S -~~~B E B , 1925 MONTHLY WEATHER REVIEW 387
Surface.
2. l'ooo m 3. m 4. m
when about 300 miles from San Francisco. He was promptly icked up. Commander Rodgers was less for-
tunate. h e n approachin the Hawaiian Islands, after some 1,800 miles of flight,%s gas supply gave out and he was compelled to land. Although the plane was in communication by radio with the patrol ship Arooostook until nearly the moment of her descent, efforts to locate her were unavailing. A11 surface craft which the Navy could assemble in those waters en aged in the search. Nine days later, at 4 p. m., Septem % er 10, after hope of effecting a rescue had been prncticall abandoned, the
$-4, 15 miles east of the island of Kauai. During the interim between the time of the plane's disappearance and her discovery various theories were advanced to account for the failure to locate her. It was naturally assumed that she had foundered, and attem ts were made to attribute the catastrophe to the
at the time she went down. In many cases newspaper accounts exploited this possibilit with the tone of
sea, and sank immediate1 . In fact, this im ression
Bureau issued to the press statements testifying to the nonexistence of abnormal weather conditions during the time the plane was in fli ht and for several da s after she came down. tion was based are reproduced in Figure 2 to show the wind, weather, and ressure situation over the Pacific
- the one hundred and seventieth meridian, west longi-
tude. They include the period from the morning of August 31 t.0 the evening of September 1, the entire interval of flight. They me practically replicas, on small scale, so far as the situation at sea is concerned, of the optic charts for that period prepared in the Snn xncisco office of the Weather Bureau, on the basis of
radiogra hic weather reports from ships in the North Pacific &em, the observations being macle at 7 a. m.
. m., seventy-fifth meridian time. These observa- tions and 'B o not, it will be observed, imply the exist,ence of abnormal weather conditions in the area of the Hawaiian Islands at any time during the eriod. .
wind direction and state of weather. An unfilled circle indicates clear weather at the time of observation, a half- filled circle partly cloudy weather, and a filled circle
lane and all her crew were picked up %I y the submarine
preva P ence of foul weather in the vicinity of the islands
assurance, assuming that she was l? uffeted by wind and
seemed to become so widey 9 current that the #?eather
The weat a er charts on which t 3: is conten-
Ocean between the 3 acific coast of North America and
The symbols employed are t % e usual ones to indicate
NE 10 NE I6 13 la NE NE NE 12
cloudy wea.ther. Arrows fly in the direction in which the wind is reported as blowing. The velocit of the wind
weather is understood to be calm. While the concluding chart of the series, that for the evening of September 1, indicates a moderate depression some distance off the southern California coaat, conditions everywhere west of longitude 145' are of t-he type that might be espected to prevail there over the great.er part of the summer. Cloudiness is neither extensive nor of an unusual character, while winds as regards both direc-
tion and force are normal. The evening report from the U. S. S. Langley on September 1 incorporaOed the following additional data, obtained from ilot balloon observations, exhibiting the
8s estimated b the observer is given in mi i? es per hour at the point of t i e arrow. Where no arrow is shown the
movement of t E e wind aloft:
I I I I
Altitude Wind
I
(feet)
I
direction
I mgrur 1
The Langley's position, in approximately latitude 26'
N., lon itude 146' W., while not close to the point at whit% Commander Rodgers was forced down, was nevertheless not so remote as to render free-air data inapplicable, and her observations serve to confirm the inferences drawn from surface data throughout the area
as to the nonexistence of any abnormal tendencies either local or widespread west of 'longitude 145'. I t is a leasure to record the cordiality of cooperation
in the transactions incident to the west coast- awaiian flight. The following letter to the official in charge at the San Francisco office of the Weather Bureau from Capt. Stanford E. Moses, United States Navy, com- mander, nircraft squadrons, Battle Fleet, who was desig- nated to act as project commander for the flight, bears significant testimony thereto:
I naiit to thank you and your assistants at the Weather Bureau for their kindness and splendid cooperation with US in connection with the west coast-Hawaiian seaplane flight. Your work was escellent and your long knowledge of weather conditions was of great help to us.
