XIBRAR.Y OF THE UNIVERSITY: OF ILLINOIS' 630.7 WGb cop - 2. AGRICULTURE NOTICE: Return or renew all Library Materials! The Minimum Fee for each Lost Book is $50.00. The person charging this material is responsible for its return to the library from which it was withdrawn on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for discipli- nary action and may result in dismissal from the University. To renew call Telephone Center, 333-8400 UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN mi 29 L161 0-1096 UNIVERSITY OF ILLINOIS Agricultural Experiment Station BULLETIN No. 286 FERTILIZER EXPERIMENTS WITH GREENHOUSE LETTUCE AND TOMATOES BY J. W. LLOYD URBANA, ILLINOIS, FEBRUARY, 1927 SUMMARY The experiments in the production of greenhouse lettuce and toma- toes reported in this bulletin were designed primarily to test the effec- tiveness of various forms of commercial fertilizer as supplements to a soil mixture of 4 parts brown silt loam, 2 parts rotted manure, and 1 part sand. However, for purposes of comparison two other soil mix- tures were used, and also the effect of steam sterilization of greenhouse soil was tested. Four crops of lettuce and one crop of tomatoes were grown each year. The 4-2-1 soil mixture supplemented with nitrate of soda or with dried blood produced better average yields of lettuce than the untreated 4-4-1 soil mixture (4 parts brown silt loam, 4 parts rotted manure, 1 part sand) , and fully as good average yields of tomatoes. The addition of acid phosphate to the nitrate treatment reduced the yields of lettuce but increased the yields of tomatoes. However, when lime was added to the nitrate and acid phosphate in treating the 4-2-1 soil mixture, the detrimental effect of the acid phosphate on the lettuce was overcome and the high yield of tomatoes maintained. Another way in which the detrimental effect of acid phosphate on the lettuce was avoided was by using nitrate alone on the 4-2-1 soil mixture for producing the lettuce, and then applying a top-dressing of acid phosphate for the tomatoes after the lettuce was harvested. This treatment produced considerably higher average yields in both lettuce and tomatoes than the 4-4-1 soil mixture without commercial fertilizer, andjnearly as high a combined yield of lettuce and tomatoes as the 4-4-1 soil mixture treated with nitrate for the lettuce and acid phos- phate and potassium sulfate for the tomatoes. Steam sterilization of the 4-4-1 soil mixture increased the yield of lettuce but so decreased the yield of tomatoes that the combined yield of the two crops was considerably less than from the unsterilized soil of the same composition, and also much less than from the 4-2-1 mixture treated with nitrate alone. In the light of these experiments it is recommended that in grow- ing a combined crop of greenhouse lettuce and tomatoes on brown silt loam in raised benches, a 4-2-1 soil mixture be employed, and that this soil be fertilized by using nitrate of soda (approximately .86 of a pound per 100 square feet of bench space) before planting each crop of lettuce, and by applying a top-dressing of acid phosphate (approxi- mately 2.3 pounds per 100 square feet of bench space) for the tomatoes after the last crop of lettuce for the season has been harvested. FERTILIZER EXPERIMENTS WITH GREENHOUSE LETTUCE AND TOMATOES By J. W. LLOYD, Chief in Olericulture Greenhouse vegetable growers in Illinois have in the past de- pended upon stable manure almost entirely as a fertilizer for lettuce and tomatoes. During the last few years, however, it has become more and more difficult to get supplies of manure, and growers have been looking for a method of producing these crops without the use of as large quantities as formerly. A previous experiment at the Illinois Station, 1 in which garden loam (brown silt loam), rotted manure, and sand were combined in different proportions for the growing of greenhouse lettuce and toma- toes, had shown that with every increase in the proportion of manure in the soil mixture there was an increase in yield. However, the soil composed of 4 parts garden loam, 2 parts rotted manure, and 1 part sand (by volume) gave good yields and contained sufficient humus to be fairly friable and retentive of moisture. The essential physical conditions for good growth of crops appar- C ently being supplied by this amount of manure, the problem became one of ascertaining whether the plant-food materials in the mixture might be satisfactorily supplemented by commercial fertilizing mate- rials so as to provide for the needs of maximum crops. Taking the 4-2-1 soil mixture as standard, therefore, commercial fertilizing mate- rials containing nitrogen, potassium, and phosphorus were applied to different greenhouse plots and the yields resulting from the different treatments recorded. A comparison was also made between soil mixtures containing different proportions of manure, both with and without commercial