Majid Mahmood Tahir

Lignite-Derived Humic Acid Effect on Growth of Wheat Plants in Different Soils

Abstract Humic acid (HA), a fairly stable product of decomposed organic matter that consequently accumulates in ecological systems, enhances plant growth by chelating unavailable nutrients and buffering pH. We examined the effect of HA derived from lignite on growth and macronutrient uptake of wheat (Triticum aestivum L.) grown in earthen pots under greenhouse conditions. The soils used in the pot experiment were a calcareous Haplustalf and a non-calcareous Haplustalf collected from Raisalpur and Guliana, respectively, in Punjab Province, Pakistan. The experiment consisted of four treatments with HA levels of 0 (control without HA), 30, 60, and 90 mg kg−1 soil designated as HA0, HA1, HA2, and HA3, respectively. In the treatment without HA (HA0), nitrogen (N), phosphorus (P), and potassium (K) were applied at 200, 100, and 125 mg kg−1 soil, respectively. Significant differences among HA levels were recorded for wheat growth (plant height and shoot weight) and N uptake. On an average of both soils, the largest increases in plant height and shoot fresh and dry weights were found with HA2 (60 mg kg−1 soil), being 10%, 25%, and 18%, respectively, as compared to the control without HA (HA0). Both soils responded positively towards HA application. The wheat growth and N uptake in the non-calcareous soil were higher than those of the calcareous soil. The HA application significantly improved K concentration of the non-calcareous soil and P and NO3-N of the calcareous soil. The highest rate of HA (90 mg kg−1 soil) had a negative effect on growth and nutrient uptake of wheat as well as nutrient accumulation in soil, whereas the medium dose of HA (60 mg kg−1 soil) was more efficient in promoting wheat growth.

Effect of Azadirachta indica (neem), sodium thiosulphate and calcium chloride on changes in nitrogen transformations and inhibition of nitrification in soil incubated under laboratory conditions.

A laboratory experiment was conducted to examine the effects of nitrification inhibitors (NIs) neem seed-cake (Azadirachta indica) (NSC), sodium thiosulphate (Na₂S₂O₃) and calcium chloride (CaCl₂) on changes in NH₄(+)⁻N, inhibition of nitrification and recovery of applied nitrogen (N) in soil. Surface soil samples of 0-15 cm were collected from an arable field, amended with urea N (UN) at the rate 200 mg N kg⁻¹, UN+NSC, UN+Na₂S₂O₃ and UN+CaCl₂ and incubated at 22°C periodically over 50 d. Soil without any amendment was used as check (control). Results indicated that more than 58% of N applied as NH₄⁻ disappeared over a period of 50 d from the soil mineral-N pool. Some of this N (21%) was accumulated as NO₃⁻-N while the remaining N was unaccounted for. Addition of nitrification inhibitors NSC, Na₂S₂O₃, and CaCl₂ resulted in a decrease in the extent of NH₄(+) disappearance by 35%, 44% and 30%, respectively. In the treatment receiving UN alone, 56 mg NO₃⁻-N kg⁻¹ was accumulated over 50 d (maximum 93 mg kg⁻¹) indicated an active nitrification. Application of nitrification inhibitors NSC, Na₂S₂O₃, and CaCl₂ with UN inhibited nitrification by 54%, 64%, and 59%, respectively. Apparent N recovery (ANR) in the treatment receiving UN alone was 63% that substantially increased to 83%, 89% and 76% in the treatments receiving UN+NSC, UN+Na₂S₂O₃, and UN+CaCl₂, respectively indicating 32%, 41% and 20% increase in N recovery. Among three NIs tested, Na₂S₂O₃ proved superior in inhibiting nitrification and increasing ANR. The study demonstrated that application of NSC, Na₂S₂O₃, and CaCl₂ which are cheap and easily available NIs inhibited nitrification and improved N recovery efficiency of applied N in an arable soil very effectively. It is suggested that these inhibitors should be tested under field conditions for increasing NUE and improving crop productivity.

EFFICIENCY OF RHIZOBIUM INOCULATION AND P FERTILIZATION IN ENHANCING NODULATION, SEED YIELD, AND PHOSPHORUS USE EFFICIENCY BY FIELD GROWN SOYBEAN UNDER HILLY REGION OF RAWALAKOT AZAD JAMMU AND KASHMIR, PAKISTAN

