Need-Based Fertilizer Nitrogen Management in Spring Maize
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Date
2019
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Publisher
Punjab Agricultural University, Ludhiana
Abstract
Synchronizing fertilizer nitrogen (N) supply and plant N demand remains a major
constraint due to spatial variability in soil N supply especially when fixed time fertilizer N
applications are made as per soil test-based recommendations. Precision N management
strategies to define in-season optimum N dose and appropriate topdressing timings are desired
to achieve high N use efficiencies while sustaining potential grain yield. Field experiments
were conducted at PAU, Ludhiana and KVK, Gurdaspur with spring maize cultivars DKC-
9108 and PMH-10 for two years to study spectral properties of spring maize to help guide
need-based fertilizer N applications using leaf color chart (LCC), chlorophyll meter (SPAD
meter) and GreenSeeker (GS) optical sensor. The spectral properties measured using the
gadgets were strongly correlated with leaf N, plant biomass, biomass N content and grain
yield at different crop growth stages. A close linear relationship (R2 = 0.75) between SPAD
meter readings and LCC score indicated that LCC can be used as an inexpensive and reliable
substitute of SPAD for real-time need-based N applications in spring maize. The statistical
analysis of spectral reflectance recorded at different growth stages revealed that NDVI
readings at V9 growth stage could precisely predict the in-season N requirements for spring
maize production. Algorithm to predict grain yield and to draw in-season need-based fertilizer
N topdressing decisions using GreenSeeker optical sensor was established. Fertilizer N
topdressings based on threshold leaf greenness of LCC 5, SPAD 50 and sufficiency index
value of SPAD 0.95 and NDVI 0.90 produced significantly higher grain yield with improved
recovery and agronomic efficiencies of applied fertilizer N in comparison to soil-test based N
recommendations. The improved congruence of fertilizer N supply and crop N demand in
LCC, SPAD and NDVI-based N management treatments reduced N2O emission and global
warming potential, produced more number of grains per cob and plant height than soil testbased
N management. Insignificant differences in N indices of different soil layers between
no N control and fertilizer N treatments expressed that higher fertilizer N applications were
not helpful in increasing total soil N and N supplying capacity of the soil.