Bed Planting Techniques Improved Crop Yield by Efficient use of Added Nitrogen Fertilizer

A big cause of greenhouse gases (GHG) emissions into the atmosphere has historically been grain growing agricultural activities. Global warming is a proven reality and GHG emissions are projected to be the main causes of climate change due to humans and agriculture practices (IPCC, 2013; Ahlawat and Kaur, 2015). Nitrogenous (N) fertilizers play a major role in increasing the production of crop biomass and grain yields. Injudicious and indiscriminate application of N fertilizer has therefore led to food, soil and water contamination in many crops (Chaudhuary et al., 2020). Reducing undue N pollution and damages in the 21^st century poses a significant environmental threat (Wightman, 2015). Participation of Pakistan is invaluable for worldwide efforts to decrease N fertilizer-related GHG pollution, as Pakistan is the agricultural country and uses a large amount of N fertilizer to grow crops. Nitrous oxide (N₂O) is known as a significant source of GHG and induces 298 times greater global warming compared to CO₂ (IPCC, 2013). As opposed to other macronutrients, nitrogen fertilizer is imperative for rice and wheat growth and dry matter yield. Nitrogen is also strongly applied to both of the rice and wheat cultivation methods (Snyder et al., 2009; Bond et al., 2008; Singh et al., 2014; Majeed et al., 2017). The successful absorption of added nitrogen by soil crops promotes the production of dry matter in growing crop growth. Usage of the best N fertilizer is important to improve crop growth and reduce environmental emissions. The lower amount of N fertilizer can result in lower crop biomass, grain quality and for this reason, lower income. If a higher dosage of N fertilizer is used, it leads to a decline in NUE and raises the risk of N depletion in the form of N₂O pollution (Ju et al., 2009, Ishaq et al., 2001; Xing and Zhu, 2000). One approach to the production of greater grain yield with low nitrogen inputs is to increase NUE (Kukal and Aggarwal, 2003; Naresh et al., 2014). Flood irrigation methods for planting wheat and rice on a flat surface resulted in less water and less effective use of fertilizers (Iqbal et al., 2005, Mollah et al., 2009). Higher wheat plant biomass, dry matter yield and fertilizer usage efficacy is demonstrated by bed and furrow irrigation techniques (Majeed et al., 2015). N fertilizer addition can have a direct effect on crop yields and GHG emissions (Liang et al., 2013; Li et al., 2011; Zou et al., 2005). Different strategies such as controlled or gradual release of urea and various nitrification inhibitors are used to improve NUE, yield crops and limit GHG emissions (Majumdar, 2003). The aim of this experiment was to increase NUE with various application rates of nitrogen fertilizer under bed and flat planting techniques and to minimize indirect nitrous oxide emissions from cultivated fields.

Field experiment was carried out at Soil Chemistry Section, Ayub Agricultural Research Institute, Faisalabad Pakistan. Weather data presenting mean monthly maximum temperature and total rainfall during experimental period of wheat and rice crop showed fluctuations (Fig 7). The collected soil sample was air dried, grinded and passed through the 02 mm sieve. Finally the sample was analyzed according to different soil characteristics (Table 1). Using commonly used laboratory techniques as described in the U.S. Lab Salinity (1954) and Page (1982) soil characteristics were assessed. Electrical conductivity (EC) and pH were assessed by adding soil at 1:5, soil: water, ratio to deionized water (Nelson and Sommers, 1982). Available soil P (Olsen et al., 1954) and extractable K (Rowell, 1994). Using the hydrometer method described by Bouyoucos (1962), particle size analysis was carried out and the values obtained from soil particles were plotted against the texture triangle of the soil texture class (Table 1). Following the traditional land planning, beds were manufactured with machine to plant beds. Wheat crop seeds (Photographs A and B) and rice nursery seeds (Photographs C and D) were grown on the flat surface and in rows / lines on the bed. Every plot was harvested randomly from nine square meters of land. The plant samples were collected, dried and digested with acid for analysis after harvesting the crops (Jackson, 1962). In plant samples phosphorous was calculated using a colorimetric technique using a spectrophotometer (IRMECO-U-2020). After calibration, samples were analyzed with a 410 nm wavelength spectrophotometer. The absorbed light rate was used in plant samples to show the concentration of P (Allen et al., 1986). To test potassium, a flame-photometer was used. A series of standards for drawing up a standard curve (0, 10, 20, 30, 40 and 50 ppm) was prepared. The flame photometer K values were associated with the standard curve and the corresponding total quantity was calculated (Ryan et al., 2001). The test for nitrogen was performed using the Kjeldahl process (Jackson, 1962). All treatment was replicated three times and Statistics 8.1 software was used to evaluate statistical data (Steel and Torrie, 1997).
 

