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BULLETIN OF THE

es USDEPARTMENT OFAGRICULTURE

No. 188

Contribution from the Bureau of Plant Industry, Wm. A. Taylor, Chief. March 15, 1915.

THE IMPORTANCE OF THICK SEEDING IN THE PRODUCTION

OF MILO IN THE SAN ANTONIO REGION.'!

By Sreruen H. Hastinas, Farm Superintendent. INTRODUCTION.

One of the most important needs in the agriculture of the San Antonio region of Texas is a dependable grain crop. For a number of years, corn was generally looked upon as the best grain crop for the region, but it has not proved to be dependable. The small grains are even less satisfactory. Because of the difficulties and failures of local grain production, it has been necessary to import a large proportion of the grain needed for local consumption,

Experiments have been conducted for several years at the San Antonio Experiment Farm to determine whether or not the grain sorghums could be depended upon to increase the local supply, as well as to give some stability to local production. The two prin- cipal grain crops of the region are oats and corn. The average yields per acre of oats and corn from the rotation experiments for the past six years and of early-planted grain sorghum (milo) for the past four years at the San Antonio Experiment Farm are shown in Table I.

~Tasre I.—Average yields of oats, corn, and milo at the San Antonio Experiment Farny Jor the years 1909 to 1914, inclusive.

| Yield per acre (bushels) . | Yield per acre (bushels). | Year. | Year. | Oats. |} Corn. | Milo. Oats. | Corn. | Milo. | DUS et et es See COE eae tase PLotoe Nive rags aA 96.75 | 34.1] 40.0 | TO Ds ae eee 10. 70 SxOn ee ae ee WOVS ee eo Se aoe 8 11.70 34.9 | 47.7 3 LICE es Sao eee es ae 8.50 10.6 ONO LOUAES Sayers apne aoe 15.70 52.6} 43.2 ||

These figures indicate that, in the main, milo gives larger yields and is more dependable than either oats or corn. The average yield per acre of oats for the past four years, 1911 to 1914, was 15.7 bushels;

of corn, 33.1 bushels; while the average yield of milo for the same period was 40 bushels. The last three years have been unusually favorable for corn production and the yields were considerably

higher than may be expected, as the average yield for the past eight

1 The experiments were conducted in cooperation with the Office of Cereal Investigations.

76831°—Bull. 188—15——1

2 BULLETIN 188, U. S. DEPARTMENT OF AGRICULTURE.

years, 1907 to 1914, inclusive, was only 24.4 bushels per acre. It is during years when the rainfall is low that milo shows a marked — superiority over corn and oats, and it is probable that the figures given above do not do justice to milo. The results obtained at the experiment farm and by farmers who have given the crop a fair trial © indicate that grain sorghum can be made a highly satisfactory grain crop in the San Antonio region if the proper varieties are grown and the necessary cultural methods are followed.

CAUSES OF UNSATISFACTORY YIELDS. SORGHUM MIDGE AND THIN STANDS.

One of the chief difficulties encountered in the production of the | grain sorghums in the vicinity of San Antonio has been the sorghum midge. It has been found, however, that by using reasonably quick-maturing varieties and planting them early a good crop can be produced before the midge appears in sufficient numbers to do serious damage. This matter has already been made the subject of a publication.*

There are still numerous instances in which the yields have been low on certain farms. From the observations made on these farms, and also at the experiment farm, it appears that unsatisfactory yields are due, in many instances, to thin stands. Thin stands frequently result from thin seeding, which the farmers practice in the belief that with the low rainfall of the region thick seeding is not advisable. In this section thin stands permit excessive tillering or branching of the plants, and this results in delayed and nonuniform maturity. The thin stands and unsatisfactory maturity appear to be chiefly responsi- ble for the low yields.

The tillers and branches of sorghum plants flower and mature later than the main stalks. The successful production of sorghum in the midge-infested regions depends upon the crop getting past the flowering stage before the midge appears. Larliness is of prime im- portance. As is shown in the results obtained in 1913, there may be years when there will be no great increase in yield from thick seeding. This was due to the fact that even the late-flowering heads were mature before the midge appeared. On the other hand, when, because of unfavorable weather conditions or for other reasons, plant- ing is so delayed that the crop is in flower at about the time the midge appears, as was the case in 1914, uniform flowering is of prime importance if good yields are to be expected.

TILLERS AND BRANCHES.

Allsorghums, when widely spaced in the row, produce an abundance of tillers and less frequently branches under the same conditions.

