Managing inoculation failure of field pea and chickpea based on spectral responses

Abstract

Pulse crop production is expanding in semiarid regions of the Northern Plains, and depends on successful biological N 2 -fixation. Inoculation failure, resulting in plant N deficiency and economic crop loss, might be alleviated by remedial N fertilizer application. The experiment was conducted using no-till management at two dryland sites in Montana in 1999 and 2000, where field pea and chickpea were grown in cereal stubble. Shoot biomass, shoot biomass N concentration, seed yield and seed N concentration were measured for uninoculated and inoculated controls and compared with remedial fertilizer N applied 0, 4, 6, and 8 wk after seeding. Spectral reflectance was compared for the inoculated and uninoculated controls. For field pea and chickpea, the critical period for fertilizer N application to prevent yield loss occurred within 6 wk of seeding (P ≤ 0.05). Logistic regression models derived from spectral reflectance had overall accuracies of 84 and 60% for detecting uninoculated control treatments in field pea and chickpea, respectively. The field pea model had a high degree of accuracy 6 wk after seeding, indicating it was capable of assisting a decision to apply remedial N fertilizer. Spectral reflectance provided a window of opportunity of 1 wk to apply remedial N fertilizer to attain full yield potential. Key words: Chickpea, field pea, inoculant failure, nitrogen, spectral reflectance