Changes in the soil properties and availability of

Journal of Plant Nutrition

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Changes in the soil properties and availability of micronutrients after six-year application of organic and chemical fertilizers using STCR-based targeted yield equations under pearl millet-wheat cropping system P. C. Moharana, B. M. Sharma & D. R. Biswas To cite this article: P. C. Moharana, B. M. Sharma & D. R. Biswas (2017) Changes in the soil properties and availability of micronutrients after six-year application of organic and chemical fertilizers using STCR-based targeted yield equations under pearl millet-wheat cropping system, Journal of Plant Nutrition, 40:2, 165-176, DOI: 10.1080/01904167.2016.1201504 To link to this article: http://dx.doi.org/10.1080/01904167.2016.1201504

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Date: 28 February 2017, At: 02:28

JOURNAL OF PLANT NUTRITION 2017, VOL. 40, NO. 2, 165–176 http://dx.doi.org/10.1080/01904167.2016.1201504

Changes in the soil properties and availability of micronutrients after six-year application of organic and chemical fertilizers using STCR-based targeted yield equations under pearl millet-wheat cropping system P. C. Moharanaa, B. M. Sharmab, and D. R. Biswasb a National Bureau of Soil Survey and Land Use Planning, Regional Centre, Udaipur, India; bDivision of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi, India

ABSTRACT

ARTICLE HISTORY

Field experiments were carried out to assess the effect of nutrient management on soil properties and available micronutrients using Soil Test Crop Response (STCR) based targeted yield equations under a six-year old pearl millet-wheat cropping system. After six years, results showed that soil pH and bulk density decreased, while cation exchange capacity and organic carbon increased in farmyard manure (FYM) as compared to control and nitrogen, phosphorus and potassium (NPK) treated plots in both surface and sub-surface soil depths. Higher values of available zinc (Zn) (1.54 mg kg¡1) and iron (Fe) (5.68 mg kg¡1) were maintained in FYMCNPK treated plots, while higher values of manganese (Mn) (6.16 mg kg¡1) and copper (Cu) (1.07 mg kg¡1) were found in FYM alone at surface soil as compared to subsurface soil. This study demonstrated the importance of application of FYM in improving soil properties and maintaining micronutrients availability in soil and their uptake by wheat for sustainable crop production.

Received 20 December 2014 Accepted 25 February 2015 KEYWORDS

Soil properties; available micronutrients; STCR-based fertilizer recommendations; targeted yield equations; pearl millet-wheat cropping system

Introduction Soil organic matter (SOM) plays a major role in determining the sustainable productivity of an agroecosystem. The sustainable productivity of a soil mainly depends upon its ability to supply essential nutrients to the growing plants. The deficiency of nutrients has become major constraint to productivity, stability and sustainability of soils. Micronutrient contents of a soil and their availability to plants depends on the type of mineral present and their extent of weathering processes. In the recent past, increased use of chemical fertilizers in an unbalanced manner has created problem of multiple nutrient deficiencies, particularly micronutrients, diminishing soil fertility and unsustainable crop yields. Due to the increased productivity of the crops, the native soils have begun depleting their nutrient reserves and the crops started responding to application of micronutrient fertilizers (Sidhu and Sharma, 2010). Various studies indicated that the factor productivity of various crops declined in spite of balanced fertilization with nitrogen (N), phosphorus (P) and potassium (K). The availability of micronutrients in the soil can strongly affect the production and quality of crops. Changes in basic soil characteristics such as pH, cation exchange capacity (CEC) and soil organic carbon (SOC) content under different nutrient management systems is the main cause of change in available micronutrients status in soil. It is also observed that the availability of soil micronutrients is largely influenced by the soil

CONTACT P. C. Moharana [email protected] National Bureau of Soil Survey and Land Use Planning, Regional Centre, University Campus, Bhora Ganeshji Road, Udaipur 313001, India. © 2017 Taylor & Francis Group, LLC

