How to Manage Soil Fertility? | Soil Management

The following article will guide you about:- 1. How to Manage Soil Fertility for Rice Based Cropping System 2. How to Manage Soil Fertility for Cotton Based Cropping System 3. How to Manage Soil Fertility in Dryland Farming. 

How to Manage Soil Fertility for Rice Based Cropping System:

Among the food crops in India, rice is the major cereal crop occupies in an area of 42 m.ha and contributes 80 to 90 mt of production. Production of rice should be increased to a greater extent to feed the millions of population as rice contributes about 40 per cent of total food grain production.

Due to exploding population, increased urbanization and industrialization, increasing area under rice is not possible. But the production can be increased through intensification of cropping involving rice as a component in the cropping system. There are about 136 rice based cropping systems are being followed in different zones of India.

The predominant cropping systems are as follows:

Rice- Wheat system

Rice- Rice system

Rice- Maize/Bengal gram system

Rice- Jute/Potato system

Rice- Jute-Rice

Rice- Rice-Pulses

Rice- Sugarcane system

Soil Fertility Management:

Intensive rice cropping through the use of short duration and high yielding varieties coupled with increased use of inorganic fertilizers and improved irrigation management practices have resulted in enhanced crop productivity. This productivity enhancement gradually replaced organic sources of nutrients leading to deficiency of micronutrients, which reduce productivity of crops over the years. To overcome these problems, organic manures should be applied in combination with inorganic fertilizers which will improve fertility status of soil resulting in higher productivity of crops.

Inorganic Sources of Nutrients:

Nitrogen: Forms of Soil Nitrogen:

Losses of Nitrogen:

i. Leaching

ii. Volatilization

iii. Nutrient uptake by crops (crop removal)

iv. Through soil erosion

v. Fixation of ammonia by clay content of soil, and

vi. Immobilization.

These losses of nitrogen should be minimized for achieving maximum nitrogen use efficiency (NUE), which will result in boosting of growth and development of crops. This enhanced NUE leads to sustainable yield of crops.

Nitrogen Use Efficiency:

Nitrogen use efficiency can be increased through the usage of:

1. Nitrogen inhibitors.

2. Chemically modified fertilizers.

3. Coated fertilizers.

1. Nitrogen (Nitrification) Inhibitors:

The materials which are used to inhibit the process of denitrification are called as nitrogen inhibitors. Ammoniacal and amide form of N get oxidized to NO₃ form through biochemical oxidation which on denitrification, N₂ and N₂O are released into atmosphere. This process occurs due to low redox potential. To overcome these problems and to increase nitrogen use efficiency, usage of nitrogen inhibitors is inevitable.

2. Chemically Modified Fertilizers:

Through treatment with certain chemicals, the nature of fertilizer is changed which help in reducing the solubility of fertilizers. This reduction in solubility increases nitrogen use efficiency of crops.

i. Urea formaldehyde

ii. Iso butylene diurea (IBDU)

iii. Urea acetaldehyde

iv. Crotonylidene urea (CDU)

v. Glycoluril

vi. Difurfuryledene tri urea

vii. Guanyl urea

viii. Triazines.

3. Coated Fertilizers:

Fertilizers when coated with any suitable materials will release N at slow rate thereby increasing NUE of crops.

(a) Sulphur Coated Urea:

Urea granules are uniformly coated with a layer of sulphur for releasing N at slow rate.

i. Urea- 80- 85%

ii. Sulphur-13-16%

iii. Wax-2%

The release of N depends on:

(a) Thickness of coating

(b) Temperature

(c) Time of Incubation

(d) Redox potential, and

(e) Placement of fertilizer.

(b) Lac Coated Urea:

Composition:

i. Urea-73.7%

ii. Resin-16.2%

iii. Linseed oil – 3.3%

iv. Soapstone – 2.9%

v. Wax – 3.6%

vi. Coal tar – 0.3%

(c) Neem Coated Urea:

Composition:

i. Urea – 100 kg

ii. Coal tar – 1 kg

iii. Kerosene – 2 litres

iv. Neem cake – 20 kg

(d) Urea Super Granules (USG):

Size of the urea granule is increased for controlling the release of N. These are called as urea briquettes or super granules, which are manufactured commercially and can be applied to soil with the help of granule applicator.

(e) Gypsum Coated Urea:

Composition:

i. Urea – 100 kg

ii. Gypsum – 20 kg

Experiments with 15_N fertilizers have evinced that recovery of N for the first crop (rice) varied from 20-35%. Only a small fraction of N (2-4%) was utilized by the succeeding wheat crop. Slow release N fertilizers have shown some residual effect. The results clearly indicated that N should be applied at recommended levels to each crop except when heavy organic manures are added.

Legumes and Soil Fertility:

Inclusion of legumes like cowpea and black gram during pre-rice summer season in rice- rice-green gram cropping system yielded 5 to 7 q/ha of grain yield. Incorporation of cowpea and black gram haulms enhanced rice yield by 10.4 and 7.5%, respectively. This incorporation helped in saving fertilizer N to an extent of 30-50 kg and 20-30 kg N/ha, respectively.