R
between t P ie Weather Bureau and the Navy De artment
A FURTHER STUDY OF THE RELATION BETWEEN COVER CROPS AND ORCHARD TEMPERATURES
By FLOYD D. YOUNG
[Weatber Bureau oflice, Los Angeles, Calif., September 28,leZSl
For a number of years many citrus growers in southern It was found that t.he air temperature wa.s depressed California have believed that t,he presence of a cover crop only 0.1' F. at R. height of 5 feet above the ground, and in an orchard lowers the tem erature several degrees on . 1.Ob E". at, a height of 10 inches above the ground, due to
a frost ni lit. As a result, t 1;1 e growing of winter cover the presence of a cover cro Since there usually is
crops cas feen abandoned in many citrus groves where Mtle fruit near the ground, t t e tempernture differences this practice is quite necessary to maintain the fertility found should hare little effect on the amount of damage
of the soil. Shortage of irrigation water prevents t.he to the fruit. 0bserT-a.tions made wit.h unsheltered thermometers, at
Pomona during the winter of 1921-22, to determine just t.1ia.t t,he minimum teiiipera.ture as lowered 0.4' F. at what influence a cover crop has on the temperature on the %-inch elevat.ion and 2.4' F. at the 7-inch elevation,
frosty nights. A complete report on this work was pub- due to t,he presence of the cow- crop. Temporary tem-
lished in the MONTHLY WEATHER REVIEW.' perature differences in the earlier part of the night as
great as S.7' F. at the 34-inch elevat.ion, and 11.0' F. at the 7-inch elevation, were observed. These large differences
summer cover crops in most districts. Burem carried on esperiniental york at heights of 24 inches and 7 inches, respectively, showed
1 Young, Floyd D.: Influence of Cover Crops on Orchard Temperatures. MONTELY WEATEEB REVIEW, October, l e 50 : 621-525.
388 MONTHLY WEATHER REVIEW SEPTEMBEB, 1925
were thought to be due to wind, which mixed the colder surface air strata with the warmer strata at slight1 higher
cultivated area, but not penetrating much below the tops of the cover crop plants because the cover crop acted as a windbreak on a small scale. During the entire period covered by the experiment the ground in the orchard was very damp, and often was wet and muddy. The area of the orchard used in the 1922 experiment was only
6 acres. It was thought that a larger area in cover crops mi ht lower the tem erature to a greater degree.
Claremont, Calif., was selected for the continuation of the ex eriment. The grove selected was almost ideally locate 1 for the test. It was practically level, with mature Navel and Valencia orange trees set 20 feet apart, on the square. The cover crop consisted of purple vetch, lanted 40 pounds to the acre, a heavy volunteer crop of f h a d Windsor horse beans, and many high weeds. The soil was a rich black loam. The rove was kept well irri-
!?he entire grove was in cover crop when the experiment was begun. The rainfall during the winter was unusually light, and the ound in the orchard was dry during t,he
irri ations. h e same lan of operation was followed in this experi-
divided into two 5-acre plots designated as “east” and “west” plot, respective1 , and temperature st,ations were
The instrumental equipment and exposure of inst.ru- ments were the same a t both stations. (Fig. 1.) $.Fruit- region instrument shelters, containing masimum and mini- mum thermometers, and 29-hour thermographs were in- stalled on supports so that t,he thermometers were 5 feet
above the ground. Fruit-region shelters, containing the same instrumental equipment, were set directly on the ground, the thermometers being 10 inches abore the ground. After the st.ations had been established 10 clear, frosty nights were allowed to pass with the entire grore still in cover crop, in order to establish a definite temperature relation between the two plots. The minimum tempera- tures registered in both plots on these ni lite are given in Table 1. Temperatures averaged 0.1’ i! . lower at, t,he 5-fOOt elevation and 0.2’ F. lower at the 10-inch elevation in the west plot than in the east lot during this period. East plot cover crop removed- 8 n January 4, 1024. the cover crop in the east plot was plowed ~n d e r .~ and the ground was cultivated so thoroughly that hardly a trace of the cover-crop plants remained on the surface of the ground. (See fig. 2.) The cover cro in the west plot was not disturbed. It the cover crop P iad been exerting a marked influence on the temperature. the east plot, now clean cultivated, should be considerably warmer than the west lot, still in cover crop.
