Growth and Productivity Response of Rice to Applied Zinc and Organic Manure

Rice occupies a conspicuous position in the predominately agricultural economy of India thus attention is required to improve its yield and quality. Zinc deficiency is prevalent worldwide in temperate and tropical climate (Fageria et al., 2002). Zinc deficiency continues to be one of the key factors in determining rice production in several parts of the country (Chaudhary et al., 2007). Zinc deficiency in soil is influenced by many factors which include pH, concentration of Zn, Fe, Mn and P in soil solution, CaCO₃ (Brar and Sekhon, 1976). Zinc deficiency is usually corrected by application of zinc sulfate and response of rice to zinc under flooded condition has been reported by many workers (Fageria et al., 2011). Integrated use of organics and zinc have been found to more effective in maintaining higher productivity and stability through correction of deficiency of zinc in the course of mineralization on one hand and favorable physical soil condition on other hand. Mirza et al., (2010) reported higher rice yield when organics was applied with ZnSO₄ compared to Zn alone. Keeping in view of the importance of zinc nutrition and its use efficiency in rice and use of organics in maintaining soil fertility, field experiments were conducted in two soils deficient in zinc to study the impact of zinc and organics on growth and yield of rice.

Field experiments were conducted during Rabi 2011-2012 in Vertisol (Typic Haplusterts) and Entisol (Typic Ustifluvents) at the former’s holding place of Vadmpur. Before imposition of treatments, the soil used in the experiment had the following properties viz., pH-8.2, EC-0.49 dSm^-1, organic carbon-4.65 g kg^-1,  CEC-42.1 c mol(p⁺) kg^-1,CaCO₃- 3.38%, KMnO₄-N- 329 kg ha^-1, Olsen-P- 31.2 kg ha^-1, NH₄OAc-K- 330.8 kg ha^-1 and DTPA-Zn-0.73 mgkg^-1 (Vertisol). Similarly soils of Entisol had pH-7.5, EC-0.73 dSm^-1, organic carbon-5.36 g kg^-1, CaCO₃- 1.37%, CEC- 21.2 c mol( p⁺) kg ^-1, KMnO₄-N- 296.3 kg ha^-1, Olsen-P- 16.0 kg ha^-1, NH₄OAc-K- 299  kg ha^-1 and DTPA-Zn-0.59 mgkg^-1. The treatments  consisted of four levels of zinc viz., 0,2.5,5.0 and 7.5 mg kg^-1  applied through ZnSO₄ and organics viz., no organics, FYM- 12.5 t ha^-1, green manure- 6.5 t ha^-1, poultry manure – 10 t ha^-1 and vermicompost- 5 t ha^-1. The design was FRBD with three replications. Twenty seven days old rice seedling var. ADT 36 was transplanted in the main field. All the plots received uniform dose of 150 kg N ha^-1, 50 kg P₂O₅ ha ^-1 and 50 kg K₂O ha^-1 applied through urea, SSP and muriate of  potash respectively. Grain and straw yield was recorded at harvest and expressed as kg ha^-1. The bio metrics was recorded at different stages of crop growth

Growth analysis
 
Addition of zinc or organics or their combinations significantly improved various physiological growth parameters viz., Crop growth rate (CGR), Relative growth rate(RGR) and Net  Assimilation rate (NAR) over control in both soils (Table 1, 2, 3). CGR, RGR and NAR increased with successive addition of zinc. The highest CGR, RGR and NAR was noticed with 5.0 mg Zn kg^-1 and declined when zinc was applied at 7.5 mg Zn kg^-1 and both was comparable.  But, superior to other Zn levels. With respect to organics, addition of poultry manure recorded the highest CGR, RGR and NAR (4.65, 4.67 g m^-2 d^-1); (10.84, 10.17 mg g^-1 d^-1) and (2.94, 2.83 g dm^-1 d^-1) at 0-30 DAT and (11.54, 11.83 g m^-2 d^-1); (11.73, 11.69 mg g^-1 d^-1) and (4.89, 4.64 g dm^-1 d^-1) at 30-60 DAT in Vertisol and Entisol respectively. It was comparable with vermicompost but superior to FYM and green manures. Combined addition of zinc and organics recorded higher CGR, RGR and NAR compared to their individual application. At both the stages, addition of 5.0 mg Zn kg^-1 and poultry manure recorded the highest CGR, RGR and NAR at 0-30 DAT and at 30-60 DAT. It was comparable with vermicompost at all levels of zinc.
 

 

 

       
Interaction effect between organics and zinc was significant. Combined application of zinc and organics caused higher CGR, RGR and NAR over sole application of organics and zinc.  The highest CGR, RGR and NAR (4.89, 4.93 g m^-2 d^-1); (11.20, 10.54 mg g^-1 d^-1) and (3.13, 3.05 g dm^-1 d^-1)  at 0-30 DAT and (12.17, 12.23 g m^-2 d^-1); (12.09, 12.07 mg g^-1 d^-1) and (4.89, 4.64 g dm^-1 d^-1)  at 30-60 DAT in Vertisol and Entisol respectively was noticed with addition of 5.0 mg Zn kg^-1 and poultry manure. It was comparable with vermicompost, green manure and FYM at all levels of zinc applied. Variation in growth parameters was mainly due to different accumulation of DMP as Zn triggers metabolic process within plant. Chaudhary and Sinha (2007) reported increase in CGR, RGR and NAR with zinc additions.  Organic manures due to microbial action and improved physical condition of soil increased nutrient availability in soil.  This might have helped in enhancing leaf area, which thereby resulted in higher photo assimilation and more DMP. Variation in growth parameters among organic manures was considered to be due to variation in availability of major nutrients.
 