In rice-wheat cropping system, a lean period of 3 -4 months (March-June) is available, which can be utilized for raising pulses as catch crop during summer season. Preceding legume crops of fodder cowpea and green gram (grain) increased the yield of rice to the equivalent of 44 and 35 kg N/ha, respectively. Therefore, the fertilizer requirement of rice is substituted by the nature of preceding crop.

Under lowland ecosystem, inclusion of legumes in the rice based cropping systems and application of bio fertilizers like blue green algae and azolla in rice could help to save 20-40 kg N/ ha to be applied through fertilizers.

Similarly, inclusion of fodder legume berseem (Trifolium alexandrinum) in rice based cropping system improved soil fertility as compared with other rotations that included only cereals. This helped in achieving sustainable yield of crops in the cropping system. Incorporation of mung bean straw and application of N at 60 kg ha-1 to rice produced yields similar to those of rice receiving 120 kg N ha-1 of inorganic fertilizer. This helped in saving of 60 kg N/ha.

Field experiments were conducted at the Crop Research Centre of Govind Ballabh Pant University of Agriculture and Technology, Pantnagar during 1996 – 97 and 1997 – 98 to assess the impact of diversification of rice-wheat cropping system on crop productivity and soil fertility.

Each experiment comprised of 10 crop sequences:

(a) Wheat-rice,

(b) Chickpea-rice,

(c) Lentil-rice,

(d) Pea-rice,

(e) Wheat-mung bean (green manure)-rice,

(f) Wheat-Sesbania (green manure) -rice,

(g) Wheat-fodder-rice,

(h) Chickpea-fodder-rice,

(i) Lentil-fodder-rice, and

(J) Pea-fodder-rice.

The crop sequences were compared in terms of economic rice equivalent yield (REY), protein production, apparent nutrient balances and effect on soil fertility status. Amongst crop sequences involving two crops each year, chickpea-rice cropping sequence recorded the highest REY and protein production. Of the sequences involving three crops each year, chickpea- fodder-rice and wheat-fodder-rice cropping sequences were superior to others.

The phosphorus balances were positive for all sequences, whereas potash balances were generally negative except for sequences involving green manure and legumes. Green manuring with Sesbania or mung bean helped to restore soil fertility, indicating the advantage of green manure for higher productivity and sustainability of rice-wheat system. Chickpea-rice and chickpea-fodder-rice appeared promising alternatives to rice-wheat cropping sequence.

Green Manures and Soil Fertility:

Experiments conducted in India revealed that growing of green manure crops preceding to rice in rice-rice-pulse cropping system, registered a grain yield similar to application of 50 kg N/ ha. This was due to improved soil fertility through the incorporation of green manures. The fertilizer N equivalent of green manure on rice was 38 kg/ha during North East monsoon season and 47 kg/ha during South West monsoon season. The N equivalent was 20% higher than urea for Crotolaria juncea (sunnhemp) and 15% for Sesbania aculeata (daincha).

Studies conducted at International Rice Research Institute (IRRI) revealed that incorporation of Sesbania rostrata into the soil resulted in accumulation of 40-140 kg N ha-1. The addition of nutrients and improvement in soil physical, chemical and biological properties increased the grain yield by 1.0 t ha-1.

The incorporation of Sesbania rostrata at 50 days after emergence and 45 kg N ha-1 as urea, either split applied or all top dressed during panicle initiation(PI) recorded slightly higher grain yield than application of urea or S. rostrata alone besides having residual effect for the succeeding crop.

Experiments conducted at Raipur showed that when 50 per cent of N was supplemented through the incorporation of Sesbania aculeata at the time of land preparation in rice recorded yield on par with the same N dose supplied through inorganic sources of nutrients in rice- pulse cropping system. Beneficial effects of supplementing 25 to 50 per cent N through farm yard manure or rice residue incorporation have also been found in the above study.

Rice could tolerate intense shading in the earlier stages which will pave the way for intercropping. Research conducted at Tamil Nadu Agricultural University (TNAU), Coimbatore revealed that growing of Sesbania aculeata or Sesbania rostrata in the inter space of rice during early stage and in situ incorporation increased the uptake of nutrients by rice.

Grain yield was also increased by about 6q ha-1. Continuous intercropping of green manures in rice is expected to improve the soil fertility thus ensuring sustainable rice production. Implements were developed at TNAU for wet seeding of rice and green manure simultaneously and also for incorporating the green manure crops in between rice rows.

Research conducted at TNAU, Coimbatore revealed that there is a gradual build-up of soil organic carbon (SOC) when Sesbania rostrata was incorporated in situ at flowering stage as a basic means of improving soil fertility in rice-rice cropping system. Further, the soil organic matter fractions viz., humic acid and fulvic acid were also improved.

Influence of Organic Manures and Inorganic Fertilizers on Soil Fertility:

Increase in cropping intensity demand more nutrients to sustain high productivity. A single lowland rice crop producing 9.8 t grains ha-1 and 8.21 straw ha-1 in about 115 days removed up to 218 kg of N, 31 kg of organic P, 258 kg of K and 9 kg of S ha-1. Besides these the other micro nutrients removed by the crop must be replenished to sustain high production. Hence, application of organic and inorganic sources of nutrients is highly essential for improving soil fertility thus leading to sustainable production.

