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July 20, 1922 



The Florists^ Review 



25 



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PREPARING GREENHOUSE SOILS. 



Physical Condition Tells. 



In preparing our greenhouse soils we 

 must keep in mind the fact that both the 

 physical structure and the chemical com- 

 position of the soil are important. I have 

 pointed out on former occasions that 

 good results cannot be obtained from a 

 soil abundantly supplied with plant food 

 materials, but faulty in physical struc- 

 ture; and, likewise, that we cannot hope 

 for the best growth of plants in a soil 

 in good physical condition, but deficient 

 in those materials which the plant re- 

 quires for food. The latter fact is evi- 

 dent to every grower, for, whenever he 

 finds that his plants respond indiffer- 

 ently, he resorts to the application of 

 materials which increase the food sup- 

 ply of the plant. The importance of the 

 former, however — the proper physical 

 structure of soil — is less evident and 

 frequently this is not emphasized as it 

 should be. We must keep in mind that it 

 is only on soils which jjossess the proper 

 physical conditions that the greatest 

 benefit from the application of fertilizers 

 is obtained. The best use of a fertilizer 

 — tliat is, the largest proportionate re- 

 turn — is obtained when it is applied to a 

 soil that is well managed from the stand- 

 point of its physical condition. 



When Is SoU Healthy? 



What, then, are the proper physical 

 conditions of soils for the growth of 

 plants? Unfortunately, we cannot be 

 definite on this point, because of the 

 great variations of soils and the varia- 

 tions of the different types of plants in 

 tlu'ir requirements. When We classify a 

 soil as a sandy soil we have in mind a 

 soil consisting of coarse individual par- 

 ticles and, consequently, porous in char- 

 acter, but the so-called sandy soils vary 

 much in their mechanical and physical 

 properties. Clay soils also are classified 

 as a group, but again clay soils differ 

 widely in their physical qualities. Some 

 of them possess a reasonably good tex- 

 ture; others, although they were abun- 

 dantly supplied with all the necessary 

 mineral constituents, will not produce 

 profitable crops, because certain other 

 necessary conditions do not prevail. 



When we consider carefully the essen- 

 tials of a soil from the standpoint of its 

 physical make-up, we find that a number 

 of fundamental conditions must be ful- 

 filled. Briefly expressed, the roots of 

 the growing plant require, first, a contin- 

 uous supply of water; second, a con- 

 tinuous supply of air, and third, an avail- 

 able supply of chemical substances. I 

 consider these three the fundamental 

 conditions of greenhouse soils. What 

 must be the physical character of the 

 soil to obtain them? 



Water a Requisite. 



In order that the plant may have a 

 continuous supply of water, the soil, be- 

 cause of its physical character, must not 

 only completely absorb and retain the 

 water, but at the same time deliver this 

 water to the roots as needed. The small 

 roots take up water continuously, for 

 there is a continuous stream of water 

 passing through the plant. A break in 



I'aper on 'Treparing Oreenhoiise .Soils." rend 

 before the meeting of the St. Louis district of 

 the National Flower Growers' Association at 

 nock Island, III., July 18, by Dr. P. A. Lehen- 

 bauer, of the University of Illinois, Urbana, 111. 



this continuous stream of water in all 

 probability results in a break of the 

 growth processes and, therefore, is a 

 check to the plant. If this is true, then 

 the question may be asked: Why not 

 keep the soil wet at all times? The an- 

 swer is, because the roots also require a 

 continuous supply of air. Oxygen is as 

 essential for respiration in the cells of 

 the roots, as it is for the cells of the leaf. 

 If the soil is full of water, or if the soil 

 is clayey and compact, air cannot pene- 

 trate freely and, consequently, the roots 

 cannot function properly. There are, of 

 course, other unfavorable conditions 

 which obtain in a soil which is of such a 

 character that it remains wet. The for- 

 mation of the essential soluble nitrates 



Many florists, no doubt, 

 have learned by years of prac- 

 tice how to improve their 

 greenhouse soils by proper 

 mixture of compost and addi- 

 tion of fertilizers, without 

 knowing just why they 

 achieved their results. This 

 paper regarding the funda- 

 mental conditions of green- 

 house soils and how they are 

 obtained explains the princi- 

 ples which guide good practice, 

 helpful knowledge to experi- 

 enced and inexperienced grow- 



ers 



alik 



:e. 



by means of bacteria will not result and 

 instead substances quite probably are 

 formed which are harmful. 



