Carbon cycling in the coastal zone affects global carbon budgets and is critical for understanding the urgent issues of hypoxia, acidification, and tidal wetland loss. However, there are no regional carbon budgets spanning the three main ecosystems in coastal waters: tidal wetlands, estuaries, and shelf waters. Here we construct such a budget for eastern North America using historical data, empirical models, remote sensing algorithms, and process‐based models. Considering the net fluxes of total carbon at the domain boundaries, 59 ± 12% (± 2 standard errors) of the carbon entering is from rivers and 41 ± 12% is from the atmosphere, while 80 ± 9% of the carbon leaving is exported to the open ocean and 20 ± 9% is buried. Net lateral carbon transfers between the three main ecosystem types are comparable to fluxes at the domain boundaries. Each ecosystem type contributes substantially to exchange with the atmosphere, with CO2 uptake split evenly between tidal wetlands and shelf waters, and estuarine CO2 outgassing offsetting half of the uptake. Similarly, burial is about equal in tidal wetlands and shelf waters, while estuaries play a smaller but still substantial role. The importance of tidal wetlands and estuaries in the overall budget is remarkable given that they, respectively, make up only 2.4 and 8.9% of the study domain area. This study shows that coastal carbon budgets should explicitly include tidal wetlands, estuaries, shelf waters, and the linkages between them; ignoring any of them may produce a biased picture of coastal carbon cycling.

A procedure and equipment which make possible a continuous output of 250 to 300 determinations of in vitro digestibility of organic matter per week are described.The eifect on in vitro digestibility values of removing rumen liquor from sheep at various times before and after feeding, mixing of rumen liquors from different sheep, and nitrogen supplementation ofthe inoculum are investigated. Results are given of a comparison of" the effect of soil contamination on //; vitro data when expressed as digestibility of dry matter and digestibility of organic matter. The levels of within and between-batch errors are stated and the accuracy of prediction of feeding value is discussed.

Tilley et al. (1) have clearly demonstrated that their rumen liquor and pepsin procedure for the determination of digestibility of herbage is useful and precise. The method has, however, the disadvantage that the equipment required for the centrifugation stages is relatively expensive and, moreover, when using one centrifuge only the procedure is somewhat tedious. The method outlined below completely eliminates centrifugation; the rumen‐liquor stage is terminated by acidification and the residues from the pepsin stage is recovered by filtration, using a filter aid. Digestible dry matter or digestible organic matter may be determined; results for the former estimation on thirteen samples already examined at Hurley have given satisfactory results.

A report is presented on studies on the relationship between in vitro digestibility of 18 silage samples and their in vivo digestibilities. Various analytical techniques are compared and the method adopted, on grounds of suitability for routine operation and accuracy of prediction of in vivo data, is based on analysis of homogenates of fresh silage. The homogenates, sufficiently uniform to permit of volumetric subsampling at acceptable error levels, are prepared in a new design of homogenizer. The impact of the % dry matter of the silage, as fed, on the accuracy of in vitroj in vivo relationships is considered and a bivariate regression plane is proposed. REVIEWThe assessment of organic-matter or drymatter digestibility by a two-stage in vitro technique is already established as a feasible routine laboratory technique for herbages (1, 3, 4, 5, 10, 11) and certain forage crops (6). The scope of application of such techniques in silage evaluation clearly depends on the extent to which in vitro digestibility reflects any depressive changes in in vivo digestibility induced by the conservation process.Application of the in vitro technique as developed in these laboratories to silage gave only poor in vitro/in vivo relationships, the correlation for 10 silages being non-significant (1). This finding confirmed the work of Raymond and Terry (8) and that of Simpkins and Baumgardt (9). These workers, although using diiferent techniques, also foxmd the in vitrojin vivo relationships in silages to be unsatisfactory. DEVELOPMENT OF METHODBecause of the unsatisfactory correlations obtained when dried silages were analysed, alternative methods of preparation were considered. Vacuiun drying to a residual moisture content of approximately 10%, milling at this moisture content and weighing out for in vitro digestibility and residual moisture determination, gave improved results for the 10 silages (r = 0-89; R.S.D.±2-10) (1). However the difficulties of vacuum drying and the necessity to determine a residual moisture content, made further development of this procedure not worthwhile. Consideration was then given to freeze milling of wet materials (7). A number of pulverizing devices was used on a forage/COg mixture and although a fairly fine state of division could be achieved there remained some disadvantages principally associated with the handling of the solid COj and with the physical state of the milled product after thawing.Further experiments with the 10 silages, undried and relatively coarsely chopped (Crypto AC22 food mincer), indicated that analyses of undried silage would give a high degree of predictive accuracy (r=0-94; R.S.D.±l-64) (1). Sampling errors were, however, large and specific wei^ts, dictated by the DM content, were required for each estimation of digestibility.These experiments with silage confirmed the inference by Raymond and Terry (8) that the drying process is contributory to the depressed correlations foimd. The best approach was thus thought to be the homogenization of a fairly large weight of silage ...

