BYMUHAMMAD KAMIL SARDAR ALI

DR. KHADIM DAWAR

Worldwide the twin effects of rising human population and climate change is putting enormous pressure on dwindling land and water resources to produce enough food to meet its requirement.

Experts predict that by 2020, agricultural production in Asia will be severely affected by climate change and drought, which is characterized by low water levels as a result of the lack of monsoon rains; these phenomena will in turn have devastating effects on food security.

Cereals-based cropping system Nitrogen (N) is a key factor for sustainable agriculture, and the predominant form of that chemical fertilizers is Urea.

In Pakistan, urea commonly applied N fertilizer to enhance crop yield and high economic return.

However, urea has not being used for productive purposes in many cropping systems compared to other N fertilizers, and its deficiency constitutes one of the major yield limiting factors for cereal production.

Besides the economic significance for the farmers, losses may have negative ecological impact on atmospheric quality. Large percentage of the applied fertilizer N is essentially lost in the form:

• NH3 Volatilisation• NO3

- Leaching• N2O and NO emission• Excessive application rates• Substantial water input

Sources are: Fossil fuel, Fertilizer, Live stock and wastes.

The concentration of N2O has increased by 16% since 1750.

Atmospheric concentration of N2O is much smaller than carbon dioxide (CO2), its global warming potential is 296 times greater than CO2.

Average time in troposphere 114-120 yr.

Contributes about 6% of the overall global warming effect.

Contribution from agricultural sector is about 16%

Use of non-Urea N sources for surface application

Use of naturally occurring ‘Biostimulators’ for enhancing the growth of agricultural and horticultural crops. The activity of biostimulators to promote plant growth is often attributed to their ability to directly or indirectly provide mineral nutrients (mostly N, but also P, S and other macro- and micro-nutrients) to plants. Alternatively, biostimulators are postulated to increase the plant’s ability to assimilate these mineral nutrients, including gibberellins, auxins and cytokinins.

Applying urea with Urease inhibitors (UI)Use of urease activity inhibitors, is a biochemical method which retards the hydrolysis of urea by inhibiting the urease enzyme (released by many bacteria and some plants) in the soil and limit the proportion of microsites where the enzyme is inhibited.The important products include phenyl phosphorodiamidate (PPD), hydroquinone (HQ), N-(n-butyl) thiophosphorictriamide (NBPT), phenyl mercuric acetate (PMA), catechol.

Applying urea with Nitrification Inhibitors (NI) NI inhibits nitrification via suppressing growth of ammonia oxidizers. Inhibit nitrification by interfering with the ammonia monooxygenase (AMO) enzyme which catalyzes ammonia oxidation. In soil, discrete groups of nitrifying bacteria (Nitrosomonos) are known to be involved in ammonia oxidation.Important products are 3,4-dimethyl-1H-pyrazoliumdihydrogen (DMPP), dicyandiamide (DCD), thiosulphate, neem, karanjin, Nitrapyrine

The objectives of this research was to compare and assess N losses of nitrous oxide emissions and bioavailability of urea applied with N process inhibitors under different soil types and irrigation conditions.

To investigate the effect of applying urea with nitropyrene alone, or a combination of both nBTPT and nitropyrene and PGRs on plant productivity in hot climate conditions in Pakistan.

The experiment was conducted at University of Agriculture Peshawar research farm.

Maize was sown during June, 2015. Randomize Complete Block Design (RCBD) was used having four

replications. Each plot had of minimum size of 3 m x 3 m (9m2 area). Full recommended dose of phosphorus at 90 kg P2O5 ha-1 in the form

of single superphosphate, potash at 60 kg K2O ha-1 in the form of potassium sulphate was applied at time of sowing.

N fertilizer with or without N-inhibitors, Urease Inhibitors and GA-K salt was applied in 2 split applications at different growth stages.