fertilizers, and a test was included to determine the effect of sterilizing a greenhouse soil with steam previous to the planting of each crop of lettuce. The steam sterilization was originally planned to aid in dis- ease control, but as there was very little damage from disease in any of the plots, its effect on the yields of lettuce was of more significance. The first series of experiments in using commercial supplements to manure for the growing of greenhouse lettuce and tomatoes were conducted for three years. The results, reported on pages 317 to 328, in- dicated that certain treatments favorable to the production of large yields of tomatoes were detrimental to the lettuce crop, while other treatments favorable to lettuce were unfavorable to tomatoes. There- Unpublished data in experiment by C. E. Durst and H. D. Brown. [311] 312 BULLETIN No. 286 [February, fore, further tests were planned with a view to finding, if possible, a combination of treatments that would be effective in producing large yields of both crops. These are reported in the last section of the bulletin, on pages 328 to 336. METHOD OF CONDUCTING THE EXPERIMENTS The tests were made in the west greenhouse of the vegetable range at this Station. The house, which is 28 by 50 feet, is provided with both ridge and side ventilation and equipped with four benches. Three of the benches were used for the different soil treatments, while part of the fourth was employed for growing the young plants preparatory FIG. 1. LETTUCE SEEDLINGS SOON AFTER BEING SHIFTED TO 2 :L 2-lNCH POTS With both lettuce and tomatoes, the seed was sown in flats and the young seedlings shifted to 2V2-inch pots as soon as the plants were large enough to handle. The soil used in the pots was in all cases a mixture of 4 parts garden loam, 2 parts manure, and 1 part sand. to setting them in the differently treated soil mixtures. The benches were 47 inches wide, inside measure, and were divided by cross parti- tions into sections 6 feet long, so that the area of each section was approximately 24 square feet. The depth of the benches was 6% inches. In preparing the soil mixture, garden loam and rotted manure were pulverized by passing the loam thru a half-inch screen and the manure thru a manure shredder. The loam, manure, and sand were then thoroly mixed by repeated shoveling, and the mixture was placed in the benches, which were filled slightly above the level of the sides. The soil was smoothed off with a straight edge without being com- pacted. After being wet down and prepared for planting, the top of the soil was slightly below the edge of the bench, thus leaving suffi- cient space for watering. 1937] EXPERIMENTS WITH GREENHOUSE LETTUCE AND TOMATOES 313 Each season four crops of Grand Rapids lettuce and a spring crop of tomatoes were grown. At the close of the tomato harvest each year the benches were cleaned out completely and an entirely new lot of soil put in for the next season's work. Method of Applying Fertilizers. In applying the fertilizer the in- gredients for each section were weighed separately, ground in a mortar, and sprinkled carefully by hand over the surface of the soil in the given section of bench. The material was then thoroly mixed with the TABLE 1. QUANTITIES OF FERTILIZER APPLIED TO SOIL IN EXPERIMENTS WITH GREENHOUSE LETTUCE AND TOMATOES Fertilizer Amounts applied 1 Per section Rate per 100 square feet Rate per acre Nitrate of soda grams 94 432 125 250 250 500 /6s. .860 3.966 1.147 2.295 2.295 4.591 Ibs. 375 1 728 500 1 000 1 000 2 000 Dried blood Potassium sulfate Acid phosphate Steamed bone Lime : In a few sections double the above quantities of nitrate of soda, potassium sul- fate, and acid phosphate were used. With the exception of the nitrate, only one application was made for the season's cropping, which consisted of four crops of lettuce and one crop of tomatoes. In the case of the nitrate the quantity specified was usually applied previous to the plant- ing of each lettuce crop, so that the application for the entire season ordinarily consisted of four times the quantity here shown. soil by means of trowels. The fertilizer, except the nitrate of soda, was usually applied and worked into the soil several days before the planting was to be done. The nitrate ordinarily was applied not more than 24 hours before the planting. As soon as one crop of let- tuce was harvested, the soil was dug up with a hoe and leveled with a rake, the nitrate applied, and another crop started if the plants were large enough for setting. Occasionally it was necessary to wait a few days for the plants to develop to the proper size and condition for set- ting. Usually, however, very little time was lost between the harvest- ing of one lettuce crop and the planting of another. The quantities of fertilizer applied, whether used alone or in com- bination, were in most instances as given in Table 1. Temperature of the House. After