Much of the published digestibility data refer to swards grown in the south of Britain. In order to study digestibility curves in a more northerly latitude, several pure swards were established in the west of Scotland in 1962 and 1963. Varieties included S22 and Tetila Italian ryegrass, S37 cocksfoot, S170 tall fescue, S215 meadow fescue, Scots timothy, English broad red clover, and SI00 white clover. In addition to primary growth in vitro digestibility, the effect of various cutting managements on digestibility and productivity was measured. Flowerhead emergence was delayed, with the result that the digestibility curve was later than is reported from southern Britain. Highest yields of digestible organic matter were obtained from the less frequent cutting regimes, but the mean digestibility of the herbage was lower. Predictibility of herbage digestibility is desirable as the basis of a reliable and planned herbage utilization programme, particularly for conservation.

Tb« cfTecis of variety, dale of cutting ffush gitmih ami Icvd of niimgenoin manunnson thecrodcprotcin omicni of lt.iltan O'cgrass were studkd on ploM cut (i\x timw in I**?** Raixini! the level of nitro^nous fcrtiliTer from 174 Ih. to 348 Ih, N acre rcdu^d ihe penxnta^of dry rnatlcr from 0-5 to 2-0 and incrraised tlic perventaitc nf crude piolcin m lhe dry matlcr from 09 lo 5-1, with net increases in crude pnMein/frcsh rnalctial of frnni 0 W> lo 0 .S7°u. Varielics fihowfJ consistent ditTcrcnccs. the three Westcrwollh tv|H•^. New /ctiliiml H.l und New Zealand tlutiiui t^cinu liiulKr in |H-rccntage crude protein than Ayrshire, hlith, OiLnish und S22.Ciiilhilf Ihc ttinU (growth carticr resulted in nn iiKroascd iictvciitii||c of crude protein for that particular cut, but nu uvemtl increase In mean crude-protcin percentage.Italian r)CKra» grown without an accompanying legume has a disappointingly low crudc-protcin content, c\en when lush and green-An experiment was set up at Auchincniivv lo compare the cnidc-proteiQ contents of nine Italian ryegrass \arietks on two cutting schedules ai two le\els of nitrogenous manuring. rXPtKlMENTAL METHODS Slalixtical layoutA split-plot randomized block layout involving 108 plots each 8x1*5 yd. was chosen. Tlic following treatments were replicated ihrcu limes: Main plotH High nitrogen 4 cwt.

No abstract

When light dressings of 0-75, 1-50 and 2-25 cwt muriate of potash per acre (60% KgO) were applied in autumn and spring to swards receiving two levels of sulphate of ammonia, 30 or 60 lb N/acre, and kieserite (29% MgO) at 0, 4 or 12 cwt/acre, magnesium content was reduced as the level of muriate of potash increased. Autumn application resulted in a higher magnesium content, at the expense of the amount of the potash absorbed in the spring herbage. The effects at the lowest levels of application of muriate of potash were slight and became insignificant in later herbage samples.