flea/Zelda s05 ' E fleet 0 f Fertilizer Placement ' 0n Perennial Pastn ref 14pm‘! I955 TEXAS AGRICULTURAL EXPERIMENT STATION R. D. LEWI5. DIRECTOR. COLLEGE STATION. TEXAS SUMMARY Three experiments were conducted at Substation N0. 3 near Angleton on Dallisgrass and w ‘ clover and one experiment was conducted on little bluestem to determine the fertilizer and method fertilizer placement required to maintain established perennial pastures and hay meadows on the Te Coastal Prairie. Any tillage, such as only a slight disturbance of the Dallisgrass and white clover sod as in band’ fertilizer below the surface, or complete tillage as with a rotary tiller, favored the growth of ragwe Tillage favored the growth of white clover over the growth of Dallisgrass. Application 0f phosph increased the percentage of white clover in the mixture, irrespective of tillage treatment. Nitro in addition to phosphate increased the percentage of Dallisgrass in the mixture and decreased t percentage of clover. Potash did not affect the botanical composition. A Disking or rotary tilling the fertilizer into the soil or placing the fertilizer in a band below the surf _ did not increase forage production above that from the broadcast application in any experim' In every case, both nitrogen and phosphate significantly increased forage yields. Radioactive phosphate was used to measure the uptake of fertilizer phosphorus by Dallisgr and white clover. Broadcast phosphate was utilized more efficiently than phosphate placed in subsurfi bands 7 inches apart and 2 inches deep. Phosphate broadcast or placed in bands 10 inches apart and 2 inches deep resulted in a hig percentage of phosphoric acid in forage of little bluestem than phosphate placed in bands 2O inc apart, regardless of the depth. Phosphate increased the percentage of phosphoric acid in the for but nitrogen tended to lower it. The total phosphoric acid removed by the forage was significa greater when phosphate was broadcast than when it was placed in bands below the surface. nitrogen and phosphate significantly increased the total phosphoric acid removed in the forage. CONTENTS Summary Introduction Soil, Climate and Rainfall Tillage and Fertilizer Treatments Required Materials and Methods Results Fertilizer Placement on Established Sodr--- Materials and Methods Results __ Utilization of Phosphate Materials and Methods Results ______ -_ Phosphate Placement on Pure Grass Sod Materials and Methods Results .................................. -- Forage Yields ................................. w Percentage of Phosphoric Acid in Forage ________________________________________________________________________________________ __ Total Phosphoric Acid Removed by Forage ..................................................................................... N Discussion of Results l Acknowledgments“ ............................ -- Literature Cited . . . . _ . . _ . . _ . . . . . . . _ . . . _ - - . . d E TEXAS COASTAL PRAIRIE IS A NATURAL GRASS- d area. It supports the densest cattle popula- 71» of any region in Texas. Continuous heavy j ing, however, has resulted in a decrease of 've bluestem grasses (Andropogon sp.) and "increase in low-growing grasses, particularly _’ etgrass (Axonopns COTVLIJTQSSZLS). “The introduction of new forage species and 1' development of methods of pasture improve- 't are two purposes for which Texas estab- ed an experiment station near Angleton in 9. As a result of the forage testing program, species as Dallisgrass (Paspalum dilata- q ), Bermudagrass (Cynodon dactylon), An- 1 ngrass (Andropogon nodosus), and white er (Trifolinm repens) now contribute mater- 1' to forage production on the Texas Coastal irie. These species are better than native ‘estem pastures (9, 10). Some native bluestem dows, however, are maintained for hay pro- . 