Direct reseeding under rape has been a long-established practice in many parts of Western Britain. In the development of New Zealand and especially in those districts where the call was chiefly for grass, direct reseeding has always been a normal practice. Indeed, in the grassing out of newly deforested lands, direct reseeding provides almost the only rapid method of establishing new turf. Seeds of grasses and clovers are sown in the ashes of the forest fire, and the grazing animal is introduced as soon as ever feed becomes available. In many parts of Australia, too, direct reseeding with mixtures containing subterranean clover has become the established practice.
It is only within recent years, however, that British farmers generally have turned their attention to the possibilities of direct reseeding. Because of the better conditions of climate and of the damper soils generally for the establishment and growth of grass, direct reseeding as a method of grassland improvement has been taken up more seriously in the west and north of the country than in eastern districts. Even so, there is now little doubt that direct reseeding, employed as a measure of land improvement, may be applied over large areas in Britain. During the war, when an extension of the arable acreage was a national necessity, direct reseeding provided a method whereby derelict acres could be made cereal-worthy. Furthermore, through the establishment of new and productive leys on previously derelict and unproductive land, other grassland on the farm more immediately capable of arable crop production can be at once released for cropping purposes during any period of crisis.
Methods and Mixtures
When dealing with derelict land and with areas of low general fertility, it is often best to begin with a short-duration seeds mixture. Where the immediate purpose is to prepare the land for a cereal crop, a pioneer grazing mixture of Italian ryegrass and rape may be used. Where cereal cropping is to be deferred, then begin with a short-term ley to be used primarily (and, if possible, wholly) for grazing. Where improved grassland, rather than subsequent arable cropping, is the aim, then the initial ley may with advantage be left down for longer periods, but usually, and when starting from old turf, this initial ley should be reploughed not later than during its fifth year. Direct reseeding provides a method whereby not only is immediate productivity increased, but where the new grass is grazed on a proper basis, the fertility of the land is enhanced. Cereals and other non-leguminous arable crops are, to a large extent, exhaustive of soil fertility. Grasslands are, in general, upbuilders of fertility. Grazed pastures are superior in this respect to meadow and hay lands. The grazing ley, with its high proportion of clovers, together with its high level of production, is capable of carrying a large concentration of livestock and ranks among the best of soil fertility builders.
Direct reseeding should be viewed not as an end in itself, but rather as part of a planned rotation. It should, therefore, be discussed in relation to the system of rotations as a whole. On good average soils the rotation might properly start with an arable crop or a sequence of such crops and the ley would be deferred. This ley could often be sown with the last cereal crop in the rotation or might be autumn-sown in the stubble or be deferred until the following spring, to be sown without a cover crop. The rotation on poorer-than-average soils might also commence with a cereal, but the rotation would be shortened, and the ley would take a much more prominent part in it. On very poor soils the rotation could properly begin with a short ley or a series of short leys prior to being put to arable crops and to end up with a long-duration ley. At high elevations, and on rough and hill grazings generally, the arable crop would take no more than a negligible part in the rotation. Having regard to rotations, generally therefore, and in relation to soil conditions, on the poorest soils the emphasis should always be on the ley and on direct reseeding. On medium soils there would be less emphasis on the ley, while in the case of really fertile soils the ley, although still an essential part of the rotation, could be longer deferred.
Cultivations Preparatory to Reseeding on Old Turf
Old turf may be cultivated in a variety of ways in preparation for direct reseeding. Under average conditions, the land may be ploughed without previous cultural treatment. Where ploughing is the first operation, the furrow should be fairly wide and not too deep -- say eight to ten inches wide and four to five and a half inches deep. The furrow-slice should be placed well on its back and the land disked many times, using the heaviest available disks. Where there is mat or where there is accumulation of ungrazed (often ungrazable) roughage, it is best to begin by disking the surface. In other cases, the surface treatments immediately preparatory to ploughing may be done satisfactorily by the pitchpole or by the Aitkenhead rippers and similar tools. The various ways and means of preparing the seed-bed for direct reseeding may be listed as follows:
- Once-ploughing, followed by harrows, disks, furrow-press and rolling.
- Predisking, followed by ploughing and other cultivations.