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microenvironment besides soil properties, such as pH, calcium carbonates (CaCO3), organic matter and CEC (Wei et al., 2006). Soil organic matter exerts a significant and direct impact on the availability of zinc (Zn), iron (Fe) and manganese (Mn) but it has little influence on the availability of copper (Cu) in soil (Aulakh and Mahi, 2005; Chaudhary and Narwal, 2005; Li et al., 2007). In addition, the interaction of other macronutrients and micronutrients in soil affect the availability of micronutrients and their uptake by crops. Application of appropriate rates of N, P and K fertilizers can increase soil Cu, Zn and Mn availability and the concentrations of Cu, Zn, Fe and Mn in wheat (Li et al., 2007). Maintaining or increasing SOM is very important in providing available micronutrients for crop production. Depletions in available micronutrients status under unfertilized as well as NPK fertilized plots indicated that these nutrients were utilized from soil to meet the requirements of crops; hence their supplement cannot be over looked. However, little attention has been paid to micronutrients in response to different fertilization practices, and how soil fertility impacts on the uptake of micronutrients from soil and their transfer from tissues to grains are not well documented. Pearl millet-wheat sequence is the second most important sequence after rice-wheat in the Indo-Gangetic Plains of India. It is being realized that when crops are grown in sequence, the fertilizer needs of the cropping sequence as a whole is important than that of the individual crop. Most often, the prior knowledge of soil fertility status and nutrient requirements of a particular crop are needed for application of fertilizers by the farmers. The targeted yield concept vis-a-vis fertilizer prescription based on soil test crop response correlation takes into account the soil fertility status and nutrient requirements of crops. The fertilizer recommendations based on targeted yield approach have been well established in India through number of follow-up trials and frontline demonstrations conducted under the network of All India Coordinated Research Project (AICRP) on Soil Test Crop Response (STCR) Correlation including Delhi center (Subba Rao and Srivastava, 2001). However, information on long-term effect of these recommendations used with or without farmyard manure (FYM) in a pearl millet-wheat cropping system on soil properties and available micronutrients in soil is scare. Keeping these points in mind, the present field experiment was conducted at the research farm of Indian Agricultural Research Institute (IARI), New Delhi to investigate and see the long-term effect on soil properties and available micronutrients as influenced by nutrient management with FYM and chemical fertilizers applied either alone or in combination using STCR-based targeted yield equations under a six-year old pearl millet-wheat cropping system.

Materials and methods Site and soil The present field experiment on pearl millet–wheat cropping system was initiated in monsoon 2003 at the research farm of IARI, New Delhi under the network of All India Coordinated Research Project (AICRP) on Soil Test Crop Response (STCR) Correlation Studies. The experimental field is located at 28.4  N latitude, 77.1  E longitude and at an elevation of about 250 m above the mean sea level. The climate of the experimental site is semi-arid with hot and dry summer and severe cold winter intervened by short monsoon period of 2–3 months spreading from July to September. On the basis of 30 years climatic data, the mean maximum temperature, minimum temperature and rainfall are 31.2 C, 17.0 C and 821 mm, respectively. The experimental area represents Indo-Gangetic Plains which belongs to Mehrauli series. The soil is Inceptisol having sandy loam texture, alkaline reaction and free from salinity occurring on nearly level to very gently sloping land. Soil structure is sub-angular blocky. Clay mineralogy is dominated by illite along with presence of kaolinite, chlorite and chloritized montmorillonite. Taxonomically it belongs to Typic Haplustept. The initial soil samples from surface (0–15 cm) and sub-surface (15–30 cm) were analyzed for mechanical composition, pH, electric conductivity (EC), cation exchange capacity (CEC), bulk density (BD), organic carbon (OC) and available micronutrients following standard procedures. The physicochemical properties of the initial soil under study are presented in Table 1.

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Table 1. Physicochemical properties of the experimental soil before commencing the study. Soil depth Soil characteristic

0–15 cm

Mechanical composition Sand (%) Silt (%) Clay (%) Texture pHW (1:2.5) EC (dS m¡1) Bulk density (Mg m¡3) Organic carbon (g kg¡1) CEC [cmol(pC) kg¡1 soil] Available micronutrients (mg kg¡1) Zn Fe Mn Cu

15–30 cm

Method followed Bouyoucos (1962)

56.5 25.0 18.5

56.4 26.0 17.6

Sandy loam 8.44 0.32 1.59 5.2 10.7

Sandy loam 8.44 0.25 1.72 2.6 6.15

0.98 7.14 13.4 0.52

0.66 5.44 7.72 0.34

Jackson (1973) Jackson (1973) Veihmeyer and Hendrickson (1948) Walkley and Black (1934) Jackson (1973) Lindsay and Norvell (1978)

Experimental design and treatments The field experiment on pearl millet-wheat cropping system was designed under AICRP on STCR with three different nutrient management practices along with a control in a randomized block design with four replications. The treatments selected for this study consisted of (i) unfertilized/unmanured control (Control); (ii) FYM alone at 20 magnesium (Mg) ha¡1 to each crop (FYM); (iii) STCR-based fertilizer NPK alone for grain yield target of 2.5 Mg ha¡1 of pearl millet and 5.0 Mg ha¡1 of wheat (NPK); and (iv) STCR-based integrated use of 10 Mg ha¡1 of FYMC fertilizer NPK for grain yield target of 2.5 Mg ha¡1 of pearl millet and 5.0 Mg ha¡1 of wheat (FYMCNPK). The purpose of selecting FYM alone was to investigate the long-term use of organic manure alone on yield and soil productivity. Application of FYM at 20 Mg ha¡1 was adopted so as to provide 100 kg N ha¡1 considering that 0.5% N is present in FYM on fresh weight basis. The treatments, NPK fertilizer alone and FYMCNPK were selected to investigate the effect of STCR-based fertilizer NPK management (i.e. fertilizers only) and STCR-based integrated management of FYM C fertilizers NPK on soil properties and available micronutrients at the same level of targeted yield production. In the present field experiment, the soil test based fertilizer adjustment equations with and without FYM for targeted levels of grain production of pearl millet and wheat grown in sequence for six years as reported earlier (Moharana et al., 2012) under AICRP on Soil Test Crop Response Correlation at IARI, New Delhi were used for fertilizer management in NPK and FYMCNPK treatments, respectively. The following fertilizer adjustment equations were used for calculation of fertilizer doses: Pearl millet Without FYM FN D 69.7 T ¡ 0.36 SN FP2O5 D 57.3 T ¡ 4.81 SP FK2O D 39.2 T ¡ 0.28 SK