‘Tillers are produced at or near the surface of the ground and appear

when the plant has reached a height of only a few inches, but their

1 Ball, C. R., and Hastings, S. H. Grain-sorghum production in the San Antonio region of Texas. U.S. Dept. of Agriculture, Bureau of Plant Industry Bulletin 237, 30 p., 1912. _

THICK SEEDING OF MILO IN THE SAN ANTONIO REGION. 3

appearance may be delayed until the plant is 18 inches or more in height. Tillers seldom appear after the stems of the plants have begun to develop, particularly if the plants are left close enough together to shield the lower parts from the light. The development of tillers is largely controlled by the distance aps rt of the plants and, to a lesser extent, by the soil and climatic conditions. Tillers have small heads and are later in maturing than the main stalk.

_ Branches indicate abnormal conditions and do not appear until the plant is well along in its growth. They occur only when the plants are spaced too far apart in the row or are supplied with an abundance of moisture. Every node above the ground except the terminal node “may produce branches. The heads of the branches are still smaller and later in maturing than those of the tillers.

_ Branching is even more objectionable than tillering, as the ripening ‘season is still further extended. Branches occur in abundance only

EXTENT OF SORGHUM-MIDGE DAMAGE DURING 1913 AND 1914.

The season of 1913 was very favorable for the production of grain ‘sorghum. Although the rainfall was about 2 inches below normal, the crop did not suffer severely from drought. The crop was well past the flowering stage before the sorghum midge appeared in suffi- cient numbers to do serious damage. Consequently, the insect had ‘very little, if any, effect on the yield, even of the later plantings. On the other hand, the season of 1914 was particularly unfavorable. ‘The spring was unusually wet and cool, and, owing to these conditions ‘at and after planting time, such poor stands were obtained that it was necessary to replant twice, which made the crop so late in coming to flower that there was a ier severe infestation of the midge in all the plats. This late flowering afforded an opportunity for determining the effect on the yield of suppressing the tillers and branches. Suppressing the tillers, and thereby causing the plant as a whole to flower more uniformly, was of little value as far as the sorghum midge ‘was concerned in 1913, but in 1914 the yields were extremely low on the plats where the plants tillered and branched freely. These low yields were due entirely to the fact that the heads of all the tillers and branches were sterile, owing to the ravages of the midge.

RESULTS OF THE EXPERIMENTS.

4 Experiments were conducted at the San Antonio Experiment Farm in 1913 and in 1914 to determine the effect of planting milo in tows at different distances apart and of thinning the plants to dif- ferent distances within the row on the qillenae branching, uni- formity, date of ripening, and yield of grain. These experiments are reported and discussed in this bulletin.

4 BULLETIN 188, U. S. DEPARTMENT OF AGRICULTURE.

EFFECT OF PLANTING ROWS AT DIFFERENT DISTANCES APART.

The different widths between rows were tested in one-fifth acre |

plats, the rows bemg 264 feet long. The plants within the rows } stood approximately 5 inches apart on all the plats, except where the stand was somewhat reduced by imperfect germination. The

average number of plants per row, of mature heads per row and per }

plant, and the yield per acre are given in Table IT. In this table,as well as in the following tables, the number of mature heads per plant and per row includes the main stalks and tillers, but not the branches, which when given are in another column.

TaBLE II.—Results of planting milo in rows at varying distances apart at the San Antonio Experiment Farm in 1913 and 1914.

In 1913: Per cent. Bushels. ~ BOUNCES Sa ee eee 350 | 879 y Je Ya pee en ek hy bere bd 42.9 AQHNICHES eee hate ee 405 899 2.2) | oc pe SEE ASE ee 45.8 Ad NGheS! 8 eee ee 339 959 258° \2 oo ee eee 45.3 ASW NICHES ceeee eee sees 459 15155 2.60 low. SE eee 46.2

In 1914: :

SHU NCDOS <a eee 478 508 1. 06 0. 22 4 25.3 SGN ches aay eee ee 439 472 1.07 .41 9 24.9 AD ANCHES# es ee ee 498 532 1.08 -45 9 23.6 A INCHES ee oes 529 552 1.04 64 9 18.6 48inCheS a -S2ec5 so Se | 504 542 1.08 } 50 7 16.1

As Table II shows, no very marked effects were produced on the number of heads per plant by varying the width between the rows. | The. differences in yield were small. The results of the 1914 tests were similar to those conducted in 1913, except that an extra plat was included, as shown in the table.

