Salinization of soils is one of the major factors which severely affect the agricultural productivity worldwide. Due to salinity, more than half a billion hectares of land are not being properly used for crop production. Thus, there is a need to search means to improve saline soils so that such soils could support highly productive and meaningful land-use systems to meet the current challenges of global food security. Although permanent solution of soil salinity problem necessitates a sound drainage system to manage the rising water table, this option, being energy-and cost-intensive cannot be employed on a large scale on vast areas. Phytoremediation or biological approach, i.e., plant-based strategies for improvement of deteriorated soils is an appropriate option. Phytoremediation of saline soils can be done by cultivating suitable plant species as well as by Exploiting the ability of plant roots to improve the dissolution and enhance levels of Ca in soil solution to efficiently remove Na from the soil cation exchange complex and leach it from the root zone. During the amelioration process, soil-aggregates stability, root proliferation, soil hydraulic properties and availability of nutrients to plants are also improved. Such improvement in soil properties facilitates cultivation of less tolerant plants, improves the environment in general, and the climatic conditions by enhancing carbon sequestration.
Laboratory experiments were carried out to study the influence of various salinity levels [1 (control), 9 (medium), 17 (high), and 27 dS m -1 (strong)] on nitrogen (N) transformations in soil fertilized with urea and ammonium sulfate. Generally, soil salinization affected the normal pathway of N transformations. The results showed that salinity (medium to high) inhibited the second step of nitrification, causing nitrite (NO 2 − ) accumulation in soil. The inhibition was more severe in cases of high level of salinity. The greatest salinity level caused inhibition of even the first step of nitrification, leaving more ammonium (NH 4
)-N accumulation in soil. Severity in nitrification inhibition was observed with increase in salinity and rate of N application, which declined with time. Ammonium accumulation with increased salinity caused N losses in the form of ammonia (NH 3 ) volatilization.After 14 days, the NH 3 losses were 1.4-, 2-, and 5-fold greater at 9, 17, and 27 dS m -1 than that of the control (1 dS m -1 ). After 42 days, the losses reached up to 6-fold more than the control at the greatest salinity level. Initially (up to 14 days), NH 3 losses were more from urea than from ammonium sulfate, whereas at the later stages (42 days), the losses were almost equal from both the fertilizers. The overall results revealed significant adverse effects of salinity on N transformations in soil.
AbsractTwenty-six cowpea cultivars were tested for yellow mosaic virus resistance at NIAB Faisalabad. NCPM-1, Elite, IT-84-552, No.44, P-518, S.A. Dandy, IT-97k-350-4, IT-93K-452, IT-97K-1042-8 and IT-97K-497-2 showed resistant reaction to yellow mosaic virus disease. As the study was aimed to select disease resistant and high yielding cultivars. Five cultivars viz. NCPM-1, Elite. S.A. Dandy, IT-97K-497-2 and IT-97K-1042-8 were chosen and evaluated at five different ecological zones during the year 2003. At each location, the experiment was laid out in a randomized complete block design keeping 7.2 m 2 plot size in three repeats. At maturity the seed yield was collected and subjected to analysis of variance following stability parameters, varieties, environment and varieties x environment showed significant differences. Significant and highest seed yield (880 kg/ha) was observed in NIAB cowpea mutant-1 followed by Elite (729 Kg/ha). The highest yielding genotypes i.e. NIAB cowpea Mutant-1 and Elite showed non-significant differences of regression coefficient from one. Moreover these genotypes also exhibited non-significant difference of standard deviation to regression from zero. Based on three parameters i.e. high mean seed yield, regression coefficient and standard deviation to regression, these genotypes showed excellent and trustworthy stable performance over different environment. Hopefully these genotypes will definitely be helpful for increasing one local production of cowpea crop.
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