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. 2018 Nov 16;25(1):303–312. doi: 10.1007/s12298-018-0624-2

Green manuring effects on crop morpho-physiological characters, rice yield and soil properties

Md Moshiul Islam 1,✉, Tahmina Akter Urmi 2, Md Sohel Rana 1, Mohammad Saiful Alam 2, M Moynul Haque 1
PMCID: PMC6352541  PMID: 30804651

Abstract

A field experiment was carried out to evaluate the effect of green manure and nitrogen fertilizer on morpho-physiological traits, yield and post-harvest nutrient status of the soil during kharif season of 2017. The experiment was laid out with a randomized complete block design with twelve treatments, and was replicated thrice. The treatments were T1 [Control (no green manure + no fertilizer)], T2 (Sesbania aculeata + N0), T3 (Sesbania aculeata + N15), T4 (Sesbania aculeata + N30), T5 (Sesbania aculeata + N45), T6 (Sesbania aculeata + N60), T7 (Crotalaria juncea + N0), T8 (Crotalaria juncea + N15), T9 (Crotalaria juncea + N30), T10 (Crotalaria juncea + N45), T11 (Crotalaria juncea + N60), and T12 (N60). Incorporation of green manure with nitrogen fertilizer generated consistently positive responses in important morpho-physiological traits such as chlorophyll content (SPAD value), leaf area index (LAI), light interception percent (%LI), and net assimilation rate (NAR), which may result in higher grain yield compared to control, and N60 due to greater contribution of yield determining traits. Treatment comprising green manure with N60 produced significantly the higher grain yield even over the N60. The results of this research indicated that balanced nutrients supply increased leaf chlorophyll content, LAI, %LI, NAR, and finally led to higher dry matter production and yield of rice. Incorporation of green manure also had significantly increased the macro- and micronutrient content of post-harvest soil. These results suggest that continuous use of fertilizer might lead to a yield loses of rice, and that situation could be escaped by a combined application of green manure and judicial nitrogen fertilizer management.

Keywords: Green manure, SPAD, Leaf area index, Light interception, Growth, Rice yield

Introduction

Rice is the vital food for more than two billion people in Asia and four hundred millions of people in Africa and Latin America (IRRI 2006). Bangladesh is one of the major rice growing countries of the world. Bangladesh is in fourth position among the top rice growing countries. In Bangladesh, total rice production was 34.55 million tons (BBS 2016). Agriculture contributes 14.79% of national economy of Bangladesh (BBS 2016) and only the rice sector contributes one-half of the agricultural GDP and about one-sixth of the national income in Bangladesh. Although modern rice variety has the highest yield but still there is a serious yield gap. In Bangladesh, lack of judicial nutrient management is considered as the major causes of yield gap in rice production.

Soil fertility has deteriorated over the years and the productivity of major crops have either stagnated or declined in Bangladesh. Increase in the cropping intensity, and higher rates of organic matter decomposition under the existing hot and humid climate, lesser application of organic manure and negligible dependence on green manure practice etc. (BARC 2005) has led to decline in the crop productivity due to depletion of soil nutrients. As the fertility status of Bangladesh soils are very low, farmers normally apply higher rate of chemical fertilizers (especially nitrogen fertilizers) as the principal source of plant nutrients for rice production but their loss is very high. Higher dose of chemical fertilizers (especially inorganic nitrogen fertilizers) result in soil acidification and structure damage, water depletion, and alteration in the populations of soil microbes as well as their activities (Liu et al. 2010; Guo et al. 2010; Liu et al. 2013). Hence over-fertilization damages soil quality and thereby decrease productivity. Therefore, any alternative means has to be suggested to the farmers to maintain the high level of productivity. That’s why, integrated use of organic manure and chemical fertilizers can be an effective solution for nutrient management in rice as well as to sustain long term productivity and to enhance ecological sustainability.