Long term experiments conducted at Indian Agricultural Research Institute (IARI) revealed that application of 50% NPK + FYM at 10 t/ha + BGA at 13 kg/ha recorded higher grain yield compared to 100% NPK in rice-wheat cropping system. In another long term experiment, application of FYM with 100% NPK to wheat in rice-wheat cropping system recorded an additional total grain yield of 1.74 t/ha compared to no FYM + 150% NPK.

Research conducted through All India Coordinated Agricultural Research Project (AICARP) on rice-wheat cropping system evinced that efficacy of applied fertilizers was increased significantly when inorganic fertilizers were applied in combination with organic manures. Therefore, to reduce the cost of production, and improve the soil fertility status, substitution of inorganic fertilizers with organic manures is necessary. In rice-wheat cropping system, it was possible to substitute 50 per cent of N through the usage of FYM and green manures.

Soil fertility status after rice-mustard cropping system under integrated nutrient management:

Experiments conducted at Rahuri in rice-mustard cropping systems under integrated nutrient management revealed that fertility status of soil was improved when inorganic fertilizers were applied in conjunction with organic manures.

Studies conducted in lateritic soil revealed that application of green leaf manure (Glyricidia maculata) at 5 t/ha and 50 kg N ha-1 through fertilizers for rice and entire dose of recommended fertilizer (25 kg N + 50 kg P₂O₅ ha-1 ) for groundnut in rice – groundnut cropping system recorded the highest yield through improved soil fertility.

A long term fertilizer experiment was conducted on the rice-wheat cropping system at four locations in India with the following fertilizer treatments to assess the trends in partial factor productivity of applied nitrogen, benefit: cost ratio of fertilizer application, grain yield, changes in soil organic carbon, available nitrogen (N), phosphorus (P) and potassium (K).

On average at all locations, continuous rice-wheat cropping system for 16 years decreased the yield of rice by 57% in unfertilized plots and by 32% in plots receiving nitrogen and phosphorus fertilizers. Over the same period wheat yields only declined in unfertilized plots by 18%; in plots receiving nitrogen, phosphorus and potassium yields increased by 18% and they increased by 33.6% in plots receiving nitrogen and phosphorus fertilizer. Partial factor productivity of applied nitrogen (the ratio of output value to the cost of a specific input) exhibited similar trends.

The long-term rice-wheat cropping system became depleted in soil organic carbon, available nitrogen and phosphorus at two locations but increased in organic carbon, available nitrogen and potassium at the third location. The available phosphorus and potassium content of the soil also increased at the fourth location.

Based on the aforementioned research findings, the following recommendation should be adopted for achieving sustainable production:

i. For rice – wheat cropping system, N should be applied to both rice and wheat, P only to wheat and K and Zn to rice.

ii. For rice – rice – green gram / soybean system, N should be applied to both the crops (rice), P to dry rice and K, S, and Zn to second crop (rice).

iii. In rainfed rice-pulse system, fertilizer should be applied to rice alone. If moisture is adequate, apply 20 kg P₂O₅/ha to pulses.

iv. Inclusion of legumes in the cropping systems and application of blue green algae/azolla in rice contribute 20 – 40 kg N/ha.

How to Manage Soil Fertility for Cotton Based Cropping System:

Growing of cotton continuously in the same field as monocrop is detrimental and yield will decline faster over seasons irrespective of the appropriate crop management strategies. Introduction of legume crop either in rotation or in cropping system will improve yields of the succeeding crops.

Nevertheless, in cotton based cropping systems, the research carried out at different agro climatic zones revealed that growing of sorghum, ragi, rice and maize as preceding crops was found to enhance yield of cotton significantly. Hence, diversified cropping systems and crop rotations are to be adopted for maintaining soil fertility, which help to enhance productivity of cotton.

Double cropping sequences are more popular in the agro climatic zones of India where the supply of irrigation water is plenty. ‘Cotton-Wheat’ is a dominant cropping system in North zone, while ‘Cotton-Sorghum’, ‘Cotton-Maize’ and ‘Cotton-Rice’ are the dominant cropping system in central and Southern zones. In parts of Andhra Pradesh, ‘Cotton-Chilli’ and ‘Cotton-Tobacco’ are grown as sustainable cropping system. In parts of Tamil Nadu, cotton is raised as summer catch crop after Banana variety Nendran.

The predominant cropping systems adopted by the farming community in different agroclimatic zones are as follows:

a. Cotton – Wheat

b. Cotton – Sorghum

c. Cotton – Maize

d. Cotton – Rice

e. Cotton-Chilli

f. Cotton – Tobacco

g. Banana – Cotton

h. Cotton – Mustard

i. Cotton – Green gram – Cotton

j. Cotton – Chilli – Cotton

k. Ragi – Cotton

l. Cotton – Sorghum – Ragi

Nutrient Management:

The indigenous cotton (Desi) is less responsive to nutrient management practices as evidenced by earlier research works. However, with the introduction of American fertilizer responsive cotton, consumption of fertilizer for cotton has gone high leading to increased yield. Fertilizer use received further boost in cotton with the development of hybrids since 1970s.

In cotton, it has been found that for each one quintal of seed cotton yield, it removes about 6, 2 and 6.8 kg of N, P and K, respectively as crop uptake. Based on these studies, the targeted yields and nutrient requirements are worked out for sustaining the productivity of cotton.