There was practically no difference in the number of heads per plant when the rows were spaced at different distances, nor was there © any consistent variation in the number of branches or pendent | heads, although there is a tendency for the number of branches to increase as the distance between the rows increases, as shown by — the 1914 results. The yields, however, uniformly increased as the distances between the rows decreased. This was-to be expected,

as the season was so favorable as to rainfall that even with the rows }

3 feet apart the plants did not suffer from the want of rain. This | table indicates that varying the distance between the rows does not © appreciably affect the tillering or branching. The distance between } rows will have to be governed by local conditions. Where the soil } is rich and the rainfall abundant, the rows may be much closer — together than they otherwise should be planted.

-

~

THICK SEEDING OF MILO IN THE SAN ANTONIO REGION. 5

_ EFFECT OF DIFFERENT SPACINGS WITHIN THE ROW.

In six plats on which milo was planted in rows 4 feet apart in 1913

the plants were thinned to 18, 12, 8, 5, and 2 inches, respectively,

within the row, one plat being left unthinned as a check. All the

plats were one-tenth of an acre in size except the one on which the plants were thinned to 5 inches; this plat contained one-fifth of an

acre. The results of this test are given in Table III. The ‘perfect stand”’ has been calculated as the number of plants which each row would have contained if the stand had been perfect. The actual stand stated was the average number of plants per row as estimated

by counting the plants in one representative row in each plat. The

number of heads was obtained by actual count, using the same rows

that were used in determining the stand.

TABLE II1.—Results of thinning milo plants to different distances within the rows, which were 4 feet apart and 264 feet long, at the San Antonio Experiment Farm in 1913 and 1914.

Stand (plants | Number of ma- | Average

Actual per row.) ture heads 1— aa Heads Rca Yield Perfect stand. sm | ipentanes Bends bein Be .Per- etaal Per Per | per ; Jants. | fect. | Tow. | | Plant. plant.? Pp In 1913: Inches. Per ct |\Bushels. 18 inches apart.....--- PA ber- 176 157 814 a AM VS eee, a Pn ap are |S ee 42.5 12 inches apart... ..--- 13.3 264 237 | 1,034 Td (al debt is ied [tosses ct ea eed | 42.1 8 inches apart......... 10.5 398 293 | 1,066 Fae Pe ei os 2 (Coa erage Me ge 43.8 S inches apart. ....---- (Er: 634 439 1,155 DO Ne eee eee oes eee (pe pe ke 46. 2 2 inches apart.. ean 3.8 | 1,584 833 | 1,209 Lede 3 ie ce se ee ee ae | ee 46. 4 Ni eRINneds (= 52 3 hE) il eee ee 895 1,169 DB. Reece oe ee La bs oe ee 46.4 In 1914: 24 inches apart......... 24.5 132 129 393 3. 04 | 3. 44 £9 4.8 12 18 inches apart........ LIT 176 179 445 2.48 | 3.31 45 5.1 3.6 12 ANCHES APAL be. 52 3=< == 12.7 264 254 375 1. 48 | 2. 64 32 5.5 6.6 8 inches apart.......... 9.8 398 324 398 1:23 2. 02 31 7 11.8 5 inches apart.......-- 6.3 634 504 541 1.07 | OL 7 5.9 16.1 2 inches apart...-.....-- 3.9 1,584 902 936 1. 04 | 41 5) 6.8 18.2 WNouphinned 0.2 ...:. 3) Ree aeuee 1,364 | 1,415 1. 04 | -Bil 6 (683 21.8

’ 1Jncludes tillers and main stalks. 2 Based on the counts from one row only. All other results are the average of four rows.

The most important fact shown in Table III is that the number of

| heads per plant decreased consistently as the spacing within the row

decreased. The average number of heads per plant in the 18-inch

spacing was 5.2, while in the 2-inch spacing it was only 1.5, a decrease

of 3.7 heads per plant. The yield, however, increased slightly as the plants were crowded within the row; that is, the thicker stands

produced the higher yields.

The results of the tests made in 1914 are essentially a duplicate of those in 1913, an extra plat being added in which the plants were thinned to 24 inches in the row. All the plats used in 1914 were

“one-twentieth of an acre in extent, except the one thinned to 5 inches between plants, which was one-tenth of an acre. Additional columns show the average number of branches, the percentage of

pendent heads, and the average height of the plants.

