A function for describing nitrogen uptake, dry matter production and rooting by wheat crops.

摘要: The quantities,Y, of nitrogen taken up, and dry matter produced, at various times during the growth six winter wheat crops Rothamsted were shown to be related thermal time,x, based on soil temperature, by a simple equation $$Y = (A^{ - 1/n} + \exp ( kx))^{ n} $$ whereA is ultimate maximum ofY, n shape factor andk rate constant that toA andn throughx′, inflexion point function. value ofn was 1.5 for both N uptake matter. ofA uptake,A , well described multiple regression sowing data,t s expressed as number days after August 31st, rainfall,R Apr in April before harvest, but no such could found matter,A D . constants,k N-uptake dry-matter production respectively, date weather through corresponding points,x′ andx′ Highly significant regressions found, forx′ time,t sf between return field capacity reciprocal oft function used generate curves from values (obtained fromx′ ) given inserting appropriate ofR ,t andt regressions. These fitted measured uptakes satisfactorily obtain regressions, four grown subsequently, Rothamsted, also Woburn. Values had set arbitrarily because been predict them, using these arbitrary gave measurements all ten two Woburn crops. Tests seasonal site effects showed thatA influenced more differences sites than other those inR whereasA strongly differencess very little sites.