A field experiment was conducted in continuity of our previous study to assess the effect of Rhizobium inoculation (RI) and phosphorus fertilization (P) on growth, yield, nodulation, and P use efficiency of soybean. Different treatments were i) Rhizobium strains (0, S377, S379, and the mixture of S377+S379 i.e. S0, S1, S2, S3); ii) phosphorus fertilizer (0, 50, 100 kg ha−1 i.e. P0, P1, P2). Soybean variety NARC-1 was as used as a testing crop. Results indicated that root and shoot growth increased by RI treatments whether used alone or in combination with P. Rhizobium inoculation increased plant height up to 12% while P did not show significant effect. Increases in soot dry weight, root length and root dry weight due to RI and P was 57 and 22%, 42 and 7%, 55 and 25%, respectively, over the control treatment. Number of nodules increased from 73 in the control to a maximum of 151 in S2 while the number increased from 90 in the control to 147 in P2. Combine application of strains and P increased nodules number from 65 at S0P0 to a maximum of 183 at S2P2. Similar response was also observed for nodules mass. Soybean seed yields ranged between 1710 and 2335 kg ha−1 against 1635 kg ha−1 in the control indicating a maximum of 43% increase over control. Concentration of N and P in plants and their uptake was significantly increased by RI and P. RI also increased the N and protein content of soybean seed. Apparent recovery efficiency (ARE) of applied P was 10−12% and the agronomic, agrophysiological, recovery, utilization efficiencies, and harvest index of P decreased with increasing P rates. Nodule number significantly correlated with the DM yield (r2 = 0.78) and seed yield (r2 = 0.63) while P uptake significantly correlated with root length (r2 = 0.48) and root mass i.e. dry weight (r2 = 0.65). Also a significant correlation existed between N uptake and DM yield (r2 = 0.98) and N uptake and seed yield (r2 = 0.65), P uptake and DM yield (r2 = 0.73), and P uptake and seed yield (r2 = 0.83). The results of present study indicated a substantial growth and yield potential of soybean under the hilly region and increase in yield and N2 fixing potential (nodulation) can be achieved by applying Rhizobium inoculation with P fertilization.

Forage Production, Nitrogen Fixation, and Soil N Accumulation of White Clover in the Hill Farming System of Azad Jammu and Kashmir

Quantitative measurements of plant growth characteristics, forage production, nitrogen (N) fixation, and soil N accumulation by white clover were determined in a field experiment at the subhumid hilly region of Rawalakot, Azad Jammu and Kashmir (AJK). Three indigenous and two exotic ecotypes of white clover were used in the study. Indigenous ecotypes were collected from three different locations (i.e., Tollipir, Banjosa, and Rawalakot), whereas exotic ecotypes (NuSiral and Irrigation) were collected from New South Wales Agricultural Research and Advisory Station, Australia. Data were collected for two seasons (spring 2004–autumn 2004). Total average values for height, number of stolons, length of stolons, number of leaves, and leaf area were 13–50 cm, 9–20, 2–4 cm, 23–81, and 7–16 cm2, respectively. The morphological characteristics of exotic ecotypes were significantly higher than the indigenous ecotypes, and the percentage increase in different plant characteristics was +6% to 214%. Total herbage dry‐matter yield (DMY) in the indigenous and exotic ecotypes varied between 0.5–2.3 and 3.6–4 Mg ha−1, respectively. All the ecotypes showed substantial nodulation potential, and the number of nodules in plant roots ranged from 65 to 119, confirming the presence of indigenous Rhizobium population in the soil. The N contents of harvested herbage of white clover were 2.3–3.0% compared to 0.85% in the grass, and the estimated rates of N2 fixation were 26 kg N ha−1 in the indigenous to 79 kg N ha−1 in the exotic ecotypes. Amount of N2 fixed was strongly correlated with DMY, suggesting that crop DM can be used as an indicator of N2 fixation in white clover. Protein content of white clover was 14–19%, compared to 5% in the indigenous grass species. Total organic carbon (C) and N in control soil were 8.5 and 0.75 g kg−1, which increased significantly to 13.1 and 0.93 g kg−1 in soil under white clover. It is concluded that white clover has substantial potential for growth and establishment in the subhumid hilly regions and can be used to recuperate degraded soils because of its ability to sustain high level of pasture production and increase the N status of soil. These benefits could be of particular use for small‐scale resource‐poor farmers.

Characterisation and evaluation ofRhizobium leguminosarum bv.trifolii nodulating rhizobia isolated from white clover native to Azad Jammu and Kashmir, Pakistan

The present study was conducted to evaluate and characteriseRhizobium leguminosarum bv.trifolii nodulating rhizobia isolated from root nodules of indigenous and exotic ecotypes of white clover (Trifolium repens L.) in the mountain region of the State of Azad Jammu and Kashmir Pakistan. Isolates from indigenous ecotypes were collected from three different locations i.e. Tollipir, Banjosa, and Rawalakot while exotic ecotypes i.e. Irrigation and NuSiral were collected from Australia. Preliminary characterisation of isolates was carried-out on the basis of colony characteristics, phosphorus solubilisation, osmotic potential, relative absorbance, indole acetic acid spot test, mean doubling time and C-source utilisation.Rhizobium population in the respective soils was also estimated by using most probable number (MPN). The maximumRhizobium population of 5.8 × 106 g−1 soil was recorded in Tollipir soil compared with population of 3.1. × 105 g−1 soil in Rawalakot soil. All strains showed homology to a typicalRhizobium strain and identified asRhizobium on the basis of growth pattern and other testing parameters. The isolates were Gram negative, small rods and acid producing fast growers with a mean generation time in between 2.7 to 3.4 h. All isolates except isolates from Tollipir showed resistant against four antibiotics except tetracycline. Isolates from Banjosa, Tollipir and Rawalakot (indigenous) had larger surface charge than isolates from Irrigation and NuSiral (exotic). Highest osmotic potential of −31.02 bar was recorded in the isolates from Banjosa while isolates from Tollipir and Rawalakot had an osmotic potential of −22 bar. Field evaluation of isolated isolates showed significant increase in plant growth and root nodulation. The study will be useful for identifying the isolates under laboratory conditions and developing successful inoculation strategy for the production of white clover in the mountain region of Azad Jammu and Kashmir.