the warm weather of early fall was over, so that it was possible to control the temperature in the 314 BULLETIN No. 286 [February, house, the following schedule of temperatures was maintained in the lettuce house until the third crop was harvested: night, 50 F.; cloudy day, 55 F.; clear day, 60-65 F. When the fourth crop of lettuce, which was interplanted with tomatoes, was put on the benches, the temperature was raised 5 degrees. After the fourth crop of lettuce was harvested and the tomatoes occupied the benches alone, the tem- FIG. 2. LETTUCE NEARLY READY TO HARVEST The lettuce was harvested when the most advanced plants had reached prime condition for market. All the harvesting was done in the morning, and whenever possible on a cloudy day, in order to lessen the variation in weights caused by differences in turgidity of lettuce harvested at different hours of the day and at different temperatures. perature was raised to the following schedule: night, 65 F.; cloudy day, 70 F.; clear day, 75-80 F. Growing the Seedling Plants. For growing the plants of both lettuce and tomatoes, the seed was sown in flats and the young seed- lings were shifted to 2% -inch pots as soon as the plants were large enough to handle. The potting soil used was in all cases the 4-2-1 mixture described on page 311. The pots were plunged to their rims in the soil of a greenhouse bench. The lettuce plants were transplanted from the 2 l / 2 -inch pots to the benches, but the tomato plants were shifted to 4-inch pots before being benched. When conditions were favorable, the seed for the first crop of lettuce was sown from August 19 to 25. For the succeeding crops a new batch of seed was sown at about the time the plants of the preceding crop were placed on the benches. The tomato seed was sown at or about the same date as the lettuce for the fourth crop. 1927} EXPERIMENTS WITH GREENHOUSE LETTUCE AND TOMATOES 315 Distance of Planting. The soil of each section was marked off in checks 8 inches apart, and a lettuce plant was placed at each intersec- tion. Each section thus accommodated six rows of 9 plants each, or a total of 54 plants. When the tomatoes were interplanted in the lettuce, 4 lettuce plants were omitted from the second row and 4 from the fifth row, and tomato plants were sub- stituted for them. Thus for the fourth crop there were 46 lettuce plants and 8 tomato plants in each section. Care of the Growing Crops. The crops were carefully watered and cultivated as often as was necessary. The soil without ma- nure required more frequent wa- tering than that with manure. After the lettuce had begun to cover the benches, the hose was handled in a manner to avoid wet- ting the leaves. Fumigation for the control of aphids and white fly was resorted to whenever con- ditions demanded it. The tomatoes were pruned to single stems, and were trained to perpendicular cords fastened to wire loops that extended thru the cracks between the bottom boards of the benches, where they were anchored by means of small wooden blocks. The tops were tied to horizontal wires supported by the framework of the house. The vines were tied to the upright cords by means of soft twine. Hand pollina- tion was resorted to in order to insure setting of the fruit. Harvesting. When the most advanced lettuce had reached prime condition for market, the entire crop was harvested. The plants were cut off at the surface of the ground, and any dried or yellow leaves were removed. The net trimmed lettuce from each section was weighed separately and the yield recorded. The weights of the four crops from a given plot were added to determine the yield for the season. The harvesting was invariably done in the morning, and when- ever possible a cloudy day was chosen, so that there might be less variation in weights due to differences in the turgidity of lettuce at different hours of the day and at different temperatures. FIG. 3. TOMATO PLANT IN 4-lNCH POT, READY TO SET IN BENCH The lettuce plants were trans- planted from the 2^inch pots to the benches, but the tomato plants were shifted to 4-inch pots before being benched. 316 BULLETIN No. 286 [February, I < K p i o" g H i g x a K o 1 X I m o" g S o W2 O s 5 H O T3 G O - o I g.g G G G -*> -*-* -*- -t-* ^- O O o O O O 02:0000 . a+? a a a a o w a> aj > -5 1-5 1-5 h^ C^iC . i _- g^ g G g G ^ 2rofo2 (N 00 I ~ l IN ^ T > O O rH (N (N (M (M (N GOO5 O ri (N CO i-H ^H IM (M s. oz. 54 6 Ibs.oz. 6212 Ibs. oz. 56 9 lb. oz. 5714 68 Sterilized 60 7211 5414 62 8 the sterilized plot was 4 pounds 10 ounces greater than from the cor- responding unsterilized plot. The heavy crops of lettuce in the ster- ilized plots were distinctly different in appearance from any other let- tuce in the house; the leaves were larger, coarser, and darker colored than the foliage of the other lettuce. The increased yield from the sterilized plot was due largely to the especially heavy yields in the second and third crops each