Nitrogen:

i. Cotton responds favourably to nitrogen application both under irrigated and rainfed conditions. The responses to nitrogen application under irrigated conditions are higher than under rainfed conditions.

ii. Generally, 40-50 kg N/ha is adequate for sustaining productivity of cotton under rainfed conditions.

iii. Under irrigated conditions, doses higher than 100 kg N/ha are recommended for achieving optimum yield.

iv. The nitrogen use efficiency was more in hybrids and American cottons than in ‘Desi’ varieties as per the research findings. These differential responses of varieties/hybrids to nitrogen are attributed to their root characteristics.

v. Application of nitrogen in 2-3 splits is more beneficial than a single basal application.

vi. When urea is applied to soil, loss of N occurs due to volatilization under high temperatures. To minimize the losses, placement and spot application of urea in moist zone should be done.

vii. Excessive use of nitrogenous fertilizers should be avoided as it will promote vegetative growth leading to increased occurrence of pests and diseases.

Phosphorus:

i. The seed cotton yield depends on phosphorus content at different stages of growth from 70 to 150 days after sowing. The increase in yield is attributed to number of seeds per boll, boll weight and oil content in seed.

ii. Application of phosphorus counteracts the excessive vegetative growth and hastens the maturity of the crop.

iii. Phosphorus deficiency leads to short and brittle internodes with small and thickened leaves, lower seed production and poor quality of cotton.

iv. Research carried out at different agroclimatic zones evinced that application of 60 kg phosphorus increased seed cotton yield by 33% under rainfed conditions and by 17% under irrigated conditions.

v. Various research findings revealed that split application of phosphorus and was desirable in enhancing the productivity of cotton.

vi. Foliar application with DAP at 1 to 2% for 2-3 times starting from square formation stage at 15-20 days interval is found to be effective for improving growth and development.

vii. Fertigation with NPK in as many as six splits are found to enhance crop productivity besides ensuring more efficient use of fertilizers.

viii. The nitrogen use efficiency is increased when phosphorus is applied in combination with nitrogen.

ix. Direct effect of phosphorus is found to be better than that of residual P or cumulative effect or both.

Potassium:

i. Application of potassium counteracts the ill effects of excessive ‘N’ doses and hastens the maturity of the crop.

ii. Potassium application induces both abiotic and biotic stress resistance and improves lint quality through the mitigation of stress, pests and diseases incidence.

iii. Application of potassium at 50 kg /ha is optimum for obtaining desirable yield in cotton.

iv. Nutrient management studies conducted at Tamil Nadu Agricultural University, Coimbatore under permanent manorial experiment on irrigated cotton since 1925 revealed that the highest increase in seed cotton yields are obtained under NP and NPK treatments, as compared to N alone indicating the role of balanced nutrient application.

v. The efficiency of potassium is increased when K is applied in combination with N and P.

vi. Split application of K is recommended recently under high yielding crop situations. To achieve yield targets of above 25 q/ha, a minimal dose of 100 kg K/ha is recommended in split doses.

vii. Foliar application of potassium in the form of K₂SO₄, KCl and KNO₃ at 1 to 2% is very effective and economical and can be combined with application of pesticides for getting optimum yield.

Magnesium and Sulphur:

Recent experimental findings revealed that foliar spray of 2% magnesium sulphate from square formation stage to boll development stage helped in alleviating nutrient deficiencies thus favouring yield of cotton. Soil application of magnesium and sulphur can also be done through dolomite, magnesium sulphate and super phosphate for meeting out the nutrition requirement of cotton.

Micronutrients:

Deficiency of micronutrients viz., Zn, Fe, Cu, Mn and B in cotton is generally observed in coarse textured and calcareous soils. Among the micronutrients, B deficiency leading to boll rot and lime induced iron chlorosis in calcareous soils are the most prevalent deficiencies in cotton which affect the productivity and quality. Since these soils are strongly alkaline, the problem can be solved by foliar spray. Micronutrient deficiencies are corrected by either soil application of micronutrient salts at 25-50 kg/ha or foliar spray at 0.3 to 0.5% or both.

Integrated Nutrient Management:

Sound nutrition is one of the ingredients for high yields of crops. Chemical fertilizers no doubt increase productivity but the escalating cost of fertilizers, associated environmental hazards and failure in sustaining yields have given way for integrated use of organic and inorganic sources of nutrients, which will help to mitigate the abeyance state of soil thus improving biological power of the soil.

Organic Sources of Nutrients:

The global crisis of energy and escalating prices of chemical fertilizers paved the way for usage of low priced organics. Application of organic sources of nutrients along with inorganic fertilizers leads to increase in productivity of crops. This is due to improved soil structure, water holding capacity, aeration, cation exchange capacity, soil temperature and drainage, besides supplying organic carbon and nutrients. Organic sources of nutrients applied to the preceding crop benefits the succeeding crop to a greater extent.

