AbstractSoilquality is severely affected by climate and land use change. The aim of thestudy was to identify the effects of different land uses on the magnitudes anddirections of soil fertility parameters. Land use selected for the study wasnatural forest, coconut, pepper, tapioca and mixed home garden croppingsystems. Generally, comparisons between the crop fields, and the forest landson the other revealed a significant difference on soil fertility parameters.The results showed that soil organic carbon and total N declined in the case ofcultivated land.
OC content was highest (3.78 %)under forest land and lowest (0.76 %) with acacia. Among the size fractions finer particles showed highercarbon content and it decreased with increase in particle size and it islinearly related. The attributesof soils such as organic carbon, carbon fractions such as humic acid, fulvicacid, total C, N available nutrients, physical properties, aggregate sizefractions, microbial biomass carbon, spectral signature under the cultivatedlands showed difference among the land uses and overall change towards the direction of loss oftheir fertility compared to the soils attributes of the adjacent forestsoils.
However under mixed cropping thesoil fertility is being sustained in comparison to the other mono cropping landuses. These variations of soil physicochemical properties between land use typesindicate the risk to the sustainable crop production under changing climate inthe area and hence management practices to improve the fertility under theseland uses has to be adopted . Keywords : Mixed cropping,Humic acid, Fulvic acid, aggregate stability, Microbial biomass carbon,Spectral data. IntroductionMan made actions have led to an amplificationin atmospheric concentration of CO2 from as low as 280 ppm (pre-industrialera) to more than 400 ppm at present (WMO, 2008 ; IPCC 2014), and is regularly escalatingat the rate of about 2.
2 ppm/yr (IPCC, 2007). Even though spirited discussionand negotiations are occurring across the globe on global warming (Kerr, 2009),mean global temperature has increased by 0.8oC since 1880, and mayincrease by an additional 3 to 6oC by 2100 under business as usualscenario (IPCC, 2014). A temperature rice of about 0.5 to 1.2°C by 2020, 0.
88to 3.16°C by 2050 and 1.56 to 5.44°C by 2080, depending on the futuredevelopment 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), maximumtemperature rose by 0.
64° C, and minimum temperature increased by 0.23° C. In general, it point towards a clear upwardtrend in surface air temperature in Kerala with an increase in annual averagetemperature upto 0.44° C (Rao et al., 2009).
A comparable tendency was observedat Kozhikode in which the maximum temperature rose to the tune of 0.6° C duringwinter and 0.55° C during summer between1983 and 2010 ( Joseph et al., 2011; Surendran et al.
, 2014; 2017). This hike in temperature can influencemany soil characteristics that are linked to SoilOrganic Carbon (SOC) in a direct / indirect way, due to its capacity to retainwater and nutrients. SOC is indispensable tosafeguard a good physical state and to absorb, preserve and supply water andnutrients to crops. In tropics, once people till the soil for cultivation, SOC is rapidlydecomposed due to the change in conditions such as aeration, temperature, andwater content.
Soil Organic Matter (SOM) plays a crucialrole in enhancing the productivity of tropical soils because it offer substratesand energy, and enhances the biological diversity that helps to maintain soilquality and ecosystem functionality (Wendling et al., 2010). As uneasiness about the greenhouseeffect keep on scaling up, there has been increased discussion about the use ofvegetation and soils to reduce global warming (Jacobson, 2009), by using sequestrationof carbon (C) in agro ecosystems, especially in agricultural soils. Land usemanagement practices that improves the SOC by removing CO2 from theatmosphere and accumulate it in the soil, is termed as carbon sequestration.The prospective of agricultural soils was duly recognized in article 3.4 of theKyoto 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 itselfenhance SOC pool and off-set man made / anthropogenic emissions while benefitsboth agricultural productivity and mitigating temperature rise.