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Climate change is not only increasing the Earth’s temperature but is also altering the hydrological cycle. This study aims to identify indicators of long term climate change in relation to hydrological cycle – changes in precipitation, pan evaporation, aridity index and to identify footprints of climate change in agricultural ecosystem– changes in thawing period, changes in freezing period of soil, changes in growing season, and air temperature. The data for precipitation, pan evaporation, and precipitation from metrological stations from 10 states (Alaska, Minnesota, Ohio, Tennessee, Alabama, Hawaii, Florida, Arizona, New Mexico, and Texas) across a latitudinal gradient in the U.S. were analyzed for 20-80 years. Selection of the sites was based on the type of biome it represents, accuracy of data, length of the observation period, data availability online, and on the least missing data since the historical climate records have been archived for these stations. Precipitation was analyzed annually and for the warm season. Precipitation trends are increasing in some regions across U.S., such as Minnesota, Tennessee, Ohio, Oklahoma and Alabama while decreasing in others such as, for example Florida and Hawaii. In New Mexico, Arizona and Texas there is an increasing trend in long-term precipitation. However, in the last 20 years precipitation has been decreasing. The pan evaporation trends were analyzed for the summer season (May to September). Based on the trends, it is apparent that the pan evaporation has increased overtime in some regions across U.S. (i.e. Tennessee, Ohio, Florida, Hawaii and Alabama) but has also decreased in others (i.e. Alaska, Arizona, New Mexico, Minnesota, Texas), assuming that there are no systematic error in the weather stations’ observations. The sites which showed an increase in mean annual temperature (MAT) are the ones in Alaska, Texas, Florida, New Mexico, Arizona and Hawaii. In contrast, sites which showed a decreasing trend in average temperature are in Minnesota, Alabama and Tennessee. The increase in minimum temperature has been much higher and prominent than the increase in maximum temperature. Fairhope (Alabama) is the only site in this study which showed a significant decreasing trend in minimum temperature. At all the other sites, the minimum temperature increased in the last few decades. The thermal or climatological growing season is the frost-free period between the last frost in spring to the first frost in autumn. The number of consecutive days with minimum temperature above 0°C can be assumed to be conducive for growth. The length of climatological growing season was studied for 5 sites in Ohio and one site each in Alaska and Minnesota. All five sites in the Midwestern state Ohio (Wooster, Coshocton, Circleville, Bellefontaine and Bowling Green) as well as the two sites in the northern states of Minnesota (Waseca) and Alaska (University Experiment Station) show an increasing trend in the length of growing season. The rate of increase varies amongst different sites, but they are all statistically significant. This means the frost-free period is getting longer, advancement of spring season and delay of autumn frost.

This study was conducted with the objectives to (i) assess the agricultural C emissions in relation to predominant farming systems in Punjab and Ohio, (ii) evaluate C use efficiency of production systems, (iii) compute the sustainability index, and (iv) formulate a set of recommendations to make the agricultural practices in both states more C efficient by increasing the ratio of C output:input. The data on C based input into the soil for predominant crops were collected for Ohio, USA and Punjab, India. Data collected included the amounts of fertilizers (N, P, K), herbicides and pesticides used for each crop annually, tillage methods, cropland area, total production of each crop, and the area under various farming systems, water management practices, such as tube well irrigation, and total number of livestock. These data were used to calculate C equivalent per hectare of input and output, and sustainability indices which is a measure of C use efficiency. The C sustainability indices were computed to identify sustainable soil and crop management practices. There was a linear relationship observed between C input and C output in Punjab. With an increase of 1 Tg/yr of C input, the corresponding C output increased by ~ 12 Tg/yr (Fig. 3.24), with an output:input ratio of about 12. Likewise, in Ohio a linear relationship was apparent between the C input and net C output in the initial years (from input = 0.1202 - 0.4288 Tg/yr). And after that, the graph almost reached a plateau. The average C sustainability index value for Ohio in the last 15 years is around 35-43, which is almost 2.5 times that of Punjab. Since 1989 there has been a huge shift from conventional tillage to reduce and conservation tillage in Ohio. During the same time, the fertilizer consumption of Ohio decreased significantly. Fertilizer use in Ohio is based on the soil test and crop requirement. The use of scientific methods causes reduction in fertilizer use. Judicious use of fertilizers is a more C efficient practice. No till is being practiced on more than 35% of the cultivated area presently. Conservation till practices are more C efficient than conventional tillage practices. More than 30% of crop residues are retained during conservation tillage, and approximately 15-30% during reduce tillage practices. In Punjab, crop residues are removed resulting in loss of C from SOC pool. Hence C efficient systems, such as those used in Ohio are more sustainable than inefficient farming systems such as Punjab. Policy issues are identified with regards to the management of crop residues to increase the SOC pool, control erosion and improve soil quality. These technologies include no-till farming, drip irrigation, cover cropping with residue mulch, precision agriculture, judicious use of chemical fertilizers, use of nano technology based applications for soil such as zeolites, use of high analysis fertilizers, contour farming, integrated nutrient management practices and cost effective utilization of organic waste. Imposing taxes on fertilizer use, trading C credits from agriculture, deciding the appropriate subsidies, maintaining the desired fertilizer and food price ratio, restricting burning of straw in open fields are some of the policy recommendations which would help in maximizing the C-use efficiency and in decreasing the C footprints of agriculture in Ohio, USA and Punjab, India.