Evaluation of Organic Farming Package for Cotton – Wheat Cropping System:

Experiment conducted at Cropping Systems Research Project, Rahuri revealed that the highest seed cotton yield and wheat grain yield were observed in the treatment (T6) involving 100 % recommended NPK + Secondary and micronutrients based on soil test. This was due to higher availability of nutrients for the uptake by crops in the cropping system. However, treatment involving organics (T3) recorded comparable yield which was on par with T6 in respect of cotton yield.

Green Manures:

Green manures are grown in the field and incorporated in situ as these crops grow rapidly and produce large quantities of biomass in about 40 to 45 days after sowing. The incorporation of green manures releases immense nitrogen, which will be utilized by crops for their growth and development.

C: N Ratio, N Content and Biomass Production of different Unconventional Green Manures:

Research conducted at Tamil Nadu Agricultural University, Coimbatore revealed that intercropping marigold in two rows in between cotton rows and insitu incorporation on 30days after sowing (DAS) had contributed more kapas and lint yield securing higher yield advantage in both summer and winter seasons. Sunnhemp as intercrop had given higher biomass of 10.37 t/ha followed by marigold with 9.48 t/ha.

Sesamum yielded 8.98 t/ha of biomass. Both conventional and unconventional green manures thus contributed fairly higher biomass as compared to normal recommendation as basal. Green manuring significantly improved the soil physical and chemical properties viz., total and available N, available P and available K contents and reduced the C: N ratio.

The positive effect of intercropping and in situ incorporation of green manures on growth parameters and yield attributes reflected on kapas yield in both the seasons. As regards sources of green manures, marigold out yielded other sources and the difference was very clear in winter crop.

The organic carbon content of soil was significantly increased by the incorporation of all green manure treatments. The effect of green manuring on available P and available K content of soil was found to be significant. These results indicate that despite quick mineralization of carbon and nitrogen in green manures, these unconventional green manures can make measurable contribution to residual soil fertility under mild climatic conditions.

Crop Residues:

Crop residues rich in nutrients are used to improve and maintain productivity of soil. With the increased use of chemical fertilizers alone, particularly in an unbalanced manner, problems such as diminishing soil productivity and multiple nutrient deficiencies appeared. Depletion of non­renewable sources of energy, escalating cost of fertilizers and environmental quality aspects also emerged as important issues.

This necessitated a review of various approaches focusing on the use of available renewable sources of plant nutrients for complementing and supplementing the commercial fertilizers. As a result, numerous research efforts were made to systematically evaluate the feasibility and efficacy of organic residues, not only for improving soil productivity but also for promoting the efficiency of inorganic fertilizers.

Effect of Green Manure Intercrops on Yield, Organic Carbon and Available NPK Content of Soil after Cotton Harvest:

Experiment conducted at Central Institute for Cotton Research (CICR), Nagpur, evinced that the amount of litter fall during cotton crop growth was quantified at 929 kg/ha for the cv. LRA 5166 with about 8.1 kg N/ha and 2.1 kg P/ha was recycled during crop growth which improved fertility status of soil. The decomposition rate of cotton leaves was slightly enhanced when the leaves were incorporated into the soil as compared to surface application.

Most of the decomposition process was found to occur within a month of residue application. Due to release of bases during decomposition, the soil pH was found to be higher in the residue amended soil than the control soil. The nutrients released after the process of decomposition improved soil fertility and these nutrients were utilized by the succeeding crop for the growth and development.

Biofertilizers:

Biofertilizers are preparations containing live or latent cells of efficient strains of nitrogen fixing, phosphate solubilizing or cellulolytic micro-organisms. They can supplement the inorganic fertilizers for meeting out the nutrient requirement of crops and help in improving yield and quality of crop plants.

Nitrogen fixing biofertilizers like Azotobacter and Azospirillum are used for improving the yield of cotton. The N fixing potential of Azotobacter and Azospirillum has been reported to be 40 to 60 kg N/ha /year. The acid delinted cotton seeds are treated either with Azotobacter or Azospirillum at 600 g (3 packets)/ha and 1000 g (5 packets)/ha as soil application.

Inorganic Sources of Nutrients:

Proper and balanced use of fertilizers should be done to maintain balance in the agro ecosystem. This balanced application will improve the yield of crops through increased crop uptake. Fertilizers on application help to increase the yield of succeeding crop through the addition of more root biomass, which on decomposition release nutrients.

In intensive cropping systems, all the crops should be given adequate nutrition supplement. However, it was found that when the crops in cotton system are complementary, 50% of the recommended dose of fertilizes are found sufficient for maintaining cotton yield and yield of other crops in the cropping system.

Research conducted in northern region of India in cotton-wheat system, application of NPK at 120:60:60 kg ha^-1 for wheat and N at 80 kg ha^-1 for cotton is optimum, since residual effect of phosphorus and potassium applied to wheat takes care of requirements of succeeding cotton. The study on the nitrogen requirements of different cropping systems revealed that cotton sown after fallow and wheat responded up to 80 kg N ha^-1.

Studies conducted in Northwest Rajasthan under cotton – wheat system have evinced that on a sandy loam soil, combined application of N and P increased cotton and wheat yields additively over N alone. Potash application could not increase seed cotton yield but increased grain yield of wheat significantly over NP application.