With FYM FN D 53.5 T ¡ 0.29 SN ¡ 2.23 FYM FP2O5 D 47.2 T ¡ 3.29 SP ¡ 2.48 FYM FK2O D 28.8 T ¡ 0.17 SK ¡ 1.35 FYM Wheat

Without FYM FN D 43.0 T ¡ 0.44 SN FP2O5 D 37.9 T ¡ 6.02 SP FK2O D 23.4 T ¡ 0.33 SK

With FYM FN D 3.85 T ¡ 0.41 SN ¡ 1.64 FYM FP2O5 D 27.8 T ¡ 4.12 SP ¡ 1.72 FYM FK2O D 20.4 T ¡ 0.29 SK ¡ 0.88 FYM

where, FN, FP2O5 and FK2O stand for fertilizer rate (kg ha¡1) of N, phosphorus pentoxide (P2O5) and potassium oxide (K2O), respectively; SN, SP and SK stand for soil test values (kg ha¡1) for potassium permanganate (KMnO4-N) (Subbiah and Asija,1956), Olsen-P (Olsen et al., 1954) and ammonium acetate-extractable (NH4OAc-K) (Hanway and Heidel, 1952), respectively; FYM stands for dose of farmyard manure (Mg ha¡1) and T denotes the targeted yield (Mg ha¡1).

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Field technique Prior to start of the experiment, two exhaustive crops namely, pearl millet during monsoon and wheat during winter season were grown to bring the uniformity in soil fertility in the field. After harvesting the second exhaustive crop of wheat, the composite initial soil samples from surface (0–15 cm) and sub-surface (15–30 cm) layer were collected and analyzed for physicochemical properties. The field was divided into four equal size strips and each strip was divided into four equal size plots of 20 m £ 4 m each. The treatments were distributed randomly using a randomized block design. Before application of fertilizer doses in each crop, plot-wise soil samples from 0–15 and 15–30 cm depth were collected and analyzed for available N, P and K status and soil test based fertilizer doses for NPK and FYMCNPK treatments were calculated from the fertilizer adjustment equations for pearl millet and wheat. The pearl millet (cv Pusa 383) and wheat (cv HD 2687) were grown in sequence for six years with the same treatments. Fertilizer materials used were urea, diammonium phosphate (DAP) and muriate of potash (MOP). The FYM used in the present study had 0.50% N, 0.32% P, 0.46% K, 0.32% S, carbon/nitrogen (C/N) ratio of 26.5 and 8.9% moisture content (w/w). Half dose of N and full doses of P and K were applied as basal in both the crops by broadcasting followed by mixing by disc plough. Remaining half of N was applied as top-dressing at knee-height stage (45 days after sowing) in pearl millet and at panicle emergence (55 days after sowing) in wheat. Irrigation and other agronomic management practices were carried out as and when required. Soil analysis After completion of six cropping cycles of pearl millet-wheat, soil samples from surface (0–15 cm) and sub-surface (15–30 cm) were collected. In each plot, the soil was collected from ten points randomly and mixed into one sample. The sample was air-dried in shade, ground to pass through a 2-mm sieve and used for the estimation of soil chemical properties. Bulk density was determined by using rings of known volume (5 cm inner diameter and 5 cm height). Soil cores were dried at 105 C in an oven for 48 h. Bulk density was calculated by dividing weight of dried soil by the volume of core used (Veihmeyer and Hendrickson, 1948). The pH was measured in 1:2.5 soil:water suspension with a glass electrode. The electrical conductivity (EC) was measured in supernatant liquid of soil: water (1:2.5) suspension with the help of conductivity meter as described by Jackson (1973). The CEC was determined by saturating the soil with neutral normal ammonium acetate followed by estimation of ammonia by distillation as described by Jackson (1973). Soil organic carbon was determined by the rapid titration method (Walkley and Black, 1934). The available micronutrients viz., Zn, Cu, Mn and Fe were extracted using DTPA (diethylene triamine pentacetic acid) extractant as developed by Lindsay and Norvell (1978). For this, 20 mL of DTPA solution containing 0.005 M DTPA C 0.1 M TEA (tri-ethanolamine) C 0.01 M calcium chloride (CaCl2) having pH 7.30 were added to 10 g soil. The solutions were shaken for 2 h at 25 C, filtered through Whatman No. 42 filter paper and the concentrations of micronutrients (Zn, Cu, Mn and Fe) were analyzed by an atomic absorption spectrophotometer (AAS). Plant analysis Plot-wise samples of wheat grain and straw were dried at 65 § 1 C in oven and ground in a Wiley mill for chemical analysis. The samples were digested with di-acid mixture of nitric acid-perchloric acid (HNO3:HClO4) (10:4 ratio) and the micronutrient contents (Fe, Cu, Mn and Zn) in the di-acid digested plant samples were determined by an AAS. Statistical analysis For statistical analysis of data, Microsoft Excel (Microsoft Corporation, Redmond, WA, USA) and SPSS (Statistical Package for the Social Science, SPSS, Inc., Chicago, IL, USA) window version 16.0

