Influence of spatial variability of soil physical and chemical properties on the rooting patterns of...

مرکز و کتابخانه مطالعات اسلامی به زبان های اروپایی

منو

" Influence of spatial variability of soil physical and chemical properties on the rooting patterns of pearl millet and sorghum. (Volumes I and II) "
J. G. Davis-Carter L. R. Hossner

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1112571
Doc. No	:	TLpq303793215
Main Entry	:	J. G. Davis-Carter
	:	L. R. Hossner
Title & Author	:	Influence of spatial variability of soil physical and chemical properties on the rooting patterns of pearl millet and sorghum. (Volumes I and II)\ J. G. Davis-CarterL. R. Hossner
College	:	Texas A&M University
Date	:	1989
student score	:	1989
Degree	:	Ph.D.
Page No	:	420
Abstract	:	Extreme crop stand variability is widespread throughout Niger and is visible at the seedling stage. Plant stress is common even when water is available in the soil profile due to fertility limitations to root growth. The objectives of this study were to (1) identify which soil chemical properties contribute to variability in millet fields, (2) study the effect of chemical properties on millet germination and seedling survival, (3) model millet and sorghum root growth as a function of physical and chemical properties, and (4) determine the influence of soil amendments on millet root growth and yield. Extensive soil sampling was performed, and coefficients of variation and semi-variograms were calculated. Nutrient solution and root window studies were conducted to determine the sensitivity of millet seedlings to chemical properties. Root-trench profiles were completed for sorghum and millet, and root systems were modeled. Exchangeable Mg, Al and Ca and available P were the most variable soil properties measured. Phosphorus applications increased millet yields, and P and S were both leached 40 cm deep. Spatial variability in crop stands is strongly related to P variability. The coefficients of variation calculated were similar to those in the literature. On soils with low buffering capacity, normal soil variability may result in unusually large crop differences. Toxicities were expressed in decreased root growth more than in reduced shoot growth. Small changes in the soil may have a large impact on the roots and later be expressed as stand variability. The R2 values relating root counts to soil properties were higher for sorghum than for millet, and depth was an important variable in the models for both crops. Millet root counts were more dependent on depth at harvest than at tillering. Magnesium had consistently high R2 values for millet roots; R2 values were also high for Fe and pH. Sorghum root counts were best correlated with P and Al; sorghum root counts increased linearly with available P. Though the LOCAL millet variety had greater rooting density than the improved varieties at harvest, the improved varieties had greater root counts at the tillering stage.
Subject	:	Agronomy
	:	Biological sciences
	:	soil physical properties