Impact of genetically modified crops on rhizosphere microorganisms and processes: A review focusing on Bt cotton

Transgenic Bt cotton hybrids, in India, now constitute more than 90% of the cotton area. Conservation tillage systems such as reduced tillage (RT) improve soil health and crop productivity. Field experiments were conducted to study the response of Bt cotton hybrids to the tillage methods in a split plot design for three years (2005–2006 to 2007–2008) with tillage practices as main plots (conventional tillage {CT}, RT with two inter-row cultivations {RT 1 } and RT with no inter-row cultivation {RT 2 }). In the sub-plot, in situ green manure (GM) was included along with 100 (GM + N 100 ), 80 (GM + N 80 ) and 60 kg N ha −1 (GM + N 60 ) and were compared to N alone (N 100 ). Growth, yield and fibre quality of Bt transgenic cotton hybrid (RCH-2 Bt) were monitored during the study. In all seasons, weed density and biomass were significantly lower in the RT treatments than in the CT treatments. Taller plants with more main stem nodes were produced on the RT plots (63.6–75.8 cm) than on the CT plots (58.1–70.2 cm). Thus, plants of RT treatment retained more bolls (60.8–62.0 m −2 ) than those of the CT treatment (52.4 m −2 ). Averaged over seasons, RT treatment had seed cotton yield (1717–1740 kg ha −1 ) significantly higher than the CT treatment (1489 kg ha −1 ). The treatments N 100 , GM + N 100 and GM + N 80 (1687–1734 kg ha −1 ) did not differ and were significantly better than the GM + N 60 (1303 kg ha −1 ). Tillage × GM interaction was significant in two of three years and data combined over years. The RT plots with GM had significantly greater yield than the CT plots. Compared to the CT treatment, the RT plots had significantly greater proportion of water stable aggregates (48.6% vs. 54.4–56.0%) and mean weight diameter (0.47 mm vs. 0.49–0.51 mm). The GM plots had significantly higher WSA and MWD than those without. Further, soil moisture content was greater in the GM mulched plots up to 0.60 m depth compared to without GM treatment (CT + N 100 ). Favourable soil physical properties may have contributed to improved seed cotton yield in the RT treatments with GM than in the CT treatment. Fibre quality was not affected by either the tillage systems or GM. This study indicates that Bt transgenic cotton can be grown under RT systems with an in situ legume GM.

Tillage and green manure effects on Bt transgenic cotton (Gossypium hirsutum L.) hybrid grown on rainfed Vertisols of central India

A better understanding of the fate of nutrients in transgenic cotton (Gossypium hirsutum L.) fields will improve nutrient efficiencies, will optimize crop growth and development, and may help to enhance soil quality. A study was made to evaluate and quantify the effect of cropping system [sole cotton and groundnut (Arachis hypogaea) intercropping with transgenic cotton] and nitrogen (N) management [control (0N), 100% recommended dose of nitrogen (RDN) through urea, substitution of 25% RDN through farmyard manure (FYM), and substitution of 50% RDN through FYM] on dry matter (DM) and nutrient partitioning and accumulation by transgenic cotton and groundnut at New Delhi during 2006–2007. Soil and plant samples were collected and analyzed at 60, 90, and 120 days after sowing and at harvest. Results revealed that intercropping of groundnut with cotton did not significantly affect DM and nutrient partitioning in cotton, but residual soil fertility in terms of potassium permanganate (KMnO4) N showed an improveme...