6 BULLETIN 188, U. S. DEPARTMENT OF AGRICULTURE.

In general, the results of the tests made in 1914 agree with those obtained the previous year. For instance, in the 5-inch planting the tillers per plant in 1913 averaged 2.6, whereas in 1914 the average was only 1.07, or less than in the un- thinned plat in 1913. This was un-

48. DISTANCE BETWEEN PLANTS -/NCHES EO 2 VK SOS 7 OE I BSS;

aa doubtedly due to the seasonal condi- tions. The weather during April and May, 1914, was unusually wet and \j : “1. . ag cloudy, during April especially so, a while in 1913 the conditions were N more nearly normal. Temperature 328 x 24 DISTANCES GETWEEN PLANTS — INCHES 324 ZEAL VIELE GSES tO OMS, 20 8 20 N J Ris 5

~ Ny

ANY

YIELD IN BUSHELS PER ACRE.

a

SS

Ny

Y

AVERAGE NP OF FILLERS ANDO SRANCHES PER PLANT 4 ‘

AVERAGE NUMBER OF TILLERS PER PLANT. WY

Fic. 2.—Diagram showing graphically the grain

Fic. 1.—Diagram showing graphically the yields of milo and the tillers and branches pro-

grain yields of milo and the tillers pro- duced in the 1914 experiments. The solid duced in the 1913 experiments. The solid columns denote the yield in bushels, while the columns indicate the yield in bushels, and tillers are represented by diagonally shaded the shaded columns represent the tillers. columns and the branches by dotted columns.

and sunlight, it appears, have a very marked effect on the number of tillers that are produced.

Another point brought out in the test of 1914, which was not notice- able the preceding year, was the branching of the- plants, which took place after the warm weather set in. Counts were made of all the different plats at the time of ripening, and the number of branches averaged as high as 3.44 where the plants were spaced 24 inches apart. From this the number of branches decreased uni- formly until there were only 0.31 per plant in the unthinned rows. It is probable that, as tillering did not take place until the plants vere well along in growth and as there was an abundance of moisture in the soil, the plants spaced to a greater distance than 5 inches offset this wide spacing by sending out branches.

THICK SEEDING OF MILO IN THE SAN ANTONIO REGION. 7

- That the wider spacing in the rows increased the number of pend-

ent heads is also brought out. The percentage of pendent heads increased from 0.6 per cent in the plat not thinned to 49 per cent in the plat where the plants were spaced to 24 inches apart.

It is evident that the yields from the plats in which the plants were spaced 12, 18, and 24 inches apart in the 1914 experiments were much lower than would be expected if the midge damage was uni- form in the heads of the main stalks. Observations made at the time the heads were maturing showed that the damage by this insect in the three plats mentioned was much more severe than on the plats where the plants were spaced less than 12 inches apart in the row. It should be understood that this does not refer to the tillers or branches, for in no case, even on the plats where the plants were closely spaced in the row, did over 5 per cent of theseed set. The four rows of the plat where the plants were spaced 12 inches apart were located beside the four rows of the plat thinned to 2 inches apart, so that they were as nearly as possible on an equal footing, and there was no apparent cause for a greater midge infestation in one than in the other. The date of flowering of the main stalks was practically the same in both cases.

The effect of varied spacing on the yield and the production of tillers and branches is shown graphically in figures 1 and 2.

EFFECT OF ROW WIDTH AND SPACING ON TILLERING AND HEAD PRODUCTION.

On May 15, 1913, counts were made of the number of stalks per row and per plant on the plats already discussed. These counts were made when the plants were about 18 inches high. At harvest time the number of heads per plant on the same plants counted May 15 wasdetermined. The results of these counts are given in Table IV.

TaBLte 1V.—Stalks and heads per row and per plant on May 15 and at harvest time on nine plats of milo planted at different widths and spaced differently at the San Antonio Experiment Farm in 1913.

| |

1 Not thinned.

§ BULLETIN 188, U. S. DEPARTMENT OF AGRICULTURE.

Table IV shows that there was a marked decrease in the number of stalks per plant where the plants were crowded. From the yields obtained on these plats, particularly those shown in Table II, it appears that this reduction of tillering is advantageous from the standpoint of crop returns. As shown in Table IV, a large number of the stalks found on May 15 failed to mature heads. The produc- tion of nonbearing stalks or tillers uses soil moisture without any | compensatory results. This being true, it seems desirable to reduce |

Fig. 3.—Close-spaced milo plants, showing almost total freedom from tillers and the resulting high uniformity. (Photographed June 4, 1913.)

the number of stalks per plant, and it appears that this can be readily done by crowding the plants within the row, as is shown in figures a4 0, and 6.

EFFECT OF SPACING ON MATURITY.

One of the most important requirements for the successful pro- duction of grain sorghum in the San Antonio region is early and uniform maturity. This is necessary, in order that the crop may escape the ravages of the sorghum midge.

