Abstract was to identify the effects of different land

Abstract

Soil
quality is severely affected by climate and land use change.  The aim of the
study was to identify the effects of different land uses on the magnitudes and
directions of soil fertility parameters. Land use selected for the study was
natural forest, coconut, pepper, tapioca and mixed home garden cropping
systems. Generally, comparisons between the crop fields, and the forest lands
on the other revealed a significant difference on soil fertility parameters.
The results showed that soil organic carbon and total N declined in the case of
cultivated land. OC content was highest (3.78 %)
under forest land and lowest (0.76 %) with acacia. Among the size fractions finer particles showed higher
carbon content and it decreased with increase in particle size and it is
linearly related. The attributes
of soils such as organic carbon, carbon fractions such as humic acid, fulvic
acid, total C, N available nutrients, physical properties, aggregate size
fractions, microbial biomass carbon, spectral signature under the cultivated
lands showed difference among the land uses and overall change towards the direction of loss of
their fertility compared to the soils attributes of the adjacent forest
soils.  However under mixed cropping the
soil fertility is being sustained in comparison to the other mono cropping land
uses. These variations of soil physicochemical properties between land use types
indicate the risk to the sustainable crop production under changing climate in
the area and hence management practices to improve the fertility under these
land uses has to be adopted .

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Key
words : Mixed cropping,
Humic acid, Fulvic acid, aggregate stability, Microbial biomass carbon,
Spectral data.

 

Introduction

Man made actions have led to an amplification
in atmospheric concentration of CO2 from as low as 280 ppm (pre-industrial
era) to more than 400 ppm at present (WMO, 2008 ; IPCC 2014), and is regularly escalating
at the rate of about 2.2 ppm/yr (IPCC, 2007). Even though spirited discussion
and negotiations are occurring across the globe on global warming (Kerr, 2009),
mean global temperature has increased by 0.8oC since 1880, and may
increase by an additional 3 to 6oC by 2100 under business as usual
scenario (IPCC, 2014). A temperature rice of about 0.5 to 1.2°C by 2020, 0.88
to 3.16°C by 2050 and 1.56 to 5.44°C by 2080, depending on the future
development scenarios have been projected by IPCC for the Indian region (South Asia)
(IPCC 2014). In Kerala, during the period of 49 years (1956 to 2004), maximum
temperature rose by 0.64° C, and minimum temperature increased by 0.23° C.  In general, it point towards a clear upward
trend in surface air temperature in Kerala with an increase in annual average
temperature upto 0.44° C (Rao et al., 2009). A comparable tendency was observed
at Kozhikode in which the maximum temperature rose to the tune of 0.6° C during
winter and 0.55° C  during summer between
1983 and 2010 ( Joseph et al., 2011; Surendran et al., 2014; 2017). This hike in temperature can influence
many soil characteristics that are linked to Soil
Organic Carbon (SOC) in a direct / indirect way, due to its capacity to retain
water and nutrients. SOC is indispensable to
safeguard a good physical state and to absorb, preserve and supply water and
nutrients to crops. In tropics, once people till the soil for cultivation, SOC is rapidly
decomposed due to the change in conditions such as aeration, temperature, and
water content. Soil Organic Matter (SOM) plays a crucial
role in enhancing the productivity of tropical soils because it offer substrates
and energy, and enhances the biological diversity that helps to maintain soil
quality and ecosystem functionality (Wendling et al., 2010).

As uneasiness about the greenhouse
effect keep on scaling up, there has been increased discussion about the use of
vegetation and soils to reduce global warming (Jacobson, 2009), by using sequestration
of carbon (C) in agro ecosystems, especially in agricultural soils. Land use
management practices that improves the SOC by removing CO2 from the
atmosphere and accumulate it in the soil, is termed as carbon sequestration.
The prospective of agricultural soils was duly recognized in article 3.4 of the
Kyoto Protocol and the idea of sequestering C in soils as soil organic carbon
(SOC) was considered as a possible means of reducing atmospheric CO2.
Furthermore, the process of sequestering atmospheric CO2 will itself
enhance SOC pool and off-set man made / anthropogenic emissions while benefits
both agricultural productivity and mitigating temperature rise.