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Prime Journal of Physical Science (PJPS) Vol. 1(5), pp. 53-57, December 19 th , 2012 www.primejournal.org/PJPS © Prime Journals Full Length Research Effect of humic acid and phosphorus on yield, nutrient availability in soil and uptake by peas Sarwar M, Ehsan Akhtar M and Hyder SI Land Resources Research Institute, National Agricultural research Centre, Islamabad-45500, Pakistan. Accepted 14 th November, 2012 A field experiment was conducted at experimental area of vegetable programme, NARC, Islamabad, to investigate the interactive effect of Phosphorus (P) and humic acid (HA) on macro and micro nutrients use efficiency in soil and their uptake by peas during Rabi 2011. The data translate that soil application of humic acid at 100 kg ha -1 along with 40 Kg P 2 O 5 ha -1 significantly enhanced green peas’ yield 35% higher than 100% dose of Phosphorus fertilizer alone. The data revealed that addition of humic acid at 100 kg ha” along with 50% recommended dose of fertilizer that is, 40 Kg P 2 O 5 ha -1 significantly improved the availability of Phosphorus, Potassium and micronutrients viz., iron and zinc and enhanced their uptake. Soil application of humic acid at 100 kg ha -1 along with 50% recommended dose of fertilizers improved the availability and uptake of nutrients than 100% recommended dose of fertilizers alone. Keywords : humic acid, phosphorus, green peas, iron and zinc. INTRODUCTION With the continued and rapid increase in world population, it has become vital importance to obtain higher yields per unit area agricultural production. For this reason the plant’ water and nutrients need must be met. In our case where soils are predominantly calcareous in nature, that affect the soil properties related to plant growth whether they are physical or chemical such as its fertility. Excess calcium carbonate poses serious problems to plant nutrition; it raises pH more than 8 of soil at which plant nutrients are relatively unavailable. Increased loses of nitrogen ammonia and reduced solubility of phosphorus (Celik et al., 2008). Since excessive application of chemical fertilizers may affect soil health and sustainable productivity. It is imperative to search for possible alternate organic source that can sustain soil health and crop production. Humic substances improve soil fertility by modifying soil physical and chemical properties (Asik et al., 2009). Humic acid derived from lignite is the most concentrated form of organic material and it is a ready source for carbon and nitrogen. Humic acid improves the physical, chemical and biological properties of the soil and influences plant growth (Chen et al., 2001). Nitrogen and phosphorus are the most limiting nutrients to vegetative production but their sufficient use by majority of the smallholder farmers become limiting due to their high costs. There are several problems which are impeding the balance and efficient use of fertilizers. They may be well addressed by the application of humic acid. It seems that humic substances may influence both respiration and photosynthesis (Nardi et al., 2002). Humic substances have a very profound influence on the growth of plant roots. When humic acids and fulvic acids are applied to the soil, enhancement of root initiation and increased root growth was observed (Pettit, 2004). The stimulatory effects of humic substances have been directly correlated with enhanced uptake of macronutrients, such as nitrogen, phosphorus; sulfur (Chen et al., 1999), and micronutrients, that is, Fe, Zn, Cu and Mn (Chen et al., 1999). Humic substances may possibly enhance the uptake of minerals through the stimulation of microbiological activity (Mayhew, 2004). When adequate humic substances are present within the soil, the requirement for nitrogen, phosphorus and potassium fertilizer applications may be reduced (Pettit, 2004). The combined effects of HA and P application was more effective on growth and growth parameter than each separate effect. Humic acid application significantly