temperature records were obtained covering 24 frosty nights. Minimum temperatures recorded at t.he two elevations in both plots each night during this period are shown in Table 3.
It will be noted that the average difference in minimum temperature between the two p1ot.s is only 0.6O at the 5-foot elevation and 1.5’ a.t t,he 10-inch elent,ion. Com- paring these differences with t,lie average diff ercnces
levels, the effect reaching down t.0 the ground in t K e clean
buring the fall o B 1923, a 10-acre orange grove mar
ated, and the cover crop ma % e a luxuriant growth.
greater part o F the time, except immediately following
ment as in t K e former one at Pomona. The grove was
placed near the center o s each.
After t E e cover crop in the east plot was removed
. I The wrlter wishes to express his appreciation for the action of the Ontario-Cucnmonga Fruit Exchange and the Pomona Valley Orchard Protection Amclotion In paying the
erpenae of plow& under the cover crop in the &acre plot durlng the 1823-24 experiment.
between the two plots before the cover cro was removed
lowered the minimum temperature 0.5’ at the &foot elevation and 1.3’ at the 10-inch elevation. We might assume from these fi ures that the temperature was
On a night when the temperature barely falls to the dan er oint in a clean cultivated grove this difference
fruit in the lower portion of the trees in an orchard with
a cover crop.
from the east plot, it will be seen that t R e cover crop
lowered about 1’ at a a eight of 3 feet above the ground.
of 1 B P might account for considerably more damage to
P Y. A. N. NOON 2 4 6 8 IO MOT. 2 4 6 8 IO NOON
FIG. %.-Average semihourlv temueratures durinn einht clear. frostv ninhts. at east and west e x ~p e r i m ~~~~~p l o t s ~~w h .~~~t .h e grove w-8s st ,]., ~~ih~~co~~er-c~r~op~, -~s .~~~ thermometers. 5 feet above the ground.) Thls B y e shows the normi relation between the temperature in the two plots, and Is to e used 8s a check for Figure 4
In order to have a complete record of the influence of the cover crop on the temperature throughout the day and night semihourly teinperatures for the whole 24
hours on each of the 19 days on which frost occurred after the cover crop was removed from the east plot
FIG. 4.-A~erace semihourlv temnerarures durinn 19 clear. frostv ninhts. ax east ma west erperim~ptnl lots, a&r tiiico6rcropin~he &stplot ash be&-pl&w&unde~ The west lot IS s t i l i ” cover crop. (Sheltered thermometers, 5 feet above the ground.) A comparyson between Figures 3 and 4 shows the eEect of the cover crop on the tem- perature at this elevatlon
were averaged and plotted. The same data were secured for 8 days while both plots were in cover crop, to show the normal relation between the daily march in tempera- ture at the two stations. As 29-hour thermographs were used, and the records mere checked frequently on cold nights, both as to time and temperature, it was possible
FIQ. 1.-M x ri owin instrument @elters and grow f covf band of ~9ve.r cr( tE, olody sirnilat to t b t on the west t lo vie nted]
A#
,.
4-
.1 ..
,.-.
