The crop residue and Zn addition impacts on above ground biomass yield, Zn uptake and physical properties, viz. mean weight diameter (MWD) of water stable aggregates, bulk density (BD) and water holding capacity (WHC) were measured under a rice-wheat system in the 17 th and 18 th crop cycles. Results indicate that the highest yield in both the crops was recorded in the treatment receiving 10 kg Zn/ha as starter dose + 100% straw produced by each crop. Long-term application of crop residues along with Zn increased grain yield. The MWD, BD and WHC of post-harvest soil measured after harvest of the wheat crop varied from 2.80-3.88 mm, 1.27-1.42 Mgm -3 and 33.32-47.53%, respectively. The treatment with 100% CR and 10 kg Zn/ha had the highest level of MWD and WHC, whereas it resulted into the lowest BD. Increasing levels of Zn also influenced the MWD of water stable aggregates, BD and WHC positively. The correlations of WHC and MWD of water stable aggregates with different plant parameters were positive and highly significant, thus, indicating their synergistic relationship, i.e. higher the WHC and MWD of water stable aggregates higher the crop yield and Zn utilization by crops.

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IntroductionConservation agriculture is a sustainable system of farming that safeguard and conserves natural resources besides enhancing crop production. The biological properties of soil are the most sensitive indicator to assess the short term impact of management practices such as tillage and residue incorporation.MethodsNine treatments of tillage and residue management practices [Reduced till direct seeded rice-zero till barley (RTDSR–ZTB); RTDSR–ZTB–green gram residue (Gg); Zero till direct seeded rice–zero till barley–zero till green gram (ZTDSR–ZTB–ZTGg); RTDSR–ZTB + rice residue at 4 t ha 1 (RTDSR–ZTBRR4); RTDSR–ZTBRR6; un-puddled transplanted rice (UPTR)–ZTB–Gg; UPTR–ZTBRR4; UPTR–ZTBRR6, and puddled transplanted rice (PTR)–RTB] executed under fixed plot for five years on crop productivity and soil biological properties under rice-barley production system.ResultsThe shifting in either RTDSR or ZTDSR resulted in yield penalty in rice compared to PTR. The PTR recorded highest pooled grain yield of 3.61 ha−1. The rice grain yield reduced about 10.6% under DSR as compared to PTR. The ZTB along with residue treatments exhibited significantly higher grain yield over ZTB, and the RTDSR-ZTBRR6 registered highest pooled grain yield of barley. The system productivity (12.45 t ha−1) and sustainable yield index (0.87) were highest under UPTR-ZTBRR6. Biological parameters including microbial biomass carbon, soil respiration, microbial enzymes (Alkaline phosphatase, nitrate reductase and peroxidase), fluorescein diacetate hydrolysis, ergosterol, glomalin related soil proteins, microbial population (bacteria, fungi and actinobacteria) were found to be significantly (p < 0.05) effected by different nutrient management practices. Based on the PCA analysis, Fluorescein diacetate hydrolysis, microbial biomass carbon, soil respiration, nitrate reductase and fungi population were the important soil biological parameters indicating soil quality and productivity in present experiment. The results concluded that UPTR-ZTBRR6 was a more suitable practice for maintaining system productivity and soil biological health.DiscussionThe understanding of the impact of different tillage and residue management practices on productivity, soil biological properties and soil quality index under rice-barley cropping system will help in determining the combination of best conservation agriculture practices for improved soil quality and sustainable production.

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A field experiment was conducted to evaluate the rice varieties suitable for organic farming. The experiment was carried out in the rabi season of 2013-14 at Tamil Nadu Agricultural University, Coimbatore to study the yield, quality and economics of different rice varieties. The experiment was laid out in a RBD replicated thrice. The treatments consisted of 12 rice varieties viz., Bhavani, W hite ponni, Mappillai samba, Kitchili samba, IR 20, CO 43, CO(R) 48, CO(R) 51, CB 05022, KDML 105, Red kavuni and Jeeraga samba. The culture CB 05022 produced significantly higher grain yield of 4877 kg ha -1 and registered a yield increase ranging from 32 to 82 per cent over the other varieties under evaluation. With regard to quality parameters, grains of the culture CB 05022 was medium slender based on the kernel length and L/B ratio. The highest net return of ` 40,015 ha -1 with B:C ratio of 2.28 was realised under the rice culture CB 05022 followed by Kitchili samba (net return: ` 32,423 ha -1 ; B:C ratio: 2.04) and Jeeraga samba (net return: ` 31,431 ha -1 ; B:C ratio: 2.01). It is inferred that varieties and cultures differ widely among themselves when grown under organic farming. In terms of grain yield, quality and economics, the culture CB 05022 performed better under the organic production system.