Green manuring (GM) crops generally have a considerable amount of biomass which comprises of aboveground and belowground biomass. They also have the ability to increase solar energy harvest and C flux into the soil and provide food for soil macro- and micro-organisms (Dabney et al. 2001). Green manuring with nitrogen fixing legume crop can provide a substantial portion of N requirement for rice and also add organic matter (OM) to maintain soil fertility (Latt et al. 2009) which is essential for sustainable agriculture. Green manuring crops not only transfer nutrients to soil but also can lead to deep root system for nutrient uptake from deeper soil causing absorbtion of less available nutrients, thereby increasing concentration of plant nutrients in the surface soil (Noordwijk et al. 2015), and reducing the use of fertilizer (especially N). Hence GM can prevent the environmental risks related to NO3− leaching. Dhaincha (Sesbania aculeata) and sunhemp (Crotalaria juncea) are well known in South Asia for their capability of nodule formation and nitrogen fixation and produce relatively higher organic matter (Panneerselvam and Manuel 2004). Well nodulated Sesbania plants can derive up to 90% N from fixation (Pareek et al. 1990) and consequently contribute N in rice cultivation. Sunhemp is also a vigorous upright legume growing 2 m tall and like other legumes, has the ability to fix nitrogen symbiotically.

So far, most of the studies on the green manuring crops have concentrated on the fate of N in the soil or in succeeding main crops. Light is one of the main growth and biomass production factors in plant population. Increasing leaf area index (LAI) leads to more light interception in plants. Scientist believe that the radiation use efficiency is controlled genetically (Monteith 1972), however, environment factors such as variety, climatic changes, density and soil fertility particularly available nitrogen have an important role on photosynthesis (Akmal and Janssens 2004; Rosati et al. 2004). It has been reported that sunlight radiation received by plants, is converted to chemical energy and lead to growth and yield of crops (Purcell et al. 2002). Nitrogen is an important component of chlorophyll, protein and nucleic acid (FAO 2000) and regulates LAI, light interception and finally lead to increase yield of crops. Sesbania aculeata and Crotalaria juncea are well known as nitrogen fixing green manuring crops. However, the performance of Sesbania aculeata and Crotalaria juncea alone or combination with N on morpho-physiological characters of rice has not been studied in the scientific literature. Therefore, the present study was conducted to examine the effect of green manure with Sesbania aculeata and Crotalaria juncea on morpho-physiological characters and yield of rice, as well as to study their influence on post-harvest soil properties.

Materials and methods

The experiment was carried out at the research field of Bangabandhu Sheikh Mujibur Rahman Agricultural University, Bangladesh, during kharif season (March to August) of 2017. The experimental site is located at the agro-ecological zone (AEZ) Madhupur tract (24009/N latitude and 90026/E longitude with an elevation of 8.2 m above sea level; AEZ 28). The soil of the study area belongs to salna series and has been classified as Shallow Red Brown Terrace soil in the soil classification system of Bangladesh and Inceptisol in the United States Department of Agriculture (USDA) classification system. The soil is characterized by clay within 50 cm of the surface and is acidic in nature and the climate of the site is sub-tropical, wet and humid. The soil of the experimental field was silty clay loam in texture, bulk density (g/cc) 1.35, particle density (g/cc) 2.66, soil pH 5.76, organic carbon (%) 0.81, total nitrogen (%) 0.064, available P (mg kg−1 soil) 4.86, exchangeable K (meq/100 g soil) 0.138, available S (ppm) 21.21.

The experiment was laid out in a randomized complete block design (RCBD) with twelve treatments and three replications. The treatments were T1 [Control (no green manure + no fertilizer)], T2 (Sesbania aculeata + N0), T3 (Sesbania aculeata + N15), T4 (Sesbania aculeata + N30), T5 (Sesbania aculeata + N45), T6 (Sesbania aculeata + N60), T7 (Crotalaria juncea + N0), T8 (Crotalaria juncea + N15), T9 (Crotalaria juncea + N30), T10 (Crotalaria juncea + N45), T11 (Crotalaria juncea + N60), and T12 (N60). Unit plot size was 4 m × 2.5 m.

