-:!-^ii:;i|^^ t^ ©J dc2 m^m^. -9 -in. Of -6 T 8T ijg-T Xter ''^' X- 28 N. H. AGR. EXPERIMENT STATION. [Bulletin II H S ^ rt 7 ^ DC S ~ October, '16] NITRATES IN ORCHARD SOILS. 29 mSi-'\ : i H:lna^^fen::.l:-=:t:Htii^:f:^mif^rt-^--t™t::n^-::f:r;tf:.n}:.:4:t^;.:^44i •'^ I ®i CO e < h of 6 6t ZX ^"'frun J \ I \ I L tVI Ci 30 N. H, AGR. EXPERIMENT STATION. [Bulletin 11 ticular determination or even the average for one season is not very satisfactory but where four consecutive years are consid- ered, the average can be pretty well relied upon. The following tables show the nitrate and moisture determinations: Table No. 17. Summary of Nitrate and Moisture Determinations. Limed and Unlimed Plots. Nitrates. Plot 11— Limed. Plot 12— Unhmed. Year. Surface soil. Subsoil. Surface soil. Subsoil. 1913 1914 1915 1916 82.33 82.46 29.98 98.48 19.60 23.43 13.78 24.10 57.46 57.09 24.26 80.36 6.16 15.21 17.24 11.56 Average 73.31 20.23 54.79 12.54 Table No. 18. Moisture. Plot 11— Limed. Plot 12— Unhmed. Year. Surface soil. Subsoil. Surface soil. Subsoil. 1913 1914 1915 1916 19.14 15.42 21.19 22.47 ' 11.92 10.28 12.33 13.72 16.75 15.99 21.38 23.98 11.22 10.50 13.64 16.72 Average 19.55 12.06 19.52 13.02 rmmry J mARY October, '16] NITRATES IN ORCHARD SOILS. 31 SUMMARY. 1. Nitrification proceeded slowly on the sod plots of these orchards. 2. Stirring the soil readily increased the rate of nitrification. 3. Under a good system of tillage nitrates were usually present in excess of the needs of the trees. 4. Lime consistently increased nitrification. 5. Moisture was not the limiting factor in the sod plots. UBRAkf M. C. State College '^yi'.'^'S T fe*i up^ •ill -v *>«■ ^^.^'i:^? }^iMMkA