ESTABLECER PUNTO OCUPADO

Selection of proper crop in the initial stages of reclamation is very crucial because crop differs widely in their tolerance to soil sodicity. Some crops are sensitive, whereas others are either semi-tolerant or tolerant to a given level of sodicity (Table 5). The selected crops should not only be tolerant but should also exert reclaiming effect on the soil. Therefore in the initial years of reclamation, only tol- erant crops should be grown and gradual choice may be shifted to relatively less tolerant and sensitive crops. Amongst the agricultural crops, rice in kharif season is most ideal as the first crop because it can tolerate standing water and has very high tolerance to sodicity, extensive shallow root system and ability to accelerate avail- ability of native Ca for replacement of exchangeable Na through root activities, and in rabi season, only shallow-rooted crops like wheat, barley, berseem and mustard could be grown in the initial years (Yadav and Agarwal 1959). In Uttar Pradesh, rice in kharif season followed by berseem, wheat or barley in winter season reported better crops in the initial years of reclamation. When salt-tolerant varieties of rice were grown in crop sequences for 3 years, the reclamation of sodic soils was increased and the pH of surface soils reduced, and it becomes possible to grow highly value crops like oil seed crops (mustard, linseed) and medicinal and aromatic crops (tulsi and Matricaria) (Singh et al. 2008). The study conducted at CSSRI, Regional Research Station, Lucknow, determined the time frame for substitution of

Table 4 Promising varieties of important crops released and in pipeline for cultivation in sodic

soils

Crops Varieties Tolerance level

Rice CSR10 pH 9.8–10.2 CSR 13, CSR 23, CSR 27 CSR 36, CSR 43, CSR 46 pH 9.4–9.8 CSR30 (Basmati) pH 9.4 Wheat KRL 1-4, KRL 19, KRL 210, KRL 213, KRL 283, WH157, Raj 3077 pH 9.2–9.3 HD2009, HD2285, PBW343, HD2329, pH 8.7–9.0 Mustard CS52, CS54, CS56, CS 58 pH 9.0–9.2 Pusa bold, Varuna, Kranti pH 8.8–9.0 Barley CSB 1, CSB2, CSB 3, Ratna pH 9.3

Gram Karnal chana No. 1 pH 8.8–9.0

Sugar beet Ramonaskaya-06, Polyrava-E pH 9.5–10 Sugarcane CO453, CO1341, CO6801, CO62329, CO1111 pH < 9.0 Crops and Cropping Sequences for Harnessing Productivity Potential of Sodic Soils

60

salt-tolerant varieties of rice and wheat with non-salt-tolerant high-yielding varieties or high-value crops to get higher return (Singh et al. 2010).

In recent years, the tolerance of several forage grasses under greenhouse and field conditions has been evaluated, and Karnal grass (Leptochloa fusca (Linn.)), Rhodes grass (Chloris gayana Kunth), Gatton panic (Panicum maximum), Bermuda grass (Cylodon dactylon (Linn.) Pers) and Para grass (Brachiaria mutica (Forsk)) were found relatively more tolerant grass species (Kumar and Abrol 1986).

Selection of a suitable cropping system at initial stage of reclamation hastens the reclamation process of sodic soils through addition of root biomass in the soil pro- file. Salt-tolerant varieties of rice in kharif followed by salt-tolerant varieties of wheat in rabi and dhaincha (Sesbania), green manuring in summer has been found most suitable during the initial stage of reclamation. The Central Soil Salinity Research Institute has identified or developed salt-tolerant varieties of various important crops with their tolerance level of sodicity (Table 6).

Table 5 Relative crop

tolerance to sodicity ESP range_{30–50 20–30 <20} Moderately tolerant Semi- tolerant Sensitive Barley Linseed Bengal gram Mustard Garlic Soya bean Rapeseed Sugarcane Maize

Wheat Cotton Safflower

Sunflower Guar Peas

Sorghum Groundnut Lentil

Shaftal Onion Pigeon pea

Berseem Pearl millet Urdbean Tulsi

Matricaria

Bakla

Table 6 Effect of gypsum alone and in combination with green manure on rice grain yield

Treatments Grain yields (t/ha)

Years 2005 2006

Cropping system R-W D-R-W Mean R-W D-R-W Mean

Control 3.06 3.41 3.24 3.45 3.66 3.56 25 % GR 3.43 4.23 3.83 4.31 4.62 4.47 50% GR 3.78 4.52 4.15 4.49 4.94 4.72 Mean 3.42 4.05 – 4.08 4.41 – CD (0.05) G = 0.21 G = 0.16 CS = 0.22 CS = 0.17 G × CS = 0.08 G × CS = 0.12 R-W rice–wheat, D-R-W dhaincha–rice–wheat Y.P. Singh

61

Results of several agronomic trials, having various rice-based cropping seque nces, have shown that rice–wheat–dhaincha and rice–berseem cropping sequences were more remunerative in sodic soils. This rotation should continue for at least first 3 years, and the field should not be left fallow to ensure continuity of reclamation process and to avoid reversion of sodic conditions. Growing of rice often promote a more favourable physical condition in sodic soils. Recent studies on cropping sequences with rice and sorghum (fodder-based cropping sequences) revealed that rice-based cropping sequences were better than sorghum-based crop- ping sequences in terms of yield as well as reclamation of sodic soils. These studies further revealed that rice–berseem cropping sequence was best followed by rice– mustard and rice–wheat (Table 7). The study conducted at CSSRI, Regional Research Station, Lucknow, revealed that after 3 years of rice–wheat cropping system, some high-value crops like tulsi, Matricaria, garlic and linseed may be grown successfully (Singh et al. 2008). Some of the oil seed crops like sunflower, mustard, safflower, linseed, groundnut, soya bean and sesame were tested for their performance in sodic soils. It was observed that mustard, rapeseed and sunflower were moderately tolerant, linseed and groundnut semi-tolerant and the rest of the crops were sensitive to sodicity.

Results of several field experiments with various cropping sequences conducted at different places have shown that dhaincha-rice–wheat, rice–berseem, rice– mustard and rice–wheat are more remunerative at the initial stage of reclamation of sodic soils. Studies conducted to determine the time frame for crop diversification

Table 7 Cropping sequences recommended at different stages of reclamation

Soil pH2

Reclamation

period (years) Cropping sequences Initial stages of reclamation

9.2–9.8 1–3 Dhaincha-Rice–wheat Rice–berseem Rice–mustard Rice–barley Post-reclamation period 9.0–9.2 4–5 Sorghum–wheat or mustard

Pearl millet–wheat or mustard, cotton–wheat 8.8–8.9 6–8 Groundnut–mustard or wheat

Sunflower–wheat, maize–linseed Tulsi–Matricaria, chilli–garlic Sorghum–mustard–sugarcane 8.6–8.7 9–10 Sorghum–gram or pea

Pearl millet–lentil or gram Pigeon pea–wheat Soya bean–wheat

8.5–8.6 After 10 All cropping sequences including vegetables and flowers Crops and Cropping Sequences for Harnessing Productivity Potential of Sodic Soils

62

revealed that diversification of rice–wheat cropping system depends on the extent of reclamation; however, it can be possible after 3 years of continuous rice–wheat cropping system (Singh et al. 2010).