season. The fourth crop of the season was sometimes very light and disap- pointing. The repeated sterilizing seemed to render the plant food in the manure more quickly available, so that the supply was considerably depleted by the time the fourth crop was reached. However, the ster- ilizing did not, on the average, increase the yield in the first crop; the principal effect was on the second and third crops of the season. EFFECT OF TREATMENTS ON YIELDS OF TOMATOES During the harvesting period the tomatoes were picked twice each week. Except in 1920, when a late start was secured on account of delay with the first crop of lettuce the fall before, the harvesting of the greenhouse tomatoes was completed by the time the main crop of outdoor tomatoes became abundant. The total yields of marketable *The method of sterilization was as follows: A galvanized iron pan was in- verted over the section of the bench to be sterilized, and live steam at a pressure of about 5 pounds was introduced under the pan by means of a rubber hose con- nected with a steam pipe in the heating system of the greenhouse. The treat- ment was continued for two hours. 1927] EXPERIMENTS WITH GREENHOUSE LETTUCE AND TOMATOES 323 tomatoes from the respective plots each year are given in the accom- panying tables. NITRATE OF SODA, DRIED BLOOD, ACID PHOSPHATE, AND POTASSIUM SULFATE TESTED SINGLY AND IN COMBINATION The effect upon tomato yields of supplementing the 4-2-1 soil mix- ture with a single element of plant food is indicated by the yields shown in Table 11. TABLE 11. YIELDS OF TOMATOES: EFFECT OF ADDING DIFFERENT FERTILIZING ELEMENTS SINGLY TO A 4-2-1 SOIL MIXTURE Plot Treatment Spring, 1919 Spring, 1920 Spring, 1921 3-year average 51 Check Ibs. oz. 58 13 Ibs. oz. 45 6 Ibs. oz. 53 14 Ibs. oz. 52 11 52 Nitrate 62 4 53 62 10 59 4 53 Dried blood 63 8 57 1 64 6 6110 54 Acid phosphate 54 8 54 10 61 13 57 55 Potassium sulfate 5114 46 66 8 5413 The plot treated with nitrate of soda and the one treated with dried blood invariably gave larger yields than the untreated plot, the average increase apparently due to the nitrate treatment amounting to approximately 6% pounds to the plot of 8 plants, and the increase in yield apparently due to the dried blood amounting to almost 9 pounds to the plot. The two plots receiving acid phosphate and potas- sium sulfate respectively showed increased yields two years out of the three, and increases also as an average for the three years. The effects on the yields of greenhouse tomatoes obtained by add- ing more than one fertilizing element to the 4-2-1 soil mixture are in- dicated in Table 12. Wherever nitrogen was included in the fertilizer mixture, the average yields were markedly increased ; and where nitro- TABLE 12. YIELDS OF TOMATOES: EFFECT OF ADDING Two OR MORE FERTILIZING ELEMENTS TO A 4-2-1 SOIL MIXTURE Plot Treatment Spring, 1919 Spring, 1920 Spring, 1921 3-year average 51 Check Ibs. oz. 5813 Ibs. oz. 45 6 Ibs. oz. 5314 Ibs. oz. 5211 59 60 Acid phosphate, potassium sulfate . . . Acid phosphate, nitrate 6114 67 3 4413 57 5014 67 9 52 8 6315 61 Potassium sulfate, nitrate 67 2 42 5 7411 61 6 62 Acid phosphate, potassium sulfate, nitrate 64 52 1 6112 59 4 324 BULLETIN No. 286 [February, gen was omitted, the average yield was slightly lowered. A compari- son with the yields given in Table 11 shows also that the nitrate of soda used in conjunction with acid phosphate or potassium sulfate gave larger average yields of tomatoes than when nitrate of soda was used alone. ADDING LIME GIVES NO MATERIAL INCREASE IN YIELD The addition of lime to the soil treated with acid phosphate did not materially increase the average yield of tomatoes as compared with the yield from the plot treated with acid phosphate alone (Table TABLE 13. YIELDS OF TOMATOES: EFFECT OF ADDING LIME TO PLOT OF 4-2-1 SOIL MIXTURE TREATED WITH ACID PHOSPHATE Plot Treatment Spring, 1919 1919-20 1920-21 3-year average 51 Check Ibs. oz. 5813 Ibs. oz. 45 6 Ibs. oz. 5314 Ibs. oz. 5211 54 Acid phosphate 54 8 5410 6113 57 58 Acid phosphate, lime 5412 57 2 6011 57 8 13). Both these plots, however, gave distinctly higher average yields than the check plot of the same kind of soil. o> DOUBLING THE QUANTITY OF FERTILIZER LOWERS YIELDS A comparison of the yields of tomatoes from plots where the reg- ular quantities of the fertilizing materials were used, with those from plots receiving double those quantities, is shown in Table 14. In no case was the average yield increased by doubling the quantity of fer- tilizer; in fact, it was distinctly smaller in three cases and slightly smaller in the other than the yield from the corresponding nor- mally treated plot. The decrease in yield apparently due to the heavy fertilizing was especially marked in the case of the soil mixture which contained no manure. COMPARISON OF THE THREE SOIL MIXTURES The check plots of the three different soil mixtures showed marked differences in yields of tomatoes, the increase in yield following the in- crease in the proportion of manure in the mixture (Table 15). The untreated 4-2-1 mixture gave an average yield of over 11 pounds more than the 4-0-1 mixture, while the 4-4-1 mixture gave an aver- age of nearly 10 pounds more than the 4-2-1 mixture. The differ- 1927} EXPERIMENTS WITH GREENHOUSE LETTUCE AND TOMATOES 325 TABLE 14. YIELDS OF TOMATOES WHEN DOUBLE THE USUAL QUANTITIES OF FERTILIZERS WERE USED Plot Soil mix- ture Treatment Spring, 1919 1919-20 1920-21 3-year average 51 4-2-1 Check Ibs. 02. 