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were used. Analysis of variance (ANOVA) was done as per the procedure outlined by Gomez and Gomez (1984). The significant differences between treatments were compared with the least significance (LSD) at 5% level of probability.

Results and discussion Changes in soil properties Bulk density (BD) The results revealed that the values of BD at 0–15 cm soil depth were significantly lower in treatments receiving FYM than in treatments without FYM (Table 2). The BD decreased significantly in the following order: control (1.59 Mg m¡3) D NPK fertilizer (1.59 Mg m¡3) > FYMCNPK fertilizer (1.53 Mg m¡3) > FYM alone (1.51 Mg m¡3). No significant effect of treatments on BD was observed in sub-surface soil layer. The values of BD in FYM treated plots were less as compared to control which may be due to higher accumulation of organic carbon in the former than the later treatment. The surface soil having high in organic carbon also exhibited lower BD than the sub-surface soil. Decrease in BD in FYM alone and FYMCNPK treatments in surface soil might be due to improvement in soil structure and porosity due to application of FYM. Our results corroborated the findings of others (Rudrappa et al., 2006; Gong et al., 2009). pH The pH of the soil in different treatments ranged from 8.22 to 8.50 in surface soil (0–15 cm) and from 8.44 to 8.48 in sub-surface (15–30 cm) soil. Lower pH values of 8.22 and 8.30 in surface soil were observed in FYM alone and FYMCNPK fertilizer treatments, respectively as compared to the pH values of 8.50 and 8.48 in NPK fertilizer and control treatments, respectively (Table 2). However, the treatment effects were not significant among the different nutrient management. A comparison of fertilizer treatments within each cropping system indicated that the long-term application of manure and N fertilizer also led to a decrease in soil pH. The decrease in the pH in the N fertilized treatment may have been due to nitrification of ammonium (NH4C) to nitrate (NO3¡). The decrease in soil pH in the FYM treatments might have resulted from the release of organic acids and carbon dioxide (CO2) into the soil during the decomposition of the manure. The production of aliphatic and aromatic hydroxyl acids as a result of decomposition of FYM could also result in complexing of free and exchangeable aluminum ions and thus decrease the pH (Grewal et al., 1981; Swarup and Wanjari, 2000; Hati et al., 2008). Electric conductivity (EC) The electric conductivity as a measure of soluble salts or salinity varied in different nutrient management from 0.33 to 0.34 dS m¡1 in surface soil and 0.25 to 0.27 dS m¡1 in sub-surface soil (Table 2). However, no significant differences in EC values were observed among the treatments in both the soil depths. The results under long-term fertilizer experiments conducted at different locations also showed no appreciable change in salinity in most of the soils except in Ustochrept soil, where EC increased Table 2. Effect of FYM and fertilizers on soil properties in a six-year old pearl millet-wheat cropping system using targeted yield equations. BD(Mg m¡3) Treatment Control FYM NPK FYMCNPK SEM (§) LSD (P D 0.05)

EC(dS m¡1)

pH

CEC[cmol(pC) kg¡1]

0–15 cm 15–30 cm 0–15 cm 15–30 cm 0–15 cm 15–30 cm 0–15 cm 15–30 cm 1.59 1.51 1.59 1.53 0.02 0.06