THICK SEEDING OF MILO IN THE SAN ANTONIO REGION. 9

In the experiments conducted in 1913 a part of a row containing 50 plants was laid off on each of the six plats where the rows were 4 feet apart and where the spacing distances were varied. These plants were tagged and the date of maturity of each head was noted. Observations were made every two or three days during the ripen-

Fic. 4.—Milo plants thinned to 2 inches apart, showing the erect heads and the plants free from tillers and branches. Very little midge damage was done to the rows where the tillers and branches were suppressed by close spacing. (Photographed July 15, 1914.) ; i

ing season, The results of these observations are given in Table V. The number of heads per plant of the 50 plants observed in each plat in this distance, as shown in the third column, is shghtly different

76831°—Bull. 188—15

a} 4

LO ‘BULLETIN 188, U. S..DEPARTMENT OF AGRICULTURE.

in some cases from the estimate made to represent the entire plat, as shown in Table IIT, but the general relationship between the spacing of the plants and the number of heads per plant remains unchanged.

Fic. 5.—Wide-spaced milo plants, showing excessive tillering and lack of uniformity in heading and ripening. The seed is set on the main stalk, while on some of the tillers the heads are just beginning to flower and on others the heads are just emerging from the boot. (Photographed June 4, 1913.)

Taste V.—Heads of milo matured on different dates in six plats, where the plants were spaced differently, the percentages being based on actual counts of 50 plants in each plat, at the San Antonio Experiment Farm in 1913.

Number of heads— Percentages of mature heads. Spacing. June. July. ee a Per plant. ees ayy tae ei ee TERRES IT a pats PAL AN PL ea ress RIN Wh 5 8 : Abie cee ess) | z 2 aaa te : Plats considered separately: INotsthinn ed aes oe eee. 63 ed, 62 75 7 88 | . 89 Dol eLOOn eee ZANCHeS aApan eas ss ae 78 15S 60 79 91 91 92 95 98 100 MINCHES ADA ieee seins sae 177 oa 11 31 46 60 65 7 92 100 Sinchesiapantes-o 2 seo 174 3.5 14 34 46 54 65 82 94 100 i2inches'apart2-—- 22.222 52- | 234 | 4.6 19 43 59 68 82 95 99 100 TSanchesapariie: oes sees | 231 4.6 13 43 53 67 83 97 99 106 Plats averaged in pairs: | Not thinned and 2 inches | | | ADAT Ue een eens = eae 70 1.3 61 77 89 89 | 90 95 99 100 5 and 8inches apart .....-.--- 175 3.5 12 32 46 57 65 80 93 100 12 and 18inches apart........ 231 4.6 16 43 56 67 | . 82 96 99 100

Hi ‘ ' ; 4 : i 7

THICK SEEDING OF MILO IN THE SAN ANTONIO REGION. ju!

As shown in Table V, about 60 per cent of the heads on the close- spaced plants (unthinned and 2-inch spacing) ripened before June 21, and five days later practically 90 per cent of the heads on these plants were ripe. The ripening period, therefore, was approximately one week. On the other hand, only 11 to 19 per cent of the heads on the wider spaced plants (the spacings varying from 5 to 18 inches) ripened

Fic. 6.—Milo plants, spaced 24 inches apart, showing that when thus widely spaced practically all of the plants had one or more tillers and all branched freely. (Photographed July 15, 1914.)

before June 21, and on June 26, when about 90 per cent of the heads on the close-spaced plants were ripe, only about 53 per cent of the heads on the wider spaced plants had ripened. The ripening period of the heads on the wider spaced plants was about two weeks, or twice as long as that of the heads on the close-spaced plants. The earlier and shorter ripening period is a distinct advantage, particu-

larly in allowing the crop to escape midge injury. It is evident,

therefore, that in this connection, as well as in regard to crop yield, the thicker stands produced the best results.

12 BULLETIN 188, U. S. DEPARTMENT OF AGRICULTURE.

A special point in connection with the maturing. period of the differently spaced plants is that the plants in the six spacings fall. into three distinct classes, based on time of maturity. In order to show this clearly, the lower part of Table V was compiled from the data in the upper part of the same table. The. unthinned plants and those spaced to 2 inches are considered together as.one class, those spaced to 5 inches and those spaced to 8 inches are considered as a second class, and the plants spaced to 12 and 18 inches are con- sidered as a third class. The figures given are the averages of two spacings in each instance. . ;