5813 Ibs. 02. 45 6 Ibs. 02. 53 14 Ibs. 02. 52 11 52 4-2-1 Nitrate 62 4 53 62 10 59 10 56 54 4-2-1 4-2-1 Nitrate (double quantity) . . . Acid phosphate 65 54 8 46 54 10 66 5 6113 59 2 57 57 4-2-1 Acid phosphate (double quantity) 58 3 46 4 54 9 53 62 4-2-1 Acid phosphate, potassium sulf ate, nitrate 64 52 1 6112 59 4 63 4-2-1 Acid phosphate, potassium sulfate, nitrate (double quantities) 56 4 50 2 62 4 56 3 65 4-0-1 Acid phosphate, potassium sulfate, nitrate 67 8 39 8 5414 5315 66 4-0-1 Acid phosphate, potassium sulfate, nitrate (double quantities) 58 2 40 6 3112 43 7 ence in average yield between the 4-0-1 mixture and the 4-4-1 mixture was 21 pounds and 8 ounces per plot, or more than 2% pounds per plant. In other words, the heavily manured plot yielded over 50 percent more than the plot without manure. When a complete fertilizer was added in normal amount, the re- sponse to the fertilizer treatment was greatest in the case of the soil without manure, on which the increase in average yield apparently due to the commercial fertilizers was nearly 13 pounds to the plot. The TABLE 15. YIELDS OF TOMATOES: COMPARISON OF THREE SOIL MIXTURES, WITH AND WITHOUT SUPPLEMENTAL FERTILIZERS Plot Soil mix- ture Treatment Spring, 1919 1919-20 1920-21 3-year average 51 4-2-1 Check Ibs. 02. 5813 Ibs. 02. 45 6 Ibs. 02. 5314 Ibs. 02. 5211 62 4-2-1 Acid phosphate, potassium sulfate, nitrate 64 52 1 6112 59 4 64 4-0-1 Check 44 1 4110 37 4 41 65 4-0-1 Acid phosphate, potassium sulfate, nitrate 67 8 39 8 5414 5315 67 4-4-1 Check 7114 52 4 63 7 62 8 69 4-4-1 Acid phosphate, potassium sulfate, nitrate 70 3 5812 73 2 67 6 326 BULLETIN No. 286 [February, increase in average yield in the 4-2-1 mixture, apparently due to the same fertilizer treatment, was only 6 pounds and 9 ounces, or approx- imately half as much as in the case of the soil without manure. The commercial fertilizer gave a still smaller increase when added to the 4-4-1 mixture, the difference in average yield evidently due to the fer- tilizer treatment being only 4 pounds and 14 ounces for the plot. STEAM STERILIZATION REDUCES YIELD OF TOMATOES FOLLOWING FOUR CROPS OF LETTUCE The yield of tomatoes from the sterilized plot was invariably lower than that from the unsterilized plot, the three-year average showing a difference of more than 15 pounds in favor of the unster- ilized plot (Table 16). As mentioned in the discussion regarding the TABLE 16. YIELDS OF TOMATOES: EFFECT OF STEAM STERILIZATION Plot Treatment Spring, 1919 1919-20 1920-21 3-year average 67 Check Ibs. oz. 7114 Ibs. oz. 52 4 Ibs. oz. 63 7 Ibs. 02. 62 8 68 Sterilized 46 3 51 2 43 6 4614 lettuce on the sterilized plot, this treatment seemed to render the plant food in the soil mixture more quickly available, so that it was drawn upon very heavily by the second and third crops of lettuce. This sometimes left little available plant food for the fourth crop of lettuce and the crop of tomatoes following the lettuce on the sterilized plot. COMBINED YIELDS OF LETTUCE AND TOMATOES Since it is desirable to know the total yield of greenhouse crops from a given bench area during the greenhouse cropping season, the average yields of lettuce and marketable tomatoes per season from each plot or bench section have been calculated in terms of pounds per square foot of bench area (Table 17). The average total yield of let- tuce and tomatoes combined is also given. The lettuce and tomatoes were sold at wholesale to merchants in Champaign and Urbana. The price received for the lettuce ranged from 12% to 25 cents a pound, averaging slightly over 20 cents. Twenty cents a pound was approximately the average price received for the tomatoes also; they sold at 25 cents a pound early in the season, 20 cents later on, and finally at 15 cents after the local early outdoor crop was supplying the market. At 20 cents a pound for both crops, four plots yielded a gross income of more than one 1927} EXPERIMENTS WITH GREENHOUSE LETTUCE AND TOMATOES 327 a w X fn X & o I ^> H h4 fe O OQ 3 a 2 3 GO O< O CO-* CO CO "* GO CO CO 1-1 b- OOOOC5GO co oco OGO CO t** CO OS OS OS GO OS GO OS CD rt< -*f t^* co t" 005 GO * CO CO CO CD **! COGO t^ CO Ort* OO5 O " H& i 1 i 1 * i-H i 1 a 55 . COCO COCO l> eo rf* I-H i i iC CO CO 1C i 1 1C OS COCO GO TjH O3 cot^ t^ GO CO CO CO CO I-H COCO l> I-H 1C CO H ^T+I^^T+( TjHTjH T}< CO ^ CO c-*c CO 8 ~C3 . O5 t^ t^ t^ GO 00 1-1 TjH 1C CO CO CO i-H O> GO CO rfi CO COi-H CO iO "^ CO 1 1 T+t 1-H l> CO GO SIC i i O5GO 1 H ~ COCO CO CO CO COCO CO CO CO COCO CO fHCO i-l COTTHCO o . Tfi ic CO OS OS oo CO CO >C i I O CO i-H TfH CO CO CO O CO coco o i 1 O5 O COO O5 1 1 O i-H CO ~* CO CO CO CO CO CO CO COCO CO COCO CO i-H CO i-H COCO CO ' ' 1 ' s s o o .