Dear Dr. Islam (Aminul),

Dr. F. N. Ponnamperuma*, the celebrated Rice Soil Chemist and former Principal Soil Chemist, International Rice Research Institute (IRRI), Los Banos, Philippines listed the following following chemical characteristics of fertile wetland rice soils:

pH 5.0-6.5, ECe (mS/cm) 0.2, total P (%) >0.02, Olsen P (mg/kg) >10, exch K (mmol/kg) >2, avail S (mg/kg) >10, CEC (mmol/kg) >200, clay composition >50% montmorillonite, active Fe (%) >0.5%, active Mn (%) >0.05, avail Zn (mg/kg) >1, avail B (mg/kg)

The soil used for growing rice should have a good water holding capacity. Silt clay, silt clay loam and clay are some of the soil textures that are best for rice cultivation. The pH of soil should be 6 or 7.

Thanks Dr Arvind. You rightly mentioned some major criteria. I think soil pH does not a matter for wetland rice soil since it remain near neutrality after submergence irrespective of acid or alkaline soil.  I want more about chemical criteria. 

Rice is a tropical plant that requires sufficient water to grow well. Therefore, the soil used in growing rice should have a good water holding capacity. Silt clay, silt clay loam and clay are some of the soil textures that are best for rice farming. Fertile riverine alluvial soil is best for rice cultivation. Although pH of rice soil become neutral, it should be 5 - 8.  Because, if soil is more acidic or more alkaline, it will need more time to become neutral. As a result, plant have to face unfavorable situation. For example, rice cultivation or yield is not satisfactory in acid soil.

Furthermore, flat lands are better for rice farming to allow balanced water distribution. 

Rice is a tropical plant that requires sufficient water to grow well. Therefore, the soil used in growing rice should have a good water holding capacity. Silt clay, silt clay loam and clay are some of the soil textures that are best for rice farming. The pH of the soil should be 6 or 7, but rice can also do well in a pH ranging from 4 to 8. Flat lands are better for rice farming to allow balanced water distribution

Rice grows best on clayey loams to clays that turn into soft mud, when puddled, and develop cracks on drying. Low-lying clay soils are preferred for long duration varieties, and relatively high-lying loams and lighter soils for quick maturing types. It can also be cultivated on damp alluvial soils, light sands, gravelly or stony soils, deep soils, shallow soils, soils with relatively high lime or alkali content, boggy soils, terraced hill slopes, highlands and lowlands subject to flooding and even lands on which water keeps standing for several months.

Excellent answer by J. C. Tarfder. Actually rice can grow in diversified land from top of the hill to bottom of the river or canal etc. However, yields may vary with the type of land because the soil properties varies with soil type. But an ideal soil for good paddy harvest must have some properties like OM content, rhizosphere depth, plow pan, NH4-N content etc. Another important thing it must be free from any pollutant and toxic level of any nutrient.

Dear M. N. Islam

Thanks for valuable discussion. I appreciate your thinking about the rice soil. One thing I want to mention for you. Do you know about the pH of BRRI farm soil at Habiganj? This farm belongs to haor area and the pH is 4.44. This soil is capable of producing about 9 t/ha rice yield where terrace soil of BRRI farm Gazipur (pH about 6.4) produce only 6 t/ha with same variety and same fertilizer dose. So, I again mention that pH is not a major factor for wetland rice. Remind it for wetland rice soil not for upland or dry land soil.

Complements to Dr Aminul Islam Sir for initiating a very important discussion, and thanks to all colleagues for their valuable inputs. The discussion is mostly centred on soil type and soil reaction. The question coming to mind is should we look beyond these parameters for long-term sustainability of rice-based cropping? Another aspect is the criteria discussed for ideal rice soil are in terms of monoculture or cropping sequence? Should the criteria be different for each case? In case of rice-based cropping system, the soil texture becomes perhaps the most crucial factor for long-term sustainable productivity of the crops. Because, the crop establishment, crop residue management (affecting C and N cycles, partly P also), nutrient management (most works reported of K), soil compaction etc are significantly influenced by the soil texture.

Higher nutrient use efficiency with split application of potassium fertilizer in both rice and wheat had been reported for coarse textured soils through reduction in leaching losses and luxury consumption of potassium (Tandon and Sekhon, 1988). Further, continuous rice-based cropping systems are implicated for increased bulk density of soil, irrespective of soil types (Kukkal and Aggarwal, 2003; Motschenbacher et al, 2011). Recent works in our University (unpublished data) suggested bulk density, soil organic matter and select soil enzymes (like acid phosphatases) as soil quality indicators towards sustainable long-term rice-based cropping with oilseed (rapeseed), pulses in medium to fine textured soils.

Tandon HLS, Sekhon GS (1988) Potassium Research and Agricultural Production in India. 144 pp. Fertiliser Development and Consultation Organization, New Delhi.