After land preparation, seeds of both dhaincha (Sesbania aculata) and sunhemp (Crotalaria juncea) were sown on 1 March 2017. Sesbania aculata and Crotalaria juncea were cut, chopped by sharp knives after 50 days of emergence and incorporated with soil through plowing and laddering. Initial soil properties were collected before incorporation of green manure. At final land preparation, the full amount of triple super phosphate (TSP), muriate of potash (MoP), gypsum and zinc sulphate were applied as the sources of phosphorus (P), potassium (K), sulfur (S) and zink (Zn) at the rates of 13, 38, 8 and 1 kg ha−1, respectively as recommended dose of fertilizers (RDF) according to Fertilizer Recommendation Guide of Bangladesh (BARC 2012). Different doses of nitrogen (0, 15, 30, 45 and 60 kg N ha−1 from Urea) were applied in three equal splits. First split of urea was applied immediately after seedling establishment, second split was applied at early tillering stage and the third split of urea was applied at 5–7 days before panicle initiation (PI) stage. BRRI dhan48, a popular rice variety for rain fed condition, was used as test crop. Twenty-five days old seedlings were transplanted. Standard crop management practices were practiced.

The yield data such as plant height, number of effective tillers hill−1, panicle length, number of filled grain panicle−1, 1000-seed weight and grain yield were recorded from five randomly selected hills in each plot, excluding border hills. Dry matter productions of rice were recorded at different days after transplanting (DAT). Leaf area index (LAI) and net assimilation rate (NAR) were calculated following the standard formulae (Radford 1967). Chlorophyll meter, also known as Soil Plant Analysis Development (SPAD) (SPAD-502, Minolta Co. Ltd., Japan) was used to obtain readings estimating leaf chlorophyll concentration (SPAD value). Ten plants from each treatment were selected randomly and SPAD values were recorded from the fully matured leaves counted from the top of the plants. Three SPAD readings were taken from each plant. SPAD values were recorded at 50, 60, 70, 80 and 90 DAT. Photosynthetically active radiation (PAR) of rice canopy was recorded at 60, 70, 80 and 90 DAT by Sunfleck Ceptometer (LP-80, Decagon Devices, Inc. USA). Measurements were taken every ten days at 10:00 am under clear skies in the same sample area in each plot during the crop season. Light interception percent of rice canopy was calculated by the following formulae.

LightTransmissionPercentageLTP=PARbelowthecropcanopyPARabovethecropcanopy×100

% light intercepted (%LI) = 100 − LTP.

Post-harvest soils were also collected (up to 0–15 cm depth) from four different spots in each plot. The composite soil sample of each plot was brought to the laboratory for different analysis following the standard procedure (Page et al. 1982).

Data analysis

The collected data were analyzed to assess their statistical significance. Statistix 10 and SPSS program were used to perform statistical analysis. Means were separated by least significant difference (LSD).

