H. S. Thind

Need based nitrogen management using the chlorophyll meter and leaf colour chart in rice and wheat in South Asia: a review

Fertilizer nitrogen (N) is one of the major inputs in rice–wheat production systems in South Asia. As fertilizer N has generally been managed following blanket recommendations consisting of two or three split applications of preset rates of the total amount of N, improvement in N use efficiency could not be achieved beyond a limit. Feeding crop N needs is the most appropriate fertilizer N management strategy to further improve N use efficiency. Since plant growth reflects the total N supply from all sources, plant N status at any given time should be a better indicator of the N availability. The chlorophyll meter and leaf colour chart have emerged as diagnostic tools which can indirectly estimate crop N status of the growing crops and help define time and quantity of in-season fertilizer N top dressings in rice and wheat. Supplemental fertilizer N applications are thus synchronized with the N needs of crop. The chlorophyll meter may not be owned by South Asian farmers individually, but it can be made available to farmers through village cooperatives, extension specialists, and crop consultants. Leaf colour chart, a simple and cost-effective device has already penetrated into South Asian farming and increasing numbers of farmers are finding it helpful in efficiently managing N fertilizers. This paper reviews the results of investigations carried out using these diagnostic tools in managing need based N applications in rice and wheat in South Asia.

Site-Specific Nitrogen Management in Dry Direct-Seeded Rice Using Chlorophyll Meter and Leaf Colour Chart

The need to maintain high rice yields and improve fertilizer nitrogen (N)-use efficiency has fueled the use of tools such as leaf colour chart (LCC) and chlorophyll meter (SPAD meter) in managing fertilizer N based on colour of the leaf. Field experiments were conducted during 2011 to 2013 at Ludhiana, India to assess the need for basal N application and to establish critical threshold values of leaf greenness as measured by LCC and SPAD meter for formulating strategies for in-season management of fertilizer N in dry direct-seeded rice (DDSR). Avoiding application of N at sowing did not adversely affect rice grain yield, indicating that basal N application in DDSR was not necessary and might lead to reduced N-use efficiency. Monitoring N uptake rate during the growing season of DDSR suggested that N uptake rate peaked at the two growth stages: maximum tillering (42 to 56 days after sowing (DAS)) and panicle initiation stages (70 to 84 DAS). Using the Cate-Nelson procedure, critical LCC and SPAD meter values for fertilizer N application worked out to be 4 and 37, respectively. Real-time fertilizer N management strategy based on applying 30 kg N ha−1 whenever SPAD meter or LCC readings fell below the critical values maintained optimum rice yields along with higher N-use efficiency than that observed by following blanket recommendation for fertilizer N in the region. The fixed-time variable-dose strategy consisted of applying prescriptive doses of 20 kg N ha−1 at 14 DAS and 30 kg N ha−1 at 28 DAS and corrective doses of 30, 40 or 50 kg N ha−1 at 49 and 70 DAS depending upon LCC shade to be ≥ 4, 4–3.5, or < 3.5 and SPAD meter readings to be ≥ 40, 40–35, or < 35, respectively. This strategy also resulted in optimal rice yield along with higher N-use efficiency as compared to the blanket recommendation. This study revealed that in DDSR, fertilizer N could be managed more efficiently using the tools of LCC and SPAD meter than the current blanket recommendation.

A framework for refining nitrogen management in dry direct-seeded rice using GreenSeeker optical sensor

