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Title: Light Intensity Effects on Growth and Nutrient Use Efficiency of Tropical Legume Cover Crops

item Baligar, Virupax
item PAIVA, A
item SOUZA, JR., J
item LUCENA, E
item FARIA, J
item CABRAL, R
item JORDA, JR., J

Submitted to: Agroforestry Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2006
Publication Date: 4/1/2009
Citation: Baligar, V.C., Fageria, N.K., Paiva, A., Silveira, A., Souza, Jr., J.O., Lucena, E., Faria, J.C., Cabral, R., Pomella, A.W., Jorda, Jr., J. 2009. Light Intensity Effects on Growth and Nutrient Use Efficiency of Tropical Legume Cover Crops. Agroforestry Systems. 4:67-70.

Interpretive Summary: In tropical regions, plantation crops are planted with wide spacing. Such planting leads to soil loss by erosion. Inclusion of quick growing cover crops in early stages of plantation crop establishment will help to reduce soil loss by erosion and assist in buildup of the soil organic matter content of these tropical soils. Invariably, plantation crops in the tropics are grown under shade trees, and as plants develop, a small amount of light reaches ground level. Cover crops that tolerate low levels of light intensity have a better chance of surviving and protecting the soil from erosion. An experiment was conducted in a growth chamber to evaluate the performance of nine cover crops under low and high light intensities. Among the nine cover crops tested, cowpea, sesbania, lab-lab and sunhemp, produced good growth and a higher nutrient uptake than other legumes at lower, as well as higher, light intensities. These plant species appear to be suitable cover crops to grow under plantation crops to help protect soils from erosion and increase the soil organic matter content. Such an improvement in soil productivity could enhance the yield potential of plantation crops such as cacao, coffee, banana, and tea.

Technical Abstract: Cover crops in tropical plantations are grown as understory plants, and light intensity at ground level has major effects on growth, development, nutrient requirement, and survivability of these plants. A growth chamber experiment was conducted to assess the influence of low levels of photosynthetic photon flux density (PPFD) on growth and macro nutrient uptake parameters (uptake, influx, transport) and use efficiency in erect legume cover crops. Two PPFD (200, 400 umol m-2 s-1) were imposed by constructing mini shade frames covered with various layers of plastic cloth. Nine cover crops used in this study include: joint vetch, sunhemp, crotalaria ochroleuca, showy crotalaria, hairy indigo, lab-lab, sesbania, tropical Brazilian stylo, and cowpea. Significant PPFD affects were observed on growth and nutrient uptake parameters (uptake, use efficiency). Crop species X PPFD interaction was significant for nutrient uptake and efficiency ratio. Cowpea, sesbania, lab-lab, and sunhemp, produced good growth and higher nutrient uptake than other legumes at lower as well as at higher PPFD. The lowest yielding species were Brazilian stylo and hairy indigo. These species also had the lowest nutrient requirements. Higher shoot growth at higher PPFD treatment, suggested higher productivity of the crop species tested in higher radiation environments. Furthermore, legume cover crop species tested in this experiment were sensitive to low PPFD, but showed inter specific differences in growth and nutrient uptake and use efficiency. Adapting an appropriate cover crop species might help to enhance soil and water conservation, and improve soil fertility under low PPFD tropical plantation crops.