- W. D. Hay's method, involving thrice-ploughing with bastard fallow with the aim of producing a weed-free sward at the first intention.
- Disking many times and to the point at which the land would appear as if ploughed.
- Drastic harrowing with heavy-toothed harrows, but without the depth of tilth made by the heavy disks.
- Surface cultivations by rotary cultivators (Austral, Fishleigh, and so on).
1. Ploughing as the first operation, followed by other cultivations
Up to the present, this has been the most generally adopted practice in connection with direct reseeding throughout the country as a whole. Where the furrow-slice is turned over fairly flat and the subsequent cultivations are good, the method has proved satisfactory enough. Success or failure will often resolve itself around good or bad cultivations. Not even under the high rainfall conditions of the West of England and Wales are successful takes assured unless cultivations are well done. Good cultivations should be supported by adequate manuring, which includes a sufficiency of phosphates, lime where necessary and a dressing of easily soluble nitrogen. Nitro-chalk is to be preferred to sulphate of ammonia on acid soils.
On most soils the after-ploughing cultivations should be as follows: disking with the heaviest available disks, starting in the direction of the plough furrows. The disks should at first be set fairly straight, so as to cut into the sod. It is an added advantage to 'stagger' the diskings by taking a half-width previously disked and half-width of first disking. In this way the tractor wheels press a very large proportion of the furrows and effect a considerable amount of additional consolidation. When the field has been thus gone over, it has, in fact, been twice disked. The later diskings are taken diagonally across the furrows and in all directions. Normally, an aggregate of four diskings will suffice, but obdurate turfs may require five or more times over with the disks. The sum effect of adequate disk harrowing is threefold, namely:
- making a tilth;
- breaking up the old sod, and
- consolidation of the soil to the depth of the plough furrows.
The disks provide the means for consolidation over the whole depth of the plough furrow. Without the disks, it is almost impossible to remake organic connection between plough furrow and the subsoil below. On dry soils, and in droughty weather, the adverse effect of any hollowness under the grassy furrow emphasizes the influence of drought, the furrow-slice becomes abnormally dry and a desiccated condition may set in. The result is loss of establishment by death of seedlings.
Rolling alone is not effective where there is any tendency to mat. The roller only consolidates the top inch or so of the soil and does not press down the spongy turf below. Neither, of course, has it any cutting action on the turf. Similarly with the peg- or tined-harrows -- their influence is chiefly confined to the top layer of soil.
2. Predisking before ploughing the sod.
There is a good deal of evidence which suggests that thorough disking of the turf preparatory to ploughing is an added advantage. Predisking seems to have an important application on matted turfs, and further experience tends to show it has an even wider application. The aim in predisking is to cut up the turf so as almost to make a compost of soily turf ready to be ploughed in. If predisking is carried far enough, it should obviate the need for excessive diskings after ploughing -- perhaps not more than two post-plough diskings will be necessary, even on difficult sods. One of the objects of ploughing up an old tough grass sod is to promote rapid rotting, with the consequent rapid release of plant foods. There is little doubt that chopping up the turf in situ, as is done by predisking, accelerates the rotting process. In districts of high rainfall there is a good case for doing the whole of the predisking, ploughing and the post-ploughing cultivations as one continuous operation. In this way, the available moisture is conserved in the soil, and the organic connection between the soil and the moister subsoil is maintained. Under these conditions, the risk of failure in establishment of the seeds appears to be definitely reduced.
3. Hay's rnethod.
The method of direct reseeding advocated by Mr. W. D. Hay, and which has been adopted with marked success in many parts of Somerset, lays particular emphasis on cultivations. The method involves what is practically a fallow. The old turf is ploughed up in the late summer, and if necessary cultivated to kill any weeds. Early in the following spring, the land is reploughed and the'dead' turf brought to the surface for final killing and disintegration by surface-harrowing and other cultivations. The land is then ploughed a third time, cultivated, manured and sown to the new ley. By this method not only is the old turf, with its buttercups and other grassland weeds, completely killed, but no doubt a substantial proportion of buried weed seeds is caused to germinate and then killed off as seedlings. Given any sort of luck with the weather, the establishment of the new ley is assured and to a large degree an almost weed-free sward is achieved. The thoroughness lof the cultivations ought to minimize any risk of failure as to take.