10n. § The problem of maintaining an improved per- ial pasture capable of producing large quan- of high quality forage is of real importance farmers and ranchmen in the humid section of as. Dallisgrass and white clover are two of Y main species used in improved perennial pas- , s on the Texas Coastal Prairie from the Sa- River to and including the Colorado River Y mlands. In the establishment of such pas- is it usually is necessary to prepare a seed- improve existing drainage and apply pho- I fertilizer before satisfactory stands can be f ined (10). Initial applications of at least 60 inds of phosphoric acid per acre usually are ssary for the satisfactory establishment of lite clover in the pasture. Initial applications 5100 pounds of phosphoric acid or more per - may last as long at 3 years. As the phos- 'rus is used up by the plants, undesirable spe- >. such as carpetgrass and smutgrass (Spora- poiretii) replace Dallisgrass and common Ideza (Lespedeza. striata) often replaces “te clover. If an additional application of phos- te could be made to maintain an improved qnnial pasture, the cost of establishing a new ing could be eliminated. », Several workers (1, 6, 11) have shown that ~ penetration of surface-applied phosphate is ' limited. However, other workers (4, 8) reported that surface-applied phosphate fer- has ‘been effective in increasing yields of roved meadows in several instances. l: ectively, junior agronomist and superintendent, Sub- ‘Jtion No. 3, Angleton, Texas. E fleet of Fertilizer Placement 0n Perennial Peuturer MARVIN E. RIEWE and J. C. SM1TH* SOIL. CLIMATE AND RAINFALL This report gives the results of a series of ex- periments conducted to determine the fertilizer and method of fertilizer placement required to maintain perennial pastures and hay meadows on the Texas Coastal Prairie at a high level of production. These experiments were conducted near Angleton on Lake Charles clay soil. The topography of Lake Charles soils, especially the clay, is so nearly flat that natural drainage is very slow. Lake Charles clay is a black, deep and very heavy soil, slowly permeable to rain- fall. Native phosphorus content of this soil is very low, often less than 1 part per million of available phosphorus. Soil pH is in the range of 6.5 to 6.8. The Lake Charles soils, o-f which the clay is the principal type, are the m-ost extensive on the Texas Coastal Prairie and probably total 3,750,000 acres (2). The Texas Coastal Prairie has a warm tem- perate climate, with an mean annual temperature of 67 ° to 70° F. The average growing season from the last killing frost in the spring to the first killing frost in the fall is about 9 months. The average annual rainfall at Angleton for a 40-year period is slightly over 48 inches. The average monthly rainfall is fairly uniform throughout the year, although it may be quite variable within any given year. The average rate of evaporation, however, varies considerably. The average monthly rainfall exceeds the average rate of evaporation by over 200 percent during December and January while the rate of evapor- ation exceeds rainfall from April through August. This usually results in wet winters and intermit- tent periods of drouth during the summer. The monthly rianfall from 1949 through 1953 and the average monthly rainfall from 1914 through 1953 are given in Table 1. TABLE 1. MONTHLY RAINFALL IN INCHES FOR THE YEARS 1949-53 AND AVERAGE MONTHLY RAIN- FALL FOR 1914-53 l Year 40-year M°“"‘ F1949 | 1950 J 1951 | 1952 | 195s averaae Ianuclry 3.83 3.93 4.27 1.13 0.65 3.49 February 6.66 3.79 0.75 7.41 4.96 3.13 March 5.69 1.06 5.89 3.17 0.08 3.36 April 14.94 4.95 2.06 4.21 0.52 3.23 May 1.12 1.69 1.93 3.50 10.08 4.08 lune 4.41 7.05 3.56 1.76 4.88 3.90 Iuly 7.44 4.59 3.46 7.70 3.82 5.37 August 5.58 1.20 3.16 2.35 13.58 4.71 September 2.09 1.76 9.25 4.64 0.80 4.81 October 21.59 0.26 1.07 0.00 3.69 3.89 November 0.17 0.16 1.34 7.29 5.68 3.83 December 9.88 1.49 1.59 6.66 3.90 4.57 Total 83.40 31.93 38.33 49.82 52.64 48.37 TILLAGE AND FERTILIZER TREATMENTS REQUIRED An improved perennial pasture consisting of Dallisgrass, Bermudagrass and White clover was established at Substation No-. 