Sarwar et al., 54 Table-1: Effect of humic acid and phosphorus application on green peas’ yield (t ha -1 ) P Levels H Levels 1 2 3 4 Means 1 1.75 l 2.30 k 2.66 i 3.04 h 2.44 C 2 2.53 j 3.22 f 4.19 a 4.17 b 3.53 B 3 3.10 g 3.31 e 4.14 c 3.99 d 3.63 A Means 2.46 D 2.94 C 3.66 B 3.73 A increased N, P, K, Ca, Mg, S, Mn and Cu contents of shoot of pepper seedling (K. Mesut 2010). Pea (Pisum sativum) belongs to family leguminous is a well known vegetable of the temperate region. This herbaceous plant is the major food ingredient of vegetarian diet and meets the dietary requirement of the people throughout the world. It also contains most of the essential nutrients like fiber and protein. The pea is a legume with great nutritional potential because of its high content of protein (27.8%), complex carbohydrates (42.65%), vitamins, minerals, dietary fiber and antioxidant compounds (Urbano et al., 2003). Addition of humic acid with chemical fertilizer has a long promising effect on crop production. This research experiment was planned to access the interactive effect of P and lignite-derived HA on growth and mineral uptake of peas and soil health. MATERIALS AND METHODS A field experiment was conducted in the farm area of the Vegetable Programme (LRRI), National Agricultural Research Centre (NARC), Islamabad, Pakistan, in soil representing ( clay loam in texture, pH 8.4, ECe 0.29 dSm -1 , low in available NO 3 nitrogen (0.64 mg kg -1 ), low in available phosphorus (3 mg kg -1 ) and adequate in available potassium (50 mg kg -1 ). The plots were assigned according to their respective treatments and arranged in randomized complete block design (RCBD) under two factors (HA and P levels). Humic substances have characteristics of pH 7.83, EC 0.94 and OM 68% N, P and K were 3.40, 0.15 and 3.42% respectively. Basal dose of N and K was uniformly applied to all plots. The treatments were: Factor 1: Fertilizer levels P1: Control P2: 50% Recommended Dose of P (40 Kg P 2 O 5 ha -1 ) P3: 100% Recommended Dose of P (80 Kg P 2 O 5 ha -1 ) Factor 2: Humic acid levels HA1: Control (No humic acid) HA2: Soil application of HA at 50 kg ha -1 HA3: Soil application of HA at 100 kg ha -1 HA4: Soil application of HA at 150 kg ha -1 Soil samples were collected before sowing and at harvest stage and analysed for available P, K, Zn, Mn and Fe following standard procedures (ABDTPA). Data on yield parameters like green peas’ yield (table-1) were also recorded. Plant samples were analysed for the content of P, K, Mn and Zn adopting standard analytical methods. The data thus obtained were subjected for statistical analysis using MSTATC package. RESULTS, DISCUSSION AND CONCLUSION Green Peas’ Yield (t ha -1 ) The data pertaining to green pea’s yield of the experiment is mentioned in table 1. It reveals that there was significant effect of humic acid and P on green peas yield .The highest peas yield (4.19 t ha -1 ) was attained in treatment where humic acid was applied at 100 kg ha -1 along with 50% dose of Phosphorus (40 Kg P 2 O 5 ha -1 ) . It was 35% more than the treatment receiving 100% dose of Phosphorus fertilizer application alone (80 Kg P 2 O 5 ha - 1 ). Significant effect of humic acid on pea’s yield is the result of sustained macro and micro nutrients availability to plants through out growing season as humic acid reduces P, K and Zn fixation through chelation by David et al., (1994). Secondly HA Inhibit of urease activity by HA (Vaughan and Ord, 1991), led to reduced losses of N by volatilization, as described by Flaig (1984) could have also contributed to increased availability of nitrogen. In the light of available nutrients, soil application of humic acid at 100 kg ha -1 significantly favoured the uptake of P, K, Fe and Zn which ultimately increased the yield. Available Phosphorus (mg kg -1 ) Phosphorus content in the soil was positively affected with applied HA levels. Results indicated in table 2 confirm soil P content was increased by increasing HA levels. The highest concentration of soil P (5.1 mg kg -1 ) was observed with the application of (HA) 150kgha -1 along with P 80kgha -1 which was 70% higher than control .It shows that humic acid application significantly reduce the phosphorus fixation and increase its availability through chelation effect This is in consonance with the findings of David et al., (1994). Who reported due to that slow and continuous dissolution of phosphate minerals in soil by humic acid increased P availability (Pal and Sengupta, 1985). The soil phosphatase activity improved by humic acid might have resulted in increased P availability as phosphatase hydrolyses the phosphate esters into inorganic phosphorus Malcolm and Vaughan (1979). Heng (1989) reported that HA reduces P fixing capacity of the soil, which closely corroborate with the present study where HA enhanced the P availability.
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