Soil Test Crop Response Correlation Studies Under Integrated Plant Nutrition System for Hybrid Maize on an Alfisol

Soil Test Crop Response correlation studies were carried out in maize under Integrated Plant Nutrition System (STCR-IPNS) on Typic Rhodustalf of Tamil Nadu, adopting “Inductive cum Targeted yield model”. The basic parameters for the “Targeted yield model” viz. nutrient requirement (NR), contribution of nutrients from soil (Cs), fertilizer (Cf) and farmyard manure (Cfym) were computed from field experimental data. Using these parameters, the fertiliser prescription equations were developed under IPNS and ready reckoner of fertiliser doses were formulated for desired yield target of maize for a range of soil test values. The quantity of fertilizer nutrients that could be saved due to the application of FYM @ 12.5 t ha -1 was assessed to the tune of 40, 20 and 26 kg fertilizer N, P 2 O 5 and K 2 O respectively, when applied along with the NPK fertilizers. The per cent reduction in fertilizer N, P 2 O 5 and K 2 O under IPNS increased with increasing soil available NPK.

present investigation was undertaken adopting this model so as to derive a basis for recommending balanced nutrition to hybrid maize on an Alfisol.

Materials and Methods
The present study consisted of two field experiments in two phases viz.,fertility gradient experiment with fodder maize CO 1 (phaseI) and the test crop experiment with maize hybrid NK6240 (phase II).The experiments were conducted during 2010-2011 on Palaviduthi (Pvd) soil series (Typic Rhodustalf) at farmer's holding of Perumalkovilpatti village in Dindigul District, Tamil Nadu.The surface soil (0 -15 cm deep) of the experimental field is yellowish red (5YR 4/6 D) to dark reddish brown (5 YR 3/4), moderately well to well drained, red, noncalcareous, sandy loam in texture with a bulk density of 1.44 Mg m-3.The pH, electrical conductivity and cation exchange capacity of the soil were 7.43, 0.14 dS m-1 and 9.1c mol (p+) kg-1, respectively.The initial soil organic carbon available alkaline potassium permanganate nitrogen (KMnO4 -N), Olsen phosphorus (Olsen -P) and ammonium acetate potassium (NH4OAc -K) were 2.4 g kg-1,198 kg ha-1, 21.5 kg ha-1 and 205 kg ha-1, respectively.The P and K fixing capacities of the soil were 100 and 120 kg ha-1, respectively.The available Fe and Mn were in the sufficient range (3.90 and 7.64 mg kg-1 respectively) while available Zn and Cu were in the deficient range (0.98 and 0.73 mg kg-1 respectively).The total N, P and K contents of the soil was 0.06, 0.07 and 0.12 per cent respectively.
In the gradient experiment, wide variation in soil fertility was created by adopting the Inductive Methodology developed by Ramamoorthy et al. (1967).For this purpose, the experimental field was divided into three equal strips, the first strip (strip I) received no fertilizer (N0P0K0), the second (strip II) and third strips (strip III) received one (N1P1K1) and two (N2P2K2) times the standard dose of fertilizer N, P2O5 and K2O respectively and a gradient crop of fodder maize (var CO 1) was grown.Eight presowing and post-harvest soil samples were collected from each fertility strip thus making a total of 24 samples and analysed for alkaline KMnO4-N, Olsen -P and NH4OAc-K.At harvest, 24 plant samples were collected, processed and analysed for N, P and K contents.
After the harvest of fodder maize, in the test crop experiment each strip was divided into 24 plots and pre-sowing soil samples were collected from each plot and analysed for alkaline KMnO4-N (Subbiah and Asija, 1956), Olsen -P (Olsen et al.1954) and NH4OAc-K (Stanford and English, 1949).The experiment was laid out in a fractional factorial design comprising twenty four treatments and the treatments consisted of four levels of N (0, 100, 200 and 300 kg ha-1), four levels of P2O5 (0, 40, 80 and 120 kg ha-1) and four levels of K2O (0, 40, 80 and 120 kg ha-1) and three levels of FYM (0, 6.25 and 12.5 t ha-1).The IPNS treatments (NPK alone, FYM @ 6.25 t ha-1 and 12.5 t ha-1) were superimposed across the strips.There were 21 fertilizer treatments along with three controls a.Nutrient requirement (NR) kg q-1 which were randomized in each strip in such a way that all the treatments occurred in both the directions.The treatment structure is given in Table 1.Twenty five per cent of N and whole of FYM, P2O5 and K2O were applied as basal dose.After the basal application of FYM and NPK fertilizers, the test crop maize (Hybrid NK 6240) was sown with a spacing of 60 cm x 25 cm.Fifty per cent of N was top dressed at 25 days after sowing and remaining 25 per cent of N was applied as second top dressing on 45 days after sowing.Routine cultural operations were followed periodically.The crop was grown to maturity, harvested and plot wise grain yields were recorded.The grain, plant and post-harvest soil samples were collected from each plot and processed and analysed for N (Humphries, 1956), P and K contents (Jackson,1973), and NPK uptake by maize was computed using the dry matter yield.
Making use of the data on the yield of maize, total uptake of N, P and K, pre-sowing soil test values for available N, P and K and doses of fertilizer N, P2O5 and K2O applied, the basic parameters for maize viz., nutrient requirement (NR), per cent contribution of nutrients from soil (Cs), fertilizer (Cf) and farmyard manure (Cfym) were calculated as outlined by Ramamoorthy et al. (1967).