Site-specific N management using GreenSeekerTM was evaluated in direct-seeded rice.Panicle initiation is the appropriate stage to make corrective N management.Two algorithms for N management based on GreenSeekerTM proposed in this study.The proposed algorithms could maintain high grain yield and high N-use efficiency. To reduce the amount of wasted reactive nitrogen (N) reaching the environment and to achieve high N fertilizer use efficiency, a site-specific N management strategy using GreenSeeker� optical sensor (GS) was evaluated in dry direct-seeded rice (DDSR) in the north-western India. Four field experiments were conducted during 2011-2013 to develop an optical sensor algorithm for fine tuning in-season N fertilizer applications. It was demonstrated that panicle initiation of rice is the appropriate stage for applying GS guided N fertilizer dose. Application of a prescriptive dose of 60kgNha-1 in two or 90kgNha-1 in two or three equal split doses, followed by a corrective N dose guided by GS at panicle initiation stage resulted in rice yield levels comparable to that obtained by following general recommendation, but with lower total N fertilizer application. On an average, N use efficiency was improved by more than 12% when N fertilizer management was guided by GS as compared to when general N fertilizer recommendation was followed. The results prove the inadequacy of general recommendations for N fertilizer management in DDSR and possibility of increasing N use efficiency along with high rice yield levels through site-specific N fertilizer management using GS.

Optimal rate and schedule of nitrogen fertilizer application for enhanced yield and nitrogen use efficiency in dry-seeded rice in north-western India

ABSTRACT Dry direct-seeded aerobic rice (DSR) is an emerging attractive alternative to traditional puddled transplanted rice (PTR) production system for reducing labour and irrigation water requirements in the Indo-Gangetic plains (IGP) of India. The fertilizer N requirement of DSR grown with alternate wetting and drying water management may differ from that of PTR grown under continuous flooding due to differences in N dynamics in the soil/water system and crop growth patterns. Limited studies have been conducted on optimizing N management and application schedule for enhanced N use efficiency in DSR. Therefore, field experiments were conducted over 3 years in NW India to evaluate the effects of N rate and timing of its application on crop performance and N use efficiency. Interaction effects of four N rates (0, 120, 150, and 180 kg ha−1) as urea and four schedules of N application on yield and N use efficiency were evaluated in DSR. The N schedules included N application in three equal split doses (0, 35 and 63, and 14, 35 and 63 days after sowing, DAS) and four equal split doses (0, 28, 49 and 70; 14, 28, 49 and 70 DAS). There was no significant interaction between N rate and schedules on grain yield. Significant response to fertilizer N was observed at 120 kg N ha−1 and economic optimum dose for three equal split doses and skipping N at sowing was 130 kg N ha−1. Highest mean grain yield of 6.60 t ha−1 was obtained when N was applied in three equal split doses at 14, 35 and 63 DAS which was about 8.5% higher compared with N applied in four equal split doses at 14, 28, 49 and 70 DAS. Under the best N application schedule, agronomic N use efficiency (26 kg grain kg−1), recovery efficiency (49%) and physiological efficiency (53 kg kg−1) were comparable to the values reported in Asia for PTR. Results from our study will help to achieve high yields and N use efficiency in DSR to replace resource intensive PTR.

Soil biochemical changes at different wheat growth stages in response to conservation agriculture practices in a rice-wheat system of north-western India

Intensive tillage, removal or burning of crop residues, limited organic manure use, declining irrigation water resources and scarcity of labour are the major causes of soil degradation and unsustainability of rice (Oryza sativa L.)–wheat (Triticum aestivum L.) system (RWS) in South Asia.Resource conservation technologies (RCTs) such as zero tillage (ZT), dry direct seeded rice (DSR) and crop residues retained as mulch have shown promise to increase the productivity and profitability of RWS in South Asia. Effects of RCTs on soil biological parameters are unclear and contradictory. We evaluated the effects of conservation agriculture practices on changes in soil biochemical properties at different growth stages of wheat grown as the fifth crop in RWS. Twelve treatment combinations of tillage, crop establishment and crop residue management included four main plot treatments in rice: (1) conventional tillage (CT)-DSR,(2) ZT-DSR, (3) DTR, ZT machine transplanted rice and (4) PTR, conventional puddled transplanted rice. The three subplot treatments were: (i) CTW-R, CT wheat with both rice and wheat residues removed, (ii) ZTW-R, ZT wheat with residues of both the crops removed and (iii) ZTW+R, ZT wheat with rice residue retained as surface mulch in subsequent wheat. Irrespective of rice establishment methods, mean wheat grain yield under ZTW+R was 6% and 10% greater than CTW-R and ZTW-R respectively. Soil enzyme activities increased (5–18%) under ZTW+R compared with ZTW-R and CTW-R at different growth stages of wheat. The residual effect of rice establishment methods was significant on soil enzyme activities during wheat cropping, which were highest under ZT-DSR followed by CT-DSR, DTR and PTR. Soil organic carbon content in the 0–7.5 cm layer was significantly higher (7–9%) under the ZTW+R treatment compared with all the other treatments. Principal component analysis (PCA) identified three enzyme activities (dehydrogenase, fluorescein diacetate and phosphatase), and soil organic carbon content as the most sensitive indicators for assessing soil quality for RWS based on conservation agriculture. The PCA discriminated rice establishment systems with rice residue as surface mulch from rice establishment systems without rice residue and the maximum tillering stage from the other stages of wheat. The present study provided reliable biochemical indicators to monitor soil biological quality changes in response to conservation agriculture practices in RWS.