FIQ. %-East experimental plot after removal of cover crop
S-ER, 1925 MONTHLY WEATHER REVIEW 389
to calculate these semihourly temperatures to tenths of a de ee with considerable accuracy. T E average semihourly temperat;ures for the 5-foot shelters a t the east and west stations during the period while the entire grove was still in cover crop are shown in Fi ure 3. The same dat,a for the period after the cover crppghad been removed from the east plot are shown in Figure 4. These dia ams show that the temperature
out the period from 6 p. m. to 10 a. m.
was lowered about 0.5 F F. a t the 5-foot elevation through-
FIG. 5.-Average aemlhourly temperatures durlng elght clear, frosty nights, at east and west experlmsntal plots, whlle the entire grove wa8 still la cover crop. (Sheltered thennometers 10 Inchas above the ground.) Thls figure shows the normal relation between the hperature in the two plots. This diagram Is to be used 38 a check for Figure 6
The effect of the cover crop was considerabl greater at the 10-inch elevation. A comparison of &gums 5
and 6, which show the difference in temperature at tliis elevation before and after the cover crop was removed
FIG. &-Average semihourly temperatures durlng 19 clear frosty nlghts, at east rind west erperlmental plots after the cover mo In the east p i t had been removed. The west plot Is still In cove;crop. (Sheltered t~ermomettrs, 10 inches above the ground.) A comparison between Figures 5 and 6 shows the effect oGthe cover crop on the tem- perature at this elevation
from the east plot, brings out this point. Figure 6
shows that the temperature in the cover-cro plot was
night.”c The fall in temperature during the evenine was earlier’and the morning rise in temperature wm dePayed
lower than in the clean cultivated plot bot 1 day and
in the cover-crop plot. During the period from 6 p. m. to S a. m. the temperature in the cover-crop plot wm de- pressed from 1’ to 2‘. During the period from 8 a. m. to 11 a. m., while the temperature was rising rapidly, the lag in the rise in temperature in the cover-crop plot was sometimes as much as 4’.
FIG. 7.-cOITWtd thermograms for night of January S 2 4 , 1924 from 5-foot elevatkm sheltered thermometers in east plot (clean cultlvation) and was\ plot (in cover crop) showing effect of the cover mop on the temperature. See Flgure 3 for normal relation between temperature ~n the two plots
In Fi re 7 are shown corrected thermograms for the
33-34, 1924, the coldest night which occurred after the A com-
cover crop on the temperature at the 5-foot level on this night.
east an r west &foot stations for the night of January
parison coTer o Figure 7 with Figure 3 shows the effect of the was removed from the east plot.
P. M. A. M. 8 9 10 I I M D T .1 2 3 4 5 6 7 0 0
4 2’
360
30.
280
FIG. 8.-CorrecM thermogram for night of January 23-24. 1924. from lOlnch elevatlon sheltered thermometers in east plot (clean cultlvatlon) and wast plot (In cover cro J
showing effect of the cover crop on the temperature. See Flgure 5 lor normal rela& between the temueratures in the two plots. From the character of the record It I# evidcnt that the lower temperature In the cover crop area during the enrller art of the
night is due to the greater mixing effect of the wicd In the clean cultivateaplot
Corrected thermograms for the same night, Januaiy
23-24, at tlie 10-inch elevation in both the east and west plots, are shown in R,me S. They should be compared with Figure 5, which shows the normal relation between the two plots while both were still in cover crop. Note tlie greater fluctuations in temperature in Figure 7 as
coiiipared with Figure 8, due to the mixing of the air
390 MONTHLY WEATHER REVIEW SEPTEMBER, 19%
strata of different temperatures b light winds at the
vation. The records for this night, both at the 5-foot and the 10-inch elevation, show an unusually large dif- ference in temperature between the plot in cover crop and that in clean cultivation during the early part of the ni ht. Bt the 10-inch elevation there was more
