Impact of organic and integrated production systems on yield and seed quality of rainfed crops and on soil properties.

Mineral and vitamin deficiencies together affect a greater number of human populations in the world than does protein malnutrition. Organic farming is reported to improve nutritional quality of food grains while also improving soil health. However, sufficient scientific information on several aspects of organic farming based on long-term studies is lacking particularly under rainfed conditions of India. The purpose of this study was to assess the long-term impact of organic and integrated production systems on crops yield and quality, economic returns and soil properties. The study was conducted with three crops, sunflower (Helianthus annuus L.), pigeonpea (Cajanus cajan L.), and greengram [Vigna radiata (L.) Wilczek] under three different production systems, control (use of chemical inputs alone), organic and integrated. The results of the 10-year study revealed that, the average production of integrated system was on par with organic management and recorded significantly higher pigeonpea equivalent yield (PEY) (827 kg ha-1) compared to control (chemical inputs) (748 kg ha-1). In general, the yield gap between organic and integrated production systems declined from fourth year for greengram and eighth year for sunflower, during the 10-year experimental period whereas the pigeonpea yield was similar under both production systems from first year. Plots under organic management had significantly lower bulk density (1.18 mg m-3), higher water holding capacity (38.72%) and porosity (53.79%) compared to integrated production system and control (chemical inputs). The soil organic C (SOC) content in the plots under organic production system was 32.6% more than the initial organic carbon of the soil (0.43%), with higher soil N (205.2 kg ha-1). Plots under integrated production system, however, had higher soil P (26.5 kg ha-1) compared with other treatments. The dehydrogenase activity (5.86 µg TPF g-1 soil h-1) and microbial biomass carbon (317.3 µg g-1 soil) content was higher in the plots under organic production system than under other systems. Organically produced pigeonpea and greengram seeds had similar protein content with that of integrated system, and higher K and micronutrient (Fe, Zn, Cu, and Mn) contents than other treatments. The results show the potential of organic production system in improving crop yields, soil properties and produce quality in semiarid rainfed areas.

Influence of organic and inorganic sources of nutrients on the functional diversity of microbial communities in the vegetable cropping system of the Indo-Gangetic plains.

The aim of the present study was to assess the effects of different organic and inorganic fertilizers on the functional diversity of soil microbial community under a vegetable production system. The Biolog® Eco-plate technique and indices, such as average well-colour development (AWCD), McIntosh and Shannon diversity were employed to study the diversity of soil microorganisms. The AWCD, i.e. overall utilization of carbon sources, suggested that different organic treatments had a significant impact on the metabolic activity of soil microorganisms. After 120h, the highest AWCD values were observed in poultry manure (2.5 t·ha-1)+vermicompost (3.5 t·ha-1) (0.63) and farm yard manure (FYM) (10 t·ha-1)+vermicompost (3.5 t·ha-1) (0.61). After 72h, the highest value of the McIntosh diversity index was recorded in poultry manure (2.5 t·ha-1)+vermicompost (3.5 t·ha-1) (3.87), followed by poultry manure (2.5 t·ha-1)+vermicompost (3.5 t·ha-1)+biofertilizers (Azotobacter 500 g·ha-1 applied as seed treatment) (3.12). In the case of the Shannon diversity index, the highest values were noticed in organic treatments; however, there was no significant differences between organic and inorganic treatments. Biplot analysis showed a clear differentiation of organic treatments from the inorganic control. The amino acids, phenolics and polymer utilizing microorganisms were dominant in organic treatments. Inorganic control recorded the lowest values of the microbial diversity indices. Through this study, we have identified the best combination of organic nutrients, i.e. poultry manure (2.5 t·ha-1)+vermicompost (3.5 t·ha-1) for the stimulation of metabolically active soil microbial communities.

Beneficial cyanobacteria and eubacteria synergistically enhance bioavailability of soil nutrients and yield of okra.

Microorganisms in the rhizosphere mediate the cycling of nutrients, their enhanced mobilisation and facilitate their uptake, leading to increased root growth, biomass and yield of plants. We examined the promise of beneficial cyanobacteria and eubacteria as microbial inoculants, applied singly or in combination as consortia or biofilms, to improve growth and yields of okra. Interrelationships among the microbial activities and the micro/macro nutrient dynamics in soils and okra yield characteristics were assessed along with the changes in the soil microbiome. A significant effect of microbial inoculation on alkaline phosphatase activity was recorded both at the mid-crop and harvest stages. Microbial biomass carbon values were highest due to the Anabaena sp. - Providencia sp. (CR1 + PR3) application. The yield of okra ranged from 444.6-478.4 g(-1) plant and a positive correlation (0.69) recorded between yield and root weight. The application of Azotobacter led to the highest root weight and yield. The concentration of Zn at mid-crop stage was 60-70% higher in the Azotobacter sp. and Calothrix sp. inoculated soils, as compared to uninoculated control. Iron concentration in soil was more than 2-3 folds higher than control at the mid-crop stage, especially due to the application of Anabaena-Azotobacter biofilm and Azotobacter sp. Both at the mid-crop and harvest stages, the PCR-DGGE profiles of eubacterial communities were similar among the uninoculated control, the Anabaena sp. - Providencia sp. (CW1 + PW5) and the Anabaena-Azotobacter biofilm treatments. Although the profiles of the Azotobacter, Calothrix and CR1 + PR3 treatments were identical at these stages of growth, the profile of CR1 + PR3 was clearly distinguishable. The performance of the inoculants, particularly Calothrix (T6) and consortium of Anabaena and Providencia (CR1 + PR3; T5), in terms of microbiological and nutrient data, along with generation of distinct PCR-DGGE profiles suggested their superiority and emphasized the utility of combining microbiological and molecular tools in the selection of effective microbial inoculants.