1.72 1.67 1.68 1.68 0.03 NS

8.48 8.22 8.50 8.30 0.03 0.09

8.47 8.44 8.48 8.45 0.02 NS

0.33 0.34 0.33 0.34 0.01 NS

0.26 0.27 0.25 0.26 0.01 NS

9.44 13.60 11.50 12.60 0.59 1.9

6.26 7.05 6.32 6.56 0.2 NS

SOC(g kg¡1) 0–15 cm 15–30 cm 6.50 4.90 5.10 7.30 0.30 0.80

3.80 2.50 3.00 4.10 0.20 0.70

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from the initial value of 0.20 to 0.80 dS m¡1 in 100% N treatments (Nambiar, 1994). Brar and Pasricha (1998) also reported that continuous use of fertilizer and manures under maize-wheat cowpea cropping systems did not affect the EC values. In another study under continuous rice-rice system, there was a marginal increase in EC values by 0.1 to 0.2 dS m¡1 after 24 years of cropping (Tembhare et al., 1998). Cation exchange capacity (CEC) The cation exchange capacity of the soil in different treatments ranged from 9.44 to 13.6 cmol(pC) kg¡1 in surface soil (0–15 cm) and 6.26 to 7.05 cmol(pC) kg¡1 in sub-surface soil (15–30 cm). The CEC in FYM alone and FYMCNPK fertilizer treatments showed significantly higher values over control in surface soil (Table 2). The CEC of the soil decides the nutrient carrying capacity of the soil. All the buffering action undergoing in soils are mainly dependent on CEC. Organic matter is the principal source of CEC in soil. The increase in CEC is, therefore, attributed to increase in organic matter content in FYM treated plots as organic matter has very high CEC as compared to clay minerals. In case of surface soil, significant improvement in CEC from its initial value was observed in FYM alone and FYMCNPK treated plots over unfertilized control as well as NPK fertilizer plots. However, such improvement in CEC values due to different nutrient management was not found in sub-soil. This might be due to large amount of organic matter applied through FYM which remained and confined onto the surface soil. Soil organic carbon Monitoring of soil organic carbon (SOC) either for agricultural sustainability or environmental quality have been carried out in the recent past by various workers. In our study, it is evident that continuous application of FYM either alone or in combination with NPK resulted in considerable changes of SOC in the surface (0–15 cm) soil layer than that of unfertilized control as well as NPK treated plots (Table 2). Soils under the FYMCNPK treated plots maintained higher SOC in the 0–15 cm soil layer over those under the NPK treated plots. In the present study, the plots that received FYM (7.30 g kg¡1) and FYMCNPK (6.50 g kg¡1) had significantly higher build-up in SOC over unfertilized control (4.90 g kg¡1) and NPK treated plots (5.10 g kg¡1) in the surface soil. The increase in build-up in SOC under FYM and FYMCNPK treatments was 43.1 and 27.5 per cent greater over treatment receiving NPK fertilizer alone and 49.0 and 32.7 per cent greater over treatment receiving no fertilizer or manure (control). In case of sub-surface soil, the build-up in SOC under plots receiving FYM alone (4.1 g kg¡1) and FYMCNPK fertilizer (3.8 g kg¡1) was higher than in the plots receiving only NPK fertilizer (3.0 g kg¡1) and in the control (2.5 g kg¡1). In general, the values of SOC in sub-surface soils due to application of different treatments were low compared to surface soil. The significantly greater SOC in the fertilized plots over the control may be explained by the greater yield and associated greater amount of root residues and stubbles of all the crops added to the soil (Ghosh et al., 2003). Greater SOC under complete doses of NPK fertilizer as compared to unfertilized soil has also been reported in long-term studies (Swarup and Wanjari, 2000). Application of organic amendments (FYM) also increased the SOM content to a much greater extent than that of inorganic fertilizer alone. This may be attributed to enhanced crop growth which in turn, resulted in increased above and below-ground organic residues (e.g., roots), and thus raised the SOM content. The increased SOM in FYM added plots also due to slower breakdown rate (less and constant mineralization rate) of FYM in soil. Kundu et al. (2007) reported that SOC content improved in fertilized plots as compared to the unfertilized plots due to carbon addition through the roots and crop residues, higher humification rate constant, and lower decay rate. Similarly, in a long-term experiment, Moharana et al. (2012) observed that the SOC was considerably greater in soils receiving FYM along with NPK fertilizer than in plots receiving merely NPK fertilizer. Changes in available micronutrients Available Zn Available Zn concentrations varied greatly amongst the different treatments. Application of FYM significantly increased available Zn concentration. Significant increase in available Zn in surface