~tn ^ . . CO I-l '3 o3 . . CO 03 'S 43 S :g 1 i II "S w 1 J :| 3 : s l 02 5 Eg S / 7T X n* ^ S fl.3 / S H .-S co -2 o g's-1 "ffl '.':$ Hill 5-3.^: as a || $ ~ A "o aT 1 c ' ' """^M i'g'lg ai3 ^3.2 lll'll o a o- a a ~ 02 03 02 CO * ' O O O ^n'S'G'o'S Potassium sulfa Acid phosphate Acid phosphate, ties) Check Acid phosphate Acid phosphat quantities) . . CO f. o 11 S i i i t i CO CO CO CO CO CO CO CO CO CO 999 iii o S i-l CO CO-* 1C 1C >C *C iC 1C CO IN- GO O5 O 1C C *C *C CO i-HCO CO CO CO CO * 1C CO CO COCO 1>OOOS CO CO CO ~e w V 03 J5 J3T3 11 3 li 328 BULLETIN No. 286 [February, dollar for each square foot of bench space, and the fifth plot yielded almost one dollar a square foot, while the poorest plot (the check plot without manure or fertilizer) yielded products worth only a fraction more than 66 cents a square foot. The lettuce and tomatoes did not respond equally well to the same fertilizer treatment (Table 17). The lettuce responded especially well to nitrogen alone, whether it was supplied by means of sodium nitrate, dried blood, heavy manuring, or steaming of the heavily manured soil. Acid phosphate seemed to be detrimental to the lettuce crop unless supplemented by lime or sodium nitrate; and even then the yields were less than from the use of nitrate alone. The complete fertilizer, consisting of acid phosphate, potassium sulfate, and sodium nitrate, apparently reduced the yields of lettuce, except on the soil which con- tained no manure. On the other hand, the tomatoes, while responding quite favorably to the nitrogen treatment, gave considerably higher yields where the nitrate was supplemented with acid phosphate, and the highest yield of all where the complete fertilizer was used on the plot already heav- ily manured. Reasonable quantities of acid phosphate, whether used alone or in combination, apparently were not detrimental to the to- mato crop. It would appear from these results that no acid phosphate should be used for the lettuce crop, except possibly in combination with lime, and that acid phosphate used with plenty of nitrogen is a very desir- able combination for the production of good crops of greenhouse toma- toes. In view of these circumstances, additional tests were planned for the purpose of finding, if possible, a method of fertilizing that would be highly beneficial to both crops. These further tests are dis- cussed in the following pages. To obviate the harmful effect of acid phosphate on lettuce noted in the preceding experiments, and yet furnish phosphorus for the suc- ceeding tomato crop, three methods of supplying this plant food were compared: (1) lime was applied along with the acid phosphate; (2) steamed bone meal was substituted for acid phosphate; and (3) acid phosphate was applied as a top-dressing to the tomatoes after the last crop of lettuce was harvested. In the earlier tests steam sterilization of the soil, while resulting in heavy initial crops of lettuce, seemed to effect such depletion of the soil that the fourth crop of lettuce and the crop of tomatoes were sometimes greatly reduced. An effort was made to overcome this dif- 1927] EXPERIMENTS WITH GREENHOUSE LETTUCE AND TOMATOES 329 ficulty by applying nitrate for the fourth crop of lettuce, and then using a top-dressing of acid phosphate for the tomatoes. A mixture of acid phosphate and potassium sulfate also was tested as a top-dressing for the tomato crop. Other tests were in- cluded to compare further nitrate of soda and dried blood as sources of nitrogen for the crops in question. The kinds of soil mixture used in the various sections, or plots, and the soil treatments applied are given in Table 18. TABLE 18. SOIL TREATMENT OF THE DIFFERENT PLOTS IN LETTUCE AND TOMATO EXPERIMENTS, 1921-1924 Plot Soil mix- ture Treatment 71 4-2-1 Check 72 4-2-1 Nitrate of soda 73 4-2-1 Dried blood 74 4-2-1 Acid phosphate, lime 75 4-2-1 Acid phosphate, lime, nitrate 76 4-2-1 Steamed bone, nitrate 77 4-2-1 Acid phosphate, lime, potassium sulfate, nitrate 78 4-2-1 Nitrate for lettuce, acid phosphate for tomatoes 79 4-2-1 Dried blood for lettuce, acid phosphate for tomatoes 80 4-2-1 Nitrate for lettuce, acid phosphate and potassium sulfate for tomatoes 81 4-4-1 Check 82 4-4-1 Sterilized 83 4-4-1 Sterilized; nitrate for fourth crop lettuce, acid phosphate for tomatoes 84 4-4-1 Nitrate for lettuce, acid phosphate and potassium sulfate for tomatoes The initial applications of fertilizer and the top-dressings of ni- trate were made in the same manner as in the preceding tests. The top-dressings for the tomatoes (acid phosphate, and acid phosphate and potassium sulfate) were