TOP-DRESSING OF FIORIN GRASSLAND.

New Zealand Journal of Agriculture, Volume XXVI, Issue 3, 20 March 1923, Page 178

TOP-DRESSING OF FIORIN GRASSLAND.

THE ALFREDTON EXPERIMENT CONTINUED.

F. W. GREENWOOD,

8.A., Instructor in Agriculture, Wellington

In the Journal- for March, 1922, the writer gave an account of a pasture top-dressing experiment conducted at Alfredton, situated in the Wairarapa bush country about twelve miles east of Eketahuna. The ground chosen for the experiment was a badly drained but gently sloping white-papa clay. The flora of the paddock two seasons ago, before top-dressing was undertaken, consisted almost entirely of grasses of the Agrostis species. This particular paddock was chosen for experiment because it was typical of much of the sheep-country in the surrounding district, and especially of part of the Tiraumea Soldiers’ Settlement. ' The 7-acre paddock treated was divided into seven plots, each an acre in area. The lower half of the paddock was limed, so that, half of each plot received a dressing of lime at the rate of 1 ton per acre. The experiment has now been in progress for two seasons. In the 1921-22 season four of the plots' were top-dressed, while three remained as control areas. No further fertilizer was applied last autumn, and Plots 6 and 7 were eliminated from the area under experiment. For the sake of convenience it will be well to repeat the arrangement of the plots and their treatment : Plot 1, control, (a) limed, (&) unlimed. Plot 2,2 cwt. Nauru superphosphate, (a) with lime, (&) without lime. Plot 3,2 cwt. Nauru ground-rock phosphate, (a) with lime, (&) without lime. Plot 4, control, (a) limed, (&) unlimed. Plot 5,2 cwt. Ephos phosphate, (a) with lime, (6) without lime. The higher portion of the paddock, which was unlimed, is somewhat irregular in contour, but the lower portion, which was limed and which includes half of each plot, slopes evenly towards the road, and contains soil of a fairly even type, so that comparison made from weights taken from the limed areas should admit of a reasonable degree of validity. The paddock chosen, so far as its contour is concerned, is typical of the average paddock likely to be top-dressed in the district, and for this reason the. choice was the best that could possibly have been made in the circumstances. The paddock has been inspected from time to time, and interim reports made on the various plots. It must be remembered that in such an experiment more is to be gained by a close study of pasturecomposition and of the transitions that take place than is to be gained from a casual perusal of weights taken in December or January. There is ample evidence to show that top-dressing ■ has been of great benefit on this area.- During the first twelve months after the application of fertilizers the English grasses which had been sown in previous years, but had been smothered out by brown-top, began to make their appearance again. This was especially noticeable with perennial

rye-grass on the plots treated with superphosphate after lime. In the spring a great growth of meadow-foxtail was to be seen, while in January timothy-heads made their appearance. White clover made a good showing on all the manured plots. ' ■

A careful study of the flora reveals the fact that the omission to top-dress the paddock last autumn has been responsible for the marked intrusion of weeds and poorer grasses, notably tarweed (Bartsia viscosa), Yorkshire fog (Holcus lanatus), and sweet vernal (Anthoxanthum odoratum): It is evident that land such as that under study at present should receive an 'annual dressing of at least 2 cwt. of phosphatic manure per acre,, but a larger dressing of 3 cwt. to 4 cwt. would be preferable. The following interim report will give some idea as to the state of the plots at the time of an inspection made on 10th October, 1922 :

Plot i (control) : Fair growth, poor colour, not as good as central control. Sweet vernal and moss very noticeable, also red-top on unlimed portion. " Plot 2 (Nauru superphosphate) : Decided difference between this plot and No. 3at the boundary. This plot is undoubtably the best in the paddock ; colour and growth good. Growth on limed and unlimed portions about the same. Plot 3 (Nauru ground rock) : Unlimed portion looks decidedly better than the limed ; very little foxtail and cow- grass to be seen. Plot 4 (control) : Easily picked out : sweet vernal noticeable ; poor colour. No perceptible difference between limed and unlimed portion. Plot 5 . (Ephos) : Fair amount of foxtail and clover showing ; unlimed portion slightly better than limed.

Weighings were taken from the various plots on 21st. December, 1922. If we were able to balance the extra water-content of the grass at this date against the extra growth that would have taken place between 21st December and 18th January (the date on which -weighings were made last year), it is probable that our results would admit of comparison with those of last season. The following were the green weights for this season ■ (taken on 21st. December) in tons per acre : - (1.) Control, limed, 6-2 tons ; unlimed, 4-9 tons. (2.) Nauru superphosphate, limed, 13 tons ; unlimed, 10 tons. (3.) Nauru ground-rock phosphate, limed, 6-75 tons; unlimed, 8-8 tons. (4.) Control, limed, 5-9 tons ; unlimed, 6-7 tons. (5.) Ephos phosphate, limed, 5-7 tons ; unlimed, 7-9 tons. On a percentage basis the results may be stated as follows : Controls, unlimed, 100 ; controls, limed, 104 ; Nauru super with lime, 224; Nauru super without lime, 172 ; Nauru rock with lime, 116 ; Nauru rock without lime, 152 ; Ephos with lime, 100 ; Ephos without lime, 136. The use of lime without manure does not appear so far to have shown any very appreciable effect this season, either in the actual pasture-composition or in the yields from the respective plots. It will be seen from the foregoing figures that the difference between the average from the limed controls and that from the unlimed controls is a negligible one. Nauru superphosphate used 'with lime has doubled the results given on the control plot. Superphosphate used alone has shown an advantage of 72 per cent, over the controls. . Nauru ground rock used with lime has shown very little advantage over the untreated

plots. As might be expected, however, on this soil, which is very sour, the ground-rock phosphate used without lime has increased the yield, in this case by 52 per cent. Ephos with lime has not increased the yield, while Ephos alone (if experimental error is allowed for) has given somewhere about the same return as Nauru ground rock. On sweeter and drier soil Ephos would probably have acted much more quickly than rock phosphate used alone. Since the rainfall and its distribution have such an important influence .upon the growth of pasture-plants, the following record, kindly supplied by the Director of the Dominion Meteorological Office, is of interest : , ' '

Year. Jan. Feb. Mar. April. May. June. July. Aug. Sept. Oct. Nov. Dec. Total. Rainfall (Inches). 1921 .'. i-93 1’35 7 i-86 lainfall (Inches). 1-67 2-871 3’7°l 5-3°' 6-96 2-871 3’7°| 5-3°' 6-96 2-93 2-931 8-84 5-54 8- 4 2[ 51-37 5’54 8-42 51-37 1922 . . 2-3&I 4-23I 4-15 4’ 12 ! 44-90 1922 . . 3’82 3-82 2-14 2-14! 8-391 4-67 i-54 1-92 3-341 4-22 2-36 4’23 4-i5 4-12 44’90 Number of Wet Days. 1921 . . 11 4 Number of Wet Days. 9 I 9 I 13 1 16 I 19 9 18 13 11 l6 21 19 14 18 14 11 159 21 14 14 159 1922 . . 15 10 24 13 12 ■ 18 15 16 13 13 21 17 187