Variations in Soil Physical Properties in a Cleared Forestland Continuously Cultivated for Seven Years in Eastern Nsukka, Nigeria

Abstract

In this study, soil physical properties were evaluated in the top 40 cm of cleared forestland that had been subjected to continuous cultivation for 7 years to ascertain selected crop or crop combinations that influenced the soil physical properties the most. There was no significant effect of crop treatment on particle-size distributions over 6 years of cultivation. In year 7, clay values were significantly (p 5 0.05) greater in plots grown with solely cassava (SC) and solely maize (SM) than in the plots grown with solely pigeon pea (SP). The soil depth effects over the 7 years were significant on the clay content. The mean values of bulk density, pore-size distribution, and hydraulic conductivity obtained from each plot fluctuated over the years. The bulk density values in 1998 ranged from 1.29 to 1.43 g cm 3 , but from 1999 to 2004, the range was from 1.12 to 1.40 g cm 3 . Thus, bulk density generally decreased when compared with their respective values in 1998. The greatest decrease of < 22% was in 2000. More than 70% of the macroporosity values were significantly less than their respective values in 1998. The greatest decease of 72% was obtained from SM plots in 2001. All the microporosity were significantly more than the 1998 values. All the increases were .100% of the original values. These increases were reflected in the variations of total and saturated hydraulic conductivity (Ks) values. However, in 2004, Ks values decreased in the plots grown to C + P, SP, and SM. Generally, the C + M + P mixture appeared to be the most consistent in improving micro-and total porosities and Ks among the crop treatments.

Spatial variability of uncultivated soils in derived savanna

“…Research has shown that topsoils usually show a higher sand content than subsoils (Nartey et al, 1997;Usowicz et al, 2004), and the present results suggest that this is due mainly to coarse sand and not fine sand ( Table 2). The silt content showed no appreciable change with depth, and this agrees with other reports from the area (Igwe, 2005;Asadu et al, 2010). For the clay content, the soil depth zone ranked closely next to location.…”

“…This is possibly due to pronounced clay illuviation in these Ultisols, especially with their coarse texture. Asadu et al (2010) reported a similar observation in cultivated plots in the Nsukka site of the present study. It appears thus that sampling at a soil-depth interval of 30 cm could permit the expression of clay eluviation/illuviation phenomenon in these soils.…”

“…Thus, the focus has been placed on variations in physical properties of the soils due to cropping systems (Amana et al, 2010;Asadu et al, 2010;Obalum and Obi, 2010), but knowledge of their spatial variability under uncultivated conditions is limited to date. Since soil spatial variability is better manifested under uncultivated than cultivated land uses (Ogunkunle, 1993), data for uncultivated soils are preferable in deciding the permissible spatial extent of composite soil sampling.…”

Comparison of the Suitability of Contiguous Fallow-forest Lands for Cassava, Yam, Cocoyam and Sweet Potato Production in Nsukka, Southeastern Nigeria

“…It lies within the latitude 6º 52´ N and longitude 7º 23´ E in the Savannah zone of Southeastern Nigeria with an elevation of 447.2 m above sea level [43]. The climate of the area is characterized by an average annual rainfall of about 1550 mm and average temperatures (minimum and maximum) of 22 ˚C and 30 ˚C respectively while the average relative humidity is 60% [12]. Soils in this area are generally derived from the residua of False-bedded Sand-stone or Upper-coal Measure Formation as a result of disintegration of the rocks [10].…”

The effects of continuous cropping and fallowing on the chemical properties of an Ultisol in Nsukka, Nigeria

“…More details on this study can be obtained from the following journal publications; Dixon and Asadu 2001;Asadu and Dixon 2005;Asadu et al 2010;Asadu et al 2013 andAsadu et al 2014. The summary may be given as follows: In 1998, after clearing the forest and before embarking on the establishment of the trials, soil samples were collected at random to assess the variability in the soil properties in order to ascribe subsequent variations to treatments applied.…”