at times. It is believed that these temporary differences in tem- perature were due to a light wind in the orchard, which affected the temperature to a greater estent in the clean cultivated plot than in the plot in cover crop, owing to the windbreak effect of the cover crop. When the wind died out about 3 a.m. the temperature in the clean cul- tivated area fell rapidly until it came into aoreement with the temperature in the cover-crop area. ?he mini- mum temperatures in the two plots were y t i c a l l y the same. Fi ures 7 and S tend to confirm t e conclusions
temperature differences between oves in cover crop
due to the different effects of li ht winds. Obsmlions with unsheltercs thwmomrtws.-Unshel- tered minimum thermometers were esposed on posts, at hei hts of 5 feet and 2 feet, respectively, above the
plots. Minimum temperatures registered by these thermometers durin 10 clear, frosty nights before the east plot was plom-ei, and during 24 clear, frosty nights afterward, are given in Table 3. The average depres- sion of the minimum temperature clue to the presence of the cover crop as shown by these unshelterecl tliermome- ters, was 0.5 at the 5-foot elevation and 1.1' at the 3-
foot elevation. Current temperature readings of the unshelt,ercd ther- mometers niade during colcl night.s, before and aft.er the cover crop in the east plot was plowed under, are shown in Table 4. During the 1932 experiment large temporary differences in ten1 erature between the cover crop and
of the night. It was believed these di erences were clue to light winds, which raised the temperature in the clean cultivated plot. No large teni erature clifferences of
it is believed, to the fact that the grove was well sheltered. Because of the fact that the winter of 1023-24 was unusually dry, moisture was seldom deposited on any of the esposed thermometers. During the progress of the first e,uperiment, in 1921-32, the lower exposed thermom- eters, especially in the cover-crop plot, were covered with water, ice, or frost on most clear nights.
5-foot elevation, which were not fe s t a t the 10-inch ele-
than 3 5 difference in temperature between the two plots
reached fo 5 lowing the 1938 experiment, that the large
and those clean cultivated, observe 8 by fruit growers, are
groun d at the stations in the east and west experimental
clean cultivated p f ots were noted durinz the earlier part
this kind wore noted during the P utest esperinient, clue,
ACTUAL DAMAGE RECORDS
Estimates made soon after a cold night, which indicate increased danittge to fruit in orchards with cover crops, often have not been borne out by the packing-house records when the fruit was picked. Soon after the cold weather of early January, 19'34, tho manager of a packing house, who was firmly convinced taliat cover crops greatly increased the frost damage, made a careful estimate of the amount of ditnilt ecl fruit ill his district.
in orchards containing corer crops. Howerer, later
He concluded that the damage P lad been much greater
examinations macle in the presence of the writer failed to confirm this belief. An unusually close esamination of the fruit from three adjoining orc.harcls, on almost level ground, was made at the time the fruit was icked, to determine the amount
Gove d o . 1 , clean cultivut.ion.-This grove contained the largest amount of frost-damaged fruit of the three gmves considered. When picking was begun in the dis- trict, this grove showed so large a percentage of damaged fruit, as indicated by t.he presence of hesperidin c.r stals, that picking had to be stopped, and was postpone B until near the end of the season, when much of the fruit had recovered. Grove No. S (ud.bining No. 1 on the .north), in vetch
Grove No. S (adjoil&1g No. R on the north.), in vetch
The grade records for the three groves are given below.
of frost in'ury. The fin& P record was as follows:
cover crop.--See t,a .b le below.
cover crop.-See table below.
Grove I 1 Choice 1 Culb
1-1-1--
Per ern; Per cent Pcr etnl
1.8 No.2 ________________________________________----------- I
79.41
ifi)
13
68 No.3 ................................... ------- --------- 80.7
NO. I _______________________________
~
___________________ 7a9
In this case the apparently increased amount of frost damage due to the presence of a cover crop in the grove
was not verified by the actual damage records.
