Yields, and nitrogen and phosphorus use efficiency as influenced by fertilizer NP additions in wheat (Triticum aestivum) under rice (Oryza sativa)-wheat and pigeonpea (Cajanus cajan)-wheat system on a Typic Ustochrept soil

Abstract

AfIeld experinlent \vas conducted on a Typic Ustochrept soil ofModipuram during 1998-99 to 2000-01, to evaluate

the

ctTcct offertilizer N and P rates on wheat (Triticum aestivuln L emend. Fiori & Paol.) yield, Nand P use efficiency, soil

fertility, and apparent nutrient balances under rice

(Oryza sativa L.)-wheat and pigeonpea [Cajanus cajan (L.) MiIlsp.]\

wheat systenls. Pigeonpea substitution for rice during monsoon season ,improved wheat yield by 16%, and total Nand P

uptake in wheat

by 31 and I0~1J respectively. At these uptake, output: input ratio under pigeonpea-wheat system (i e 1.17

for Nand 0.65

for P) were also greater con1pared with rice-wheat system. Averaged across fertilizer NP rates and years of

cxperitnentation

the values ofagronolllic efficiencies ofN and P were greater by 3.7 kg/kg Nand 10.5 kg/kg P respectively

in wl"eat following pigeonpea than that following

rice. At the tennination ofthe experin1ent soil organic carbon and total N

in

0-15 C111 profile depth were increased (8 and 31% respectively) over the initial contents in the plots cropped with

pigcOrtpca-wheat. The available

Pcontent was, however, greater (80/0) under rice-wheat system. Continuous rice-wheat

cropping led to increase jn soil bulk density (0.06 Mg/m

3), and a decline in total porosity (4.6%) over the initial values,

particularly at J0-45

cm profile depth. Rice substitution forpigeonpea helped to maintaining these soil physical parameters

at the initial level,

and thus prevented sub-surface soil compaction. After 3-crop cycles apparent Nand P balance were

positive

in both the systems and for all the treatments, except a negative N balance (84 kg/ha) under pigeonpea-wheat

systen1.