T1Control

T2Urea only @ 200 kg N ha-1

T3Urea with Nitropyrene (200 g ha-1) @ 200 kg N ha-1

T4Urea with nBTPT (3 Litre Tonne-1) @ 200 kg N ha-1

T5Urea with GA-K-salt (60 g ha-1) @ 200 kg N ha-1

T6Urea with Nitropyrene +nBTPT + GA-K salt @ 200 kg N ha-1

Nitrous oxide (N2O) measurement and analysis Soil mineral N determination Soil pH and EC Soil Organic Matter Soil Texture Moisture content Total N in soil, plant and grain samples

Plant height Number of leaves plant-1 Number of grains ear-1 Thousand grains weight (g) Biological yield Grain yield Stover yield (kg ha-1) Plant samples were analyzing for total N determination

Property Units Concentration

Sand % 14.22Silt % 76.68Clay % 9.10

Textural class - Silt loampH (1:5) - 7.23

Electrical conductivity(EC) d Sm-1 0.174Lime % 17.3

Organic matter content % 0.9Total nitrogen content % 0.23

Bulk density gm cm-3 1.35

Treatment Plant Height (cm)

Number of Leaves plant-1

Number of grains ear-1

Thousand grain wt

(gm)Control 162.77c 10.5e 270d 196.48b

Urea 176.65bc 11d 326.75cd 265.00aUrea + Nitropyrene 178.63b 11.15cd 361.25bc 278.91a

Urea + nBTPT 181.22ab 11.45bc 375.25abc 288.73aUrea + GA-K-salt 190.35ab 11.55ab 408ab 294.50a

Urea + Nitropyrene +

nBTPT + GA-K salt

194.65a 11.925a 430.25a 319.18a

LSD (0.05) 14.220 0.392 58.85 67.15

Treatment Biological yield (kg ha-1)

Total Increase (kg ha-1)

% Increase by Inhibitors, GA-K

Control 6744.444c -- --

Urea 8730.556b -- --

Urea + Nitropyrene 9472.222b 741.66 7.83

Urea + nBTPT 10050ab 1319.45 13.13

Urea + GA-K-salt 10208.33ab 1477.78 14.48

Urea + Nitropyrene +

nBTPT + GA-K salt

11619.44a 2888.90 24.87

LSD (0.05) 1908.8

Treatment Grain yield(kg ha-1)

Total Increase(kg ha-1)

% Increase by Inhibitors, GA-K

Control 2297.22c -- --Urea 3519.44b -- --

Urea + Nitropyrene 3797.22b 277.78 7.32Urea + nBTPT 4061.11b 541.67 13.34

Urea + GA-K-salt 4327.77ab 808.34 18.68Urea + Nitropyrene

+

nBTPT + GA-K salt

4963.89a 1444.45 29.10

LSD (0.05) 846.76

Treatment Stover yield(kg ha-1)

Total Increase(kg ha-1)

% Increase by Inhibitors, GA-K

Control 4447.22c -- --

Urea 5211.113bc -- --

Urea + Nitropyrene 5675abc 463.8867 8.17

Urea + nBTPT 5988.89ab 777.7744 12.99

Urea + GA-K-salt 6130.56ab 919.4428 15.00

Urea + Nitropyrene +

nBTPT + GA-K salt6905.56a 1694.444 24.54

LSD (0.05) 1469.6

TreatmentTotal Nitrogen

Uptake(kg ha-1)

Total Increase( kg ha-1)

% Increase by Inhibitors, GA-

KControl 57.81103e -- --

Urea 87.96837d -- --

Urea + Nitropyrene 103.9065c 15.93815 15.34

Urea + nBTPT 111.6099bc 23.64151 21.18

Urea + GA-K-salt 118.5496ab 30.58122 25.80

Urea + Nitropyrene +

nBTPT + GA-K salt130.095a 42.12661 32.38

LSD (0.05) 13.32

2NH4+ 3O2 2NO2

-+ 2H2O+ + 4H+Nitrosomonas

Nitrobacter

2 NO3-

(eq. 1.6)

NH4+ NH2OH NO3

-NO2-

NO2NHOH

HNO

NO NO

N2O

NO

(eq. 1.7)

Combined application of GA-K+urease + nitrification inhibitors was superior to inhibitors alone and urea in increasing the yield and yield components of maize.

Both inhibitors increased N uptake compared with non-inhibitor treated urea. And reduce leaching because plants absorb more of the applied nutrient (less N available to leach).

Coated urea slowly released NH4 and NO3 ions as compared to non coated Urea treatments revealed that Inhibitors play a vital role in releasing N and also keeping it in more available form for plants.

Mean values for total herbage produced by treatments receiving GA-K co-applied with controlled release urea fertilizer were mostly high.

Further, this research shows that the chemical stabilization of Urea fertilizers, through inhibitors may increase yields N use efficiency and reduce N2O in this agricultural system.

Thus, the use of N inhibitors with urea and GA-K is recommended for increasing crop production and restrict N2O emission on a calcareous alkaline soil.

However, economics of the use of inhibitors and PGRs must be worked out carefully before it is recommended.