CONCLUSIONS
The resu1t.s obtained from this experiment confirm in almost. every detail the conclusions drawn from the esperimentd work c.arried on during the winter of 1921-
28. Tho depression of t.he tempemture due to the pres- ence of the cover crop was somewhat greater in the latest esperinient,, but this was to be espe,ct,ecl, since the area in cover crops was larger. It is believed that the results obtained in the two esperinients, conducted in different orchards and during two frost seasons, are reasonably conclusive, since the agree closely. Cover crops do increase the frost hasar8 but only to a slight extent. In many cases the increased dama e in resence of a cover crop is probably due to the fact t t R at t e grove is on lower ground, where the tem- perature is naturally lower. In other cases the increase may be accounted Tor by the small temperature differ- ences which have been found in the experimental work. Actual differences in the amount of damage between clean cultivated groves and those in cover crops, which can not be esplained by the differences in temperature found in the two ex erinients, must be attributed to some other influence t I! an temperature, such as decreased vi or of the tree, due to com etition from the cover crop,
frequent irrigations, or increased deposit of moisture on the fruit and foliage from dew or frost, when a cover crop
is resent in the orchard. R'roni a study-of all the experimental data it appears that the difference in temperature between a clean j
cultivated citrus grove and one in cover crop, especially i
during the earlier part of the night, is largely due to the 1
a 7 ess dormant condition o P the trees caused by more
SEPTEMBER, 1923
Dee. 18 _________________ Dec.20 _________________ Dec. 21 _________________ Dw.22 _________________ Dar.23 _________________ Dec. 25 _________________ Dee. 31 _________________ Jan. 1 ___________________ Jan. 2 ___________________ Jan. 3 ___________________
Average __________
MONTHLY WEATHER kXVIl3W
33.9 2s9
28. 1 l6.0 30.7 3 2 9 27.9 28.8 21.0 25.4
28.6
391
33.1 28.7 2 9 3 27.6 29.7 31.1 28.0 28.8 21.0 25.0
28.1
TABLE 3.-Mininium temperatures on frosty nights (unshsltersd t herniometers)
ENTIRE QROVE STILL I N COVER CROP
33.8 29.7 27.9 28.8
29.7 32.0 28.9
29.5 220
zi.7
28.8 --
cover crop acting as a windbreak, allowing the cold air to accumulate near. the ground, and preventing it from mixing with the warmer air above. The condition of the surface soil with regard to moisture content was radically different during the two seasons when the esperimental work with cover crops was in progress. During the winter of 1921-22 the ground was wet throughout the season, while it was unusually dry thou hout the 1923-24 season. The results obtained
wet or dry. shod % therefore be indicative of all seasons, whether
29.0
27.3 28.9 31.3
28.9 21.3 25.3
32.9 28.0
+.l -.8 +.9 +.6
+.l +.3 -.l
+.l 0
Jan. 4 ___________________ Jan. 5 ___________________ Jan. 6 ___________________ Jan. 7 ___________________ Jan. 8 _________________._ Jan. 9 ___________________ Jan. 10 __________________ Jan. 11 __________________ Jan. 12 __________________ Jan. 13 __________________ Jan. 14 __________________ Jan. 15 __________________ Jan. 16 __________________ Jan. 17 __________________ Jan. 18 __________________ Jan. 19 __________________ Jan. 20 __________________ Jan. 21 __________________ Jan. 22 __________________ Jan. I __________________ Jan.24 __________________ Jan. 25 __________________ Jan. 26 __________________ Jm.27 __________________