3 near Angleton in the fall of 1942. Prior to seeding, the land was back furrowed into lands of 150-foot widths to facilitate drainage and a clean, firm seedbed was prepared. The entire field was fertilized with superphosphate equivalent to 100 pounds of phos- phoric acid per acre. The pasture remained in peak production for 3 years then began to de- cline. By the fall of 1949 the pasture had reach- ed a lOW state of productivity, with white clover making very little growth and carpetgrass re- placing Dallisgrass. For this reason it became necessary to develop suitable methods of reno- vating and maintaining the productivity of per- ennial pastures that would be applicable to the region. Materials and Methods The purpose of the first experiment, initiated in the fall of 1949, Was to determine the tillage and fertilizer treatments required to renovate a Dallisgrass and White clover pasture. The three tillage treatments in this test consisted of no till- age, disking and rotary tilling. These tillage treatments were used as main blocks on which were superimposed 16 fertilizer treatments con- sisting of four levels of phosphoric acid (40, 80, 160 and 320 pounds P205 per acre) with and with- out 50 pounds of nitrogen (N) per acre and with and without 100 pounds of potash (K20) per acre. On the main blocks, Where disking and rotary tillage were used, the fertilizer was broadcast on the surface of the soil before each tillage treat- ment was made. The disking was sufficient to destroy about half of the existing sod and rotary tilling completely destroyed all vegetative growth present. Two clippings were made for forage yields during 1950. A study of botanical composition TABLE 2. AIR-DRY FORAGE YIELD IN POUNDS PER ACRE OF DALLISGRASS AND WHITE CLOVER AS INFLUENCED B“ FERTILIZER AND TILLAGE TREATMENTS. 1950 TABLE 3. SEASONAL AIR-DRY FORAGE YIELD IN POUNDS. PER ACRE OF DALLISGRASS AND WHITE CLOVER AS INFLUENCED BY CULTURAL TREAT- MENTS1 Tillage treatment season None | Disked l Rotary tilled . Spring 1950 1.960 1.550 1.070 Summer 1050 2.800 2.950 1.690 Total yield 4.780 4.500 3.560 1 The difference in yield for any two cultural treatments for any given season must equal or exceed 380 pounds to give odds of 19 to 1 that such difference is real and not due to chance. of the various treatments was made during the first part of May 1950 and the later part of April 1951 by use of an inclined point quadrat. Results In this experiment, cultural treatments influ, enced both the total and the seasonal yield of for age (Tables 2 and 3). Rotary tilling resulted i a pronounced reduction in forage yield in th; summer of 1950. The vegetation produced dur ing the summer of 1950 on rotary-tilled plots con sisted almost entirely of ragweeds (Ambrosip psilostachya) . A Phosphate alone and nitrogen with phosphat significantly increased forage yields. Potas with phosphate or with both nitrogen and phos phate had no influence on forage yields. The ad dition of 40 pounds of phosphoric acid per acr was sufficient for Dallisgrass to replace mos of the carpetgrass in the mixture. Carpetgras was almost eliminated with the application o higher rates of phosphate. Figure 1 shows the influence of tillage trea ment on botanical composition. These data sho that the tillage treatments greatly increased th percentage of clover and ragweeds in the forag mixture, but decreased the percentage of gras The use of the rotary tiller almost eliminat Dallisgrass from the mixture. Irrespective 0 tillage treatment, phosphate increased the per Pounds per acre Tillage treatment Fertilizer treatment N P205 None I Disked l Rotary tilled averagesl 0 40 3.760 3.890 2.760 3.470 50 40 4.580 3.990 2.780 3.780 Average 0 80 4.110 4.130 3.170 3.800 50 80 5.270 4.770 3.390 - 4.480 Average 4.700 4.450 3.280 4.120 0 160 4.660 4.210 3.440 4.100 50 160 5.480 5.010 4.620 5.040 Averqqe 5.070 4.610 4.030 4.580 0 320 4.780 4.750 p 3.960 4.500 50 320 5.620 5.230 4.380 5.080 Average 5.200 4.990 4.170 4.790 Cultural treatment averages? 4.780 4.500 3.560 1 The difference in average yield for any two fertilizer treatments must equal or exceed‘ 430 pounds to give odds of 19 to that such difference is real and not due to chance. 2 The difference in average yield for any two cultural treatments must equal or exceed 190 pounds to give odds of 19 toi that such difference is real and not due to chance. 4 ‘ge 0f clover, with a resulting decrease of s in the mixture (Figure 2). Nitrogen with lphate decreased the percentage of clover and eased the percentage of grass. Potash had influence on botanical composition. DALLISGRASS O O I950 (FIRST YEAR) l95I (SECOND YEAR I ‘I Q FERTILIZER PLACEMENT ON ESTABLISHED SOD fThe results obtained from the first experi- f» showed that the intensity of tillage influ- “I the botanical composition and yield of a isgrass and white clover pasture following vation. A second experiment designed to pare surface broadcast fertilizer with sub- ace banded fertilizer on a Dallisgrass and E clover sod was started in the fall of 1951. 