4. Disking and cross-disking without ploughing.
This method has a good deal to commend it on the heavy clays as a means of dealing with the problem of regrassing derelict land. Experience gained at the Grassland Improvement Station indicates that sowings of grass seeds made in the autumn on disked surfaces have provided markedly better takes than similar sowings made on ploughed surfaces. The method is one that requires extended trial under a variety of conditions throughout the country. Essentially a method for dealing with derelict land, it has the added advantage that it can be employed on fields difficult to plough.
One point of particular interest regarding disked surfaces is that the soil richest in humus and in organic matter generally is retained on top, and it is into this layer that the seeds mixture is sown. As a first stage in the reconditioning of derelict land, whether on the heavy clays of the Midlands or on the acid soils of the West (with their unweathered and often toxic lower soil) it is sound common sense to place the seeds in humus-rich material rather than on unweathered clay or on sour subsoil.
5. Drastic harrowing to make a seed-bed.
Much good can be done by the severe harrowing of derelict, and sub-derelict grassland. Harrowing in itself helps to break up the root mat and, if supported by the sowing of seeds (outstandingly of wild white clover) and manures, the improvement is still more marked. The heaviest grassland harrows, however, do not normally give a complete kill of the original vegetation. Neither, also, is their power of penetration deep enough to provide a deep tilth. The most drastic of tined harrows do little more than scratch the surface, even after being taken over a field many times. However, they do provide enough bare space and a superficial tilth sufficient to establish white clover, together with (in favourable situations) ryegrass, dogstail and rough-stalked meadow grass. As a pretreatment on derelict lands (including the rough and hill grazings) drastic harrowing, preferably done in the winter months, can prove extremely useful. The method, however, must be regarded as a pretreatment designed to prepare land for the plough or for future disking and direct reseeding to a proper seeds mixture. Similarly, on lowland situations drastic harrowing may be looked upon as a pretreatment for future arable cropping. As a method of cultivation for direct reseeding, drastic harrowing does not compare in efficiency with the plough and/or disks.
6. Rotary cultivators.
Most rotary cultivators provide a surface tilth which is midway between that made by disking and that made by tined harrows respectively. A more or less large proportion of kill of the old vegetation is achieved, but the tilth is rough and not so deep as that made by disks. Rotary cultivators, including the Austral (with duck-foot tines) and Fishleigh, have been used with great success in the roughing-up of hill pastures at Aberystwyth in preparation for immediate reseeding. The advantages obtained by rotary cultivations lie in the fact that, as with the disks, raw, unweathered soil and subsoil is not brought to the surface and the new seeds are, therefore, sown in the humus-rich layers of topsoil.
Pre-frost and Post-frost Ploughing
The evidence as to the benefits of pre-frost ploughing is inconclusive in relation to the problems of direct reseeding. There is no doubt that weathering of deeply ploughed surfaces is beneficial as regards tilths, but whether this advantage has any real bearing upon the success or failure of the ley is not wholly clear. On acid soils in districts of high rainfall, autumn ploughing of sod, while providing good tilths, often results in turf growing up between the furrows during the wet winter months. This old turf is competitive with the new seeds. On the heavy clays of the Midlands, frost action provides a superbly fine top tilth. Land ploughed and prepared during the autumn and late summer of 1940 on the Lias clays of South Warwickshire produced excellent tilths. These appeared in the spring of 1941 almost 'sandy' frost moulds, which became alternately wet and dry, depending upon weather conditions. This 'onion bed' tilth is often an inch deep, and in dry weather it forms a natural mulch overlying the damp soil. The formation of this alternately wetting and drying top layer suggests that spring sowings of grass and clover seed should be drilled in to a depth of about one inch, so as to be readily in contact with soil moisture. The general rule in the drier parts of the country, therefore, is to drill the seeds mixture at about one inch deep in spring, but in autumn to broadcast and place the seed in the ground as shallow as possible. In the more humid western districts and in Wales, where droughts are less intense and where the air conditions generally are more humid, broadcasting will usually provide good takes even in the drier spring months.
