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North-Eastern India is blessed with a vast diversity of rice genotypes with varying yielding abilities. However, the predominant strong soil acidity induced nutrient stresses from the toxicity of aluminum (Al3+) ions often causes sub-optimal rice productivity. The lack of suitable nutrient media for the screening of aluminum (Al) toxicity tolerance of rice genotypes is one of the limiting factors in Al tolerant varieties' development. Modified Magnavaca's solution has been the most recommended nutrient solution for this purpose where ammonium nitrate is the primary nitrogen source. However, strict regulations related to the handling and storage of ammonium nitrate in India limit the preparation of Modified Magnavaca's solution for laboratory use. Here, a modified ammonium nitrate-free formulation based upon the Magnavaca's solution has been proposed. The modified formulation was found to have 160.9 µM of active Al3+ concentration when 550 µM of aluminum chloride hexahydrate (AlCl3.6H2O) was added at pH 4.1 to the solution. Through a plant growth screening experiment using ten diverse rice genotypes a significant difference in the response of various genotypes to differential Al toxicity levels on root growth performance indicators was observed. Based on the response, we could able to categorize the genotypes into tolerant and sensitive in relative terms. Thus, the present experiment provided an important nutrient formulation suitable for screening rice genotypes under Al toxicity conditions. Moreover, the selected tolerant and sensitive genotypes can further pave the way for studying the molecular mechanism of Al toxicity response in rice and their use in the breeding program. [ABSTRACT FROM AUTHOR]

Phosphorous (P) is one of the most deficient nutrients owing to its fixation and low mobility in acid soils. A total of 324 genotypes were screened in both P sufficient and insufficient conditions to evaluate the P uptake efficiency. Thirty-four responsive genotypes were evaluated in solution culture with two checks, ICGV 86590 and JL 24. The components of variability revealed high magnitude and highly heritable nature of the variation. Highly responsive genotypes to P insufficiency; ICG 14475, ICGV 92188, and M 68 were further tested for phosphorus uptake efficiency at 15, 30, and 45 days after sowing (DAS) along with checks in sand culture in pots. ICG 14475, ICGV 92188, and ICGV 86590 were found superior in both acquisition and utilization of phosphorus due to enhanced root production for P exploration and shoot expansion, respectively. JL 24 was poor in acquisition due to lack of response in root traits under P insufficiency. [ABSTRACT FROM PUBLISHER]

Imbalanced and indiscriminate use of chemical fertilizers has been adversely influencing the quality of soil, environment, biodiversity and nutrient status in soil. Conjoint application of bio-inoculants (BI) with organic or inorganic sources of nutrients tweaks nutrient synchrony in soil and improves plant nutrition. With this backdrop an experiment was conducted at Indian Agricultural Research Institute, New Delhi during 2016–2018. The objectives were to identify the suitable combinations of BI-mediated nutrient sources for higher productivity and profitability in pigeon pea–wheat cropping system (PWCS). The nine pigeon pea treatments; four sole applications viz., recommended dose of fertilizers (RDF), vermicompost (VC), farm yard manure (FYM), leaf compost (LC) and four conjoint applications viz., RDF + BI, VC + BI, FYM + BI and LC + BI and one control were replicated thrice under randomized block design (RBD). However, in succeeding wheat, each of the treatments applied to pigeon pea was further allocated to two levels (50% and 100%) in factorial RBD. Findings exhibit that FYM + BI could result into higher equivalent-system grain productivity (10.4 and 10.8 t ha−1 during 1st and 2nd year, respectively) of PWCS. However, profitability parameters of PWCS were higher with the RDF + BI. Uptake of nutrients (NPK) was significantly higher with FYM + BI in pigeon pea and RDF + BI in wheat. Nutrient harvest index (NHI) did not vary significantly in both the crops. Conclusively, bio-inoculation is more productive and beneficial in general, while, over the various combinations, recommendation of FYM + BI combination could be more productive and sustainable. [ABSTRACT FROM AUTHOR]

Imbalanced application of nutrients in the intensively cropped areas results in deterioration of soil fertility. Application of recommended dose of potassium (K) is essential for improving the use efficiency of other nutrients. To assess the buffering capacity of soil, three composite soil samples were collected from the surface soil (0–30 cm) during 2015 from 3 production systems viz., organic, inorganic and integrated which was maintained from 2004 with basmati rice–wheat–Sesbania system under Network Project on Organic Farming at ICAR-Indian Institute of Farming Systems Research, Modipuram. Fractionation of potassium (K) was achieved by sequential extraction of soil samples with distilled water, ammonium acetate and nitric acid in the same order. The relationship between the adsorbed and equilibrium potassium concentration, quantity was determined by plotting Freundlich adsorption isotherms. This was used to determine the buffering capacity and the concentration levels of potassium adsorbed on un-specific sites in the soil. The suitability of the adsorption equation was determined by applying the least square regression analysis. The results revealed that available potassium in the soils ranged from 119.51 to 135.01 mg/kg with 126.02 ± 5.24 mg/kg as mean (ammonium acetate method) while water soluble and nitric acid extracted potassium ranged from 28.51 to 29.05 mg/kg and 2594.49 ± 19.33 mg/kg (mean) in various production systems. The mean free energy of replacement was found to be −1998.01 ± 28.38 cal/mol indicating that soils have comparatively higher potassium supply under organic system. The potassium buffering capacity of the soils was found to be 0.7462 ± 0.16 mg/kg, 0.6295 ± 0.20 mg/kg and 0.6774 ± 0.09 mg/kg in organic, integrated and inorganic systems, respectively. The amount of potassium adsorbed on un-specific sites of the organic, integrated and inorganic systems was found to be 7.4730 ± 1.81, 15.11 ± 2.40 and 11.6 89 ± 3.58 mg/kg, respectively. It can be concluded that long-term organic production system improves K+ buffering capacity of Typic Ustochrept soil as compare to the integrated as well as inorganic production systems. [ABSTRACT FROM AUTHOR]