Juglans Regia ‘Xinxin2’ Leaf Spectral Analysis Based On The Fertilization Experiment

Juglans regia ‘Xinxin2’ is one of the main walnut tree cultivars in walnut producing area of Nanjiang Basin, which occupies an important position in Xinjiang characteristics forest fruit industry. But the long-term lack of timely and effective means of tree nutrition monitoring affects the realization of tree nutrition diagnosis and optimal fertilization. In this study, J.regia ‘Xinxin2’ in flourishing period was taken as research object, based on field trial of fertilizer effect, using live and healthy leaves spectroscopic technique combined with indoor chemical analysis, leaves spectral reflectance of fruit different growth period under different nitrogen(N), phosphorus(P) and potassium(K) levels was analyzed, the response of leaves reflectance on fertilization was clarified, sensitive bands under different N, P, K levels were determined, the related equations of foliar N, P, K element concentration with spectral index as independent variables were constructed.Specific results are as follows:The spectral reflectance of walnut J.regia ‘Xinxin2’ leaf depends on its wavelength. Reflectance presented certain spectral characteristics which were "blue valley", "green peak", "red valley", "red edge" and high reflective platform at 440-500 nm, 520-600 nm, 610-670 nm, 690-750 nm and 750-1 010 nm. Reflectance of fruit different growth period changed similarly, it decreased at 535-565 nm from fruit-set period to fruit fat changes period and at 750-1 010 nm with growth period changing, varied under different N, P, and K levels, exhibited certain regularity in response to N, exhibited no regularity in response to P, K. Under different N levels, reflectance decreased with increased N levels at 520-640 nm in fruit-set period, 510-650 nm in fruit fast-growing period, 515-620 nm in fruit hardcore period, 460-695 nm in fruit fat changes period, 440-640 nm in fruit mature period.The sensitive bands of N, P, and K were different. Under different N, P, and K levels, in different fruit growth periods, N, P, and K sensitive bands were 525-605 nm, 525-655 nm, 750-1 100 nm.In fruit-set period, fruit fast-growing period, fruit fat changes period, fruit mature period, spectral index ND( 525,605)had highly significant linear positive correlation with N concentration. In fruit hardcore period, spectral index ND(525,605)had significant linear positive correlation with N concentration. In fruit-set period, fruit fast-growing period, fruit hardcore period, fruit mature period, spectral index ND(525,655)had highly significant linear positive correlation with P concentration. In fruit fat changes period, spectral index ND(525,655)had significant linear positive correlation with P concentration. In whole fruit growth period, index ND(750,1100)had highly significant linear positive correlation with K concentration.The results of the study showed that there was a possibility to achieve walnut tree nutrition monitoring by spectral analysis.