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soil (0–15 cm) was maintained in plots receiving FYM (1.36 mg kg¡1) and integrated use of FYMCNPK fertilizer (1.54 mg kg¡1) over NPK treated (1.24 mg kg¡1) and unfertilized control plots (0.99 mg kg¡1) (Table 3). However, increases in available Zn in sub-surface soil (15–30 cm) were observed only under plots receiving FYM and FYMCNPK fertilizer over unfertilized control. FYM not only supplies large amounts of Zn to the soil, but also promotes biological and chemical reactions that result in the dissolution of non-available Zn. For the NPK alone treatment, the available Zn was lower than the critical value, possibly due to Zn precipitation by high concentrations of available soil P (Chaudhary and Narwal, 2005; Sidhu and Sharma, 2010). Available Fe Significantly greater amount of available Fe in surface soil was maintained in all the three treatments receiving manure and fertilizer applied either alone or in combination over unfertilized control plot. The build-up of available Fe in surface soil (0–15 cm) was 5.68, 5.56 and 4.99 mg kg¡1 in plots receiving FYMCNPK, FYM and, NPK respectively as against 4.06 mg kg¡1 in unfertilized control plot (Table 3). Increase in available Fe in surface soil was 36.9 and 39.9 per cent in FYM and FYMCNPK fertilizer treated plots over control, respectively. However, no significant differences were found in sub-surface soil. The available Fe in sub-surface soil (15–30 cm) varied from 3.36 to 3.62 mg kg¡1 in different nutrient management practices. The available Fe showed higher increases in the surface layer as compared to sub-surface soil depths. Available Fe concentrations were higher for FYM receiving treatment than the others, due probably to high concentrations of soil organic carbon. For all treatments, available Fe levels were above the proposed critical levels of 0.3–10 mg kg¡1 (Lindsay and Cox, 1985) and hence adequate for wheat grown in the soil. Available Mn The plots receiving FYM alone had a higher concentration of available Mn than the other treatments in both the soil depths. The available Mn content in soil under different treatments varied from 4.40 to 6.16 mg kg¡1 in surface soil and from 2.74 to 3.27 mg kg¡1 in sub-surface soil (Table 4). Plots that received FYM maintained significantly highest amount of available Mn (6.16 mg kg¡1) followed by integrated use of FYMCNPK (5.65 mg kg¡1), NPK fertilizer alone (5.65 mg kg¡1) and control (4.40 mg kg¡1) in surface soil (0–15 cm). These data indicate that the long-term fertilization as in the present study under a six-year old pearl millet-wheat cropping system led to a large increase in available Mn. This increase might have been related to changes in the soil microenvironment that resulted in the release of plant available Mn. For example, in the continuous FYM treatment, soil pH was lower and organic matter levels were higher compared to the control. The lower pH may have resulted in the release of previously non-available Mn from soil minerals. In addition, the decomposition of organic matter would have provided protons to the soil solution and also decreased soil Eh values. These changes could have resulted in the dissolution and reduction of Mn, thus increasing its availability.

Table 3. Effect of FYM and fertilizers on available Zn and Fe using targeted yield equations in a six-year old pearl millet-wheat cropping system. Available Zn (mg kg¡1)



Treatment

0–15 cm

Control FYM NPK FYMCNPK SEM (§) LSD (P D 0.05)

0.99 1.36 (37.4) 1.24 (25.3) 1.54 (55.6) 0.11 0.34

Figure in parentheses indicate percent increase over control.

15–30 cm 0.53 0.69 (30.2) 0.62 (17.0) 0.61(15.1) 0.04 NS

Available Fe (mg kg¡1) 0–15 cm 4.06 5.56 (36.9) 4.99 (22.9) 5.68 (39.9) 0.15 0.49

15–30 cm 3.36 3.62 (7.7) 3.42 (1.8) 3.43 (2.1) 0.07 NS

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Table 4. Effect of FYM and fertilizers on available Mn and Cu using targeted yield equations in a six-year old pearl millet-wheat cropping system. Available Mn (mg kg¡1)

Available Cu (mg kg¡1)

Treatment

0–15 cm

0–15 cm

0–15 cm

15–30 cm

Control FYM NPK FYMCNPK SEM (§) LSD (P D 0.05)

4.40 6.16 (40.0) 5.65 (28.4) 5.65 (28.4) 0.57 NS

2.74 3.27 (19.3) 3.47 (26.6) 3.23 (17.9) 0.26 NS

0.65 1.07 (64.6) 0.90 (38.5) 0.93 (43.1) 0.09 NS

0.51 0.60 (17.6) 0.56 (9.8) 0.56 (9.8) 0.05 NS



Figure in parentheses indicate percent increase over control.

