Small Scale Spatio-Temporal Variabilities in Soil Nitrogen, Leaf Nitrogen, and Canopy Normalized Difference Vegetation Index of Cotton

Xinhua Yin

doi:10.4236/gep.2016.412005

Abstract

Strip plots have been increasingly used in agricultural field experiments to better reflect the true situation of crop production on farmers’ fields, but failure to account for spatially and temporally related errors when present in the data analysis of strip plot field experiments may cause inefficient assessment of treatment effect significance. The objective of this study was to investigate patterns and degrees of the spatial and temporal variabilities in soil inorganic N level, leaf N concentration, and Normalized Difference Vegetation Index (NDVI) of cotton under no-tillage and the influences of N treatments on these variabilities. A strip plot experiment was conducted on a private farm near Brazil, Gibson County, Tennessee from 2009 through 2011. Five N treatments of 0, 45, 90, 134, and 179 kg N ha-1 were implemented as side dress N in strip plots under a randomized complete block design with three replicates after 45 kg N ha-1 was applied in the form of chicken litter before cotton planting. Spatial variability was present in soil inorganic N before cotton planting and after harvest, and in leaf N and canopy NDVI at the early square and early, mid-, and late bloom stages although the patterns and degrees of the spatial variabilities sometimes varied with growth stages and years. Application of the in-season side-dress N treatments often reduced the spatial variations of leaf N and NDVI, but increased those of post-harvest soil inorganic N. Out results suggest that the spatial and temporal variabilities of soil inorganic N, leaf N, and NDVI are high, and should be taken into account if possible in the data analyses of N treatment effects on related soil properties and plant characteristics of cotton in strip plot field experiment research.

Highlights

Fertilizer N has been the agricultural input with the largest increase of use during the past several decades [1]
Spatial variability was present in soil inorganic N before cotton planting and after harvest, and in leaf N and canopy Normalized Difference Vegetation Index (NDVI) at the early square and early, mid, and late bloom stages the patterns and degrees of the spatial variabilities sometimes varied with growth stages and years
Our results indicated that the spatial variation of initial soil N fertility existed in this field prior to experimentation. 3.1.2

Summary

Introduction

Fertilizer N has been the agricultural input with the largest increase of use during the past several decades [1]. Nitrogen fertilization is a key management practice in nonlegume crops including cotton. Fertilizer N is one of the largest expenses in cotton production. It is the most difficult nutrient to manage, and has substantial potential negative impacts on the environment. Excessive application of N on cotton can inhibit boll formation and retention, pose serious threats to the environment [2], and reduce producer profitability, while under-application causes poor vegetative and reproductive growth, premature senescence, and low yield. Due to substantially enhanced environmental concern and rising fertilizer N price during the last decade, development of innovative systems and technologies that can apply N more efficiently is warranted to reduce N losses, increase crop yield and profitability, and protect environmental quality

Objectives

Methods

Results

Conclusion