Lowland Rice Response to Urea Following Three Cowpea Cropping Systems

Abstract

The integrated use of legume green manure or legume residue with inorganic N fertilizer could offer rice (Oryza sativa L.) farmers an opportunity to reduce their expensive inorganic fertilizer inputs. A 2‐yr field experiment was conducted on an Andaqueptic Haplaquoll in the Philippines to determine the effect of cowpea [Vigna unguiculata (L.) Walp.] cropping systems on response of a subsequent rice crop to applied urea and effectiveness of several urea management practices for rice. The pre‐rice cropping systems including fallow, cowpea incorporated at the flowering stage as a green manure, and cowpea grown to maturity with either grain and pods removed or all aboveground vegetation removed prior to soil puddling for rice. The mean aboveground N content was 66 kg N ha−1 for green manure and 54 kg N ha−1 for mature cowpea without grain and pods. Rice yield responses following fallow and cowpea cropping with removal of all aboveground cowpea vegetation were similar, but mean rice grain yields were 0.9 and 0.7 Mg ha−1 higher following incorporation of green manure and residue, respectively. The green manure substituted for 34 and 54 kg urea‐N ha−1 in 1986 and 1987, respectively. Residue substituted for 44 and 50 kg urea‐N ha−1 in 1986 and 1987, respectively. Early application of urea (two‐thirds basal and one‐third at 5 d before panicle initiation) was superior to delayed application (one‐half at 14 d after transplanting and one‐half at 10 d after panicle initiation), even when supplemental N as green manure or residue was incorporated 15 d before transplanting. Cowpea grown for green manure or for grain, with incorporation of residues remaining after harvest, made similar positive contributions to rice yield, but growing cowpea to maturity offered the advantage of attaining approximately 1.0 Mg ha−1 cowpea grain production.

The role of mungbean residues and Sesbania aculeata green manure in the nitrogen economy of rice-wheat cropping system

“…Mungbean without residue incorporation had no advantage over pre-rice fallow in grain yield in both the years and in straw yield in the first year. John et al (1989b) also reported similar results with cowpea.…”

Nitrogen contribution of cowpea green manure and residue to upland rice

“…In the absence of urea, green manure increased aboveground plant N by 12 kg ha -~ and residue by 14 kg ha -t. Recovery of green manure N and residue N by rice, which was calculated by difference with the residueremoved treatment without added urea, was 13 and 24%, respectively. In a complementary experiment with lowland rice, John et al (1989b) reported higher recoveries of added N. In their study, lowland rice recovered approximately 24 and 26% of applied cowpea green manure N and 33 and 36% of applied cowpea residue N.…”

“…Agronomic efficiency for 30 kg urea-N ha -1 was not affected (p<0.05) by pre-rice treatment, indicating that incorporation of green manure or residue did not increase the use efficiency of urea fertilizer, as shown in selected field studies reviewed by Bouldin (1988). In a complementary study with lowland rice, agronomic efficiency of 21 to 29 kg kg t was estimated for 30 kg urea-N ha -~ with corresponding quadratic models (Buresh and De Datta, 1991) adapted from data of John et al (1989b). The higher agronomic efficiency of lowland rice 'IR64' (21 to 29 kg kg -1) compared with that of upland rice 'UPLRi5' (11 to 15 kgkg -1) was at least partly the result of a higher harvest index (HI) for the lowland rice (0.49) than for the upland rice (0.30).…”

“…The fit of the quadratic model decreased, R = 0.84, when results for 1986 and 1987 were combined. Westcott and Mikkelsen (1987) and John et al (1989b) similarly reported a quadratic model with combined results from organic and inor- Table 1. ganic N sources, whereas Morris et al (1986b) found differing utilization efficiencies for green manure N and inorganic N.…”

Agronomic Management of Cowpea for High Grain Yield and Sustainable Agriculture in Western Indo-Gangetic Plain of India

“…Cowpea produced significantly (P=0.01) more straw than mungbean in 2008 (Table 8) Using values of the average N content (%) in straw at maturity of 1.22% for cowpea (John et al, 1989;and Sharma and Behera 2009b), and 1.16% for mungbean (Sharma and (Table 9). In Experiment 3, straw yield was considerably higher than in Experiments 1 and 2, with the result that the nitrogen accumulated in the straw was also higher, ranging from 44 to 48 kg N ha -1 in the various treatments.…”