Maqsood Ahmad Gill

GENOTYPIC VARIATIONS OF PHOSPHORUS UTILIZATION EFFICIENCY OF CROPS

Intra-specific variations of phosphorus-utilization efficiency (PUE) hold great promise in rationalizing the application of cost-intensive phosphatic fertilizers in resource-poor situations, and to extend the useful life of the phosphate reserves in the world. In developed countries, efficient P-using crops may find significance in protecting the environment by reducing pollution of surface and ground water resources. This paper briefly reviews some of the work done so far on genotypic variations of Phosphorus (P)-nutrition of crops. Several physiological mechanisms responsible for such variations have been recognized. Various screening techniques to select P-efficient genotypes are also discussed. In addition, a brief historical account is also given on plant genetic approach to tackle soil problems.

Phosphorus nutrition of cotton cultivars under deficient and adequate levels in solution culture

In low-input agricultural systems that characterize most of the developing world, nutrient-efficient crop cultivars may play significant role in improving crop productivity. Phosphorus (P) deficiency is a common phenomenon in cotton growing areas of Pakistan, however the farmers are reluctant to apply it due to its price and fear of lack of response. A solution culture experiment was conducted to evaluate 10 commonly grown cotton cultivars for their relative efficiency to utilize deficiently and adequately supplied P, using Johnsons solution. Phosphorus deficiency markedly reduced shoot dry weight (SDW), root dry weight (RDW), whole plant dry weight controlled by plant P contents under P deficient conditions, suggesting an internal regulation in addition to the influence exerted by external P supply. The conclusions from experiment were that differences in growth existed among cotton cultivars exposed to same P concentration in the growth medium. Cultivars, which were efficient in both P-acquisition and P-utilization, were efficient accumulators of biomass under adequate as well as deficient level of P supply.

Bioavailability of inorganic phosphorus fractions in calcareous soils estimated by neubauer technique, iron-impregnated filter paper, and chemical tests

Abstract Plants commonly suffer from phosphorus (P) deficiency in calcareous soils. Plant responses to P application on such soils mostly show poor correlation with their soil test P values. Experiments were conducted on 24 different soil samples under laboratory and greenhouse conditions to illustrate the relationship of various inorganic P fractions in different calcareous soils with P uptake by plants, P extraction by iron‐impregnated filter paper, and P soil test values estimated by 0.5M NaHCO3 and ammonium bicarbonate diethylene triamine penta‐acetic acid. Total P in the 24 soils ranged from 652 to 1245 mgkg−1 with a mean of 922 mgkg−1. A major proportion (98%) of inorganic P was in HCl‐P (Ca‐bound) form. The HCl‐P (Ca‐bound) ranged from 296 to 729 with a mean of 480 mgkg−1. The iron (Fe) and aluminum (Al)‐P (NaOH‐P) ranged from 0.92 to 12 mgkg−1 with a mean of 1.57 mgkg−1. The Fe‐P (citrate‐dithionite bicarbonate) ranged from 0.22 to 4.40 mgkg−1 with a mean of 5.99 mgkg−1. Data regarding P release from the soil matrix obtained by desorption with iron‐impregnated filter paper was best described by the Elovich equation. Range of slope and intercept values were found to be 5.48 to 17.3 and 17.23 to 56.27 mgkg−1, respectively. Intercept values calculated for the Elovich equation may be related to labile P initially available for plant uptake in soils. Intercept values calculated for the Elovich equation correlated (r=0.77) significantly (p<0.01) with NaHCO3 extractable (Olsen‐P)P. Significant correlation (p<0.05) of intercept with CDB‐P (r=0.44) and of slope with HCl‐P (0.43) suggested that the initially available P, regulated through CDB‐P, is replenished by HCl‐P [calcium (Ca) bound].

Potassium-deficiency stress tolerance and potassium utilization efficiency in wheat genotypes

Growth response of 20 wheat (Triticum aestivum L.) genotypes were compared under deficient (0.6 mM) and adequate (3.0 mM) K levels in solution culture. Substantial and significant differences were obvious among genotypes for shoot dry weight (SDW), relative reduction in SDW due to K-deficiency stress (KSF), root dry weight (RDW) and root/shoot ratio. Potassium concentration, uptake and its utilization efficiency under both K levels also differed significantly between genotypes. Genotype X K-level interaction was significant for most of the parameters studied. It was concluded from the experiment that wheat genotypes tolerant to K-deficiency stress can be identified for cultivation under low K-supply conditions.

Silicon Requirement of Coarse and Fine Varieties of Rice

ABSTRACT Silicon (Si) provides extra strength to plants against lodging. A hydroponic study was conducted to compare Si requirements of three high yielding, nitrogen (N) responsive, coarse varieties of rice (KSK-133, PK-3717-12, and IRRI-6) with four low yielding, lodging susceptible, fine varieties of rice (BAS-191, BAS-385, BAS-370, and PK-3300). Two-week-old uniform seedlings were grown in half strength Johnsons nutrient solution containing 0, 25, 75, and 150 mg Si kg− 1 as sodium silicate. The plants were allowed to grow for 45 days after transplanting. Silicon application significantly (P ≤ 0.01) increased root and shoot dry matter production in all the rice varieties. The maximum shoot dry matter production occurred at 75 mg Si kg−1 and decreased uniformly in all the rice varieties at 150 mg Si kg− 1. However, growth response to Si application varied significantly (P ≤ 0.01) among various rice varieties. Root: shoot growth ratio, varying from 0.11 to 0.15, did not follow any trend. Different rice varieties and Si addition had a significant (P ≤ 0.01) main and interactive effect on concentration and total uptake of Si in rice root and shoot. Relative increases in Si content, both in shoot and root, were gradual and several fold with increasing rates of Si application. The effect was more pronounced in Basmati varieties (BAS-198, BAS-385, and BAS-370) than other varieties. A 0.91 mg Si g− 1 plant tissue was optimum for growth of KSK-133 (coarse), which was significantly higher than the optimum level, 0.62 mg Si g− 1 plant tissue, for Bas-370 (fine). However, further verification of the results is warranted under field situation.