Different forms of boron and sulphur and their effect on Band S contents in mustard ( Brassica juncea L . ) and sunflower ( Helianthus ann us L . )

Green-house experiments were conducted involving four levels of boron (0, I, 2 and 3 mg kg -I) and sulphur (O, 20, 40 and 60 mg .1) in an acid Altisols collected from Ranchi, lharkhand with mustard and sunflower as test crops, Organically bound boron, specifically adsorbed and oxide bound increased with increasing levels of boron. Other forms of boron had positive relationships with B in leaf. stem and seed of the crop, Water soluble sulphur, sulphate sulphur and heat soluble sulphur increased with increasing levels of sulphur. At samt'} level of sulphur with increasing levels of boron, the water soluble sulphur and sulphate sulphur were found to decrease, but the heat soluble sulphur did not show significant change in the soils. Water soluble sulphur and sulphate sulphur were found to be positively and significantly correlated with dry-matter yield and S content in plants and seeds of the crops, Additional key words: Acid aljisof,jrac{ions a/borun andsufphur Boron exists in different forms and is distinguished in many categories (Evans and Sparks 1983), Soil B, as adsorbed by clay minerals (Goldberg el al.1996; Datta and Bhadoria 1999), organic matter (Yermiyaho el al. 1988), AI and Fe oxides (Elrashidi and O'Connor 1982). Mn oxyhydroxides (Jin el al. 1987) and calcium carbonate (Goldberg and Forster 1991), can be stored or removed depending on changes of boron concentration in soil solution (Keren and Bingham 1985). Thus. knowledge regarding distribution of B in different fractions is essential to understand soil chemistry and B-nutrition. both in organic and inorganic forms and the availability of sulphur in the soil is determined by the interaction between different forms of S, apal1 from the soil properties. The information on different fractions of Sand B particularly in acid A lfiso I of Ranchi Plateau and their influence on Band S contents in mustard and sunflower is virtually lacking and hence the present investigation was carried out. Material and Methods Green-house experiments were conducted during 2006 in Division of Soil Science and Agricultural Chemistry. JAR! Delhi, to know the particular fraction of Sand B that has larger effect on the availability of S and B. Experimental soils (Alfisols) collected from Ranchi, Jharkhand had pH SA, clay 2 I.S %, CEC Similarly, S occurs in soil in a variety of valency slates and chemical forms (Blanehar \986). It exists I Present address: National Bureau of Soil Survey and Land Use Planning, Nagpur 440 033. India 80ron and sulphur in soil and crops 11.18 c mol (p+) kg-I, organic carbon 1-82 g kg-I. available sulphur 4 mg kg· 1 and boron 0.14 mg kil. Five kg of soil was filled up in each polythene-lined earthen pots. Four levels of boron (0, I, 2 and 3 mg kg· l ) and sulphur (0, 20, 40 and 60 mg kg-I) were applied through (NHdh S04 and H3BO" respectively. The treatments were replicated thrice following a completely randomized block design. The NP K was applied @ 65:25:18 mg kg-I and 35:26: [8 mg kg-I to mustard (vat Pusa 801d) and, sunflower (val' Morden), respectively and were raised under recommended agro-management. The N supplied through (NH4h S04 was adjusted in different treatments. At the harvest of the crops, soil samples were also collected, processed and analyzed for various fractions of sulphur (Williams and Stein bergs 1959) and boron by the method outlined by Hou ef al_ (1996), which was later modified by Datta et 01. (2002). Sulphur content in the plant samples was estimated turbidimetrically after digesting with di-acid mixture (HN03:HCl04:5: I) as described by Chesnin and Yien (1951). For B, plant samples were ignited to ash in a muffle furnace at 550'" C, after extracting with dilute acid (0.1 N HCI)(Jackson 1978), the B in the extracts was estimated by azomethine-H method (John el at 1975). Results and Discussion Readily soluble boron At harvest of mustard and sunflower the readily soluble B varied from 0.17 to 0.97 mg kg-! (mean 0.54 mg kg· I ), for mustard crop and 0.32 to 1.12 mg kg'l (mean 0.69 mg kg· I), for sunflower crop (Table 1). The readily soluble boron increased with increasing levels of Band S. The readily soluble 8 had significant and positive correlation with specifically adsorbed B (r = 0.75**, r 0.86**) and organically bound B (r = 0.83**, r = 0.74**) in mustard and sunflower grown pots, respectively (Table 2). Response to added boron may be due to low available boron in soil under study (Karthikeyan and Shukla 2008). The readily soluble boron includes dissolved plus boron adsorbed 29 non-specifically on edges of clays and other variable charge surfaces (Hou et af. 1994) and often considered leachable (Rhoades et at 1970). The readily soluble 8 had positive correlation with the 8 in leaf(r 0.69**), stem (I' 0.71 **) and seeds (I' 0.64**) of mustard and 8 in leaf (r 0.62**), stem (r 0.62**) and seed (r 0.83**) of sunflower crop (Table 3). Specifically adsorbed boron The specifically adsorbed boron fraction varied from 0.09 to 0.52 mg kg-! (mean 0.24 mg kg'l) after the harvest of mustard and from 0.16 to 0.61 mg kg'! soil (mean 033 mg kg-! ) after harvest of sunflower crop (Table I). In general, increasing levels of boron and sulphur increased their concentration in soils. At the harvest of the crops, the specifically adsorbed boron in soils had significant positive correlation with organically bound B (r 0.69**, for mustard and sunflower (r 0.79**), respectively. Generally, this fraction includes the desorbed boron from the inorganic constituents (Hou et ar 1994). Further, B fraction probably originates from weak binding sites of both organic and inorganic constituents, where organic contribution dominates over inorganic ones. The specifically adsorbed boron was significantly correlated with B content in stem (r 0.65**) and seed (r 0.51 *) for mustard and B content in stem (r 0.5] **) and seed (I' 0.66**) in sunllower crop.