Time of Sowing
In the high-rainfall districts of the West and North, May-June sowing will usually be successful. In the drier districts of the Midlands and elsewhere, sowings made after the middle of April carry a correspondingly large proportion of failures. In most years in the lowland areas the optimum date for sowing the seeds mixture is in early spring from about mid-March to mid-April. Precise adherence to a definite date line is not in practice possible, nor desirable. The general rule in every district is to sow as early as the weather and soil conditions will allow. Thus in Norfolk it may often be possible to sow in February or early March whereas on the high ground in North Staffordshire the equivalent weather-cum-soil condition range would not be achieved in most years until April or even May.
In most districts mid-July to mid-August sowings do well and carry only slightly more risk than sowings made in early spring. The risk in upland districts is that the seeds will not get away quickly enough especially in certain years when the late summer period may be dry and winter starts early. Similarly in the more favoured lowlands and in the drier districts, the only real risk is that associated with autumn drought as in 1940 in the Midlands. On the other hand, September sowings of grasses and clovers have often proved to be successful in the South in years when the autumn is mild and winter conditions do not set in until after New Year.
Recent trials at the Grassland Improvement Station indicate that many of the grasses including ryegrass, cocksfoot and timothy will establish with reasonable success when broadcast under winter-sown cereals as late as November or even December. The clovers usually fail completely, however, under these same conditions. Much more detailed investigation is required into the whole question of time of sowing in relation to cultivations, cropping, manuring and seed rates employed.
Drilling versus Broadcasting
This is closely related to the question of depth of sowing. The drill sows to a uniform depth, and this depth can be controlled to a large extent by the setting of the drill. With broadcasting there is no such control of depth and the seeds get covered to all sorts of depths by the harrows and /or rollers. It would be a fair generalization to say that broadcasting is fairly satisfactory in districts with an annual rainfall above 30-32 inches, whereas in districts of lower rainfall it is best to drill the seeds in the spring (aiming to sow one inch deep).
Results of Trials Conducted under the Auspices of the Royal Agricultural Society of England (1937-41)
During recent years, quite considerable areas of land have been reseeded direct to grass in all parts of the country, and these cover a wide range of conditions. A large number of these areas have been brought to our notice and we have had the opportunity of inspecting an appreciable aggregate acreage. In addition to such areas as have been laid out by farmers and others, we have conducted a widely scattered series of experimental sowings throughout England during the course of the years 1937-40. This has been made possible largely through a grant given by the Royal Agricultural Society of England.
Direct reseeding on the upturned sod without a cereal cover crop -- results of R.A.S.E. trials in England (sown 1937 to 1940 inclusive).
Degree of Success (take and growth) No. of Centres Area involved England -- per cent Acres per cent West and North
East and South
Very successful 44 205 72 88 54 Moderately successful 9 39 14 6 27 Failures and partial failures 7 39 14 6 19 Total 60 283 100 100 100
It will be noted that the trials with which we are now concerned were carried out in England, and do not include any of the Welsh experiments in which direct reseeding has proved largely very successful. The proportion of failures is higher in the eastern and southern districts, although the evidence before us suggests it is a matter of soil treatment rather than of district and local climate. Trials situated on the Lias and other obdurate clays in the Midlands have proved less successful than most, and the majority of the failures have been on these soils. Failures are not always to be attributed to drought (but the proportion of failures in dry 1940 was appreciably higher than in previous years). They may just as often be laid against faulty cultivations, including insufficient consolidation, insufficient manuring or not sowing early enough in the spring. Frequently failure can be attributed to mismanagement of the establishing sward.
Applicability of Direct Reseeding to Contrasting Soils and Districts
The case for direct reseeding and the production of new leys has been made as it affects the problem of creating fertility and the consequent land improvements achieved. Direct reseeding without a cover crop has, however, a wider application, and in particular on dairy farms and in the dairying districts generally. There is no crop, whether grass or arable, which will produce more summer milk than will properly established maiden grass. A seeds mixture containing a generous sowing of Italian ryegrass and laid down in the early spring is capable of producing an enormously enhanced output of milk during the months of July, August and September. The dairy farmer should always have an ample acreage of young leys in their first and second years to cover the demands of the summer grazing period.