made immediately after the fourth crop of lettuce was harvested from among the tomato plants. The materials were sprinkled over the surface of the soil and worked in lightly by means of a hand weeder. Care was taken to avoid letting any of the fertilizers come in direct contact with the stems or roots of the plants. EFFECT OF DIFFERENT METHODS OF APPLYING PHOSPHORUS The combination of steamed bone and nitrate did not result in as high yields of lettuce as an average for the three years as the acid phosphate with nitrate and lime (Table 19). The latter combination gave slightly better yields than the average of the three nitrate plots, 330 BULLETIN No. 286 [February, TABLE 19. YIELDS OF LETTUCE: COMPARISON OF EFFECT OF ACID PHOSPHATE AND STEAMED BONE ADDED TO A 4-2-1 SOIL MIXTURE Plot Treatment 1921-22 1922-23 1923-24 3-year average 71 Check Ibs. oz. 5012 Ibs. oz. 42 9 Ibs. 02. 56 8 Ibs. oz. 4915 74 Acid phosphate, lime 52 6 47 2 6011 53 6 75 Acid phosphate, lime, nitrate 6111 53 8 6912 6110 76 Steamed bone, nitrate 55 10 56 12 5910 57 5 Average of 3 nitrate plots, without phosphorus (72, 78, 80) 57 1 5513 6414 59 4 while the yields from steamed bone and nitrate averaged slightly less than the yields from the plots treated with nitrate alone. The combined treatment of acid phosphate, lime, and nitrate gave much better average yields of tomatoes than the lime and acid phos- phate (Table 20) . The top-dressing of acid phosphate to the tomatoes, following nitrate treatment for the lettuce, gave still better results. Where dried blood had been used as a source of nitrogen for the let- tuce, the top-dressing of acid phosphate for the tomatoes did not ap- pear to be effective. TABLE 20. YIELDS OF TOMATOES: EFFECT OF DIFFERENT METHODS OF SUPPLYING PHOSPHORUS TO A 4-2-1 SOIL MIXTURE Plot Treatment 1921-22 1922-23 1923-24 3-year average 71 Check Ibs. oz. 56 2 Ibs. oz. 7115 Ibs. oz. 70 Ibs. oz. 66 74 Acid phosphate, lime 45 73 3 5814 59 75 Acid phosphate, lime, nitrate 59 12 72 3 7512 69 3 76 Steamed bone, nitrate 69 6 80 5 73 2 74 4 77 Acid phosphate, lime, potassium sulf ate, nitrate 62 7 69 9 8211 71 9 78 Nitrate for lettuce, acid phosphate for tomatoes 7113 69 7 75 7 72 3 79 Blood for lettuce, acid phosphate for tomatoes 51 6715 62 60 5 80 Nitrate for lettuce, acid phosphate and potassium sulfate for tomatoes 55 1 62 9 7213 63 7 The highest yield of tomatoes, as an average for the three years, was secured from the plot treated with steamed bone and nitrate for the lettuce, with no additional treatment for the tomatoes. The addi- tion of potassium sulfate as a top-dressing along with the acid phos- phate seemed to reduce the yield. 19271 EXPERIMENTS WITH GREENHOUSE LETTUCE AND TOMATOES 331 TOP-DRESSINGS APPLIED TO LAST CROPS REDUCE LOSSES FROM STEAM STERILIZATION In the previous tests steam sterilization of the soil before the planting of each lettuce crop seemed to result in such depletion of the soil as to reduce the fourth crop of lettuce and the crop of tomatoes following. A test was therefore made to determine the effect of the addition of nitrate to the sterilized soil just before planting the fourth crop, and of acid phosphate following the harvest of the lettuce. TABLE 21. YIELDS OF LETTUCE: EFFECT OF STEAM STERILIZATION Plot Treatment 1921-22 1922-23 1923-24 3-year average 81 Check Ibs. oz. 54 5 Ibs. oz. 54 9 Ibs. oz. 5813 Ibs. oz. 5514 82 Sterilized .... 67 5811 6813 6413 83 Sterilized; nitrate for 4th crop . . 70 8 6015 66 6513 84 Nitrate 61 10* 5911 69 5 63 8 Steam sterilization distinctly increased the total yield of lettuce each year, and in two years out of the three the application of nitrate of soda for the fourth crop made a slight additional increase (Table 21). Each year the fourth crop was slightly larger from the plot that was treated with nitrate preceding the planting of that crop. However, the fourth crop of lettuce was not reduced by the sterilization of the soil, as it w r as in the preceding test. TABLE 22. EFFECT OF STEAM STERILIZATION ON TOMATO CROP FOLLOWING LETTUCE Plot Treatment 1922 1923 1924 3-year average 81 Check Ibs. oz. 55 2 Ibs.oz. 6810 Ibs. oz. 5912 Ibs. oz. 61 2 82 Sterilized ... 37 15 38 3 54 9 43 9 83 Sterilized, nitrate for 4th crop of lettuce, acid phosphate for toma- toes 47 9 50 7 6112 53 4 84 Nitrate for lettuce, acid phosphate and potassium sulfate for tomatoes 71 3 7115 7214 72 The depleting effect of steam sterilization on the soil during the production of the four lettuce crops was apparent in the tomato crop following the lettuce (Table 22). The sterilized plot without supple- 332 BULLETIN No. 286 [February, mentary treatment yielded a much smaller crop of tomatoes, as an average for three years, than the untreated plot. Top-dressings of sodium nitrate applied before the last crop of lettuce, and of acid phosphate to the tomatoes, partially overcame this depleted condition, but still the average yield of the plot so treated was less than the yield of the check plot. Top-dressings of acid phosphate and potassium sulfate applied to the unsterilized soil of the same composition, following treatment with nitrate of soda for the lettuce, gave a decided increase in yield. SODIUM NITRATE AND DRIED BLOOD ABOUT EQUAL IN VALUE AS SOURCES OF NITROGEN FOR LETTUCE Each year both sodium nitrate used alone and dried blood used alone gave distinct increases in yields of lettuce, as compared with the check plot (Table 23). While the average yields from the plots treated TABLE 23. YIELDS OF LETTUCE: COMPARISON OF EFFECT OF SODIUM NITRATE AND DRIED BLOOD ADDED TO A 4-2-1 SOIL MIXTURE Plot Treatment 1921-22 1922-23 1923-24 3-year average 71 Check Ibs. oz, 5012 Ibs. 02. 