Available Cu Available Cu did not show significant change among the different treatments (Table 4). Available Cu in different treatments varied from 0.65 to 1.07 mg kg¡1 in surface soil (0–15 cm) and 0.51 to 0.60 mg kg¡1 in sub-surface soil (15–30 cm). Fertilization did not have significant effect on available Cu. The reason might have been that the application of FYM increased the amount of chelating agents in soil. In this case, Cu could be bound with organic matter and relatively unavailable to plants. The other reason for this might have been that the fertilizers used in this experiment contained very little Cu. Yield of wheat The grain and straw yield of wheat were significantly influenced by FYM applied either alone or in combination with NPK fertilizer (Table 5). Grain yield of wheat obtained in different nutrient management varied from 1.67 Mg ha¡1 in unfertilized control to 5.33 Mg ha¡1 in integrated use of FYM and inorganic fertilizers (FYMCNPK) and straw from 2.29 (unfertilized control) to 7.49 Mg ha¡1 (FYMCNPK). The highest grain and straw yield were obtained in integrated treatment (FYMCNPK) and lowest in control. This showed the superiority of integrated nutrient management over either fertilizers or FYM alone. Significantly higher yield was obtained in FYMCNPK as compared to FYM, which revealed that FYM alone cannot be a substitute for fertilizers. The highest grain yield recorded under the application of inorganic sources of nutrient may have been due to the immediate release and availability of nutrients as compared to organic sources of nutrient, which release the nutrient slowly. The yield advantage on application of organic sources of nutrients was due to addition of secondary and micronutrients (Manna et al., 2005; Banik et al., 2006) along with the major nutrients, increased nutrient absorption capacity due to the higher root density. It also improved soil physical (Boparai et al., 1992) and biological properties by increasing the soil pore space, water holding capacity (Wallace, 1996; Lehmann et al., 1999) and improving the soil structure (Prasad and Singh, 1980). Combined use of organic and inorganic sources of nutrient could be attributed to better synchrony of nutrient availability to the wheat crop, which was reflected in higher grain yield and biomass production and also the higher nutrient use efficiency. The higher wheat yield obtained on FYMCNPK fertilizer Table 5. Effect of FYM and fertilizers on yield of wheat grown in a six-year old pearl millet-wheat cropping system using targeted yield equations. Treatment Control FYM NPK FYMCNPK SEM (§) LSD (P D 0.05)

Grain yield (Mg ha¡1)

Straw yield (Mg ha¡1)

1.67 3.68 4.48 5.33 0.064 0.207

2.29 4.77 5.51 7.49 0.089 0.285

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treated plots was possibly caused by other benefits of organic matter such as improvements in microbial activities, better supply of secondary and micronutrients which are not supplied by inorganic fertilizers, and lower losses of nutrients from the soil besides supply of N, P and K (Yadav et al., 2000; Yadvinder-Singh et al., 2004). The improved soil physical properties in the FYM treated plots as observed in the present study might have also contributed to the improvement in crop yields. The present study corroborates the findings of other workers (Banger et al., 2009), where increased yield of wheat due to integrated use of manures and fertilizers over fertilizers alone were reported. Transfer of micronutrients from soil to wheat crop Zinc, Cu, Fe and Mn are essential micronutrients for crop growth, and their plant availability affects the transfer from soil to crop and thereby the crop yield and quality. The available Cu and Mn concentrations in soil did not significantly change among the different treatments, but the available Zn and Fe concentrations increased with increasing soil organic matter content. The Zn concentrations in wheat grain were 35.5 and 31.5 mg kg¡1 in the FYM alone and FYMC NPK treatments, respectively, which were higher than fertilizer NPK alone and control plots (Table 6). The Zn concentrations in wheat straw of FYM alone, FYMCNPK, NPK alone treatments (25.2–30 mg kg¡1) were higher than unfertilized control plot. The Cu concentrations in wheat grains varied from 7.50 to 9.25 mg kg¡1 and straw varied from 14.5 to 17.0 mg kg¡1 without significant differences. The treatments receiving FYM had higher concentrations of Fe in the wheat grain than that of NPK alone and control. Similar results were observed for Fe content in wheat straw. The Fe concentrations in the wheat grain were lower than that in the wheat straw. The Mn concentrations of wheat grain in different treatments varied in the range of 22.5 to 26.75 mg kg¡1. The differences of wheat grain and straw Mn concentrations with different treatments were not significant. But, wheat grain and straw Mn concentrations of FYM treated plots were higher than that of other treatments. The transfer of micronutrients from straw to grain is a slow process. Wheat grain took up more micronutrients because of their long growth period. The transfer coefficients of micronutrients from straw to grain were calculated and shown in Table 6. Due to the difference of soil micronutrient levels, the transfer coefficients of micronutrients from crop straw to grain varied. The transfer coefficients of wheat Zn, Cu, Fe and Mn varied in the range of 1.12–1.20, 0.51–0.59, 0.18–0.19 and 0.63–0.74, respectively. High contents of soil organic matter due to balanced and integrated fertilization resulted in higher transfer coefficient of micronutrients, while inadequate fertilization caused lower transfer coefficients. Data emanated from the present study revealed that the total Zn, Fe, Mn and Cu uptake varied from 99 to 392 g ha¡1, 723 to 2342 g ha¡1, 126 to 392 g ha¡1 and 52 to 167 g ha¡1, respectively in different treatments (Figure 1). Total uptake of all the micronutrients were highest in plots receiving integrated use of nutrient management FYMCNPK) followed by fertilizer NPK alone, FYM alone and unfertilized control. This was because of higher biomass (grain C straw) production in FYMCNPK treated plot as compared to NPK and FYM treatments. Table 6. Micronutrient content and its transfer coefficient in wheat. Nutrient content (mg kg¡1) Wheat grain Treatment Control FYM NPK FYMCNPK SEM (§) LSD (P D 0.05)

Zn

Fe

Mn

Cu

Zn

Fe

Mn

Cu

Zn

Fe

Mn

Cu

27.5 31.5 26.7 35.5 1.69 5.4

48.5 53.7 47.7 53.5 1.61 5.13

23.7 26.7 22.5 26.2 1.42 NS

9.25 8.25 9.25 7.5 0.94 NS

23.2 28.2 25.2 30 0.93 2.97

266 290 266 289 5.11 16.3

37.7 36.2 40.7 33.7 1.51 NS

16.2 17 14.5 17 1.26 NS

1.20 1.12 1.13 1.13

0.18 0.19 0.18 0.19

0.64 0.74 0.63 0.70

0.59 0.51 0.58 0.51

Transfer coefficient D concentration in grain/concentration in straw.