How to Manage Soil Fertility in Dryland Farming:

Indian agriculture is predominantly a rainfed agriculture under which both rainfed farming and dryland farming are included. Of India’s total land area of 305 million hectares, nearly 68 m ha are covered by forests and 143 m ha are under cultivation. Out of the 143 m ha of total cultivated area in the country, 101 m ha are under rainfed which contribute about 44 per cent of the total food grain production.

The productivity of food grains already evinced a plateau in irrigated agriculture owing to nutrient exhaustion, salinity and raising water table. Therefore, the challenges of the present millennium would be to produce more from drylands while ensuring conservation of existing resources. Hence, new strategies should be evolved which would make the fragile dryland ecosystems more productive as well as sustainable.

Characteristic Features of Dry Farming Regions:

i. Farming depends solely on rainfall.

ii. Quantity of rainfall is low and insufficient for cropping for many years.

iii. Rainfall intensity is high, leading to runoff and erosion.

iv. Erratic distribution of rainfall with long dry spells during rainy season.

v. No assurance about onset and cessation of monsoon.

vi. Immense variation exists in the duration of rainy season between years.

vii. Prevalence of high temperature, strong and dry winds during most part of the year.

viii. Potential evapotranspiration (PET) is more than precipitation for most part of the year.

ix. Soils in the dry farming regions are eroded, degraded or marginal.

x. Poor soil fertility.

xi. Inadequate soil moisture storage.

xii. Cropping is confined to short season only, usually less than 120 days.

xiii. Cultivation practice s are traditional with low input supply.

xiv. Frequent occurrence of drought and complete crop failure may occurs during some years.

xv. Low and unstable crop yields.

xvi. Farming is mostly of the subsistence type.

xvii. Unemployment and under employment of farmers and agricultural labourers, and

xviii. Poor standard of living of farmers.

Dryland Soils:

Soil is defined as a thin layer of the earth crust consisting of minerals and organic constituents, possessing definite physical, chemical and biological properties. It serves as a natural medium for the growth of plants. It is a three phase system consisting of solid, liquid and gaseous components.

The solid phase has organic matter, minerals, soil flora and fauna. The liquid and gaseous components are filled within the interspaces of soil particles. It acts as a storehouse of plant nutrients and water to plants. India has a wide range of soils, each type being particular of a specific locality.

Soil Types and their Related Constraints:

Soils under dryland conditions vary in their structure, texture, type of clay mineral, organic matter content and depth. The soil characteristics viz., infiltration rate, water holding capacity (WHC), drainage pattern, aeration, compaction and soil erosion depends on the constituents of the soil. In India, drylands occurs in almost all the regions and the major soil types in these regions are alfisols, vertisols, aridisols, laterite soils, and submontane soils.

The aforementioned soil types and their characteristic features and related constraints are discussed hereunder:

Soil Types:

1. Red Soil (Alfisot):

Alfisol is derived from granites, gneiss, and other metamorphic rocks. The red colour in the soil usually indicates a high amount of iron, in the form of iron oxide, which coats the particles of the soil. The iron oxide can be inherited from the parent material or can form as a result of intense weathering over a long period of time.

Characteristics:

i. These soils are light textured with porous structure.

ii. They are usually poor growing soils, low in nutrients and humus.

iii. Mostly shallow in depth with compact argillic horizon.

iv. This soil has very low clay content (10-20%). Among the different clay minerals, the predominance of kaolinite is more which is followed by Illite.

v. Lime concretions are absent.

vi. Rainfall in red soil areas ranges from 750 to 2000 mm per annum.

vii. High infiltration.

viii. Well drained soils with moderate permeability.

ix. Low water holding capacity (100-200mm/meter depth of soil).

x. The cation exchange capacity is medium (CEC) ranges from 1-40 meq/100 g of soil.

xi. Low microbial activity.

xii. Poor in fertility, contains low organic matter, N and P but K content is medium to high.

xiii. They are slightly acidic to slightly alkaline in nature.

xiv. This type of soil primarily found in Tamil Nadu, Karnataka, Kerala, Goa, Diu, Daman, Maharashtra, Andhra Pradesh, Madhya Pradesh, Bihar, West Bengal and Assam.

2. Black Soil (Vertisol):

Black soils are formed from Deccan basalt trap rocks and occur mostly in semi-arid and sub humid areas. They are more productive than alfisols. Compared to the red soils, the black soils are deeper and heavier and hold more water. Nevertheless, they are highly erodible and runoff can be as high as 40% or more depending on the slope and intensity of rainfall.

Characteristics:

i. High clay content (35-60%), smectite type of clay mineral is dominant.

ii. High WHC (400-500 mm/ m depth of soil) Rainfall in black soil areas ranges from 500 to 1500 mm.

iii. When wet, black soil swells and becomes sticky, but shrinks rapidly when dry, leaving large clods and deep fissures.

iv. Low infiltration.

v. Hydraulic conductivity of black soil is very low compared to alfisol.

vi. Soils have impeded drainage and low permeability.

vii. Calcareous, neutral to slightly alkaline in nature.

viii. High CEC (47-65 meq/100 g of soil).

ix. Exchangeable calcium and magnesium are more in black soils.

x. Poor in organic matter and N, low to medium P and medium to high K.

xi. Deficiency of Fe and Zn is common feature of this soil.

xii. It is found in the States of Maharashtra, Gujarat, Madhya Pradesh, Karnataka, Andhra Pradesh, Tamil Nadu, Uttar Pradesh and Rajasthan.