Results and discussion

SPAD meter reading fairly correlate with leaf greenness and N contents in crop and thus, can be used to estimate leaf chlorophyll content (Rorie et al. 2011; Hakim et al. 2015). Gholizadeh et al. (2017) showed a linear relationship between SPAD readings and fully expanded leaf N in the rice. Incorporation of Sesbania aculeata and Crotalaria juncea with N significantly increased the SPAD reading at different growth stages of rice (Table 1). According to the SPAD value, the chlorophyll content was consistently high during the period from 50 to 70 DAT in all the treatment. However, the maximum SPAD value (40.9) was found from the T6 treatment at 70 DAT which was statistically similar to T11 at same DAT, and the lowest (22.5) was recorded from the T1 (control) treatment at 90 DAT (Table 1). The chlorophyll content was increased up to 70 DAT with the progress of plant age, thereafter it declined regardless of treatments. However, the decreasing trend was slower in GM treated plants. Green manuring (GM) crops has the ability to nodulate and fix atmospheric nitrogen and converts atmospheric nitrogen into a plant–usable form. It has been reported that higher doses of nitrogen fertilizer showed significantly higher SPAD meter reading at different growth stages of rice (Gholizadeh et al. 2009). Xie et al. (2017) found that combining of chinese milk vetch as a GM with N fertilizer significantly increased the chlorophyll content (SPAD readings) compared to applying N fertilizer alone in rice. Green manure might be substitute of the N and other plant nutrients and helped in maintaining the higher chlorophyll content in rice. The SPAD values at 70 DAT demonstrated a notably higher SPAD values than the SPAD values at 50 DAT. The higher SPAD values at 70 DAT might be due to the leaf thickness and accumulation of more chlorophyll and N in the leaf. After 70 days of transplanting, the chlorophyll content was decreased regardless of treatments. This was probably because of the transferring of nutrient elements of the green leaves to the seeds. Chlorophyll meter values were closely related to grain yield of rice (Table 2). Ramesh et al. (2002) observed highly significant correlations between SPAD readings and grain yield of direct wet seeded rice. Many researchers also observed a significant and positive correlation between leaf N content as well as SPAD values and rice grain yield (Singh et al. 2002; Swain and Sandip 2010). Parvizi et al. (2004) obtained significant correlations between SPAD readings and dry matter production and yield of wheat.

Table 1.

Effect of green manuring crops and nitrogen levels on leaf chlorophyll content (SPAD value) at different growth stages of rice

Treatments Chlorophyll content (SPAD values)
50 DAT 60 DAT 70DAT 80 DAT 90 DAT
T1 = Control 32.4f 34.3f 34.5e 31.2e 22.5f
T2= S. aculeata + N0 34.6ef 37.1de 36.9cd 32.9de 24.7def
T3 = S. aculeata + N15 35.6cde 38.4bcde 38.8abc 33.4cde 26.4cd
T4 = S. aculeata + N30 36.7bcde 39.5abc 39.6ab 34.8abcd 27.6abc
T5= S. aculeata + N45 38.1abc 39.7abc 39.7ab 36.0abc 28.9ab
T6 = S. aculeata + N60 39.4a 40.5a 40.9a 37.0a 29.9a
T7= C. juncea + N0 34.3ef 36.4e 36.2de 32.2de 23.5ef
T8= C. juncea + N15 35.4de 37.8cde 37.9bcd 32.5de 25.4cde
T9= C. juncea + N30 36.1cde 39.1abcd 39.4ab 34.2bcd 26.7bcd
T10= C. juncea + N45 37.9abcd 39.5abc 39.6ab 35.8abc 27.7abc
T11= C. juncea + N60 38.7ab 40.1ab 40.4a 36.8ab 29.1ab
T12 = N60 36.8bcde 38.9abcd 39.5ab 34.6abcd 27.4bc
CV (%) 4.16 3.08 3.48 4.75 5.35
LSD (0.05) 2.56 2.00 2.28 2.76 2.41
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*Values followed by different letters in the same column are significantly different from each other at 5% level of significance. Averages from three independent experiments are shown

Table 2.

Correlation between grain yield and chlorophyll content (SPAD values) of rice as influenced by green manures and different levels of nitrogen

Parameters SPAD50 SPAD60 SPAD70 SPAD80 SPAD90 GY
SPAD50 1.000
SPAD60 0.957** 1.000
SPAD70 0.950** 0.993** 1.000
SPAD80 0.981** 0.926** 0.920** 1.000
SPAD90 0.980** 0.968** 0.971** 0.970** 1.000
GY 0.955** 0.958** 0.938** 0.909** 0.932** 1.000
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SPAD50, SPAD60, SPAD70, SPAD80 and SPAD90 are the SPAD values at 50, 60, 70, 80 and 90 DAT respectively and GY = rice grain yield (t ha−1)