Dry Matter, Nitrogen, Phosphorous, and Potassium Partitioning, Accumulation, and Use Efficiency in Transgenic Cotton-Based Cropping Systems

Of the several mechanisms that can bring about efficient resource use, the most widelyapplicable one is intercropping systems that can make better use of resources. The aim of thisstudy was to evaluate resource capture and resource use efficiency in transgenic cotton-peanutintercropping system and in their respective sole crops with using 25-50% substitution ofrecommended dose of nitrogen (RDN) of cotton through farmyard manure (FYM) along with100 % RDN through urea and control (0N). Apparent crop water productivity, nutrient useefficiency, economic returns and modern intercropping indices (system productivity index,actual yield loss, intercropping advantage index, nitrogen stress factor, etc.) were measured formaking better understanding of resource use efficiency. Comparisons of intercropped peanutwith sole peanut were emphasized because of shrinking area of peanut in the south-east Asianregion represents a threat to agricultural system sustainability. Cotton + peanut intercroppingsystem resulted in improved water productivity (19%), nutrient use efficiency (15-20%) andmonetary advantage index (16,709) as measured with modern tools of intercropping indicescompared with sole crops of cotton and peanut. Peanut cultivated as sole crop attained the leastresource productivity in terms of apparent crop water productivity (0.71 kg m-3), nutrient useefficiency (4.47 kg grain kg N-1) and total factor productivity (0.07). Among fertility levels,substitution of 25% RDN of cotton through FYM maintained higher apparent crop waterproductivity (17%), monetary advantage index (6%), system productivity index (9%) andnutrient use efficiencies (15-17%) over 100% RDN through urea only. This work provides basisfor efficient resource use by peanut intercropping with cotton which simultaneously enhancesdomestic oilseed production and reduce import load of cooking oil without sacrificing theproductivity of main crop of cotton in India and other cotton growing countries of the world.

http://ijpp.gau.ac.ir/article_2461_450f14b7407e8c423f1762deb1d5bd10.pdf

Resource use efficiency of transgenic cotton and peanut intercropping system using modified fertilization technique

Global cotton cultivation, particularly in India, was transformed after the introduction of transgenic cotton hybrids. Realizing the increasing acreage under transgenic cotton in future, the aim of this study was to evaluate growth behaviour of transgenic cotton with peanut intercropping system and sole cotton crop by using 25–50 % substitution of recommended dose of nitrogen (RDN) of cotton through farm yard manure (FYM) along with 100 % RDN through urea and control (0N). Plant growth parameters like plant height, leaf area index, leaf chlorophyll, and N contents were measured at various growth stages of cotton for correlating them with seed cotton yield. Peanut intercropping in cotton did not significantly affect cotton growth parameters and indices except leaf area duration (P = 0.04) as compared with sole crop of cotton. On the other hand, cotton growth parameters with substitution of 25 % RDN of cotton through FYM were higher than or similar to its corresponding 100 % RDN of cotton through urea only. The results showed that there were highly significant (P < 0.01) linear relationships between leaf N and chlorophyll contents at each growth stage, and with plant height and leaf area index during cotton growth. Seed cotton yield was also highly (P < 0.01) correlated with plant growth parameters like plant height, leaf area index, chlorophyll content and leaf N content at various growth stages of cotton. The present study explains plant growth behaviour of transgenic cotton with peanut intercropping system and integrated use of manure and fertilizer for simultaneously enhancing lint and oilseed production.

Growth Behaviour of Transgenic Cotton with Peanut Intercropping System Using Modified Fertilization Technique

India has emerged as a major global partner in the production, processing and trade of raw cotton and its finished products. The genetically modified Bt cotton, containing the cry gene sourced from the soil bacterium Bacillus thuringiensis sub-species kurstaki, providing resistance against boll worms, represents a landmark in cotton research and development. The large-scale adoption of Bt cotton by Indian farmers in a span of 7 years is the power of this technology. Introduction of the Bt gene has altered the morphological, phenological and physiological characteristics of these introgressed cultivars. The development and commercialization of Bt cotton varieties like BN Bt and incorporation of herbicide tolerance are likely to further revolutonize the cotton production scenario. To harness the benefits of the Bt cotton and to sustain their yield potential, sound agro-techniques need to be standardized. This review provides an update on the agronomic research undertaken on Bt cotton especially under the diverse growing conditions in India and the effect of these agro-techniques on Cry toxin expression and fibre quality parameters.

Bt cotton (Gossypium sp.) in India and its agronomic requirements – A review

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Bt cotton (Gossypium sp.) in India and its agronomic requirements – A review