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The nitrogen fixing aquatic pteridophyte Azolla h a s t h e a b i l i t y t o f i x a t m o s p h e r i c n i t r o g e n a t c h e a p e r a n d f a s t e r r a t e s d u e to the presence of a symbiotic cyanobacterium Anabaena azollae. Because of this property it has been exploited widely as biofertilizer for rice plants. In addition to this it has several other uses such as food, feed, biogas producer and hyperaccumulator of heavy metals etc. Because of the multifaceted uses the promotion and use of Azolla-Anabaena s y s t e m wo u l d b e i d e a l a n d e n v i r o n me n t fr i e n d l y i n s u s t a i n a b l e a g r i c u l t u r e . Th i s a r t i c l e p r o v i d e s a b r i e f a c c o u n t o f t h e i mp o r t a n c e as well as developments in the utilization of Azolla-Anabaena system in agriculture and allied sectors.

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The role of blue green algal (BGA) biofertilizers has been limited to its relevance and utilization in rice crops, and scanty information is available on their use in conjunction with organic amendments and their influence on wheat (Triticum aestivum) . An experiment was conducted from November 2003 to April 2004 in the fields of the Indian Agricultural Research Institute (IARI), New Delhi, India to evaluate the effect of vermicompost, farmyard manure and biofertilizers (BGA and Azotobacter ) in different combinations with chemical fertilizers (N 40 P 30 K 30 ) in wheat (var. HD 2687). Selected soil biological parameters (cyanobacterial diversity/abundance, nitrogenase activity and the phototrophic biomass of soil cores) were measured. The application of vermicompost in combination with BGA biofertilizer (B+V+N 40 P 30 K 30 ) brought about a significant increase in nitrogenase activity (from 0.1 in N 80 P 30 K 30 to 2.0 nmoles mg chl −1 h −1 ), while Azotobacter + BGA (+N 40 P 30 K 30 ) treatment gave the highest values of chlorophyll (1.19 μg g −1 soil). The addition of vermicompost and farmyard manure (+N 40 P 30 K 30 ) enhanced cyanobacterial abundance, and cyanobacterial genera such as Nostoc, Anabaena, Calothrix, Oscillatoria and Phormidium were the dominant forms observed under the wheat crop. The synergistic effect of organic amendments, biofertilizers and chemical fertilizers, especially BGA inoculants, advocates their utilization in wheat crops to improve soil fertility.

Pearl millet-based cropping systems with intensive tillage operations prior to sowing have limited sustainable productivity in the low-irrigation conditions of semi-arid farming ecologies, such as those in the north Indian plains. The adoption of improved management practices such as zero tillage with residue retention (ZTR) and diversification with the inclusion of summer pulse crops has the potential to improve cropping system sustainability. Therefore, an experiment was designed to compare two improved management practices, zero tillage (ZT) and ZTR, to conventional tillage (CT), across three pearl millet-based cropping systems: pearl millet–chickpea (PM–CP), PM–CP–mungbean (MB), and PM–CP–forage pearl millet in a two-year experiment. Experimental treatments were compared in terms of pearl millet productivity, mineral biofortification, and greenhouse gas emissions. Results showed a significant increase in pearl millet yield attributes, grain and stover productivity, nutrient uptake, and micronutrient biofortification in the PM–CP–MB cropping system under ZTR relative to other treatment combinations. On-farm evaluation at different locations also showed that the intensification of PM–CP system using summer crops enhanced pearl millet productivity across diverse tillage systems. Overall, zero tillage practices combined with diversified pearl millet-based cropping systems are likely to be management practices, which farmers can use to sustainably maintain or increase cropping system productivity in the various semi-arid areas of the world.

A field experiment was conducted during rainy seasons of 2009 and 2010 at New Delhi, India to study the influence of varieties and integrated nitrogen management (INM) on methane (CH 4 ) emission and water productivity under flooded transplanted (FT) and aerobic rice (AR) cultivation. The treatments included two rice ('PB 1' and 'PB 1121') varieties and eight INM practices including N control, recommended dose of N through urea, different combinations of urea with farmyard manure (FYM), green manure (GM), biofertilizer (BF) and vermicompost (VC). The results showed 91.6-92.5 % lower cumulative CH 4 emission in AR compared to FT rice. In aerobic conditions, highest cumulative CH 4 emission (6.9-7.0 kg ha -1 ) was recorded with the application of 100 % N by organic sources (FYM?GM?BF?VC). Global warming potential (GWP) was significantly lower in aerobic rice (105.0-107.5 kg CO 2 ha -1 ) compared to FT rice (1242.5-1447.5 kg CO 2 ha -1 ). Significantly higher amount of water was used in FT rice than aerobic rice by both the rice varieties, and a water saving between 59.5 and 63 % were recorded. Under aerobic conditions, both rice varieties had a water productivity of 8.50-14.69 kg ha -1 , whereas in FT rice, it was 3.81-6.00 kg ha -1 . In FT rice, a quantity of 1529.2-1725.2 mm water and in aerobic rice 929.2-1225.2 mm water was used to produce one kg rice. Thus, there was a saving of 28.4-39.6 % total water in both the rice varieties under AR cultivation.

This chapter reports the findings of a Working Group on how atmospheric nitrogen (N) deposition affects both terrestrial and freshwater biodiversity. Regional and global scale impacts on biodiversity are addressed, together with potential indicators. Key conclusions are that: the rates of loss in biodiversity are greatest at the