VOL. LXXVII. 
Puhlislied Weekly at 303 W. 30th St.. 
New York. I’lice One Dollar a Year. 
NEW YORK. JULY 27. lOlS. 
Entered as Second Class Matter at New York 
under the Act of Congress. March 3, 1870. 
No. 4492. 
Soil Temperatures and Crop Production 
Part I. 
NE(}LKCTEr) FACTOR.—Tt is mther strange 
that in all the extensive investigations of the 
nnmerous experiment stations, 
and all the various discussions 
of farm practice in the agri¬ 
cultural press, the effect of 
high temperatures of soil on 
crop production lias never 
been seriously investigatetl or 
considered. If there has been 
such investigation or di.scu.s- 
siou it has e.scaped my atten¬ 
tion. After residing for nearly 
10 years in the extreme south¬ 
ern part of Florid;!, interested 
in growing various truck 
crops, and .iu.st as much in¬ 
terested in noting the be¬ 
havior of oats, wheat, grasses 
and other plants native to 
more temperate zones, tliat 
occasionally spring as volun¬ 
teers from seeds carried in 
manure or otherwise. I am 
convinced that this is one of 
the most important I'iniiting 
factors in crop jiroduction 
both North and South. 
TEMPERATT^RES COM¬ 
PARED.—To simplify the dis- 
cu.ssion at this point, let us 
compare the maximum and 
minimum aerial, and also the 
deep subsoil temperatures of 
the two [loints of the country 
I am intimately acquainted 
with, namely. Southeastern 
Pennsylv.inia and Southea-st- 
ern Florida : 
Average Average Temp, of 
Temp. Teiii[>. Wei! W.-iter 
for .T.'in’y for .Tiily Year Uoimd 
Penn. .“>(> 7f! 50 
Fla.. 00 81 75 
The outstanding fact I wisli 
to call special attention to 
here is tlie slight difference in 
average Summer temperature, 
only six degrees, and the wide 
difference in deep subsoil 
temperature as shown by well 
water. 25 degrees. The maxi¬ 
mum Summer tempera¬ 
tures in Penn.sylvani:i are 
100 degrees or more; in Soutli- 
eastern Fhnida never in ex¬ 
cess of 95. though for .some 
weeks 90 degrees or more is 
reached for a few hours al¬ 
most evei\v day. Now we are 
in a position to note what 
influence tliese various phases 
of temperature have on tem¬ 
perature zone crops. 
EXPERIMENTING WITH 
VEGETABLES.—Arriving in 
I’lorida I studied Summer temperatures tliorou.ghly 
and finding them .so .slightly different from what I 
had lieen accustomed to. and. especially, as I found 
tlie maximum temperature less severe than in Penu- 
.sylvania, I concluded there was necessarily some 
mist:ike in the local information that the ordinary 
garden vegetables could not be grown successfully 
here in the Summer. So I planted a mixed g.arden 
with special care, including most of the common 
vegetables. They made a fair start during .Vpril and 
May; but as Summer came on. they gradually just 
lost interest in life and disappeifred. Duly the 
tropicals, eggplant, peppers, okra and sweet potatoes 
survived, and of these eggplant and peppers were not 
at their best. The “I-told-you-so” had his inning, 
but I keiit constant watch for every hint of a solu¬ 
tion of the prolilem utffil I was thor.nighly convinced 
that it is not the aerial portion of the plant, but the 
root .system that .suffered chiefly from sub-tropical 
conditions in Summer. The prohaliility of this asser¬ 
tion can perhaps he best appreciated in this wa 3 '’: 
To one lying on the ground, in the shade, on a hot 
da.v in midsummer, in the 
North, the ground will pres- 
entl.v feel uncomfortably cool; 
only a few feet beneath the 
temperature is 50 degree.s. 
while to one lying on the 
ground in similar situation 
and time in South Florida 
thei*e would he little or no dis- 
comfoit. The temperature 
beneath is 75 degrees. 
THE MARGIN OF COOL¬ 
NESS.—^^That margin of cool¬ 
ness of soil in Summertime 
North appears to i>e essential 
for the health.v development of 
the root .system of plants na¬ 
tive to tenqierate regions. \'a- 
rious observations point to this 
theory as correct. Thus in gen¬ 
eral it is difficult under most 
conditions to get a seed bed, 
sa.v of tomatoes, to start here 
in an.vthing like healthy con¬ 
dition before September 1. and 
careful watering, which in¬ 
sures cooling by evaporation, 
is invariably helpful. Gar¬ 
deners in the North are fa¬ 
miliar with the fact tiiat to¬ 
mato seeds will lie dormant 
in the .soil through Winter, 
and germinate as the soil be¬ 
comes warm in the Spring, 
but it limy seem odd that 
tomato seeds here will lie dor¬ 
mant during the warm Sum¬ 
mer months, and germinate 
when the soil becomes cool in 
the Fall, though most gar¬ 
deners of experience will re¬ 
call difficulties with cabba.ge, 
lettuce, and possibly some 
other -seeds sown in midsum¬ 
mer. even in the North. I 
have never seen oats thrive 
here in midsummer except a 
few' chance plants in the t)or- 
ders of our white rock roads 
where the white surface ra¬ 
diates the sun's heat and re¬ 
mains cool, though oats ;ire a 
common volunteer during Win¬ 
ter in the truck fields. I Imve 
seen good plants of Timothy 
on these same white-rock road 
borders, hut nowhere else un¬ 
der any conditions. 
I)ETRIMENTAL T E M - 
RER.VTFRE.-These various 
observations force the conclu¬ 
sion that for most plants in¬ 
digenous to temperate zones, 
there is a point in soil temperature somewdiere be¬ 
tween 70 and 80 degrees, any rise beyond which is 
detrimental to the plant Also the evidence is rather 
clear that this dama,ge point varies with diff'erent 
.species of plants. Thus turnips, wdiicli start well in 
Summer in the North are among the first to start 
Tfarvesting Oats in 8t. Lawrence Co., N. Y. Fig. /t52. 
