Results Of Overdrilling Last Autumn

Press, Volume XCIX, Issue 29264, 23 July 1960, Page 9

Results Of Overdrilling Last Autumn

[Bu D. J. DAVIS, fields instructor of the Department of Agriculture, Christchurch)

AS a result of publicity given this subject last year many farmers overdrilled pastures last autumn with varying degrees of success, the prime limiting factor this year, for those without sprinkler irrigation, being a severe moisture deficiency between February and March and later on in May, when slightly over half aij'inch of rain was recorded. This was m direct contrast to May of last year when a record fall of about seven inches was received in Christchurch. However, a redeeming feature has been the remarkable absence of heavy frosts, which has allowed pasture growth to continue well into May and even June.

This article reviews the overdrilling work carried out by the Farm Advisory Division of the Department of Agriculture this autumn. A wide range of soil and pasture conditions was treated in order to further evaluate the usefulness of this technique and the following notes describe the progress made on these soil types. Heavy Soils.-s-Several demonstration plots were overdrilled on sites extending from Cashmere to -Lincoln College, using both disc and rigid coulter drills, the latter fitted with special grooved cutters. The results to date have served to confirm the view that the poorer quality the pastures treated, i.e., an open bare sward, then the better the resultant crop of greenfeed. On the other hand, cereals and grass introduced into high quality pasture would seem of doubtful value. The application of nitrogen alone, will achieve all the stimulation’ of growth desired, Some form .Of attachment which cut an open semi-cultivated groove is essential for best results on these classes of soils, and especially where follow-up irrigation cannot be practised. Some farmers are in the exceptional position of being embarrassed by the amount of greenfeed available for feeding off. The best production has come from C.R.D. ryecorn, Wong barley and Gartons, Onwards and Russet oats, together with Italian ryegrass, following overdrilling of pea stubble paddocks in particular. Peat Soils: These are amongst the most difficult soils to work at any time, and so it was found with overdrilling. Because of the spongy, turfy nature of the soil, difficulty was experienced in getting sufficient penetration to cover cereals with soil. This applied, particularly with the disc drill, the coulters of which simply rode over tha dense turf. Some success was achieved, how.

with the coulter drill fitted with Powell’s'groover cutters. The Skid plates pressed hard to the ground allowing the knife edge cutters on each side to make a clean cut with a minimum of blocking. Blocking did occur where grass grub damage was particularly severe. For this class of country it, is important, that the sward be grazed as bare as possible to facilitate the passage of the drill. The most promising .cereals tried out, to date, are all of the erect growing type!, namely Onwards, Russets, Achilles and Milford oats and Arawa wheat. The prostrate growers have been most disappointing on peat soils in trials so far. Sandy Silts and Loams: This group of soils is perhaps the easiest to carry out over-drilling operations on and many paddocks have been successfully treated in the Halswell, Ladbrooks, Tai Tapu and Greenpark districts. The type of drill used is not of such great Importance.,Both rigid coulter and disc drills have been tried out with excellent results. An exception to this was a paddock treated with rush growth on the lake flat, and here a disc drill was the only machine which could easily travel through the rushes without any blocking. These loose, friable soils generally allow easy penetration of the drill, with a minimum of resistance on the -coulters. Of 12 fields treated in this area, all have developed satisfactorily in spite of unusually dry autumn conditions. Again the bare clover dominant sward, has been a better renovating proposition than the bare grass sward. A pasture with a high percentage of _ grasses, responds just as well to a bag of nitrogen as do the cereals and grasses introduced, and naturally a considerable amount of competition for plant nutrients and light takes place between the established and seedling species. For this type of situation the taller, erect growing cereals are to be preferred. • An interesting feature oti the sandy, moderately saline soils of the lake flats has been the successful use of Dalapon to control Creeping bent (Agrostis stolonifera) or as it is sometimes eroneously referred to as “water twitch." This has been controlled by spraying, allowing clovers to recover completely. Overdrilled cereals, notably Arawa wheat, Wong and Cape barley and Garton and Onwards oats, have provided a. useful bulk of greenfeed when introduced within four to six weeks of spraying. A paddock spray treated last spring and sown to summer greenfeed is now carrying a useful bulk of autumndrilled wftiter greenfeed. Ultimately this paddock will be overdrilled with a new' grass clover mixture. Light Stony Plalnsland Soils: Several trials combining the use of cereals, legumes and grasses, together with nitrogenous and phosphatic fertilisers, have been laid down for the first time this autumn. Two of the sites were completely Browntop (Agrostis tenuis) dominant and on one cultivation is being compared with overdrilling. The rigid coulter drill fitted with the Powell groover cutter attachment performed remarkably well on the stony, uneven surface which, in places, was badly pock-marked with rabbit warrens. The shallow, continuous, semi-cultivated groove made an ideal environment for the establishment of legumes, particularly subterranean clover and lucerne. Several varieties of cereals and grass drilled across the legumes are providing protective ground cover as well as a useful bite of sheep feed. It is anticipated that once the grazing of the cereals is completed by the spring, the clovers benefiting further from stock fertility, will be spelled to allow reseeding to take place. The big question mark in this experiment at the' moment is whether the Browntop can be controlled by fertility increasing methods, in preference to cultivation or spraying. The answer to this question should be known by the end of the season. Other light open soils have been successfully overdrilled with the disc drill, and one farmer who treated 30 acres with a mixture of clovers, lucerne, cocksfoot and phalaris, together with a light seeding of oats (Winter Grey) is very pleased with the results to date. It is important that all known deficiencies be corrected at drilling and these trials include the use of molyb-

denum, lime pelleted and inoculated seed. Follow-up treatments with lime and grasses will be attempted once legume establishment is completed.

Miscellaneous: Other treatments carried out this autumn for observation have been the introduction of cereal and legume combinations on hill country and the inclusion of soft turnips with cereal and grass mixtures. -The turnips have done particularly well, where sown in shallow cultivated grooves in the late February and early March period. More recently a trial to assess the practicability of harvesting Aotea wheat when overdrilled into a completely clover dominant sward has been established in the Halswell district. . C.R.D. ryecorn for seed has also been introduced in this manner and similar trials are planned for the spring. Several enquiries have been received from farmers who have overdrilled pastures on light, sandy and stony soils, complaining that the cereal used, mostly barley, had turned yellow. In each case investigated,, it was found that no nitrogen fertiliser had been used and in one, no fertiliser at all. Such treatment is considered a waste of- time and good seed. If farmers want a bulk of winter greenfeed for conversion to milk or meat, then they must be prepared to feed the crop and this implies the use of nitrogenous and phosphatic fertilisers and any other fertiliser where known to be deficient. Any farmers who require further information on this subject are advised to call at or write to, the Department of Agriculture, Christchurch- -