0 O LI O 8a 0| O Materials and Methods iThe experimental design was a complete fac- 'al. Three levels of nitrogen (0, 30 and 60 ‘nds per acre) and 2 levels of phosphoric acid and 30 pounds per acre) made up the fertili- ftreatments. Three methods of applying fer- r—br0adcast on the surface and in bands 2 es below the surface 10 and 20 inches apart— e used. The treatments were replicated three "o"; 0.5km, “M, NONE mm, TM“, eis. fThis samefxpegiment, blét with only two Cuururuu. TREATMENTS so nitrogen O an 60 poun s per acre was - . ated in the fall of 1952. All of the fertilizer comglcagsliltliinl-caf the botanical f. applied when the experiment was initiated. ultiple-cell fertilizer distributor (7) was used his and subsequent experiments to place the "ilizer in bands below the soil surface. Two pings were made in 1952 and three in 1953 to ~: in forage yields. PERCENT DALLISGRASSJIHITE CLOVER AND WEEDS IN MIXTURE '5 8 ' DALLISGRASS WHITE CLOVER g Results 8° ' ‘a he air-dry forage yields for 1952 and 1953 ‘given in Tables 4 and 5. Method of fertilizer ment did not affect forage yields. The for- yields were increased significantly by the ap- tion of nitrogen and phosphate. Most of the ise obtained from nitrogen was produced by r of each year. More ragweeds were present the fertilizer was banded ‘below the surface e soil. |Q§Q I95! IFIRST YEAR) (SECONDYEAR) 70‘ 60* 40- 4. AIR-DRY FORAGE YIELD IN POUNDS PER ACRE OF DALLISGRASS AND WHITE CLOVER AS IN- FLUENCED BY FERTILIZER AND METHOD OF FERTILIZER PLACEMENT, 1952 ~-: per acre Method of fertilizer placement 2.. deep 2.. deep Fertilizer P205 Broadcast 10.. band Zfjnbqnd average 30" 20- PERCENT DALLISGRASS, WHITE CLOVER AND WEED$ IN MIXTURF 0 3.1 l0 3.010 2.810 2.980 0 3.040 3.720 3.390 3.380 0 3.420 3.340 3.290 3.350 30 4.210 3.620 3.110 3.650 ,0 _ 30 3.950 4.890 3.430 4,090 30 5.790 5.890 5.540 5.740 ‘ment 1 rages? 3.920 4.080 3.600 .- difference in the average yield of any two fertilizer ‘atments must equal or exceed 240 pounds to give odds 9 to 1 that such difference is real and not due to chance. Figure 2. Effect of phosphorus with and without nitrogen Q difference in the average yield of any two methods of and with and without potash on the botanical composition of _ cement is not significant. a Dallisgrass-white clover sod. l5 PK NP mm Fennuzsn Tneamsut 5 TABLE 5. AIR-DRY FORAGE YIELD IN POUNDS PER ACRE OF DALLISGRASS AND WHITE CLOVER AS IN- FLUENCED BY FERTILIZER AND FERTILIZER PLACEMENT. I953 Pounds per acre Method of fertilizer placement _l_ 2.. deep 2.. deep Ferti izer; N P205 Broadcast 10.. band 20.. band average 0 0 2.680 2.730 2.970 2.790 60 0 3.410 3.470 3.360 3.410 0 30 3.890 3.500 3.900 3.760 60 30 4.940 4.840 4.170 4.830 Placement averagesz 3.730 3.640 3.740 1 The difference in the average yield of any two fertilizer treatments must equal or exceed 160 pounds to give odds of l9 to l that such difference is real and not due to chance. 2 The difference in the average yield of any two methods of placement is not significant. UTILIZATION OF PHOSPHATE A study with radioactive phosphate t0 meas- ure the efficiency of phosphate broadcast on the surface in comparison with phosphate banded be- low the surface was conducted in the spring of 1953. This experiment was conducted on an es- tablished Dallisgrass and white clover sod. Materials and Methods A complete factorial design was used with two levels of nitrogen ( 0 and 30 pounds per acre) and two levels of phosphoric acid (0 and 60 pounds per acre). Two methods of placement were used, WWWW P up ----AVERAGE LU 2 n; 7Q- O LL E .60- l 5 .50- '2 ‘:5 q-q- _1 ‘E w .30 - .._ m , l! O <1 .20» 0! LU ‘L .