Site-specific Fertilizer Nitrogen Management in Irrigated Wheat using Chlorophyll Meter (SPAD meter) in the North-western India

In irrigated wheat as grown in north-western India, fertilizer nitrogen (N) management following blanket recommendations is increasing resulting in stagnant yield levels with low N use efficiency. Site-specific nutrient management strategy to apply N as per need of wheat crop was formulated based on leaf colour measured by chlorophyll meter (Minolta SPAD meter) as a function of soil N supply. The SPAD meterguided protocols for fertilizer N application at crown root initiation (CRI) and maximum tillering (MT) stages, coinciding with first two irrigations, were evaluated through a series of field experiments with seven wheat varieties in Ludhiana and Gurdaspur in north-western India. Threshold leaf greenness levels equivalent to SPAD readings <40, <42.5 and <45 were tested in terms of (i) whether to apply fertilizer or not, and (ii) deciding as to how much fertilizer N needs to be applied as per requirement of the crop. At CRI stage, when the crop was about two-week old, fertilizer N dose could not be guided by SPAD meter because due to application of a basal dose of N at planting variation in the leaf colour was found to be very small. Also, due to small size of leaves at CRI stage it was difficult to use SPAD meter to measure leaf colour. Application of 30 kg N ha−1 at planting, 45 kg N ha−1 at CRI stage and a dose of 30 or 45 kg N ha−1 at MT stage depending upon leaf greenness to be ≥ or < SPAD 42.5, respectively produced wheat grain yields at par with blanket recommendation for fertilizer N, but with higher fertilizer N use efficiency.

Yield and Nutrient Uptakes in Wheat under Conservation Agriculture Based Rice-Wheat Cropping System in Punjab, India

The rice-wheat cropping system (RWCS) is a dominant cropping system in north-western part of India. This cropping system occupies around 10 Mha areas of Indo-Gangetic Plains of India. The production of RWCS decline or stagnate now a days. The sustainability of RWCS is questionable due to excessive pumping of ground water and repeated pudding for rice establishment. These problems may be generally overcome by resource conserving technologies like direct seeded rice, zero tillage wheat, rice straw as mulch etc. The wheat productivity can be increased by conservation agriculture technologies that are generally responsible for improving soil structure and soil water retention capacity. To avoid the late sowing of wheat, new technologies like Happy Seeder was developed for reduce the rice straw burning problem (Sidhu et al., 2007 and International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 6 Number 2 (2017) pp. 1698-1708 Journal homepage: http://www.ijcmas.com

Integration of Fertilizer Nitrogen, Farmyard Manure and Multi-strain Microorganisms for Sustainable Production of Rice-Wheat System

