000			03313nab a22004097a 4500
999			_c9082 _d9082
001			G18753
003			MX-TxCIM
005			20211006084805.0
008			121211s1997 xxu|||p op||| | eng d
022			_a1435-0645
022			_a1435-0645 (Online)
024	8		_ahttps://doi.org/10.2134/agronj1997.00021962008900040004x
040			_aMX-TxCIM
041	0		_aeng
043			_aMX
090			_aLook _bunder journal title
100	1		_aChapman, S. _9458
245	0	0	_aUsing a chlorophyll meter to estimate specific leaf nitrogen of tropical maize during vegetative growth
260			_aMadison, WI (USA) : _bAmerican Society of Agronomy, _c1997.
340			_aPrinted
500			_aPeer review
500			_aPeer-review: Yes - Open Access: Yes|http://science.thomsonreuters.com/cgi-bin/jrnlst/jlresults.cgi?PC=MASTER&ISSN=0002-1962
520			_aChlorophyll meters are used as a quick, inexpensive method of estimating leaf N concentration in both experiments and production fields. Direct use of the meter readings is complicated by effects of crop age and cultivar on leaf N concentration, at least partly due to variation in leaf thickness. Research in rice (Oryza sativa L.) shows that readings can be adjusted to account for these effects, and this study sought to establish whether similar relationships exist for tropical maize (Zea mays L.). Additionally, we examined several aspects of sampling methodology. In several field trials in Mexico in 1994 and at different stages of growth (6, 8, 14 leaves expanded) and for plots with different N treatments (0 N, 21 cultivars; 150 kg N h−1, 7 cultivars), meter readings were taken from five leaves per plot, with five readings near the middle of the leaf blade. Leaf N concentration (g N kg−1 dry matter) was significantly linearly correlated with the meter readings (y = 1.46x − 30.68, r 2 = 0.81), but the coefficients of fit differed greatly across data sets and growth stages. Adjusting the meter readings by dividing by specific leaf weight (SLW, g leaf m−2 leaf) resulted in an improved fit within and across data sets (y = 33.47x − 6.55, r 2 = 0.97). The meter readings were also directly correlated with specific leaf N (SLN, g N m−2 leaf) (y = 0.387x − 0.476, r 2 = 0.92) with no adjustments. Analysis of sampling patterns determined that at least four leaves per plot are needed, with several observations per leaf, and that readings should be taken at a point lying between about 40 and 70% along the leaf length from the leaf base. For scientists and farmers with limited direct access to laboratory analysis for N, the meter provides a cheap and convenient estimate of leaf N per unit leaf area during vegetative growth.
546			_aText in English
591			_a9710|EE|R97-98ANALY|Maria|anterior|Fdo|FINAL9798|1
595			_aCSC
595			_aSC
650		7	_aMaize _gAGROVOC _2 _91173
650		7	_aNitrogen content _2AGROVOC _95218
650		7	_aPlant developmental stages _2AGROVOC _95197
650		7	_aResearch projects _91237 _2AGROVOC
650		7	_91314 _aZea mays _2AGROVOC
653	0		_aTropical maize CIMMYT
700	1		_aBarreto, H. _95574
773	0		_tAgronomy Journal _gv. 89, no. 4, p. 557-562 _dMadison, WI (USA) : American Society of Agronomy, 1997. _w444482 _x0002-1962
942			_cJA _2ddc _n0