ABSTRACT
Recently high spectral resolution sensors have been developed, which allow new and more advanced applications in agriculture. Motivated by the increasing importance of hyperspectral remote sensing data, the need for research is important to define optimal wavebands to estimate biophysical parameters of crop. The use of narrow band vegetation indices (VI) derived from hyperspectral measurements acquired by a field spectrometer was evaluated to estimate bean (Phaseolus vulgaris L.) grain yield, plant height and leaf area index (LAI). Field canopy reflectance measurements were acquired at six bean growth stages over 48 plots with four water levels (179.5; 256.5; 357.5 and 406.2 mm) and tree nitrogen rates (0; 80 and 160 kg ha-1) and four replicates. The following VI was analyzed: OSNBR (optimum simple narrow-band reflectivity); NB_NDVI (narrow-band normalized difference vegetation index) and NDVI (normalized difference index). The vegetation indices investigated (OSNBR, NB_NDVI and NDVI) were efficient to estimate LAI, plant height and grain yield. During all crop development, the best correlations between biophysical variables and spectral variables were observed on V4 (the third trifoliolate leaves were unfolded in 50 % of plants) and R6 (plants developed first flowers in 50 % of plants) stages, according to the variable analyzed.
ABSTRACT
Recently high spectral resolution sensors have been developed, which allow new and more advanced applications in agriculture. Motivated by the increasing importance of hyperspectral remote sensing data, the need for research is important to define optimal wavebands to estimate biophysical parameters of crop. The use of narrow band vegetation indices (VI) derived from hyperspectral measurements acquired by a field spectrometer was evaluated to estimate bean (Phaseolus vulgaris L.) grain yield, plant height and leaf area index (LAI). Field canopy reflectance measurements were acquired at six bean growth stages over 48 plots with four water levels (179.5; 256.5; 357.5 and 406.2 mm) and tree nitrogen rates (0; 80 and 160 kg ha-1) and four replicates. The following VI was analyzed: OSNBR (optimum simple narrow-band reflectivity); NB_NDVI (narrow-band normalized difference vegetation index) and NDVI (normalized difference index). The vegetation indices investigated (OSNBR, NB_NDVI and NDVI) were efficient to estimate LAI, plant height and grain yield. During all crop development, the best correlations between biophysical variables and spectral variables were observed on V4 (the third trifoliolate leaves were unfolded in 50 % of plants) and R6 (plants developed first flowers in 50 % of plants) stages, according to the variable analyzed.
ABSTRACT
During the winter season of 1995 a field experiment was conducted in Piracicaba, SP, Brazil, to analyse the radiation use efficiency ( FONT FACE="Symbol">e /font>) and the harvest index (IC) of the wheat cultivar IAC-287 'YACO', when submitted to drought stress at different growth stages. The experiment was a randomized complete block design with five treatments and three replicates. The drought stress was applied during tillering, booting, grain filling and ripening stages. The radiation use efficiency for fitomass production ( FONT FACE="Symbol">e /font>F) was reduced by 22.8 and 15.4% when compared to the control treatment, for drought stress applied during tillering and booting stages, respectively. The drought stress, when applied during tillering, booting and grain filling stages, reduced the radiation use efficiency for grain production ( FONT FACE="Symbol">e /font>G) by 21.1, 22.2 and 22.2%, respectively, when compared to the control treatment. With regard to the harvest index (IC), the drought stress effect had a major impact on the grain filling stage, being reduced by 19.1% when compared to the control treatment. A less intense reduction of the harvest index, when compared to the control treatment, was also observed, when drought stress was applied during booting (7.5%, p 0.05) and ripening stages (7.9%, p 0.05).