Use of high rates of commercial nitrogen (N) fertilizers over the years has resulted in adverse effects on soil and environment health. Integrated use of fertilizer N and organic N sources is expected to reduce the N losses and improve N use efficiency. The present field experiment was conducted for two years to evaluate the effects of commercially available multi-strain inoculant ‘Fertimine’ and farmyard manure (FYM) applied at variable rates of fertilizer N on the nutrition of rice-wheat system. Four treatment combinations of FYM (15 t ha-1, fresh weight) and fertimine were applied to main-plots and four N levels to sub-plots in factorial split-plot design. In the absence of fertimine and FYM, significant increase in rice yield was observed up to 120 kg N ha-1 during first season and 80 kg N ha-1 during second season. The application of FYM and fertimine significantly increased mean grain yield of rice by 12 and 5 per cent over no FYM and fertimine, respectively. Significant interaction effect of fertimine and fertilizer N observed on rice grain yield suggested that fertimine significantly increased the rice yield at low rates of fertilizer N. While fertilizer N and FYM caused significant increase in the total uptake of N, P and K in rice, fertimine showed significant increase in total P uptake only. The FYM applied to rice showed significant residual effect on the yield and total N, P and K uptake in the subsequent wheat. Application of FYM significantly improved the soil chemical and biological properties after two cycles of rice-wheat rotation.

Mapping of Chemical Characteristics and Fertility Status of Intensively Cultivated Soils of Punjab, India

ABSTRACT Cultivation of high-yielding crop varieties and intensive cropping has depleted the soil fertility in Northwest (NW) India, resulting in the appearance of multi-nutrient deficiencies in different crops and cropping systems. In the present investigation, geo-referenced soil samples from Indian Punjab were analyzed to map fertility status using a Geographical Information System (GIS). Soil texture, which affects soil hydraulic properties and soil strength, varied from sandy to clayey loam, with majority (47.3%) of the cultivated area being sandy loam. About 95% of the total area of the state shows pH between 6.5 and 8.5 (40% of the area between pH 6.5 and 7.5 and 54% between 7.5 and 8.5) and electrical conductivity (EC) <0.8 dS m−1. Calcium carbonate (CaCO3) with <5% values represents 97% area of the state. The GIS-based maps indicate that irrespective of the agroclimatic variations, more than 90% of the soils showed low to medium soil organic carbon (OC) content and 50% low to medium (<22.4 kg P ha−1) available phosphorus (P) content with a marginal (7%) deficiency of potassium (K). The dominance of low to medium status of available P in these soils could be due to the mining of soil P by the rice–wheat cropping system practiced in the region. The intensively cultivated soils of Indian Punjab showed 11% of soil samples were low in zinc (Zn), 15% low in manganese (Mn), 2% low in copper (Cu), and 12% low in iron (Fe). Availability of micronutrients increased with increase in OC content and decreased with increase in sand content, pH, and CaCO3. GIS-based maps are effective in identifying hot spots, which need immediate attention and call for strategic planning for sustainable management.

Effects of Rice Husk Ash and Bagasse Ash on Phosphorus Adsorption and Desorption in an Alkaline Soil under Wheat–Rice System

Rice husk ash (RHA) and bagasse ash (BA) are available in large quantities in South Asian countries growing rice and sugarcane. Land application of RHA and BA is likely to influence chemistry of soil phosphorus (P) and thereby P adsorption and desorption. Laboratory studies were carried out to investigate the short-term and long-term effects of RHA and BA application on P adsorption and desorption in an alkaline soil under a wheat–rice system. Addition of RHA or BA (10 Mg ha−1) resulted in a significant decrease in P adsorption compared to the control. The decrease in P adsorption was lower when RHA and BA were applied to either rice or wheat as compared with when applied to both the crops. The BA was more effective in reducing P adsorption than RHA because of its greater P concentration. Fresh addition of RHA and BA at 1% (dry-weight basis) showed a small effect on P adsorption as compared to their long-term application. The Frendulich isotherm equation gave better fit with the experimental data than the Langmuir equation and is reliable to describe the P quantity/intensity relationships of this soil as affected by the additions of RHA and BA. The P-adsorption capacities (revealed from the Langmuir isotherms) of the unamended control, RHA, and BA (applied to both wheat and rice) were 256, 313, and 385 mg kg−1, respectively; the corresponding bonding energies for the three treatments are 0.0085, 0.0041, and 0.0026 L kg−1, respectively. Desorption of P was minimum in the control plots and maximum with BA followed by RHA, especially when applied to both the crops.