#

Transfer coefficient#

Wheat straw

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Figure 1. Effect of FYM and fertilizers on micronutrient uptake by wheat grown in a six-year old pearl millet-wheat cropping system using targeted yield equations. Error bars represent standard deviation of the mean.

Correlation matrix Data on Pearson’s correlation matrix (Table 7) revealed that yield of wheat was significantly (P < 0.01) and positively correlated with Zn uptake (r D 0.950), Cu uptake (r D 0.947), Mn uptake (r D 0.992) and Fe uptake (r D 0.976) by the crop. Significant and positive correlations (P < 0.01) were also observed between wheat yield with available Zn (r D 0.641) and available Fe (r D 0.772) in soil. Micronutrients uptake also found to be positively correlated with available micronutrients in soil. The soil organic carbon showed significant and negative correlation with pH (r D ¡0.077) and positive relationship with CEC (r D 0.063). Negative relationship with pH showed decrease in pH value with increase in organic matter due to more release of organic acids during decomposition of

Table 7. Pearson’s correlation matrix between soil properties, available micronutrients, micronutrient uptake and yield of wheat as affected by FYM and fertilizers using targeted yield equations in a six-year old pearl millet-wheat system. Parameters

pH

EC

CEC

Avail Zn

SOC 

Avail Fe

Avail Mn 

Avail Cu

Zn uptake

Fe uptake

Mn uptake

Cu uptake

Yield

BD ¡0.228 0.29 0.082 ¡0.661 ¡0.16 ¡0.513 ¡0.235 ¡0.394 ¡0.389 ¡0.232 ¡0.244 ¡0.322 ¡0.242 pH ¡0.145 ¡0.702 ¡0.077 ¡0.347 ¡0.107 ¡0.232 0.045 ¡0.016 ¡0.129 ¡0.096 ¡0.085 ¡0.051 EC ¡0.017 ¡0.151 ¡0.04 0.068 ¡0.087 ¡0.02 0.156 0.159 0.111 0.114 0.136 CEC 0.063 0.12 ¡0.07 0.134 ¡0.281 ¡0.214 ¡0.127 ¡0.195 ¡0.09 ¡0.24     SOC 0.555 0.626 0.294 0.600 0.522 0.425 0.402 0.472 0.398 Avail Zn 0.507 0.631 0.556 0.686 0.743 0.708 0.739 0.641 Avail Fe 0.446 0.566 0.819 0.767 0.758 0.760 0.772 Avail Mn 0.47 0.41 0.472 0.482 0.497 0.427 Avail Cu 0.524 0.496 0.498 0.411 0.487    Zn uptake 0.960 0.952 0.937 0.950 Fe uptake 0.982 0.969 0.976 Mn uptake 0.959 0.992 Cu uptake 0.947 

Correlation is significant at the 0.01 level (2-tailed). Correlation is significant at the 0.05 level (2-tailed).



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organic matter. The positive values with CEC indicate improvement in nutrient supplying capacity of soil by increase in organic matter content. Similarly the negative correlation with BD (r D ¡0.661) indicates increase in porosity by improving the soil structure due to application of FYM. The results indicate that soil organic matter exerts a significant and direct impact on the availability of micronutrients and properties of soil.

Conclusions The present study demonstrated that integrated use of FYM and NPK fertilizer using STCR-based targeted yield approach increased available micronutrients and soil properties. After a six-year of application of various fertilizer treatments, it was observed that available Zn and Fe status in soil showed significant differences among the treatments, while available Cu and Mn were not found significantly different. Addition of FYM either alone or in combination with NPK fertilizer increased soil organic carbon over NPK alone treated plots which, in turn, may have been the cause of better soil physical conditions in FYM treated plots compared with NPK treated plots. These results conclude that for sustainable crop production and maintaining soil quality, input of organic manures like FYM is of prime importance and should be advocated in the nutrient management under intensive cropping system for improving chemical, physical and biological properties of soils.

Acknowledgments The authors thank the Head, Division of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi, India, for providing facilities for successful completion of the research works.

Funding The first author thanks the Indian Council of Agricultural Research, New Delhi, India, for providing financial support as Junior Research Fellowship during his research work.

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