As already pointed out, the heads on the close-spaced plants ripened earlier than those on the plants spaced to 5 or more inches, but the table shows that the earliness was not proportionate to the closeness of spacing throughout the six plats. The unthinned plants and those spaced to 2 inches matured their seed at practically the same time; the widest spaced plants, 12 and 18 inches, came next in time of maturity; and the plants in the intermediate spacings, 5 and 8 inches, ripened last. This was probably due to the relative favorableness to tillermg and to head production by the tillers result- ing from the different spacings. The close-spaced plants. produced very few tillers and the heads on the main stalks grew up and ripened promptly and uniformly; the widest spaced plants had the best conditions for tillering and the heads on the tillers had a fairly good opportunity to develop; but the plants spaced to intermediate dis- tances, while producing a relatively large number of tillers, were sufficiently crowded to make it difficult for the heads on the tillers to reach maturity.

While the widest spaced plants matured earlier than those spaced to intermediate distances, and in this respect produced more favor- able results, it is likely that the stumps left after harvest would be larger on the widest spaced plants, and this would be a serious objection, as is pointed out later. Considering the entire series, the results obtained with the closest spacing show that thicker seeding is much to be preferred.

In the results obtained in the 1914 test, as is indicated in Table III, giving the yields, none of the tillers or branches produced seed. There was a rather severe infestation of the field with midges at the time the first heads (main stalks) were in flower, so that when the later heads (branches and tillers) flowered, the field was so pee infested that the heads were practically stelle:

As is shown in Table III, close spacing resulted in only a sliot increase in the number of erailles per row over the number produced by wide spacing, up to 12 inches. Table VI, a comparison of the 1913 results of the 12-inch spacing and of the rows in which the plants were not thinned, shows this condition.

esas 8 g

THICK SEEDING OF MILO IN THE SAN ANTONIO REGION. 13

Taste VI.-—Plants and heads of milo in rows differently spaced at the San Antonw Experiment Farm in 1918.

Number per row. Spacing. Plants. Heads. OO) ULV CO ee ee ee ae SRSA Roe SEE - Senate 895 1, 169 U0 LETRTV ES EDYU EEE See ee eS Io ee Lost boo oe dé ndudumene daeseBOSsCae 237 1,034 Differences. ose ei. ee ek eT Biel S 658 | 135

Table VI shows that while the number of plants per row in the unthinned rows exceeded by 658 that of the rows in which the plants were 12 inches apart, the number of heads per row differed by only

135. This difference

in the number of heads per row is seen to be very slight when it is considered that the rows were 264 feet long. Consequently, when seeds are so placed as to have the plants 6, 8, or 12 inches apart in the row, with the idea Fic. 7.—Diagram showing the appearance of milo plants when

: 3 spaced closely together. that less moisture will 1

be required to mature the crop, the rower may actually obtain as many heads per row as would result from thicker seeding, and he

may find that the moisture requirement has not been reduced at.

all. Furthermore, the

¢ | thin seeding, by pro-

is atin

| moting tillering,

| b Al le would delay matu- a a : t | rity.

Ta) Figures 7, 8, and 9

illustrate this. These

diagrams were made

up from Table IIT.

Fic. 8.—Diagram showing the appearance of milo plants when spaced Figure 7 shows the 12 inches apart: a@ and g, Tillers; d and j, main stalks; 6, c, e,f, h, spacing of the plants and 7, branches. io ae plat wos thinned. Figure 8 shows the spacing of the plants and the tillers: and branches in the plat thinned to 12 inches. Figure 9 is made up from figure 8; that is, it shows how the row would appear if the tillers and branches were removed and placed. between the main stalks, and it should be compared with figure 7. It will be seen that im reality there are nearly as many stalks per row in the 12-inch plant-

14 BULLETIN 188, U. S. DEPARTMENT OF AGRICULTURE.

ing as in the plat not thinned. The actual counts show that the || plants in the unthinned plat average 2.3 inches apart. Assuming | that the tillers and branches were plants in the plat thinned to 12 inches, the plants would then average 3 inches apart, or only 0.7 of an inch farther apart than the plants in the unthinned plat. | The rainfall at the San Antonio Experiment Farm from the plant- ing time to the ripening period of the milo in the 1913 experiments was about 2 inches

below normal. This

condition was partic- JS

d ularly favorable for

a Mt comparing the results | alae i obtained from differ- Alt || I | ent plant spacings. é | | | | These results, togeth-

er with numerous ob-

Fic. 9.—Diagram made up from figure 8, showing the branches and servations made in

Se getored oud phot iatran thentionants mde. Mes) prawioua, gene Aa at the experiment | farm and on other farms in the region, indicate that relatively close. | spacing within the row is preferable to wide spacing, even when the rainfall of the growing season is relatively low. The results of the experiments indicate that the plants should be approximately 3

or 4 inches apart within the row. VARIATIONS IN TILLERING.