Kukal SS, Aggarwal GC (2003) Puddling depth and intensity effects in rice– wheat system on a sandy loam soil. I. Development of subsurface compaction. Soil and Tillage Research, 72: 1–8

Another thought in this aspect is whether we should judge the criteria separately for irrigated and rainfed rice cultures? The approach to crop establishment and management in both the cases is different, and the consequences of high input driven rice-wheat cropping sequences in Indo-Gangetic Plains of India are well documented and reported. Look forward to learn more from our colleagues. The following few links may give some useful clues:

http://file.scirp.org/pdf/AS20110200011_47241506.pdf

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4060577/pdf/TSWJ2014-856352.pdf

I appreciate the thinking of Dr. Borah but my concern is the crops thrives best under the condition of high temperature and humidity. However, varieties are available now for growing under rainfall as low as 14 inches and as high as 200 inches. Being a semi-acquatic plant, the main limiting factor is an adequate supply of water. Of course we have now wide range of cultivars which can thrive as low as soil pH 3.5 to as high as 8.5. It responds well to fertilizer application both organic or inorganic. There are numerous reports that they grow well with the application of FYM, Compost, oil-cakes, tank silt, fish manure, green twigs, leaves of trees and shrubs (Gliricidia maculata, Indofera, Tephorosia etc.) and green  manuring in situ with sunhemp or dhaincha are all in common in different parts of the rice growing countries. For sub-merged rice definitely acid phosphatase plays a significant role for native P mobilization but we should take more care to build anaerobic microbial population under water logged condition. Beside phosphatases other enzymes like urease, nitrogenase, aryl sulphatase also found to be play their role under rice fields for nutrient mobilization.

Thanks Dr J C Tarafdar Sir for valuable inputs. The views and points of all the colleagues are highly appreciated and endorsed. Regarding SQI, the findings are definitely specific to soil type and soil reaction. Our query was whether in case of rice-based cropping system the criteria for ideal soil need a different approach? Sir, thanks for your observations and explanations.

Dr. Borah, if you look at the literature, you may find rice based cropping system results are available ranging from waterlogged and poorly drained areas to well drained soils. In general it includes the rotation of crops involving rice, pulses, oilseeds, cotton, sugarcane, green manuring, vegetables etc. Various rice based cropping systems have been reported from different parts of India ranging from rice-rice-rice to rice followed by different cereals, pulses, oilseeds, vegetables and fibre crops. Rice based cropping systems may include lowland and upland crops. So far , most people have been focusing an individual crops disregarding the fact that each crop is only a component of a cropping system. More foccus has been given on favourable soil and climatic condition suitable for rice growing. You may consult the attached review paper which may give some information about your queries.

I have a list of characteristics of a good rice soil

1.Depth 20 cm 2. 10 ppm 6. Exch. K > 0.2 me 7. NH4+ 200 ppm (2WAF) 8. Avail S >10 ppm 9. Zn >1 ppm 10. EC < 2 dS/m 11. Eh ± 200 mV 12. OC >2%

Please give valuable and constructive comments and suggestions

Thank you Dr J C Tarafdar Sir. Unable to download the attached file. Will you kindly reload it. Thanks.

Dr Aminul Islam Sir, is the organic carbon content is in higher side? Would like to have your comment.

Dr. Borah, I am again reloading it but I am not sure whether it will be accessible to you. Anyway it is in Scientific World Journal (2014), Published online  on June 2, 2014. doi. 10.1155/2014/856352

Soil Physicochemical and Biological properties of paddy -upland rotation : A Review

ZHou et al (2014)

Dr. Borah Yes it is surface soil C.

Thank you Dr J C Tarafdar Sir. I have gone already through this article, and I included the link in my first answer. Thanks for your kind gesture.

Some good suggestions and answers have already been uploaded. But one thing always be kept in mind that rice crop is very rarely grown on ideal soils, rather it is grown in a wide range of soils, as Tarafdar also mentioned. Of course, yield will significantly decrease with deviation from appropriate soils for growing of rice crop.  

Thanks Dear Nazir Hussain for valuable comments. It is correct that rice can be grown in any kind if soil that I mentioned in my earlier answers. However, rice soil should have some unique characters for good yield and I gave a list regarding this. I like to say jointly with you that deviation from those characters yield will be significantly decreased. 

Dear Dr. Islam (Aminul),

Dr. F. N. Ponnamperuma*, the celebrated Rice Soil Chemist and former Principal Soil Chemist, International Rice Research Institute (IRRI), Los Banos, Philippines listed the following following chemical characteristics of fertile wetland rice soils:

pH 5.0-6.5, ECe (mS/cm) 0.2, total P (%) >0.02, Olsen P (mg/kg) >10, exch K (mmol/kg) >2, avail S (mg/kg) >10, CEC (mmol/kg) >200, clay composition >50% montmorillonite, active Fe (%) >0.5%, active Mn (%) >0.05, avail Zn (mg/kg) >1, avail B (mg/kg)

Thanks dear Dilip Kumar Kundu for nice answer. I am pleased with your answer. Your answer is very much similar with my answer given earlier. I am very happy to know that you have completed your PhD under the Father of Chemistry of Submerged Soils Dr. Ponnamperuma FN. I think you you Dr. GM Panaullah former head of Soil Science Division, BRRI, Bangladesh, he also conducted his PhD under Ponnamperuma. 

Yes, Dr. Islam. I know Dr. Golam Panaullah (my senior at Soil Chemistry Department, IRRI) who completed his Ph.D. at IRRI under the guidance of Dr. F.N. Ponnamperuma. 

Its my pleasure that I have opportunity to share scientific knowledge with renowned Soil Scientist like you and my former head GM Panaullah. Sir please pray for my success in future.

Thanks, for the compliments. My best wishes for a very bright and prosperous career for you in the field of rice soil science. 

It might be higher water holding capacity, high OM content, high CEC, a hard plough pan within 20 con which helps to minimize leaching or percolation loss of nutrient.

Rice can be grown in a wide range of soils. But in permanent water logging condition rice plant may suffers from some physiological disorders. Alternate wetting and drying favors crop growth. In continuous wetland condition S and Zn deficiency may arise. Continuous drying enhances the P fixation in acid or alkaline soils. So alternate wetting and drying positively influences the rice crop growth as well as yield.