In many districts, and this is, perhaps, again applicable in particular to the large dairying districts, there are appreciable acreages of low-lying land which, because it is liable to flood, is not particularly well suited to arable cropping. A very large proportion of such land now lies in poor quality permanent grass, characteristically very weedy and whose total output is at a low ebb. The bulk of these grasslands could, with immediate advantage, be ploughed up and reseeded. Many such fields on flood lands may never have been ploughed in the past, on some of them the surface is undulating and very uneven. In those cases it will often be better to disk heavily to make a tilth (and to level up the ground surface in the process) rather than to plough. The point to be stressed is that these flood lands are highly fertile, and are not at the present time and as permanent grassland pulling their weight in the national effort. They are capable of high production if put down to leys. It is also to be emphasized that occasional floods (even deep floods) do much less harm to the ley than to any arable crop. Young seeds can stand flooding to considerable depth, and often over extended periods. First-rate leys have been successfully established on land liable to flood in many parts of the country, including the flood plains of the Rivers Severn, Avon, Lugg, Nene, Ouse and Teme. Some of these leys have been subjected to one or more heavy floodings during the first year after being sown, and still they have survived and have produced excellent swards.
On the fen-like peaty soils such as occur in many river basins in different parts of the country, direct reseeding has proved highly successful in the bringing of poor grassland into higher production. Of particular significance in this connection have been the efforts made on the peaty soils to the north of Wellington, in Shropshire (the moors associated with the valley of the River Tern). Here reseeding with grazing mixtures based on timothy and white clover has proved outstandingly successful. The leafy strains of timothy have proved to be particularly useful, as has also the large-leaved form of white clover (represented by the Aberystwyth S. 100 white clover). Seeds mixtures recommended for such situations are given in Chapter 13.
On sheep country generally, and with particular reference to hill lands in the west and north of England, direct reseeding has a special value not only in producing leys quickly, but also in providing out-of-season grazing both in the first autumn and the following spring, which cannot otherwise be easily produced. Properly constituted leys in their first and second years produce an enormous amount of autumn and winter feed, on which lambs can be fattened and on which, in the spring, ewes and lambs are adequately provided for. Young grass of this type is very palatable, and highly nutritious.
Direct reseeding, therefore, must be regarded as an integral part of our farming policy. The grass ley, be it of long or of short duration, is a crop equivalent in status to different arable crops. The ley in general, and the grazing ley in particular, is also a creator of soil fertility. If we regard the ley both as a crop and as an implement of building up soil fertility, then we can begin to employ it to the best advantage. On dairy farms and on valley flood lands the grass crop derived after direct reseeding on the. upturned sod has claim to a special place. In hilly districts and on land of low initial fertility, direct reseeding equally has its due place both for the production of immediate grass keep for livestock, but also as a means of pretreating the land preparatory to growing arable crops if and when necessary.
In company with other crops, the grass crop has its pests. Once established, leys are remarkably free from deleterious influences, but during the critical months after sowing, there are a number of insect pests which, in some seasons, do considerable damage and may cause partial failures of take. Among these, slugs, leather ackets and wireworm cause damage, and together induce patchiness of 'take'. Turnip-flea is a frequent cause of failure in spring-sown rape and other crucifers used as a part of a seeds mixture. The damage done to the establishing ley sown without a cereal nurse crop is, of course, in the same category as the damage done to a wheat or an oat crop. Experiences in most parts of the country with regard to direct reseeding show that it is only in exceptional cases that the take of seeds is in practice unduly harmed by either wireworm or leatherjackets. During 1940, and again in 1941, however, spring-sown seeds were, in many places, so slow in getting away that loss through pest attack resulted.
Such instances emphasize the general need for thorough cultivations. In the case of fields and of districts known to carry large populations of leatherjackets and/or wireworms, and especially in districts of low rainfall, thorough cultivations are essential in order to bring the caterpillars to the surface. There is a good deal of evidence which suggests that the pest population can in this way be appreciably decreased through the active agency of weather and wild bird life.
Next: 9. Pioneer Crops
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