Durante a safra de inverno de 1995 conduziu-se um experimento de campo, em Piracicaba, SP, para analisar a eficiência do uso da radiação ( FONT FACE="Symbol">e /font>) e o índice de colheita (IC) do cultivar de trigo IAC-287 'YACO', quando submetido ao estresse hídrico em diferentes estádios de desenvolvimento da cultura. O delineamento foi em blocos ao acaso com cinco tratamentos e três repetições. O estresse hídrico foi aplicado nas fases de perfilhamento, espigamento, enchimento de grãos e maturação. A eficiência do uso da radiação para produção de fitomassa ( FONT FACE="Symbol">e /font>F) foi reduzida em 22,8 e 15,4% em relação à testemunha, quando o estresse hídrico foi aplicado durante as fases de perfilhamento e de enchimento de grãos, respectivamente. O estresse hídrico, quando aplicado durante as fases de perfilhamento, espigamento e enchimento de grãos, reduziu a eficiência do uso da radiação para a produção de grãos ( FONT FACE="Symbol">e /font>G) em 21,1; 22,2 e 22,2%, respectivamente, em relação à testemunha. Com relação ao IC, o efeito do estresse hídrico foi maior quando aplicado durante o enchimento de grãos, cuja redução em relação à testemunha foi de 19,1%. Uma redução do IC, em relação à testemunha, também foi observada, em menor intensidade, quando o estresse hídrico foi aplicado nas fases de espigamento (7,5%, p 0,05) e de maturação (7,9%, p 0,05).
ABSTRACT
During the winter season of 1995 a field experiment was conducted in Piracicaba, SP, Brazil, to analyse the radiation use efficiency ( FONT FACE="Symbol">e /font>) and the harvest index (IC) of the wheat cultivar IAC-287 'YACO', when submitted to drought stress at different growth stages. The experiment was a randomized complete block design with five treatments and three replicates. The drought stress was applied during tillering, booting, grain filling and ripening stages. The radiation use efficiency for fitomass production ( FONT FACE="Symbol">e /font>F) was reduced by 22.8 and 15.4% when compared to the control treatment, for drought stress applied during tillering and booting stages, respectively. The drought stress, when applied during tillering, booting and grain filling stages, reduced the radiation use efficiency for grain production ( FONT FACE="Symbol">e /font>G) by 21.1, 22.2 and 22.2%, respectively, when compared to the control treatment. With regard to the harvest index (IC), the drought stress effect had a major impact on the grain filling stage, being reduced by 19.1% when compared to the control treatment. A less intense reduction of the harvest index, when compared to the control treatment, was also observed, when drought stress was applied during booting (7.5%, p 0.05) and ripening stages (7.9%, p 0.05).
Durante a safra de inverno de 1995 conduziu-se um experimento de campo, em Piracicaba, SP, para analisar a eficiência do uso da radiação ( FONT FACE="Symbol">e /font>) e o índice de colheita (IC) do cultivar de trigo IAC-287 'YACO', quando submetido ao estresse hídrico em diferentes estádios de desenvolvimento da cultura. O delineamento foi em blocos ao acaso com cinco tratamentos e três repetições. O estresse hídrico foi aplicado nas fases de perfilhamento, espigamento, enchimento de grãos e maturação. A eficiência do uso da radiação para produção de fitomassa ( FONT FACE="Symbol">e /font>F) foi reduzida em 22,8 e 15,4% em relação à testemunha, quando o estresse hídrico foi aplicado durante as fases de perfilhamento e de enchimento de grãos, respectivamente. O estresse hídrico, quando aplicado durante as fases de perfilhamento, espigamento e enchimento de grãos, reduziu a eficiência do uso da radiação para a produção de grãos ( FONT FACE="Symbol">e /font>G) em 21,1; 22,2 e 22,2%, respectivamente, em relação à testemunha. Com relação ao IC, o efeito do estresse hídrico foi maior quando aplicado durante o enchimento de grãos, cuja redução em relação à testemunha foi de 19,1%. Uma redução do IC, em relação à testemunha, também foi observada, em menor intensidade, quando o estresse hídrico foi aplicado nas fases de espigamento (7,5%, p 0,05) e de maturação (7,9%, p 0,05).