42 9 Ibs. 02. 56 8 Ibs. 02. 4915 72 --: Nitrate 58 5 4715 64 5 5613 78 Nitrate 5713 60 8 64 3 6013 80 Nitrate 55 3 59 1 66 2 60 2 Average of 3 nitrate plots 57 1 55 13 6414 59 4 73 Dried blood 6213 5315 65 2 6010 79 Dried blood 59 8 6110 64 1 6111 Average of 2 dried blood plots 61 2 5712 64 9 61 2 with blood were slightly higher for the three-year period than those from plots treated with nitrate, the data in Table 5 indicate that for the preceding three-year period the average yields were slightly better from the nitrated plot. If a six-year average is taken, the yields are approximately the same from the plots treated with nitrate and from those treated with dried blood. Two SOIL MIXTURES COMPARED, WITH AND WITHOUT NITRATE The 4-4-1 soil mixture (4 parts each of loam and manure and 1 part sand) gave larger yields of lettuce every year than the 4-2-1 mix- ture, when neither soil was supplemented with additional nitrogen EXPERIMENTS WITH GREENHOUSE LETTUCE AND TOMATOES 333 TABLE 24. YIELDS OF LETTUCE: COMPARISON OF EFFECT OF Two DIFFERENT SOIL MIXTURES Plot Soil mix- ture Treatment 1921-22 1922-23 1923-24 3-year average 71 4-2-1 Check Ibs. 02. 50 12 Ibs. 02. 42 9 Ibs. 02. 56 8 Z6s % . 02. dO 1 "> 81 4-4-1 Check 54 5 54 9 58 13 ^ 14 72 4-2-1 Nitrate 58 5 4715 64-- 5 56 13 78 4-2-1 Nitrate 57 13 60 8 64 3 60 13 80 4-2-1 Nitrate 55 3 59 1 66 2 60 2 84 4-4-1 Average of 3 nitrate plots .... Nitrate 57 2 6110 5513 5911 6414 69 5 59 4 63 8 (Table 24) . The addition of nitrate to both soils distinctly increased the yields, the 4-2-1 mixture with the addition of nitrate giving larger yields than the 4-4-1 mixture without nitrate. However, the largest yields of all were secured from the 4-4-1 mixture treated with nitrate. These results emphasize the importance of liberal supplies of nitrogen for the lettuce crop. COMBINED YIELDS OF LETTUCE AND TOMATOES In order to determine the total yield of lettuce and tomatoes for the greenhouse cropping season, the yields have been reduced to terms of pounds per square foot of bench space (Table 25). The products from the greenhouse in 1921 to 1924 were sold at wholesale to merchants in Champaign and Urbana. The price of let- tuce varied from 12% to 23 cents a pound, and the tomatoes were sold at 15 to 20 cents a pound. The value of the crops per square foot of bench space has been calculated on the basis of 18 cents a pound (Table 25). The value of the combined crop averaged more than one dollar per square foot of bench space for the highest yielding plot, in spite of the lower price of products in this period as compared with the pre- ceding three-year period. Several other plots produced crops to the value of almost one dollar per square foot of bench space. On the 4-2-1 soil mixture acid phosphate and lime used with ni- trate produced a satisfactory crop of lettuce and a good crop of to- matoes. Slightly better results in combined yields of the two crops, however, were secured when the nitrate was used alone for the lettuce and the acid phosphate applied as a top-dressing for the tomatoes after the last crop of lettuce was harvested. The use of steamed bone with nitrate resulted in the largest crop of tomatoes, but was less favorable to the production of lettuce than the nitrate and acid phosphate. 334 BULLETIN No. 286 [February, DO a W z a PQ H O O fe H a o ^ .28 Ps O < S S o > H * o S z g_ < ^ H g O f-< P -^3 eb a h3 Is +? K sJ m p O Oi CO CM O5 CO O O ^ l> GO C5 C5 00 Ci * GO O - i 1 O5 < 1 0000 00 O H ^05 03 co C* GC ft i-H ^ . CO 1C 1C 00 "* oo GO O CO CD rjt t^ GO cor-- * * CO U3 O I-H co I-H 10 "* ooo e co -4-= O O H r ~ a *tfH 1C C * lO 10 IO 1C lO O 1 * * Tjt IO 1 1 co 8 -*j 03 . 1C O CO CO X Jg t~ CO 00 TjH 00 ooo o-^ * o o o o o rf i 1 i 1 O 1C 00 CO 2 "" CM CM CM CM CM -9sja -ti 3 05 cxj 2 -*^ GO ^ C OS O OH S-s-^ S .2 a& jja'S f ft *r2 a * -c 5 'S ^ rt -a s -fl OH 5 S c aj oT a a & ^ oT -S ^ o o ra T}< O "- 1 aT GO 43 33 U S3 03 8 -g ,, ojBg8 05-0-5-5 .M ti-rt CU & llSsa -C --H t. o o OZQ<;< Steamed bone, nil Acid phosphate, li Nitrate for lettuce Dried blood for lei Nitrate for lettuc fate for tomato Check Sterilized Sterilized; nitrate toes Nitrate for lettuc fate for tomatoe ( S 3 .* a (N(N (NC;)