Performance and nitrogen use of wheat cultivars in response to application of allelopathic crop residues and 3, 4-dimethylpyrazole phosphate

This study investigated the impact of allelopathic crops residue amendments and a nitrification inhibitor DMPP (3, 4- dimethylpyrazole Phosphate) on germination, growth, yield and nitrogen (N) use of wheat. In the first study, wheat cultivars [Lasani 2008 (LS-08) and Faisalabad 2008 (FSD-08)] were grown in soil filled pots (18 kg soil) amended with sorghum and sunflower residues (0, 8 and 12 Mg ha^-1) in presence and absence of nitrogen fertilizer sources [urea and ammonium sulphate (N at 110 kg ha^-1)]. Plants were raised up to maturity; sorghum residue amendments improved the performance of both wheat cultivars; however sunflower residues initially inhibited wheat germination and stand establishment but at later growth stages, the inhibitory effects were diminished. Both N sources improved grain yield of wheat cultivars with greater by ammonium sulphate in LS-08. Sorghum residue at 12 Mg ha^-1 in addition with ammonium sulphate had significant influence on grain yield of cv. LS-08 than other treatments. In second experiment, cv. LS-08 was grown in soil filled pots amended with sorghum and sunflower residue (16 and 32 Mg ha^-1) in presence or absence of DMPP (0.36 μg g^-1) in greenhouse. DMPP in combination with N in the absence of crop residues improved dry matter production and reduced the C:N ratio; however any residue addition at any rate immobilized N and decreased the dry matter accumulation. In crux, residue amendments in combination with inorganic fertilizers could improve wheat grain yield, while combined use of DMMP and N can improve plant N availability and dry biomass.