| Journal Article |
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| Article Title | Fallow and Sesbania effects on soil nitrogen dynamics in lowland rice-based cropping system | | Author | Roland J Buresh, T T Chua, E G Castillo, S P Liboon and Dennis P Garrity | | Year | 1993 | | Journal Title | Agronomy Journal | | Institution | HighWire Press | | Volume | 85 | | Issue | 2 | | Pages | 316-321 | | Call Number | JA0050-04 | | Keywords | Fallow, Sesbania rostrata, soil nitrogen, Oryza Sativa |
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| Abstract: |
| Extensive areas of rice-growing (Oryza sativa) lowlands in Asia are fallowed or cropped with non-rice crops for part of the year. Nitrate can accumulate during the fallow or non-rice crop, but this nitrate can be lost upon flooding for rice production. To determine fallow and green manure crop effects on soil nitrate and ammonium dynamics in lowland riceland, a 2-yr field study was conducted in the Philippines. Treatments before wet season rice were;(i) Sesbania rostrata grown for either 45 or 60 d; (ii) weedy fallow; and (iii) weed-free fallow. Sesbania rostrata was sown with irrigation in late April-early May; rains started in early (1989) or mid-May (1990). Weeds and S. rostrata were incorporated after soil flooding on 23 June. Rains increased soil water-filled pore space to above 0.75 ml/ml between mid-May and soil flooding. Weeds and S. rostrata assimilated soil nitrate, as evidenced by lower (P < 0.05) nitrate in those treatments than in the weed-free fallow. The decrease in soil nitrate in the weed-free fallow from 24 April to before soil flooding (15 kg N/ha) was apparently due to denitrification or leaching; additional nitrate (19 kg N/ha in 1990) disappeared after soil flooding. Ammonium-N was rapidly released from incorporated weeds and S. rostrata. It reached a maximum by 36 d after incorporation, which correlated (r = 0.95) with N accumulation by rice at 45 d after transplanting. Results suggest that weeds and crops before rice can reduce soil N loss by assimilating nitrate-N and then cycling this N through incorporated plant residues back to the soil where it is rapidly mineralized and used by rice
Descriptors:Fallow. Nitrogen. dynamics. rice-soils. Soil-types-(cultural). Weeds. utilization. green-manures. Rice. cycling. nitrogen-cycle. ecology. nutrient-uptake. soil. cereals |
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