32.5 31.1 30.0 33.5 3 .9
29.7 33.3 31.8 31.2 28.3 31.1 3 2 0 29.8 30.0 28.7 28.4 29.8 25.1
30.4 29.7 26.0 25.8 32.1 34.1
a-
East plot
31.0 30. 6 29.7 29.0 29.7 31. 1
30.0 31.0 23.0
M 1
29.4
West plot
--
33.9 30. 5
29.0
!&9 20.7 31.0 2Y.7 30.2 2 2 7 25.9
29.2 --
33.0 31.3 31.2 29.7 30.2 2 9 6
33.0 30.8 29.3 28.7 30.3 29.7 33.4 31.7 32.2 30.0 32.3 30.3 29.0 27.3 31.4 30.3 32.1 29.9
30.3 2 a 9
30.3 29.0 29.3 29.0 29.2 28.5 29.9 27.9
30.9 2 8 4 30.1 29 0
29.1 26.4 -2 0
12.5
-1.1
-2.7
3 a ~ 34.9 33.0 3 2 9 atL0
2a.8
28.4
+ae +LO 4-1.0 4-1.6
+.6 +1.1
+.4
Dee. 20---
Dee. 2 L - Dec. 22 ... Dec.P ... Jan.l____ Jan.2 ____ Jan.2 ____
545 p. m ____ 39.3 3 9 4 8:4Op. m ____ 34.7 35.4 8:55 p. m ____ 34.0 34.0 3:Wa.m..-. 33.2 34.6
9:ZOp.m ____ 26.0 25.9 3:30a.m.l.- 22.9 24.3 930p.m ____ 28.9 28.8
26.2 29.9 32.0 34.7
30.8
i o ; -.2
29.3 I -1.5
28.8 I -1.1 30.1 1 9 3 2 9 I -1:s ---
Jan. 4 ___________________ Jan. 5 _______________-_-- Jan. 6 _____________---_-- Jan. 7 ___________________ Jan. 8 ___________________ Jan.9 ___________________ Jan. 10 __________________ Jan. 11 __________________ Jan. 12 __________________ Jan. 13 __________________ Jan. 14 __________________ Jan. 15 _________________- IS~. 16 __________________ Jan. 17 __________________ Jan. IS ________________-- Jan. 19 ________________-- Jan. 20 ________________-- Jan. 21 ________________-- Jan. 22 __________________ Jan. 23 __________________ Jan. 24 ________________-_ Jan. 25 ________________-- Jan. 26 __________________ Jan. 27 ________________--
'
-
29.5 30.1 33.9 3 2 8 32.3 27.9 32.4 33.7 29.5 31.0 29.7 9 .7 29.7 28.3
-.5 -.5 -.5 -.2 -.9
-1.6
+.I +.2 -1.5 0
0 -.3 -1.4 -1.5
I 5-1oot elevation I Moot elevation
Date
1 ;E
Differ- ence
+a 7 +l. 0
-. 4 +I. 3 0
+. 9
+. 9
+. 7 +l. 0
+. 7 TABLE 1.-Minimum temperatures on frosty nights (sheltered thermometers)
ENTIRE GROVE STILL IN COVER CROP
+. 7
EAST PLOT CLEAN CULTIVATION; WEST PLOT I N COVER CROP -
-. 3 0
-. 5 -1. 1
+. 3
-. 6
-. 3
-. 3
-. 1 -1.1
+. 2 0
-. 9
+. 1
-. 3
-. 1 -1.0 -1.0 -1. 1
-. 3
+. 1
-. 6
-. 1 -1.3
320 30.4 29.1 81.9
a 5 29.5 32 4 30.9 30.9 27.2 30.9 31.3 a 9
29.4 28.4 28.1 27.9 X 9 28.9
29.1 25.3 18.4
32 6 ai. 13
IOlnch elevatlon I 5-1oot elevation -0.9
+. 2 -1.2
-. 8 0
-. 1
-. e -.K
-. 1 -1.0
+. 2
+. 1
-. 7
-. 3
+. 1
+. 1 -1.1 -1.1 -1.1
-. 2
+. 4 -3
-1.4 d
32.8 30. 2 30.3 32.7 28. 5 29.6 33.0 31.4 31.0 28. 2 30.7 31.2 29.6 29. 7 28.3 28.0 29.0 28. 0 30.0 29.3 24.9 28.7 31.6 34.0
82. 2 31.1 29.5 32 4 29.2 29.1 33.0 31.5 31. 1 27.2 31.3 32.0 28.9 30.1 28.4 28.3 28.8 27.1 29.3 29.4 25. 1
32.0
3 2 8
m. 2
Differ- enca Dlffer- ence
-a 2
.o -. 6
+. 3
+. 2
.o -. 2
+. 3
+. 3
-. 3
35.0 30.3 29.7 29. s 32. 2 31.0 29.3 30.4 228
m. 1
-0. 1
-. 1
-. 7 -. 1
.o -. 1
-. 3 -. 8
-. 3
-. 2
-. 2
35. 2,
34. o
30." 29.3 29.5 32 0
29.5 30. 1
22.6 26.4
-. 1
1 1155 a. m.. ground unfrozen under cover crop: frozen where ban?; frost in the shade;
2 10:20 a. m.,'ground unfrozen under cover crop, but frozen hard where barc: tender cover crop wet. cover crop plants badly wilted and lying on ground.