3. Desert Soil (Aridisol):

Characteristics:

i. Light textured soils (fine sandy to loamy fine sand)

ii. Mostly they are structureless

iii. Lime concretions occur at various depths

iv. Very low clay content (2-8 %), Illite type of clay mineral is dominant

v. Rainfall in desert soil areas ranges from 100 to 500 mm.

vi. Deep percolation and more amenable for wind erosion

vii. Surface crusting is a serious problem

viii. Subsoil salinity is quite common due to extreme aridity

ix. Very low CEC and WHC

x. Very low organic matter due to rapid mineralization, and

xi. These type of soils are distributed in the Rajasthan, Southern part of Haryana and Punjab and Northern part of Gujarat.

4. Laterite Soil:

Characteristics:

i. Soils are pale, gritty and shallow in nature.

ii. The texture is loamy or clayey with many concretions.

iii. Kaolinite or Illite type of clay dominates in laterite soils.

iv. Well drained soils with good hydraulic conductivity.

v. These soils are seen in high rainfall areas. During laterization, the upper horizons of soils are enriched with oxides of iron and aluminium due to leaching of silica under high rainfall conditions.

vi. This soil is acidic in nature with a pH of 5 to 6

vii. Organic matter and plant nutrients are rich in lower layer of the soil compared to top layer

viii. CEC is very low (2-7 meq/100 g of soil)

ix. Calcium, magnesium, and phosphorus are present in traces

x. They are distributed in the hills of Deccan, Karnataka, Kerala, and Madhya Pradesh, Ghats regions of Orissa, Maharashtra, West Bengal, Tamilnadu and Assam.

xi. Most of the laterite soils have been classified in the order ‘ Ultisols’ and a few under ‘ Oxisols’.

5. Submontane Soil:

Characteristics:

i. The texture of the soil is silty loam to loam

ii. Landslides and erosion are quite common in these areas

iii. This type of soil is seen in high rainfall areas

iv. Medium water holding capacity (200-300mm/meter depth of soil)

v. Phosphorus is deficient in these soils

vi. Organic matter content is high

vii. Acidic in nature, and

viii. These soils are found in Sub Himalayan regions.

Soil Related Constraints:

Out of the total area of about 101 mha under dryland agriculture in India, nearly 30 per cent is covered by Alfisols and associated soils, 35 per cent by Vertisols and associated soils and 10 per cent by Entisols.

The problems associated with low dryland production may be many but there are several soil related constraints, which limits the potential productivity of these soils are as follows:

1. Red Soil:

i. Soil crusting is a major problem in red soils which reduces germination by creating mechanical barrier for the emerging seedling.

ii. Rapid drying of soil due to high temperature.

iii. Compact subsoil argillic horizon inhibits root penetration thus causing poor crop growth and development.

iv. The leaching loss of fertilizer is more in this soil.

v. Soil workability problems- These soils permit easy tillage when wet but become hard and difficult to till when dry. Tilling the soil under excessive wetness may result in compaction. Hence, ploughing should be done only under limited soil moisture conditions.

vi. Decline in land productivity resulting from huge soil loss due to erosion.

2. Black Soil:

i. Black soil swells and becomes sticky when wet, but shrinks rapidly on drying, leaving large clods and deep fissures, and posing considerable difficulties in field preparation and timely planting operations.

ii. Poor infiltration capacity causes high erodability and water logging during heavy rainfall.

iii. Presence of subsoil hardpan restricts the root penetration which ultimately affects the crop growth.

iv. Runoff is severe in black soils (40%), and the soil loss is estimated to be in the range of 11-43 ton/ha/year.

v. Subsoil salinity due to high soil pH adversely affects P, Fe, Mn, and Zn availability to crops.

vi. Being calcareous in nature enhances the volatilization losses of N.

3. Desert Soil:

i. Inadequate nutrient holding capacity.

ii. Very poor water storage capacity.

iii. Surface crusting is a serious problem which hinders germination of crops.

iv. Subsoil salinity influences crop growth and development.

4. Laterite Soil:

i. Adequate water retentivity is a problem in these soils as they are highly permeable.

ii. Extensive percolation losses of water enriched with dissolved plant nutrients.

iii. Aluminium and Iron toxicity is a problem in this soil.

5. Submontane Soil:

i. The nutrient supplying power of the soil is less as the nutrients are lost through erosion.

ii. Water logging.

The aforementioned soil types and their characteristic features and related constraints should be known for developing sound soil fertility management strategies.

Soil Fertility Management in Drylands:

“Dry land soils are not only thirsty, but also hungry”. Improving and maintaining the soil fertility through organic manures and inorganic fertilizers are imperative for high productivity in dry lands. The supply of nutrients promotes root development, which enables higher uptake of soil moisture and high water use efficiency. Nevertheless, farmers in drylands do not apply sufficient quantity of manures and fertilizers.

