Legumes as nitrate catch crops during dry to wet transition in lowland rice cropping systems

In tropical rice (Oryzas ativa L.) lowlands, NO~as similation by plants during the transition from the dry to the wet season can preclude NO~ loss upon soil ttooding and permit recycling of this N. In a 2-yr field study in an Alfisol in the Philippines, we examinedt he role of legume crops and weeds during the dry-to-wet (DTW) transition in conserving and/or recycling soil NO~ that accumulated under varied dryseason fallow management. During the May-to-July DTWtr ansition, Sesbania rostrata (Bremek. & Oberm.), mungbean [Vigna radiata (L.) W’dczek], weedy, and weed-free treatments were subplots in the Februaryto- May dry-season mainplots of weedy, weed-free, and frequently tilled fallows. Legumeb iological N2 fixation (BNF)w as measured b~v ~SNd ilution. Dependingo n dry-season management,t he maximume xtracted N (top 60-cm layer) in the DTWtr ansition ranged from 38 to 164 kg ha-~; this N was 62 to 96% NO~-. Soil N uptake by weeds ranged from 31 to 46 kg N ha-~, that by mungbeanf rom 29 to 80, and by S. rostrata from 46 to 125. The minimumes timates of DTWtr ansition NO~l oss varied from none when plants were present to 107 kg N ha-~ in weedfree fallows. LegumeB NFp artially offset NO~lo ss, although increased soil NO~- decreased BNF-N. Nitrogen fixed ranged from 37 to 63 kg N ha-~ by mungbeana nd 68 to 154 by S. rostrata. Harvest of mungbean caused negative BNF-Nc ontribution to the succeeding rice crop in a few cases. In lowland rice-based cropping systems, weeds are effective in conserving soil N during the DTWtr ansition, but legumes are more suitable nitrate catch crops because they allow the harvest of an economic product or the recycling of more N to a subsequent flooded rice crop.Discover the wor

---

• View source

---

DOI:

https://doi.org/10.2134/agronj1994.00021962008600020011x

---

Altmetric score:

Dimensions Citation Count: