Measurement and simulation of solar radiation availability in relation to the growth of coffee plants in an agroforestry system with rubber trees

Abstract

Solar radiation is an important factor for plant growth, being its availability to understory crops strongly modified by trees in an Agroforestry System (AFS). Coffee trees (Coffea arabica - cv. Obatã IAC 1669-20) were planted at a 3.4 x 0.9 m spacing inside and aside rows of monocrops of 12 year-old rubber trees (Hevea spp.), in Piracicaba-SP, Brazil (22º42'30" S, 47º38'00" W - altitude: 546m). One-year-old coffee plants exposed to 25; 30; 35; 40; 45; 80; 90; 95 and 100% of the total solar radiation were evaluated according to its biophysical parameters of solar radiation interception and capture. The Goudriaan (1977) adapted by Bernardes et al. (1998) model for radiation attenuation fit well to the measured data. Coffee plants tolerate a decrease in solar radiation availability to 50% without undergoing a reduction on growth and LAI, which was approximately 2m².m-2 under this condition. Further reductions on the availability of solar radiation caused a reduction in LAI (1.5m².m-2), thus poor land cover and solar radiation interception, resulting in growth reduction.

Phenological and physiological evaluation of first and second cropping periods of sorghum and maize crops

“…Environmental conditions in the winter period were preponderant so that net assimilation rate was lower than in the first cropping for both crops (Figure 7a,b). Low temperatures may have promoted inhibition in chloroplast function, altering the composition of foliar pigments (Maulana & Tesso, 2013), as well as lower levels of solar irradiance and water availability, especially during vegetative growth (Righi et al, 2007). Increases in VPD values, as well as low rainfall levels, probably drove the reduction F I G U R E 8 Water use Efficiency (a and b) in sorghum and maize plants, according to the evaluation period (days after emergence) and planting of the first cropping (•) and second cropping (□) in Viçosa, Minas Gerais.…”

RESPONSES OF EUCALYPTUS CAMALDULENSIS SPROUTS TO SHADE: AN EVALUATION OF CANOPY PLASTICITY

“…The SLA values exhibited by E. camaldulensis (8.6 m 2 •kg −1 ) are similar to those found in coffee plants in full sun. For the latter, values were twice as higher of those plants that submitted to about 50% IR (Righi et al, 2007). Quentin et al (2011) found a compensatory response of transpiration rate and canopy conductance of partially defoliated E. globulus.…”

“…A much denser canopy in plants exposed to high irradiation levels was expected. This is commonly found in many cultures such as coffee plants (Righi et al, 2007) where canopies are twice as dense in monocrop cultures (full-sun) than plants cultivated in agroforestry under rubber trees receiving about half of the available sun irradiation. Denser canopies found in full-sun coffee plantations can be viewed as an adaptation, not only to capture more radiation, but also to protect plants from the high irradiance levels in the tropics.…”

Arquitetura da copa do cafeeiro arábica conduzido com diferentes números de ramos ortotrópicos

“…Essa superioridade de produção em função do manejo com dois ramos ortotrópicos, para a referida safra, foi favorecida por diversos fatores, dentre os quais ressaltam-se as características favoráveis da arquitetura da copa (área e volume de copa, densidade de enfolhamento, o número e o comprimento do ramo plagiotrópico, o comprimento dos internódios dos ramos plagiotrópicos e ortotrópicos, o número de nós e a área foliar dos ramos plagiotrópicos). Pode-se dizer que essas características, possivelmente, tenham favorecido a formação de microclima no dossel dessas plantas, capaz de melhorar aspectos fisiológicos e bioquímicos, embasando estas considerações nas observações de DaMatta & Rena (2002), DaMatta (2004a), Lunz (2006) e Righi et al (2007).…”