There is a marked difference in the amount of tillering in the two years that the test has been carried on. (See figs. 1 and 2.) For the purpose of comparison, Table VII has been included.

TaBLeE VII.—Tillering of milo plants differently spaced in rows 264 feet long at the San Antonio Experiment Farm in 1913 and 1914.

| Number per plant.

| Actual spacing | Stand (plants |————

(inches). per row). Perfect stand. | Mature heads. Branches. rane 1913 1914 1913 1914 1913 1914 1913 1914 1913 4914 24 inches apart...... meen DA BAe eee 201/222 eee 304: |; a ie a ss 5. 48 18 inches apart... -- } 20.2 id, 157 179 ae 2 AG een oe See: 4.2 4.79 i2inches apart...... = 1688: Pei 237 254 4.3 ye Fats |e rie, aa 2.64 |: 3433 aoe 8 inches apart......- 10.5 9.8 293 324 3.6 2 Sile eee 2.02 250 2.29 5inches apart....-.-- dee 6.3 439 504 2.6 LOT |Seteee SOL 1.6 58 2inches apart....... | 3.8 ae. 833 902 eS T04e ct ose: -41 AO) 45 Noithinnedes=2- S20 Zee 895 1, 364 123) el OF eee -ol 3) -39

|

The most striking difference in the 1913 and 1914 results is in the reduction of the number of tillers in 1914 and the appearance of branches, which did not occur the previous year. However, in the

|

‘ THICK SEEDING OF MILO IN THE SAN ANTONIO REGION. 15

:

wider spacings the total number of branches and tillers is about equal

to the total number of tillers alone in 1913. Inthe close spacing there was a decidedly smaller number of tillers and branches combined than in 1913. This variation is unquestionably due to the rather unusual weather conditions during the months of April and May, 1914. The weather conditions for the first six months of each year and the averages, as given by the United States Weather Bureau for a number of years, are shown in Table VIII.

Taste VIII.—Aspect of the sky, temperature, and rainfall at San Antonio, Tex., for the first six months of the years 1913 and 1914, showing also averages for stated years.

Aspect ofsky. Temperature (° F.). : ‘ Rainfall (inches). ays Days part- ays Mean maxi-} Mean mini- Month clear. |ly cloudy.| cloudy. mum. mum. Wea ™ Joo | oo || Sy Gey || Sse SS HEGe) Sa ele Sa Sao. [oe) 1: Sc ox on bd BISIEIS (EES (SIS|2 (2/8/22 /2/2/2/8/ 4/215 January -..|10.6) 9) 24) 9.5) 9) 4/10.8) 13) 3/63. 1/62. 1/68. 4/42. ala 7|44. 4/52. 8/52. 4/56. 4) 1.32) 0.96} 0.09 February..| 9.6} 11) 10) 8.3} 11) 810.3) 6) 10/65. 4/62. 1/63. 5/44. 4/42. 0/42. 8154. 8/52.0/53.2) 1.71) 1.91) 1.38 march... . 9.6} 18) 17)10.5) 9} 6)10.9) 4] 8/73. 7/70. 8/69. 9/52. 1/47. 9/47. 8/62. 9/59. 4/58. 8} 1.75} 1.36 83 pri =... 8.2) 16) 13)11.6) 9} 5|10.5} 5) 12/79. 879. 1177. 8/58. 8/54. 7/55. 8/69. 2/66. 9/66. 8] 2.69] 1.32] 5.26 ee 8.0) 20) 4/11.3) 9) 16] 8.0; 2} 11/85. 1/87. 1/82. 3/65. 3/64. 1/66. 4)75. 1/75. 6)74.4) 3.04) 2.88) 5.59 Un oe a [ate ts yl ee ol 91. 2/88. 3/91. 2/70. 8] 70. 2|72. 8/80. 9|79. 2|82.0} 2.62) 2.90} .01 petal 29522 E> ees las Sa ld a ENS een cae ease eee ee (aoe Soo} diepalal) ble all als we 1 Average for the years 1877 to 1913. 2 Average for the years 1871 to 1913.

