Carbon Sink Capacity and Agronomic Productivity of Soils of Semiarid Regions of India - Principles of Sustainable Soil Management in Agroecosystems - page 424

16.11 Enhanced NUE with Manuring .................................................................448
16.12 SOC in Relation to Water Retention and Water Productivity .................... 449
16.13 Carbon Management in Rainfed Production Systems—Experiences
from Long-Term Experiments in Semiarid Tropics ................................... 449
16.13.1 Mean Yield and Sustainable Yield Index Influenced by
Different Nutrient Management Treatments in Diverse
Cropping Systems ......................................................................... 452
16.13.2 Soil Carbon and Yield Sustainability ........................................... 458
16.13.2.1 Groundnut Production System .................................... 458
16.13.2.2 Finger Millet-Based Production System ..................... 459
16.13.2.3 Winter Sorghum-Based Production System ............... 459
16.13.2.4 Pearl Millet-Based Production System ....................... 459
16.13.2.5 Safflower- and Soybean-Based Production System .... 459
16.13.2.6 Rice-Based Production System................................... 465
16.13.3 Minimal Carbon Input Requirements for Arresting Carbon
Depletion ...................................................................................... 465
16.14 Conclusions ................................................................................................ 468
16.15 Future Research Needs ............................................................................... 469
Abbreviations ......................................................................................................... 469
References .............................................................................................................. 470
16.1 INTRODUCTION
The global rainfed croplands were estimated at 1.132 billion hectares (B ha) at the end
of the last millennium (Biradar et al. 2009). This is 2.78 times the net irrigated areas
(407 M ha) of the world ( http://www.iwmigiam.org/info/main/aboutGMRCA2 .asp ).
Rainfed agroecosystems occupy a considerable place in Indian agriculture too, cover-
ing 80 million ha (M ha), in arid, semiarid, and subhumid climatic zones, constituting
nearly 57% of the net cultivated area. India has 18% of the world's population, 15%
of the world livestock with only 2.3% of the geographical area, 4.2% of freshwater
resources, 1% of forests, and 0.5% of pastureland (Srinivasarao 2011; Srinivasarao et
al. 2011a). Rainfed areas in India contribute almost 100% of forest products, 84% to
87% of coarse-grain cereals and pulses, 80% of horticulture, 77% of oilseeds, 60% of
cotton ( Gossypium hirsutum ), and 50% of fine cereals like rice ( Oryza sativa ), wheat
( Triticum aestivum ), maize ( Zea mays ), sorghum ( Sorghum bicolor ), and so forth
(Srinivasarao et al. 2010, 2011b). Rainfed regions support 60% of livestock and 40% of
the human population and contribute 40% of food grains and several special-attribute
commodities such as seed spices, dyes, herbs, gums, and so forth. (Srinivasarao et al.
2011a). However, the double-cropped area in rainfed farming is negligible. Rainfed
agroecoregions are complex, diverse, fragile, risky, and underinvested and require
regionally differentiated investments and management strategies. Achieving high pro-
duction potential is difficult in these rainfed areas due to vagaries of rainfall.
The above-mentioned statistics indicate the high pressure on finite natural
resources. The net sown area in India has remained constant for many years at 141 M
ha, but the human and livestock population has been steadily increasing. The slow-
down in agricultural productivity growth has been attributed to resource degradation