b. Per cent contribution of nutrients from soil to total nutrient uptake (Cs)
Per cent contribution of N/ = Total uptake of N/ P2O5/ K2O in control plot (kg ha -1 ) x 100 P2O5/ K2O from soil Soil test value for available N/ P2O5/ K2O in control plot (kg ha -1 )

c. Per cent contribution of nutrients from fertilizer to total uptake (Cf)
Per cent contribution of N/ P2O5/ K2O from fertilizer Total uptake of N/ Soil test value for available N/ P2O5/ K2O P2O5/ K2O in x Average Cs in treated plot = treated plot (kg ha-1) - x 100 (kg ha-1) Fertilizer N/ P2O5/ K2O applied (kg ha -1 )

d. Per cent contribution of nutrients from organics to total uptake (Co) Per cent contribution from FYM (Cfym)
These parameters were used for developing fertilizer prescription equations for deriving fertilizers doses, and soil test based fertiliser recommendations were prescribed in the form of a ready table for desired yield target of Total uptake of Soil test value for N/P/K in available N/P/K in FYM x Average Cs Percent contribution of = FYM treated plot treated plot x 100 N/P/K from FYM (kg ha-1) (kg ha-1) Nutrient N/P/K added through FYM (kg ha-1) hybrid maize under NPK alone as well as under IPNS.

Targeted yield equations ii) Fertilizer phosphorus (FP2O5)
Making use of these parameters, the fertilizer prescription equations (FPEs) were developed for hybrid maize as furnished below.

iii) Fertilizer potassium (FK2O)
where, FN, FP 2O5 and FK2O are fertilizer N, P2O5 and K2O in kg ha -1 , respectively; NR is nutrient requirement of N or P2O5 or and K2O in kg q -1 ;Cs is the yield target in q ha-1 ; SN, SP and SK respectively are alkaline KMnO4-N, Olsen-P and NH4OAc-K in kg ha-1 and ON, OP and OK are the quantities of N, P and K supplied through FYM in kg ha-1.
These equations formed the basis for predicting fertilizer doses for specific yield targets (T) of hybrid maize for varied soil available nutrient levels.

Results and Discussion
The range and mean grain yield of maize furnished in Table 2 indicated that the grain yield ranged from 3200 kg ha-1 in absolute control of strip I to 10700 kg ha -1 in N300P80K80 + FYM @ 12.5 t ha -1 of strip II with mean values of 7221, 7660 and 7881 kg ha-1 in strip I, II and III respectively.The N uptake of maize varied from 44.1 to 238.3 kg ha-1; P uptake varied from 7.5 to 42.4 kg ha-1 and K uptake from 29.0 to 130.8 kg ha-1 in strips I, II and III, respectively.
The data on pre-sowing soil test values of maize revealed that, the mean KMnO4-N was 186, 206, 225 kg ha-1; the mean Olsen-P was 19, 30 and 38 kg ha-1 ; the mean NH4OAc-K was 181, 208 and 230 kg ha-1 in strips I, II and III, respectively (Table 2).The existence of operational range of soil test values for available N, P and K status in the present investigation was clearly depicted from the pre-sowing soil available nutrient status and variations in the grain yield of maize and NPK uptake, which is a prerequisite for calculating the basic parameters and fertilizer prescription equations for calibrating the fertiliser doses for specific yield target.Anon., (2011) reported similar existence of operational range of available N, P and K on various soil types.