 

 

 

 

 

Data revealed (Fig 1) that adding N (80 kg/ha) to the bed provided a non-significant yield (4.51 t/ha) of N (120 kg/ha) in flat sowing (4.63 t/ha) as recommended. The rising application of nitrogen (up to 120 kg/ha) on beds substantially increased the crop yield (5.1 t/ha) than the yield of the traditional flat wheat sowing system by broad casting (4.63 t/ha). It revealed that with bed planting of wheat, around 1/3 of N fertilizer can be saved. Data (Fig 1) on straw yield showed that the maximum straw yield (7.66 t/ha) was achieved in flat sowing with 120 kg/ha addition of nitrogen. Results concerning the yield of rice paddy (Fig 2) showed that the transplantation of rice on bed plus furrows and 100 kg/ha N addition yielded a higher yield (3.91 t/ha) as obtained by the prescribed dose of N (150 kg / ha) addition in traditional flat transplantation (3.74 t/ha), both of which were equal to each other but substantial than all other levels of nitrogen. Raised beds offered favorable physical and chemical soil conditions for growing plant roots, increased plant use of nitrogen fertilizers and provided superior yields of wheat and rice grains as compared to flat methods (Naresh et al., 2014; Majeed et al., 2015). Higher yields of wheat and rice grain in bed techniques have been recorded due to higher nutrient uptake (Majeed et al., 2017). The water moves from furrow to up bed in the bed sowing process, which increases crop grain yield due to higher nutrient transport and uptake by crop compared to the flat process (Hobbs and Gupta 2003; Farooq et al., 2009). Data on the nutrient content of wheat leaves at the booting stage (Fig 3) showed that maximum N concentration (2.81 per cent) was observed when nitrogen was applied @ 120 kg/ha to the bed, which was not significant when 100 kg/ha of nitrogen was added to the beds, whereas it was substantial when nitrogen was applied @ 60 when planting in the bed and 120 kg/ha while sowing flat (Fig 3). Maximum P content (0.20%) was observed during treatment when nitrogen (100 kg/ha) was added to the bed which was non-significant when 120 kg/ha N was added to the flat and bed sowing, while nitrogen was significant when 60 and 80 kg/ha were added to the beds respectively (Fig 4). Data on N, P and K paddy contents (Fig 5 and 6) showed that the highest N concentration (1.47%) was observed when nitrogen (150 kg/ha) was added to the bed, which was not significant when 100 kg/ha of nitrogen was added to the bed (1.36%), while the addition of nitrogen (150 kg/ha) during flat transplantation was significant. A maximum P content was observed (0.22%) where nitrogen (100 kg/ha) was added to the bed but was equal to other levels of nitrogen, while significant over control (Fig 6). As nitrogen (125 kg/ha) was added to the bed, the highest potassium concentration (0.34%) was noted, which was at par with the T4 and T5 treatments but was substantial over control.
 

 

 

 

 

 

 
In the bed process, the higher nitrogen content in wheat leaves and rice paddy was correlated with superior crop biomass and slight loss of added N fertilizer. Greater use of N fertilizer by crop was found in the bed system (Jat et al., 2011; Majeed et al., 2017). Due to good mineralization of applied and indigenous soil nutrients, higher nitrogen utilization and crop yield were observed in the bed plantation process. In bed method plant roots take up efficiently added N fertilizer than flat method, even if N fertilizer was added in lower amounts indicating decrease in nitrogen losses (Mollah et al., 2009 and Jat et al., 2011).

Bed planting techniques increase the nitrogen content of crop plants and achieve higher wheat and rice grain yields at a lower fertilizer rate compared to flat sowing. It also suggests that bed planting technologies indirectly minimize greenhouse gas emissions from nitrogen by increasing the performance of the nitrogen-related fertilizer applied in wheat and rice crops. Therefore, in order to solve the issue of global warming by increased use of nitrogen fertilizer in crops and lower efficiency of use of N, in future wheat and rice crops should be planted on beds to improve fertilizer utilization by crops.

We are very thankful to Farm Manager of Soil Chemistry Section, Ayub Agricultural Research Institute Faisalabad, for providing the field area for this research work and also to the reviewers for the improvement of this manuscript.