Zc. Somda et al., SOIL-PH AND NITROGEN CHANGES FOLLOWING CATTLE AND SHEEP URINE DEPOSITION, Communications in soil science and plant analysis, 28(15-16), 1997, pp. 1253-1268
The relationship between animal urine deposition and variability in so
il chemical composition and crop growth is not well established in the
semiarid region of West Africa. This study was conducted to examine t
he changes over time in soil pH and mineral nitrogen (N) concentration
s at the micro sites of cattle and sheep urine patches in comparison t
o those occurring in fertilizer urea placement zones. The urine and fe
rtilizer solution containing each 400 mg N (800 kg N ha(-1)) were spre
ad onto individual plots covering a surface area of 4-cm radius. The t
reatments included a control, which consisted of distillate water. Soi
l samples from three replicate plots were taken in 4-cm increments to
a depth of 16 cm and distance of 16 cm on a grid pattern at days 1, 7,
21, 49, 90, 120, and 150 after application. Significant pH and minera
l N gradients develop in the vicinity of the fertilizer and urine plac
ement zones declining towards the periphery and the deeper soil layers
. The pH at the center of the urine zone remained above 7.5 throughout
the 150 days of the study period. After the initial increase, the soi
l pH below the fertilizer placement sites declined to the control leve
l by day 90. Concentrations of ammonium (NH4) + nitrate (NO3) also inc
reased markedly in the immediate soil layers of the urine and urea pla
cement zones, and then decreased over time probably due to N losses by
volatilization and leaching. Concentrations of mineral N at the perip
hery of the placement site were similar for all treatments throughout
the study period, indicating very little lateral N diffusion. These re
sults provided evidence that animal urine causes significant variabili
ties in soil chemical composition, even in short distance from the dep
osition zones. The high soil solution pH in the vicinity of the urine
patches alleviate the potential of aluminum (Al) toxicity while increa
sing the phosphorus (P) availability to crop plants.