Renovation of Run-out Browntop Hill Country

New Zealand Journal of Agriculture, Volume 94, Issue 2, 15 February 1957, Page 169

Renovation of Run-out Browntop Hill Country

By

N. A. CULLEN,

Research Officer, Department of Agriculture Invermay Research Station

FARMERS contemplating the improvement of browntop country are faced with deciding whether to plough and regrass or to attempt improvement by oversowing and topdressing. Until recently rejuvenation by the latter method was usually considered impracticable and uneconomic, if not worthless. Indeed those enterprising enough to attempt this method usually found the results seldom warranted the cost of heavy dressings of lime and fertiliser.

HOWEVER, ideas have changed in recent years largely as a result of two factors:—

1. The discovery of the value of molybdenum in reducing the need for heavy liming on many soil types.

2. The introduction of aerial topdressing, making the topdressing of hill country a quick, simple, and labour-saving operation.

Oversowing and topdressing have thus become both practicable and economic, results in many instances being comparable with those from ploughing and regrassing.

Details of Trial

In 1953 a trial was begun at the Department of Agriculture’s Invermay Research Station to investigate costs of and results from oversowing and topdressing compared with those for ploughing and regrassing.

An old run-out browntop pasture, considered typical of this class of country, 1 was chosen. It had been sown about 10 years previously and had received no lime or fertiliser in that time. The sward was almost pure browntop, moss, and flatweeds. A few sickly crested dogstail and clover plants were surviving, but no ryegrass could be found.

The area was subdivided into three 1-acre paddocks which then received the following treatments:—

Paddock 1 was ploughed in July 1953, received lime at 30cwt. per acre, and was sown to new pasture in December 1953 with 2901 b. of superphosphate per acre. A typical seed mixture consisting of 101 b. of shortrotation ryegrass, 151 b. of perennial ryegrass, 41b. of cocksfoot, 41b. of timothy, 31b. of Montgomery red clover, and 31b. of New Zealand white clover per acre was sown. A further 2001 b. of molybdenum superphosphate was applied during April 1954.

Paddock 2 was oversown with 31b. of New Zealand white clover and 31b. of Montgomery red clover per acre

and topdressed with 30c wt. of lime. 2cwt. of superphosphate, and 2joz. of sodium molybdate per acre in Septem-

ber 1953. A further 2001 b. of superphosphate per acre was applied in April 1954. Paddocks 1 and 2 were again topdressed with 2cwt. of superphosphate per acre in February 1955 and with 3cwt. of superphosphate per acre in March 1956. Paddock 3 was control and was left in its natural state. Results The results. from oversowing and topdressing were spectacular. Within a few weeks improvement was visible and by the end of the 1953-54 season the proportion of clover had risen to over 30 per cent. (The clover content of the control paddock was only about 5 per cent.) The sward had lost its dry, sodbound condition, and some of the better grass speciesryegrass and cocksfootwere beginning to appear. In the new grass paddock good establishment was obtained and there was no trouble from the old browntop, indicating that direct regrassing is practicable on this class of country provided adequate fertiliser is applied. The second season’s results continued to be outstanding. In the oversown plots clover growth was ex-

tr.emely good, the plants appearing vigorous and-healthy. Despite a low percentage of perennial ryegrass and a high percentage of browntop. production was high in this plot and indeed compared with that from the new pasturea really unexpected result (see Table 1). In the 1955-56 season yields from the oversown plot have been slightly higher than those from the sown pasture. In both seasons the production from the control paddock was very low. only about one-quarter that of the other paddocks. Little difference in palatability has been noted between the young sown pasture and the oversown pasture; the control browntop sward has been neglected by stock. TABLE I— DRY MATTER YIELDS 1954-55 AND 1955-58 SEASONS Dry matter Treatment 1954-55 1955-56 lb. per lb. per acre acre New grass' .. .. 6,849 6,700 Oversown and topdressed 6,890 7,400 Control .. .. .. 1,710 1,350 The costs of oversowing clover seed and topdressing have been less than half those of ploughing and regrassing

(see Table 2). As results from oversowing have been as good as those from ploughing and regrassing, the practice is economic. TABLE COSTS OF EACH METHOD PER ACRE New pasture: — £ s. d. Cultivation . . 4 9 0 z Lime, 30cwt. (including cartage and sowing) .. .. 3 0 0 Fertiliser, 4901 b. (including cartage and sowing) .. 2 13 6 Grass and clover seed 4 11 6 j Total to 7 April 1954 . . 14 14 0 Oversown and topdressed pasture;— Lime, 30cwt. (including ear- £ s. d. tage and sowing) .. ... 3 0 0 Fertiliser, 4241 b. (including cartage and sowing) . .. 2 7 0 Clover seed .. .. .. 18 6' Total to 7 April 1951 . . .. 6 15 6 Results from other trials on this class of country have shown that oversowing grasses (not clovers) is unlikely to be successful without prior cultivation. The possibility of intro-, ducing grass species by oversowing or overdrilling after the pasture has built up in .fertility is being investigated.