|o- p ‘3 / s 2 BROADCAST BANDED METHOD OF FERTILIZER APPLtCATlON Figure 3. The relative efficiency of broadcast vs. banded phosphate on Dallisgrass-white clover sod. O7 broadcast on the surface and in bands 2 inch deep and 7 inches apart. Three replications We used. The bands Were spaced 7 inches apart i an attempt to determine if closer spacing Woul increase the efficiency of fertilizer placed belo the surface. . Results Two forage clippings were made during th period in which the phosphate retained sufficien radioactivity to allow measurement. Forag yields Were lOW because of the short duration o) the experiment. Method of phosphate placeme had no effect on forage yields. Nitrogen an phosphate significantly increased forage yiel (Table 6). ' The number of pounds per acre of fertilize phosphorus removed in the forage and the pe centage of fertilizer phosphorus of the total pho phorus in the forage are shown in Figure 3. Su stantially more fertilizer phosphorus was remo ed by the forage from phosphate broadcast on t surface than from phosphate banded below t surface. A greater percentage of the total pho phorus in the forage came from the fertilize‘ The application of nitrogen increased both t amount of fertilizer phosphorus removed in t forage and the percentage of fertilizer pho phorus of the total in the forage. 35" 30‘ 25 -* 20-4 BROADCST i BAND PERCENT FERTILIZER P OF TOTAL P IN FORAGE D AIR-DRY FORAGE YIELDS IN POUNDS PER ACRE OF DALLISGRASS AND WHITE CLOVER AS INFLUENCED BY FERTILIZER AND FERTILIZER PLACEMENT, APRIL 3 TO IUNE 8. 1953 l 6n r 4 per acre Method of fertilizer placement _ _ V. 2.. deep Fertilizer P105 Broadcast 7.. band averagesl U 470 460 470 U 730 620 680 6U 630 650 640 .. 6U 990 910 950 ent ages? 710 660 3' difference in the average yields of any two fertilizer L, ents must equal or exceed 185 pounds to give odds of 1 that such difference is real and not due to chance. f difference in the average yield of any two methods of p ement is not significant. PHATE PLACEMENT ON PURE GRASS SOD t view of the results obtained from the Work ted in 1949 on a Dallisgrass and white clover ‘additional work was begun in the fall of 1951 termine the most satisfactory method of phate placement on an established native sod fged as a hay meadow. This was a pure z sod consisting almost entirely of little blue- l (Andropogon scoparius) with a trace of seed paspalum (Paspalum plicatulum). Materials and Methods p ive methods of placement were used. These r (1) broadcast on the surface; (2) in bands hes deep, 10 inches apart; (8) in bands 2 _’ deep, 20 inches apart; (4) in bands 4 in- deep, 20 inches apart; and (5) in bands 6 deep, 2O inches apart. Three levels of gen (0, 30 and 60 pounds per acre applied i ally) and two levels of phosphoric acid (0 ~60 pounds per acre in an initial application st 2 years) were included in the fertilizer (ments. Three replications Were used. The ‘phate was applied in the fall of 1951 and iini-trogen was broadcast in early April 1952 ‘again in 1953. To determine the effect of vation alone, the machine used to band the hate was used to renovate at each indicated h those plots Which did not receive phos- ome difficulty was experienced in banding ‘phosphate at depths of 4 and 6 inches. Be- _ the machine could be made to take the nd, soil moisture had to be near field capac- ity. It Would have been impossible to place the fertilizer 4 and 6 inches deep in bands 10 inches apart without completely tearing up the sod in at least a major portion of the area treated. By placing the bands 20 inches apart at these depths, this difficulty was practically eliminated. Results Yields of forage, percentage of phosphoric acid in the forage and total phosphoric acid re- moved by the forage Were determined both years of the experiment. Forage Yields Two clippings of forage were made each year. The average air-dry forage (hay) yields for the 2-year period are given in Table 7. The average air-dry forage yields for all treatments was 6,470 pounds per acre in 1952 and 3,490 pounds in 1953. The distribution of rainfall during the 1952 grow- ing season Was much more uniform than in 1953 (Table 1) and this no doubt accounts for the var- iation in yield. The trends indicated for bo-th fertilizer and method of placement, however, were the same for both years (Table 7). Both nitrogen and phosphate increased forage yields signifi- cantly. The method of phosphate placement did not influence either the average annual forage yield or the seasonal forage yield. Percentage of Phosphoric Acid in Forage The effect of fertilizer and method of phos- phate placement on the percentage of phosphoric acid in the forage