A good soil, then, as to physical char- 

 acter, is one which is sufficiently open 

 and porous so that water and air can 

 move through it freely, yet comp.Tct 

 enough to retard undue drying out. Me- 

 chanically it should be such that roots 

 can readily penetrate it and it should 

 have a texture which will permit the ab- 

 sorption of food materials applied as 

 well as the gradual distribution of the 

 latter throughout its mass by the diffu- 

 sion of the water through it. How are 

 we, th6n, to treat the soil in order that 

 it will meet these physical require- 

 ments? I appreciate the fact that the 

 grower is limited as a rule to the use of 

 a certain type of soil; namely, that 

 which exists on his holdings. This soil 

 may be faulty physically;" if it is, the 

 grower must find a method of treatment 

 which will make the soil a better soil 

 from the standpoint of its physical qual- 

 ities. 



If the soil is too compact, which may 

 be the case if much clay is present, the 

 incorporation of natural manures will 



improve this physical defect. The 

 vegetable matter contained in nat- 

 ural manures has a tendency to separate 

 the fine particles, thus making the soil 

 more open and jjorous. Adding sand to 

 a soil which is too compact will serve in 

 a similar way. A number of other ma- 

 terials as substitutes for the natural 

 manures have been tested and some of 

 them, no doubt, are useful in this re- 

 spect, if the natural manures are not 

 available. Sphagnum moss and clover 

 hay cut to a degree of fineness have been 

 tried and, although on the whole less 

 valuable than the natural manures, these 

 and other similar substances have a de- 

 sirable effect on the physical structure 

 of soils. One of the best means to im- 

 prove soils physically is the method of 

 plowing under green crops. Any form 

 of crop may be used for this purpose, 

 the kind of crop depending largely upon 

 the habit of growth of the crop and also 

 tij)on the time most convenient for turn- 

 ing it under. The crop should be plowed 

 under while it is still in the green, suc- 

 culent stage. 



Manures and Substitutes. 



If the soil is too light and porous, as 

 is often the case with sandy soils, a 

 similar treatment will improve the soil 

 physically. The natural manures will 

 change a soil too porous to one more 

 compact and more retentive of moisture. 

 This is one of the important functions of 

 both the natural manures and the green 

 manures. Aside from their value in 

 furnishing plant food materials or in 

 aiding in the improvement of those al- 

 ready contained in the soil, their value 

 in making the soil better physically for 

 the growth of plants cannot bo too 

 greatly emphasized. The farmer is be- 

 ginning to appreciate this fact and the 

 ))ractice of growing the clovers and the 

 various types of beans and other forms 

 of plants and plowing them under is be- 

 coming more and more evident as we 

 travel through our state. This practice 

 improves the soil from the standpoint of 

 its nitrogen content, it is true, but I wish 

 to emphasize the fact that it also im- 

 proves its physical qualities. If general 

 farming requires this practice, the grow- 

 ing of crops by intensive culture under 

 glass requires it to a greater degree. 

 When we grow plants for cut flowers we 

 must get the maximum results from food 

 materials applied to the soil and we can 

 succeed in this only when the soil has 

 been properly prepared and the best at- 

 tention has been given to its physical 

 qualities. 



What Fertilizers and Why? 



The problem of what fertilizers to ap- 

 ply to our soils, in what form to apply 

 them, and when to a]i[>ly them also is 

 one which can be answered only in a 

 general way. However, we have some 

 facts and a good deal of data which 

 should serve as a guide in working out 

 this problem. 



I have emphasized a liberal use of the 

 natural manures and green manures to 

 improve the soil physically. These ma- 

 terials also improve the soil chemically; 

 that is, they supply chemical substances 

 which the plant requires as food mate- 

 (Contlnued on page Ml.) 



