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The use of imaging spectroscopy to predict the herbage mass of dry matter (DM), DM content of herbage and crude fibre, ash, total sugars and mineral (N, P, K, S, Ca, Mg, Mn, Zn and Fe) concentrations was evaluated. The experimental system used measured reflectance between 404 and 1650 nm at high spatial (0AE28-1AE45 mm 2 ) and spectral resolution. Data from two experiments with Lolium perenne L. mini-swards were used where the degree of sward damage or N-fertilizer application varied. Regression models were calibrated and validated and the potential reduction in prediction error with multiple observations was estimated. The mean prediction errors for DM mass, DM content and N, total sugars, ash and crude fibre concentrations were 235-268 kg ha )1 , 9AE6-16AE8 g kg )1 , 2AE4-3AE4 g kg DM )1 , 16AE2-27AE7 g kg DM )1 , 5AE8-6AE5 g kg DM )1 and 8AE4-10AE4 g kg DM )1 respectively. The predictions for concentrations of P, K, S and Mg allowed identification of deficiency levels, in contrast to the concentrations of Na, Zn, Mn and Ca which could not be predicted with adequate precision. Prediction errors of DM mass may be maximally reduced to 95-142 kg ha )1 with 25 replicate measurements per field. It is concluded that imaging spectroscopy can provide an accurate means for assessment of DM mass of standing grass herbage. Predictions of macronutrient content and feeding value were satisfactory. The methodology requires further evaluation under field conditions.

Rapport 1064Kasper, G.J., Teelt van sorghum als voedergewas lijkt perspectiefvol in Nederland.Wageningen Livestock Research, Rapport 1064.Samenvatting NL Sorghum kan in korte tijd veel voedingsstoffen opnemen, ook op armere en droge gronden, en gaat efficiënt om met voedingsstoffen, vooral stikstof en water. Het gewas groeit goed op gronden waar ook snijmaïs het goed doet. Recente proefveldonderzoeken in Nederland tonen ten opzichte van maïs gelijke tot 25% hogere opbrengsten (ds/ha/jaar), hogere gehalten aan ruw-eiwit (tot 69%) en zetmeel (-10 tot +24%). Kennishiaten zijn: 1) kennis over de voederwaarde, 2) gebrek aan praktische kengetallen over teelt, fermentatie en dierprestaties, 3) combiteelt winterrogge-sorghum in het groeiseizoen en 4) tussenteelt van sorghum bij continuteelt van snijmaïs. Summary UKSorghum absorbs a lot of nutrients in a short period of time, even on rather poor and dry soils. The crop has a favourable nitrogen and water use efficiency. The crop grows well on soils where maize grows well too. Recent field trial studies in the Netherlands show equal or higher than 25% yields (dry matter/ha/year), higher levels of crude protein (up to 69%) and starch (-10% to +24%) than maize.Knowledge gaps are: 1) feed evaluation characteristics, 2) practical data on cultivation, fermentation and animal performance, 3) combi-cultivation winter rye and sorghum per growing season, and 4) intercropping of sorghum in continuous maize cropping. De belangrijkste kennishiaten voor onderzoek van sorghum in Nederland zijn:• voederwaardering sorghum: het ontbreekt voornamelijk aan gegevens over de (darm)verteerbaarheid en de afbreekbaarheid in de pens.• melkveehouders vragen concrete cijfers van praktijkpercelen (o.a. drogestofopbrengsten), maar ook voederwaardering, voeropname, mycotoxinendruk en dierprestaties van ingekuilde sorghum.• het bepalen van broeikasgasemissies inclusief C-vastlegging in, en erosie van de bodem.• America. In Europe, most research data on the use of sorghum as dairy cattle feed originate fromFrance and Italy, where the crop has been evaluated for yield, feeding value including animal performance. In Italy, the effects of sorghum on greenhouse gas emissions and milk composition also have been studied.The purpose of this research is to explore the potential of sorghum as a fodder crop in North WestEurope with emphasis on the Netherlands, including feed and animal performance, compared to those of maize.Sorghum as a fodder crop can be distinguished in two types: a type that resembles grass (Sorghum Sudan) and a type that contains both green leaf and grain (Sorghum bicolor). Sorghum can grow on all soils where maize also grows well, preferably with a pH of 6.5 to 8. The crop can quickly absorb a lot of nutrients, even on rather poor and dry soils. This means that sorghum is efficiently dealing with nutrients, especially nitrogen and water. In the temperate climate of North West Europe, especial attention must be taken to the seeding period (germination, young plant and period from bloom), th...