are given in Table 8. The ap- plication of 60 pounds of phosphoric acid per acre significantly increased the percentage of phosphoric acid in the forage. Nitrogen, how- ever, tended to decrease the percentage of phos- phoric acid in the forage. This trend Was sig- nificant in every case where 6O pounds of nitro- gen per acre were applied. The application of 30 pounds of nitrogen per acre did not lower the phosphoric acid content of the forage when com- pared with no fertilizer, but in combination with phosphate the phosphoric acid content Was sig- nificantly lower than Where only phosphate was applied. Method of phosphate placement had a highly significant effect on the phosphoric acid content of the forage. Phosphate broadcast or placed in bands 10 inches apart was more effective than 7. AVERAGE ANNUAL HAY YIELDS IN POUNDS PER ACREWOF LITTLE BLUESTEM AS INFLUENCED BY FERTI- LIZER AND METHOD OF PHOSPHATE PLACEMENT. 1952-53 per acre Method of phosphate placement Fertilizer P205 Broadcast 120.. izeriad 2%.. ietzerfd 2%.. iecffd 2%.. izenra averagel 0 4.050 3.600 3.860 4.180 3.880 3.910 0 4.840 4.700 4.680 4.490 4,910 4.720 0 5.810 5.430 5.260 5.390 5.550 5.490 60 4.900 4.390 4.380 4.230 4.660 4.510 60 5.430 5.330 4.960 4.980 5.400 5.220 _ 60 6.550 6.000 5.830 6.190 5.600 6.030 i ent averages? 5.260 4.910 4.830 4.910 5.000 i- such difference is real and not due to chance. difference in the average yields of any two fertilizer treatments must equal or exceed 143 pounds to give odds of 19 to l i difference in the average yields of any two methods of placement is not significant. . ly spaced for efficient utilization by most of the in the soil as found by other workers with sw TABLE 8. AVERAGE PERCENT PHOSPHORIC ACID IN LITTLE BLUESTEM HAY AS INFLUENCED BY FERTILIZER '1 METHOD OF PHOSPHATE PLACEMENT, 1952-53 Pounds per acre Method of phosphate placement F “T”! 1 .. .. .. e i i N P205 Broadcast 120.. 122p d 220.. iecxeifd 240.. iejrllad 2%.. i222! averagel. 0 0 .16 .17 .17 .18 .18 .17 i 30 0 .17 .18 .17 .17 .16 .17 60 0 .16 .16 .16 .15 .15 .16 0 60 .23 .24 .21 .21 .20 .22 30 60 .22 .22 .18 .18 .20 .20 60 60 .23 .21 .19 .18 .18 .20 Placement averages? .20 .20 .18 .18 .18 1 The difference in the average percent phosphoric acid in the forage of any two fertilizer treatments must equal or exc .01 percent to give odds of 19 to 1 that such difference is real and not due to chance. ' 2 The difference in the average percent phosphoric acid in the forage of any two methods of phosphate placement must -_ or exceed .01 percent to give odds of 19 to 1 that such difference is real and not due to chance. phosphate placed in bands 20 inches apart, re- face. There is a possibility that phosphorus l gardless of the depth. This indicates that phos- similated by white clover roots feeding at or n phate placed in bands 20 inches apart is too Wide- the surface is transmitted to roots at lower lev grass plants. clover (5). If this is true with white clover, » phosphorus in these roots should again beco Tm“! Ph°sph°ri° Acid Remwed by F°rage available to grass roots when the white clo The total phosphoric acid removed by the for- roots die and decay age, expressed in pounds per acre, is given in _ , Table 9. Both nitrogen and phosphate signifi- HOWeVeI‘, data Ohtalhed from Pure grass “ cantly increased the total phosphoric acid remov- ShOW that gPaSS POOtS are able t0 aSSlmllate S ed in the forage. Although nitrogen definitely feoe-epphed phosphorus Independent of any , tended to lower the percentage of phosphoric acid t1_ch_ by the clOVeP- Net chly may the POOtS l in the forage, the increase in the forage yield was snnllate phosphate applled on the surface. but sufficient to result in an increased removal of data g1Veh_ eafllelf ShOW that Sllch Phosphate’ phosphoric acid by the forage_ more readily utili_zed than phosphate placed. _ _ _ _ _ bands below the soil surface. Although the m Significantly more phosphoric acid was _I'e- od of placement did not influence forage yie moved by the forage from broadcast application the percentage of phosphoric acid in the for than from any other metlwd of Phosphate Place‘ and the total phosphoric acid removed by the f ment. Banded phosphate resulted in a downward age were affeeted_ ‘ trend in both