Fodder grass productivity and soil fertility changes under four grass+tree associations in Kerala, India |
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Authors: | B M Kumar S J George T K Suresh |
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Institution: | (1) College of Forestry, Kerala Agricultural University, KAU P.O., Thrissur, 680656, India;(2) College of Forestry, Kerala Agricultural University, Vellanikkara, Thrissur, 680656, India |
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Abstract: | Adapted tree+grass combinations make a valuable contribution to forage production in the Indian peninsula, but knowledge of
the interactive effects between trees and grasses on their production is limited. We, therefore, conducted a field experiment
involving combinations of four trees and grasses, besides monospecific grass controls, for seven years, to investigate grass
productivity in association with leguminous and non-leguminous multipurpose trees (MPT) having disparate canopy architecture,
and to assess the end-of-rotation soil fertility changes. Post rotation changes in herbage productivity were evaluated by
growing teosinte (Zea mexicana) for three years. The four MPTs were Acacia auriculiformis, Ailanthus triphysa, Casuarina equisetifolia and Leucaena leucocephala. Grasses included Pennisetum purpureum (hybrid napier), Brachiaria ruziziensis (congo signal), Panicum maximum (guinea grass) and teosinte. Lower tree branches were pruned from fifth year. Understorey herbage production increased until
three years in all tree+grass combinations, but declined subsequently, as tree crowns expanded. Overall, casuarina among MPTs,
and hybrid napier and guinea grass among forage crops, were more productive than others. Pruning MPTs generally favoured greater
herbage production. Understorey light levels for acacia, ailanthus, casuarina and leucaena were 17, 60, 55 and 55% of that
in the open at five years. During the post-rotation phase, MPT plots were characterised by higher soil nutrient capital and
consequently teosinte yields were higher than in the treeless control treatment. All previous tree-grass combinations showed
an increasing trend till two years after MPT felling. Yield levels declined subsequently, despite at variable rates. Careful
selection of the tree and grass components is, therefore, crucial for optimising herbage productivity in silvopastoral systems.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | crown architecture photosynthetic photon flux density shade tolerance silvopastoralism understorey herbage yield |
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