STUDIES ON THE LONG-TERM EFFECT OF MANURE AND FERTILIZERS APPLICATION ON POTASSIUM DYNAMICS IN RAINFED GROUNDNUT GROWING ALFISOLS
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Date
2016
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Acharya N.G. Ranga Agricultural University, Guntur
Abstract
The present study entitled “Studies on the long-term effect of manure and fertilizers application on potassium dynamics in rainfed groundnut growing alfisols” was undertaken during kharif-2015.The long-term field experiment was started at the Regional Agricultural Research Station, Tirupati, Acharya N.G. Ranga Agricultural University during kharif-1981 with a prime objective of monitoring the status of soil potassium fractions. The soil of the experimental field was red sandy loam (Haplustalf). The experiment has eleven treatments each replicated four times in a randomized block design. The treatments include T1 : Control (no manure or fertilizers), T2 : Farm yard manure @ 5 t ha-1 (once in 3 years), T3 : 20 kg Nitrogen (N) ha-1, T4 : 10 kg Phosphorus (P) ha-1, T5 : 25 kg Potassium (K) ha-1, T6 : 250 kg gypsum ha-1, T7 : 20 kg N + 10 kg P ha-1, T8 : 20 kg N + 10 kg P + 25 kg K ha-1, T9 : 20 kg N + 10 kg P + 25 kg K + 250 kg gypsum ha-1, T10 : 20 kg N + 10 kg P + 25 kg K + 100 kg lime ha-1, T11 : 20 kg N + 10 kg P + 25 kg K + 250 kg gypsum ha-1 + 25 kg zinc sulphate ha-1 (as basal, once in 3 years).
Soil samples were collected from each plot at two depths i.e. 0-15 and 15-30 cm at sowing, pod formation and at harvest stages of groundnut crop during kharif-2015 and analyzed for physico-chemical, chemical and K fractions viz., water soluble-K, available-K, fixed-K, exchangeable-K and non-exchangeable-K. Soil samples collected at sowing were analyzed for their physico-chemical, chemical properties and potassium fractions. Soil
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samples collected from two depths (0-15 and 15-30 cm) at pod formation and at harvest stages of groundnut crop were analyzed for different K fractions (0-15 and 15-30 cm). Similarly, haulm yield, K concentration and K uptake in the plant were analyzed at two stages of crop growth viz., pod formation and harvest and crop yields were recorded.
The soils of the experimental plots were slightly acidic to strongly acidic with pH ranging from 5.22 to 5.61, non-saline, low in organic carbon, free CaCO3 contents and available nitrogen, higher in available phosphorus and medium to high in available K whereas exchangeable Ca and Mg were present in sufficient amounts in the experimental plots irrespective of the treatments studied. At sowing, the water soluble-K was high in K alone treated plot (T5) both in surface (47.77) and sub surface (46.54) soil whereas P alone treated plot (T4) recorded lowest in surface soil (18.82) and gypsum alone treated plot (T6) recorded lowest in sub surface soil (12.88). The available-K in both the surface (312.43) and sub surface (253.54) soil was highest in K alone treated plot (T5) whereas gypsum alone treated plot (T6) recorded lowest value (135.35) in surface soil and NP treated plot (T7) (86.21) recorded lowest in sub surface soil. The fixed-K content in both the surface (1193.39) and sub surface (655.34) soil was highest in K alone treated plot (T5) whereas N alone treated plot (T3) recorded lowest (608.02) in surface soil and NP treated plot (T7) recorded lowest (436.21) in the sub surface soil. The exchangeable-K in both the surface (264.66) and sub surface (207.00) soil was highest in K alone treated plot (T5) whereas gypsum alone treated plot (T6) recorded lowest (111.16) in the surface soil and NP (T7) recorded lowest (64.43) in the sub surface soil. The non-exchangeable-K both in surface (954.19) and sub surface (544.60) soil was highest in NPK+gypsum+ZnSO4 (T11) and lowest was recorded in N alone treated plot (T3) both in surface (426.30) and sub surface (321.55) soil.
At pod formation stage, the water soluble-K in both surface (18.56) and sub surface (13.41) soil was highest in K alone treated plot (T5) whereas NPK + gypsum (T9) recorded lowest (9.21) in the surface soil and P alone treated plot (T4) recorded lowest (7.14) in the sub surface soil. The availableK in both the surface (219.83) and sub surface (214.26) was highest in K alone treated plot (T5) and lowest in NP treated plot (T7) both in surface (98.85) and sub surface (90.08) soil. The fixed-K in both the surface (989.73) and sub surface (603.06) soil was highest in K alone treated plot (T5) whereas N alone treated plot (T3) recorded lowest (516.49) in surface soil and NP treated plot (T7) recorded lowest (359.73) in the sub surface soil. The exchangeable-K in both the surface (201.27) and sub surface (200.85) soil was highest in K alone treated plot (T5) and lowest in NP treated plot (T7) both in the surface (89.41) and sub surface (82.46) soil. The non
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exchangeable-K in both the surface (822.56) and sub surface (461.39) soil was highest in NPK+gypsum+ZnSO4 (T11) and lowest in N alone treated plot (T3) both in surface (375.42) and sub surface (256.44) soil. At harvest of groundnut the water soluble-K in both the surface (39.72) and sub surface (32.12) soil was highest in K alone treated plot (T5) whereas P alone treated plot (T4) recorded lowest (14.68) in the surface soil and gypsum alone treated plot (T6) recorded lowest (9.15) in sub surface soil. The available-K in both the surface (225.35) and sub surface (177.83) was highest in K alone treated plot (T5) and lowest was recorded in P alone treated plot (T4) both in surface (83.36) and sub surface (77.81) soil. The fixed-K in both the surface (742.36) and sub surface (479.32) soil was highest in K alone treated plot (T5) whereas N alone treated plot (T3) recorded lowest (389.14) in the surface soil and NP treated plot (T7) recorded lowest (296.14) in the sub surface soil. The exchangeable-K in both the surface (185.63) and sub surface (145.71) was highest in K alone treated plot (T5) and lowest was recorded in P alone treated plot (T4) both in the surface (68.68) and sub surface (62.86) soil. The non-exchangeable-K in the surface soil was highest in gypsum alone treated plot (T6) (556.71) and lowest in control plot (T1) (250.18) whereas in case of sub surface soil the non-exchangeable-K was highest in P alone treated plot (T4) (359.28) and lowest in NP treated plot (T7) (172.52).
All these fractions were significantly influenced by different treatments studied and all the fractions recorded higher values in the surface soil than sub surface soil. All the fractions followed decreasing trend from sowing to pod formation stage whereas in case of harvesting stage except water solubleK all K fractions followed decreasing trend. At harvest higher amount of water soluble-K was noticed as compared to that of pod formation stage. The correlation studies with values of potassium fractions at harvest at 0-15cm depth revealed that pod yield was significantly and positively correlated with only non-exchangeable-K (0.300*). The K uptake at harvest was significantly and positively correlated with only water soluble-K (0.387**) whereas at 15-30 cm depth no fraction was significantly correlated with yield of groundnut crop. In the present study it is conferred that complete omission of K fertilizer continuously for longer duration results in depletion of K reserves and the equilibrium between different K fractions is adversely affected which reduces K availability to plant. Hence balanced supply of nutrients with the treatments viz., NPK + G + ZnSO4, NPK + L, NPK + G would enable in buildup of K in the soil and maintained equilibrium between different K fractions as all fractions are important for crop growth.
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