forage yields and the percentage of _ _ _ - phosphoric acid in the forage. As a result, sig- The percentage of phosphorlo aold 1n the _ nificantly less phosphoric acid was removed in age WaS Slghlflcahtly hlghel‘ Wheh the fePtll this forage than in that from plots receiving a WaS hPOadCaSt 0h the Surface 91' When Placed broadcast application of phosphate. Phosphate re- bands 2 inches deep and 10 inches apart t moval was increased by decreasing the distance Wheh Placed 111 hahdS at Several deDthS and between the bands of applied phosphate from 20 ihcheS apart- to 10 inches‘ This suggests that phosphate placed in ba 20 inches apart is not as readily accessible to DISCUSSION OF RESULTS plants as phosphate broadcast or placed in ba It was observed during this work that a ma- 10 inches apart. Plants whose roots are near jor portion of the young roots of both Dallisgrass fertilizer band are no doubt able to assimi’ and white clover were in the upper 2 or 3 inches phosphorus from the band. They may feed l of the soil. When soil moisture levels are high urinatly. It appears likely that plants at a I‘ and there is abundant vegetative growth, white tance of 6 inches or more from the band do clover roots can be found growing on the soil sur- receive full benefit from the phosphate.- TABLE 9. AVERAGE POUNDS PER ACRE OF PHOSPHORIC ACID REMOVED ANNUALLY IN LITTLE BLUESTEM HAY, INFLUENCED BY FERTILIZER AND METHOD OF PHOSPHATE PLACEMENT, 1952-53 - Pounds per acre Method of phosphate placement Fertilizer A, n 2n 4n 6n i N P205 B’°°"1°"S‘ 12o" ilrenpd 2s" ciiienpd 2n" iitenpd 2o" lolrerfii “"°"*9°‘. 0 0 6.38 6.30 6.56 7.40 6.93 6.71 30 0 8.21 8.33 7.99 7.44 7.97 7.99 60 0 9.18 8.66 8.36 8.26 8.11 8.51 0 60 11.30 10.75 9.00 8.88 9.18 8.92 30 60 12.05 . 11.95 9.04 9.10 10.95 10.62 60 60 15.17 12.36 10.94 11.30 10.06 11.97 Placement averages? 10.38 9.73 8.63 8.73 8.87 1 The difference in the average pounds of phosphoric acid removed annually by forage from any two fertilizer treat must equal or exceed .48 pounds to give odds of 19 to 1 that such difference is real and not due to chance. 2 The difference in the average pounds of phosphoric acid removed annually by forage from any two methods of phos placement must equal or exceed .39 pounds to give odds of 19 to 1 that such difference is real and not due to chant 8 hosphate is placed in bands 2O inches apart, ‘pears probable that only a limited number of p. are able to feed 0n the banded phosphate. roadcast applications should make some phorus available to all plants. This could be f: ted to favor better root development of the plant population during the spring when itions for good plant growth are more near- al. With a better overall root development, ‘pears that a broadcast application of phos- ,e would result in as high or higher phos- 'c acid content of the forage, even during 1| When soil moisture is limited. Roots able within a narrow band of phosphate may ble to absorb phosphorus at a higher rate for ven area of absorbing root surface. How- i, a broadcast application of phosphate may the absorbing root surface area to such i ent that, even with a relatively lower rate lhosphorus absorption, the amount of phos- Hus absorbed is increased, as has been shown ther workers (3). This explains, at least par- 3' the higher phosphoric acid content of for- gfrom plots whch received a broadcast appli- a of phosphate. This experiment does not ly any evidence with regard to phosphate gs spaced 10 inches apart at 4 and 6-inch hs. However, to place fertilizer in such a ner in Lake Charles clay is mechanically im- tical with present equipment and would most y result in an excessively torn sod. nother factor affecting phosphorus utiliza- by grass roots from subsurface banded phos- 5- may'be the disrupting of both the soil and existing sod. Some roots were cut by the ment shoes. With the moisture level in the jfat near field capacity, the soil was compress- either side of the fertilizer placement shoe. p left a small open trench. During the latter , of the summer of 1952 soil moisture became iciently limited for the soil to crack freely. ' most prominent cracks were along lines prev- ly delineated by the fertilizer placement shoes. cracks were particularly prominent where jfertilizer shoes had been