foliage on orange trees kllled. Frost still on ground and vegetation in the shade.
~~
Average.. ___ - __ __ I 30.3 I 29.9 -.4 I 30.0 I 29.6 I --.4
TABLE 4.--Current temperatures (icnsheltered thermornetera)
ENTIRE QROVE STILL IN COVER CROP TABLE 2.-Mininauna lenaperatures on frosty nights (sheltered thermometers)
&foot elevation %root elevation I EAST PLOT, CLEAN CULTIVATION; WEST PLOT IN COVER CROP
Date 1 Time
Differ- ence East 1 West plot plot
1 &foot elevatlon 1 lMnch elevation
I I-I- DiBer- enm +o. 1
+. 7 0 +l. 4
-. 1 +l. 4
-. 1
Dlffer-
plot
3 a 3 33.9 320 31.3 25.4 2 2 7 280
33.1
32.3 30.3 33.9
-0.8
-. 6
-. 7
-. 3
-1.7 -1.5 -1.6 -2 2 -.e
-. 6 -1.7 -2. 2 -2 0 -1.7
-1. 1
-2 2 -1.4
-1.2
-. 3
-_ 7
33.9 32.9 31.0 34.3 30.0 30.6 34.4 33.0 33.2 29.5 32 3 33.5 31.0 31.0 29.7 29.9 31. 1 29.7 31.7 30.8 26.0
29.8 33.1 35.9
EAST PLOT CLEAN CULTIVATION; WEST PLOT IN COVER CROP
g:z p. m..j 10:42 D. me-- 37.7 37.9 40.0 36. 1
37.0 37.9 38.0 35.8 35.0 36.7 35.0 34.9 29.6
29.6
3a I
85. 8
35.6 37.9 37. 5 36.6
36.0 37.3 38.0 36.7 35.9 34.8 36.2
54. 2 36.0 31.0 35.0 X 8
-2 8
-. 1
-a 0 -1.3 -2 1
-. 2
+. 1 -1.4
-. 4
-. 5
-. 5
-. 9
+. 5
+. 0
-. 6
-. 6
34.7 37.0 37.4 34.3 35.1 36.3 37.3 35.9 35.0 34.0
35.6 33.7 35.0 29.9 34.9 28.7
37.0 37.1 39.4 35.6 37.2 36.5 37. a 37.3 35.4 34.5 36.1 34.6 34.5 29. 0
35.5 29.3
-2 1 0 -2. 5
+. 5 -2. 1
+. 3
+. 1 -1.3
+. 1 -.a -. 5
-. 8 +l. 1 +l. 4
-. 8
-. 8
Jan. JSn. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan.
JSn.
i0:15 p. m--- 1135 p. m--- 12:05 a. m- __ 1:05 a. m--- 200a.m-..
4:00 a. m--- 5:ma.m ... 6:OO a. m--- 8:45 p. m--- 1O:OO p. m... 11:25 p. me-- 6ma.m..- 9:05 p. m--- 540 a. m. __
30.7 26.0
29.0 33.4 33.3
-. 1 0
-. 2
+. 3 -2 6
~~~~ ~
1 Vegetatlon on ground frozen stil?. All plants wilted; some brittle. No fmt on thermometers. Ground not from under cover crop, but frozen hard where bare. Average __________ I 31.6 31.0 I -.6