Soildegradation caused by salinity and sodicity is of universal concern. The areaof land affected by sodicity was 434 million hectare and by salinity 376million hectare in world. In India 3.79 million hectare and in Tamil Nadu 0.35million hectare have been affected by sodicity respectively.
It was caused by inadequate drainage, especially underdense soil conditions. Soil sodicity is characterized by high pH, highwater soluble and exchangeable sodium, low biological activity, poor physicalproperties and deficiency of many essential plant nutrients in crops. Plant under sodic soil condition cannot able to grow due tothe higher concentration of Na+ ionsconcentration which favors reverse osmosis and finally plant wilt then die Despite available advanced technologies of managementtoday, millions of hectares of land under sodicity, severely reduce cropproduction worldwide.
Hence, it is necessary to develop cheap andeffective technologies for problem soils utilizing the locally availableresources without disturbing the ecological balance.However, gypsum is one of the potentialsoil amendments to reclaim sodic soil and to improve plant growth anddevelopment. Other than this several amendments have been shown to protectvarious plant species against sodicity stress by reducing exchangeable sodiumion concentration, but they are not cost effective compared to gypsum. Eventhough the gypsum is effective, because of its low solubility (0.2%) in soilcondition, this process will take more time to reclaim the sodic soil. Further,gypsum also application at regularintervals needed again and again needs to be applied to keep the sodium contentbelow the favorable level.
But, insoluble portion of the gypsum will be settledat sub-soil layer and resulted in formation of calcareous sodic soil. Oncecalcareous sodic soil condition is developed we cannot apply gypsum, in that situation we need to look foralternate amendments. In addition to above, mined gypsum sources also keep ondeclining. Based on the above, identification of suitable alternate for gypsumor development of suitable process to increase gypsum solubility under sodicsoil condition is need of the hour.
Keepingthis view in mind, experiments were carried out to increase the solubility of sparinglysoluble gypsum by using pressmud and aluminum sulphate. The main objective ofthis study was to evolve an economically feasible and practicallyviable management strategy through conjoint use of gypsum with amendments like pressmudand aluminum sulphate, So as to hasten the solubilization of gypsum and enhancecropgrowth under gardenland condition in a sodic soil. The experiment wascarried out in the farm at Anbil Dharmalingam Agricultural College and ResearchInstitute, Trichy using Vamban 2 (VBN 2) variety of greengram.Thestudy included an incubation experiment, soil column leaching and a fieldexperiment with eight treatments. The treatments comprised of a gypsum @ 10 tha-1 (T1), pressmud @ 20 t ha-1 (T2), aluminium sulphate @ 2 t ha-1 (T3),gypsum @ 5 t ha-1 + pressmud @ 10 t ha-1 (T4),gypsum @ 5 t ha-1 + aluminium sulphate @ 1 t ha-1 (T5),aluminium sulphate @ 1 t ha-1 + pressmud @ 10 t ha-1 (T6),gypsum @ 2.5 t ha-1 + pressmud @ 5 t ha-1 + aluminiumsulphate @ 0.5 t ha-1 (T7) and control (T8)for incubation and leaching experiments, which were conducted in CRD design withthree replication.
The soil was sandy clay loam (Typic Ustropepts) intexture, low in organic carbon and nitrogen and medium in phosphorus andpotassium.For field experiment gypsum @ 6 t ha-1 (T1),pressmud @ 20 t ha-1 (T2), aluminium sulphate @ 2 t ha-1(T3), gypsum @ 3 t ha-1 + pressmud @ 10 t ha-1(T4), gypsum @ 3 t ha-1 + aluminium sulphate @ 1 t ha-1(T5), aluminium sulphate @ 1 t ha-1 + pressmud @ 10 t ha-1(T6), gypsum @ 1.5 t ha-1 + pressmud @ 5 t ha-1+ aluminium sulphate @ 0.5 t ha-1 (T7) and control (T8)with recommended dose of fertilizers and also two factors were maintainedthroughout the experiment viz.
, without seed treatment and foliar spray (F1)and seed treatment and foliar spray at crop growth staged with 80 µM sodiumnitroprusside (F2) respectively were used. Field experiment was laidout in FRBD (Factorial Randomized Block Design) design and replicated thrice.The soil was sandy clay loam (Typic Ustropepts) in texture, low inorganic carbon and nitrogen and medium in phosphorus and potassium.
Dose ofgypsum was given on the basis of gypsum requirement (GR), 50 % GR was followedin T1 and remaining were half of that dose. Inthe incubation and soil column leaching study the amendments were added solely or in combination. As gypsum added withpressmud resulted in a progressive decrease in soil pH with advancement inperiod of incubation.
A significant increase in the organic carbon, cationexchange capacity and available nutrients were also observed.Inthe field experiment, combined application of gypsum and pressmud along withrecommended dose of fertilizer had a profound influence in enhancing theavailability of nutrients and reducing the soil pH at post-harvest stage. Theelectrical conductivity, organic carbon and cation exchange capacity of soilwere also increased at post-harvest stage. Sodium nitropruside application asseed treatment and foliar spray (80um) at different growth periodincreased the crop growth and grain yield due to development of salt tolerancein the plant Applicationof gypsum along with pressmud led tosignificant reduction in soil pH (9.02 to 7.85), exchangeable sodium percentage(22.
15 per cent to 14.36 percent) and also increased the nutrient availability.This treatment (T4) also registered significantly the highest grainyield of 695 kg ha-1, followed by T2(660 kg ha-1) when the planttreated with 80 µM sodium nitroprusside (F2) which differedsignificantly with each other as well as the rest of the treatments. The lowestgrain yield (320 kg ha-1) wasrecorded in the control (T8) which did not receive any amendmentsand foliar spray of seed treatment (F1).