run 6 inches deen, if no phosphate was actually applied. At 7 depth much of the grass for a distance of }= 4 inches on either side of these cracks died ‘ng August and September 1952, as shown in w 4. This indicates that a drouthy condi- A was prevalent in and about the area through i h the fertilizer placement shoe had been run. » wo factors which could cause the soil to k along previously delineated lines may be lved. First, the soil in and about the vertical vage created by the fertilizer shoe would have ndency to dry more rapidly than soil away this cleavage. The soil compressed to either p of the fertilizer placement shoe would tend femain open and consequently be subject to a rapid drying. i" second factor may be the increased rate of ‘r and mineral absorption within a limited Figure 4. Soil cracking in late summer of 1953f along lines previously delineated by fertilizer placement shoe. zone in the soil. Greater root development may occur within the area where the phosphate is banded. If this was the case in this experiment, the rate of water absorption probably would have been greater than where the roots were less con- centrated. This would result in more rapid dry- ing in and about the area in which the phosphate had been banded and consequently hasten the cracking of the soil. It seems logical that plants on either side of the vertical cleavage created by the fertilizer placement shoe would die simply from a lack of moisture before plants away from this cleavage whose roots had been developed over a larger area would ‘be adversely affected. Although the banded phosphate may not have been chemically fixed, it could certainly become unavailable un- der drouthy conditions insofar as the grass plants being able to utilize the phosphorus is concerned. One of the main advantages suggested for the deep placement of fertilizer is that the fertilizer is placed at a location readily accessible to plant roots. However, such a practice would hardly be practical where roots from many plants in the population would never reach the fertilizer. The relative uptake of phosphorus by roots able to feed on the banded phosphate may have been greater, but it appears that the surface broadcast phosphate was available to a greater number of roots, resulting in a higher phosphoric acid con- tent of the forage. ACKNOWLEDGMENTS Acknowledgment is due to L. C. Kapp, for- merly associate professor, Department of Agron- omy, for assistance in planning and executing the experiment involving the use of radioactive phos- phorus, and to the State Chemist Laboratory, Texas Agricultural Experiment Station, for all chemical analyses of forage samples. LITERATURE CITED 7. Brown, L. A. A study of phosphorus penetration and availability in soils. Soil Sci. 39:277-287. 1935. Carter, W. T. The soils of Texas. Tex. Agr. Expt. Sta. Bul. 431. 1931. Gile, P. L. and Ca-rrero, J. O. Absorption of nutri- ents as affected by the number of roots supplied with the nutrient. Jour. Agr. Res., 9:73-95. 1917. Hanway, J., Stanford, G. and Meldrum, H. R. I Ef- fectiveness and recovery of phosphorus and potas- sium fertilizers topdressed on meadows. Soil. Sci. Soc. Amer. Proc. 17:378-382. 1953. Hervey, R. J ., Kapp, L. C., Johnston, J . R. and Smith, J . C. Use of sweetclover for deep-placement of phosphorus. Soil Sci. Soc. Amer. Proc. (1950), 15: 258-262. 1951. Midgely, A. R. The movement and fixation of phos- phates in relation to permanent pasture fertilization. Jour. Amer. Soc. Agron., 23:788-799. 1931. 10. 11. . Stanford, G., McAuliffe, C. and Bradfield, R. Rea, H. E., Hulburt, W. C. and Adams, J. E. A m tiple cell, belt type distributor for use with trac implements in fertilizer tests with field crops. w: Sci. Soc. Amer. Proc. (1949), 14:391-395. 1950. effectiveness of superphosphate topdressed on est lished meadows. Agron. Jour. 42:423-426. 1950. Stansel, R. H., Reynolds, E. B. and Jones, J. H. 11 ture improvement in the Gulf Coast Prairie of Te p Tex. Agr. Expt. Sta. Bul. 570. 1939. f Turner, W. R., Willey, N. F. and Jones, J . H. Ga of heifers on native and improved pastures in ._ Gulf Coast Prairie of Texas. Tex. Agr. Expt. S P. R. 1018. 1946. i Weiser, V. L. Fixation and penetration of ph phates in Vermont soils. Vt. Agr. Expt. Sta. Bul. é‘ 1933. i