Dry matter production (DMP)
 
Analysis of variance (p<0.05) on dry matter production showed that addition of graded dose of zinc and organics alone or in combination significantly improved DMP over control at both the stages and soils (Table 4). Addition of graded dose of zinc improved DMP from 2065 to 2764 kg ha^-1, 2322 to 3023 kg ha^-1 at tillering stage; 4644 to 5474 kg ha^-1, 4863 to 5773 kg ha^-1 at panicle initiation stage in Vertisol and Entisol respectively. The highest DMP was noticed with 5.0 mg Zn kg^-1 (2764, 3023 kg ha^-1) at tillering stage and (5474, 5773 kg ha^-1) at panicle initiation stage in Vertisol and Entisol respectively.  Dry matter production declined at highest level of Zn applied and it was comparable with 5.0 mg Zn kg^-1. With respect to organics, addition of poultry manure recorded the highest DMP (2764, 3138 kg ha^-1) at tillering stage and (5627, 5991 kg ha^-1) at panicle initiation stage in Vertisol and Entisol respectively. It was comparable with vermicompost but superior to other two organics.  Addition of poultry manure caused 30.5, 42.7 per cent at tillering stage; 25.8, 31.5 per cent panicle initiation stage increase over control in Vertisol and Entisol respectively. Combined application of organics and Zn recorded highest DMP over their individual application. The highest DMP was obtained when poultry manure was applied along with 5.0 mg Zn kg^-1 (3025, 3368 kg ha^-1) at tillering stage and 5963, 6311 kg ha^-1) at panicle initiation stage in Vertisol and Entisol respectively. It was comparable with vermicompost at all levels of zinc. Increase in total biomass of Zn deficient plant following zinc addition is attributable to increase in the rate of photosynthesis (Cakmak and Rengel, 1999) and increase in the activity of carbonic anhydrase (Rengel, 1995). This could be due to the involvement of zinc in chlorophyll biosynthesis and increased quantum efficiency of PS II which has been reported to be damaged under Zn deficiency in rice (Chen et al., 2008). The role of zinc on DMP was ably supported by significant positive correlation between DMP with DTPA Zn (r=0.929**) and Zn uptake (r=0.993**). With respect to organics, addition of 10 t ha^-1 poultry manure recorded the highest DMP and was comparable with vermicompost but superior to green manure and FYM. Addition of poultry manure caused 30.5, 42.7 per cent at tillering stage; 25.8 and 31.5 per cent at panicle initiation over control in Vertisol and Entisol, respectively.  But the highest DMP was recorded when zinc @ 5 mg kg^-1 was applied along with poultry manure @ 10 t ha^-1.  Increase in DMP due to zinc and organic manures might be due to intermediates / metabolites of decomposing organic manures that hold zinc in the form available to plant or release of Zn mobilizing compounds such as phytosiderophores from roots and induction of polypeptide involved in Zn uptake and translocation to shoot (Ahmed et al., 2012).  It could also be due to integrated use of both these amendments that have favorable effect on soil property by forming soluble complexes with zinc which ultimately increased nutrient availability to plant resulting in higher dry biomass. Moreover, initial nutrient concentration of poultry manure was relatively higher than other organics (Akinrinde et al., 2006).  Maftoun and Moshiri (2008) noted addition of poultry manure increased DMP compared to other organics.
 

 
Rice yield
 
Analysis of variance( p=0.05) on rice yield showed that application of graded dose of zinc or organics or both significantly enhanced the grain and straw yield over control (Table 5). Addition of 5 mg Zn kg^-1 registered the maximum grain yield (5600, 5910 kg ha^-1) and straw yield (7783, 7893 kg ha^-1) which was about (15.6, 14.3%) and (20.7, 20.9%) greater than control (no zinc) in Vertisol and Entisol respectively. The rice yield declined at 7.5 mg Zn kg^-1. The higher rice yield due to zinc is attributed to its involvement in many metallic enzymes system, regulatory function and auxin production (Hacisalihoglu and Kochian. 2003), enhanced synthesis of carbohydrates and their transport to the site of grain production. The argument on the enhanced rice yield by zinc addition was ably supported by the significant positive correlation observed in the present study between grain yield and DTPA-Zn(r =0.94**). Response of lowland rice to zinc addition has been reported widely (Khan et al., 2012). Among organics, addition of poultry manure@ 10 t ha^-1 reported the highest grain yield (5742, 6039 kg ha^-1) and straw yield (7951, 8084 kg ha^-1) in Vertisol and Entisol respectively and was comparable with vermicompost. The percent increase due to poultry manure on grain yield (23.1, 22.0) and straw yield (22.2, 21.9) was noticed over control in Vertisol and Entisol respectively. This could be due to supply of nutrients especially macro and micronutrients which induce cell division, expansion of cell wall, meristamatic activity, photosynthetic efficiency, regulation of water into cells, conducive physical environment leading  to better aeration, root activity and nutrient absorption resulting in higher rice yield (Singh et al., 2001). In the present study, poultry manure contained higher nutrient content compared to other organics which caused higher rice yield. Higher grain yield due to poultry manure was reported by (Sangeetha et al., 2013). Interaction between zinc and organics was significant. The highest grain yield (6103, 6344 kg ha^-1) and straw yield (8369, 8439 kg ha^-1) was observed on addition of 5 mg Znkg^-1 and poultry manure @ 10 t ha^-1. It caused (18.2, 16.3%) and (25.1, 20.0%) increase in grain and straw yield over control. This is due to the fact that zinc availability was expected to enhance through complexation or chelation thereby prevent fixation in soil (Latha et al., 2001).
 

It was observed that rice yield significantly improved with zinc and organics fertilization in Zn deficient soil. The highest growth and yield was noticed with 5.0 mg Zn kg^-1 along with poultry manure @ 10 t ha^-1.