While Table VIII shows no great variation in the temperature during the growing months, there was an unusual difference in the aspect of the sky for the months of April and May, the months when most of the tillers and branches were being formed. For example, there were three more clear days in April and sixteen more in May in 1913 than in 1914. There were over twice as many cloudy days in April and over five times as many in May in 1914 as in the same months of the previous year. It is certain that light has a very marked effect on the development of tillers, and the only reasonable explanation to be offered in the variation in tillermg durimg the two years seems to be a corresponding variation in light, as the soil con- ditions were very similar. There was a much greater rainfall in 1914 than in 1913 during the months of April and May, as is shown, but this, if it would influence the results in any way, would be likely to make conditions more favorable for tillering. It would seem, on the whole, that an intermediate between the two seasons is much nearer the mean than either of the two seasons during which the experiments have been conducted. It is reasonable to conclude that in most seasons tillering might be somewhat less than in 1913, but much greater than in 1914, especially in the closer spaced plantings. Branching before the plants mature is abnormal and rarely occurs to any appreciable extent in grain sorghums at San Antonio.

16 BULLETIN 188, U. S. DEPARTMENT OF AGRICULTURE.

THICK SEEDING AND THE SIZE OF PLANT STUMPS.

Another advantage derived from seeding thicker than is cus-_ | tomary is the reduced size of the plant stumps. One of the objections | advanced against the growing of grain-sorghum crops, particularly | in the black lands of Texas, is the difficulty of preparing the land for }

the succeeding crop. Where the plants grow very large the increased size of the rooting system necessary to support a plant with several stalks often causes soil to adhere to the roots, forming large masses

of mixed roots and soil. When the land is plowed, many of these |

large clods, which are very difficult to turn under, are left on the surface, greatly increasing the difficulty of properly preparing the

seed bed. Thicker seeding, by reducing the size of individual plants, —

markedly lessens this difficulty. THICK SEEDING AND CROP STANDS.

It is obvious that the best results can not be secured with milo

where the stand is irregular and spotted. Where relatively thin seed- —

ing is practiced the chances of getting a good, uniform stand are reduced. There are numerous conditions that operate to prevent

high germination of the seed and successful growth of the crop, and,

within reasonable limits, thick seeding is desirable, as it increases the chances of securing a good stand in spite of adverse conditions of soil and climate. There is little danger of getting the milo plants too close together in the row so long as the rate does not greatly exceed 5 pounds of seed per acre, the rate used in these experiments, with rows 4 feet apart. As is shown in Table III, the highest yields were obtained from the unthinned rows and the 2-inch spacing. In 1913 both these plats yielded at the rate of 46.4 bushels per acre. In 1914 the two plats so spaced yielded at the rate of 21.8 and 18.2, bushels, respectively. It seems certain that to secure satisfactory stands it 1s desirable to plant at a rate at least as high as 5 pounds of seed per acre. This would make a rather thick seeding if every seed produced a plant, but this is seldom the case. The experiments carried on with milo at San Antonio have shown that if the planter plates are so arranged that only one seed is dropped where a plant is desired, such a poor stand will generally result that the yields will be very materi- ally decreased. In the experiment described above, with a seeding rate of 5 pounds per acre, if every seed had produced a plant the plants would have averaged about 1.5 inches apart, or 2,112 plants to a 264-foot row. But, as is shown in Table III, there were only 895 mature plants per row in the plat that was not thinned.

THICK SEEDING AND MATURITY.

It has already been shown that the closer spaced plants matured earlier and more uniformly than those which were farther apart im the row. As shown in Table V, the difference in earliness of maturity

THICK SEEDING OF MILO IN THE SAN ANTONIO REGION. ity

was approximately one week. This is of profound importance in escaping injury from the sorghum midge. It has been found at the San Antonio Experiment Farm that a few days’ delay in the time of flowering may result in the almost complete destruction of the crop by this insect. This is strongly emphasized in the 1914 results. Thick seeding, then, by insuring that the plants will be close together within the row, is favorable in its effect upon the maturity of the crop.

THICK SEEDING AND CROP YIELD.

From what has been stated about the favorable effect of thick seeding upon the stand and maturity of the crop, it would be expected that the yield would be favorably affected also. This expectation was fully realized in the 1913 experiments and strongly emphasized again in the 1914 experiments, as indicated in Table III, which shows that the yield increased consistently as the spacing of the plants within the row decreased from 24 inches to 2 inches.

THICK SEEDING AND RAINFALL.

It has been supposed by many that the rate of seeding of grain crops should always be greatly decreased in regions of low rainfall. This supposition is probably not always well founded, because most grain crops tend to offset thin seeding by tillermg. Early and uniform ripening is frequently of great importance in dry regions, because it assists the crop in evading midseason droughts and also, in many cases, in escaping insect injury. It seems that thin stands promote excessive tillering of