The reasons for poor adoption of nutrient supply to rainfed crops are as follows:

i. Most of the organic sources are utilized as fuel by the farming community.

ii. Involves high cost in transportation of organic manures.

iii. Inadequate availability and high cost of fertilizers.

iv. Fear of scorching of plants due to the application of inorganic fertilizers.

v. Growing of fertilizer non – responsive varieties.

vi. Low and uncertain yield and income due to undependable rainfall behavior.

vii. There is an apprehension that a well fertilized crop growing vigorously would exhaust the soil moisture supply early and subject the crop to moisture stress at later stages.

viii. Poor economic status of farmers.

Nutrient Removal by Dryland Crops:

The quantity of nutrients removed (nutrient uptake) by different crops grown in drylands are given below:

Nutrient Requirement of Dryland Crops:

The aforementioned findings revealed the high yield potential of dryland crops with sufficient nutrient supply. Therefore, sound soil fertility management strategies are required for ensuring sustainable productivity of crops under dryland farming.

Soil Fertility Management Strategies:

1. Application of Organic Sources of Nutrients:

i. Bulky Organic Manures:

a. Farm yard manure (FYM)

b. Compost

c. Sheep and goat manure

d. Poultry manure, and

e. Sewage and sludge.

ii. Concentrated Organic Manures:

a. Oil cakes

b. Blood meal

c. Fish meal

d. Meat meal

e. Bone meal, and

f. Horn and hoof meal.

iii. Application of biofertilizers.

iv. Adoption of green manuring and green leaf manuring.

2. Application of inorganic sources of nutrients (Fertilizers).

3. Application of crop residues for improving the fertility status of soil.

4. Cropping Systems Approach for Improving Soil Fertility:

Pulse crops should be included in the cropping systems as intercrops or sole crops for improving fertility status of soil as these crops fix atmospheric N, which will be utilized by base crop or succeeding crop in the cropping system.

The inclusion of different pulses or other crops in the cropping systems is as follows:

a. Sorghum Based Cropping Systems:

Intercropping-

i. Sorghum + pigeon pea

ii. Sorghum+ lablab

Double crop system-

Sorghum – chickpea.

b. Pearl Millet Based Cropping Systems:

Intercropping-

i. Pearl millet + pigeon pea

ii. Pearl millet + green gram

Double crop system-

i. Pearl millet – chickpea

ii. Pearl millet – mustard.

c. Finger Millet Based Cropping Systems:

Intercropping-

i. Finger millet + soybean.

d. Maize Based Cropping Systems:

Intercropping-

i. Maize + pigeon pea

ii. Maize + soybean

iii. Maize + green gram

Double crop system-

i. Maize – wheat

ii. Maize – mustard.

e. Paddy Based Cropping Systems:

Double crop system-

i. Paddy – chickpea

ii. Paddy – finger millet

iii. Paddy – wheat.

f. Pulse Based Cropping Systems:

Intercropping-

i. Pigeon pea + groundnut

ii. Pigeon pea + finger millet

Double crop system-

i. Green gram – safflower.

ii. Cowpea- finger millet

iii. Cowpea – maize

iv. Black gram – sorghum.

g. Oilseed Based Cropping Systems:

Intercropping-

i. Groundnut + red gram

ii. Groundnut + castor.

5. Ley Farming:

Growing of fodder grasses, legumes and annual crops in rotation for restoring soil fertility is known as ley farming.

E.g. Stylosantlies hamata (3 years) – sorghum (1 year) – castor (1 year).

Advantages:

i. Ensures proper soil and moisture conservation

ii. Control of perennial weeds

iii. Enrichment of soil fertility

iv. Prevention of soil compaction

v. Provision of fodder for cattle, and

vi. Helps to minimize risk.

6. Growing of Fruit Crops in Drylands:

Uncertainty in rainfall, poor soil fertility, and low level of management has made annual cropping of field crops a non-remunerative enterprise in many pockets of dry lands. In certain areas, cropping has been given up altogether and lands remain fallow and become wasteland overgrown with unwanted vegetation.

To overcome this problem and to bring back the land under economically useful vegetation, alternate land use systems such as horticulture, pastures and agro forestry are recommended. Growing of fruit crops is one of the ways of crop diversification in drylands which improves the fertility status of soil through the addition of leaf litter and provides higher and stable income to the farmers besides utilizing the off-season precipitation.

i. Amla (Embilica officinalis)

ii. Bael (Aegle marmelos)

iii. Ber (Zyzyphus mauritiana)

iv. Pomegranate (Punica granatum)

v. Custard apple (Annona squamosa)

vi. Phalsa (Grewia asiatica)

vii. West Indian cherry (Malpighia punicifolia)

viii. Karonda (Carissa carandas)

ix. Jamun (Syzygium cuminii)

x. Manila tamarind (Pithecellobium dulce)

xi. Wood apple (Feronia limonia)

xii. Tamarind (Tamarindus indica).

7. Adoption of Integrated Nutrient Management Approach for Drylands:

The escalating price of inorganic fertilizers and their non-availability at appropriate time, the availability of agricultural and agro industrial wastes in large quantities and the need for prevention of environmental pollution warrant an approach of integrated nutrient management.

This approach aims for the profitable use of diverse resources such as inorganic fertilizers, organic manures, green manures and biofertilizers. It has been well established that combined use of fertilizers and organic manures is essential for sustaining the crop yields in drylands owing to more retention of water besides addition of nutrients and improving soil properties.