Nutrient requirement
To produce one quintal of maize 2.00 kg of N, 0.76 kg of P2O5 and 1.27 kg of K2O were required.Among the three nutrients, the requirement of N is the highest followed by K2O and P2O5.The requirement of N is 1.57 times higher than K2O and 2.63 times higher than P2O5.Similar trend of nutrient requirement for N, P2O5 and K2O was reported by Muralidharudu et al.(2011) for maize.

Per cent contribution of nutrients from soil (Cs) to total uptake
The per cent contribution of nutrients from soil (Cs) to the total uptake was computed from the absolute control plots and it expresses the capacity of the crop to extract nutrients from the soil.In the present study, it was found that the soil has contributed 31.54 per cent of available N, 40.93 per cent of available P and 16.83 percent of available K respectively towards the total N, P and K uptake by maize.Among the three nutrients, the per cent contribution from soil was higher for P followed by N and K.With regard to K2O, comparatively lower Cs was recorded which might be due to the preferential nature of maize towards the applied K2O than the native K2O.The above findings are in accordance with Muralidharudu et al. (2011) for maize.

Per cent contribution of nutrients from fertilizers (Cf) to total uptake
The per cent contribution of nutrients from fertilisers (Cf) of maize to the total uptake was computed from the NPK applied plots.In the present investigation, the contribution from applied fertilizer was 50.50, 48.62 and 76.56 per cent, respectively for N, P2O5 and K2O which was in the order of K2O > N > P2O5.The response yardstick recorded was 13.90 kg kg -1.The estimated Cf clearly revealed the fact that the  The estimated per cent contribution of N, P2O5 and using the basic parameters as below: where, FN, FP2O5 and FK2O were fertilizer N, K2O from FYM (Cfym) were 34.70, 12.83 and 31.25 respectively for maize which indicated that relatively P O 5 and K O in kg ha-1, respectively; T was the higher contribution was recorded for N followed by 2 2 yield target in q ha-1; SN, SP and SK respectively K2O and P2O5 for maize.Similar computation of Cfym were alkaline KMnO4-N, Olsen-P and NH4OAc-K in was reported by Santhi et al. (2002) for onion and kg ha-1 and ON, OP and OK were the quantities of N, Benbi et al. (2007) for rice and wheat.
P and K supplied through FYM in kg ha-1.Santhi et al.(2012) documented in a handbook the soil test and

Fertilizer prescription under IPNS for desired yield target of maize
A ready reckoner was prepared based on these equations for a range of soil test values and for yield targets of 10 t ha-1 for maize (Table 4).The data revealed that the fertilizer N, P2O5 and K2O requirements decreased with increase in soil test values.
For a yield target of 10 t ha-1 of maize with a soil test value of 200, 20 and 200 kg ha-1 of KMnO4-N, Olsen-P and NH4OAc-K, the fertilizer N, P2O5 and K2O requirements would be 272, 117 and 112 kg ha-1 when FYM @12.5 t ha-1 with 28, 0.66, 0.38 and 0.60 per cent moisture, N, P and K, respectively was applied along with fertilizer NPK, the required fertilizer N,P2O5 and K2O doses were 232, 97 and 86 kg ha-1 respectively.Under IPNS, the savings of fertilizer N, P2O5 and K2O were 40, 20 and 26 kg ha-1 respectively for NPK plus FYM @ 12.5 t ha-1.The per cent reduction in NPK fertilisers under IPNS also increased with increasing soil fertility levels with reference to NPK.
Therefore, in the present investigation, soil test based fertilizer prescription for hybrid maize was developed on Typic Rhodustalf soils of Tamil Nadu taking into account the nutrient requirement and contribution of NPK from the nutrient sources (soil, fertilizer and FYM).This concept provides balanced nutrition to hybrid maize through STCR-IPNS.