**Indicate correlation is significant at 1% level

Crop canopy is the spatial arrangement of the above ground portion of a plant community. Solar radiation provides free energy for plant growth through photosynthesis and yield of crops depend on the solar radiation received by the canopy. However, only the photosynthetically active part of the spectrum (400–700) known as photosynthetically active radiation (PAR) can directly drive photosynthesis. Maruyama et al. (2007) reported that interception of light by the rice canopy depends on the transmissivity and the reflectivity of the rice canopy and its leaf inclination. The canopy leaf area has a major role in the amount of light intercepted. The higher canopy leaf area results in greater interception of light and hence faster crop growth. The leaf area index (LAI) is widely used to characterize the canopy light climate. Incorporation of Sesbania aculeata and Crotalaria juncea with N significantly influenced the LAI and light interception percent (%LI) of rice (Fig. 1; Table 3). The highest LAI (6.11) and %LI (86.82) was obtained from the T6 treatment at 80 DAT which was statistically similar to T11 treatment at same DAT and the lowest LAI (1.50) and %LI (50.18) was recorded from the T1 (control) treatment. The results of these experiment showed that both LAI and %LI was gradually increased from 60 DAT to 80 DAT, and then decreased regardless of treatments (Fig. 1; Table 3). The reduction of LAI and %LI during reproductive stage might be due to decline in leaf nitrogen concentration for grain filling. This might have reduced the capacity of leaf to accumulate carbon. Moreover, a decline in leaf area also contributed to the reduction in PAR during reproductive phase. The light transmission is affected by leaf angle, the thickness and chlorophyll concentration, leaf phyllotaxis and vertical stratification, and elevation of the sun. LAI and %LI were also closely related to grain yield of rice (Table 4; Table 5). If other resources are enough to a plant, the light is only factor that can have effective result on yield (Tohidi et al. 2012). These indicate that as light interception is high, the yield will be more. Increasing leaf area index leads to more light interception which subsequently leads to more yield. It was observed that solar radiation is positively associated with dry matter production (Eloy et al. 2018), and interception of radiation by crops closely related to their leaf area index (Behling et al. 2015). Monteith (1972) reported that interception of radiation by canopy is also related to nutritional status of the soil. Nitrogen causes vegetative growth though increases leaf area index. Therefore, increased nitrogen available to plant can increase LAI. Green manuring can deliver considerable amount of nitrogen and increase the LAI of crops (Islam et al. 2015). Many researchers also reported that nitrogen fertilizer increase leaf numbers, LAI, light interception and led to higher yield of crops (Kibe et al. 2006; Liu et al. 2014). Green manuring with Sesbania aculeata and Crotalaria juncea might increase nitrogen in soil and subsequently increase LAI and %LI which led to higher rice yield.

Fig. 1.

Fig. 1

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Effects of green manuring on leaf area index at different growth stage of rice. Averages from three independent experiments are shown. Vertical lines represent LSD at 5% level of significance. Note: T1 = Control; T2= S. aculeata + N0; T3 = S. aculeata + N15; T4 = S. aculeata + N30; T5= S. aculeata + N45; T6 = S. aculeata + N60; T7= C. juncea + N0; T8= C. juncea + N15; T9= C. juncea + N30; T10= C. juncea + N45; T11= C. juncea + N60; T12 = N60

Table 3.

Effect of green manuring crops and nitrogen levels on percent light intercepted (% LI) and net assimilation rate (NAR) at different growth stages of rice

Treatments % Light intercepted (% LI) Net assimilation rate (mg cm−2 day−1)
60 DAT 70 DAT 80 DAT 90 DAT 60 DAT 80 DAT 100 DAT
T1 = Control 50.18g 59.95f 67.90g 61.00g 0.251e 0.297d 0.229c
T2= S. aculeata + N0 61.24ef 67.28de 75.94f 73.00f 0.362cd 0.385bc 0.352ab
T3 = S. aculeata + N15 65.44de 73.33bc 77.53ef 76.4de 0.365bcd 0.386abc 0.354ab
T4 = S. aculeata + N30 68.17bcd 79.05ab 82.16cd 75.99e 0.372bcd 0.390abc 0.357ab
T5= S. aculeata + N45 72.16abc 81.3a 85.31ab 83.28ab 0.379ab 0.396ab 0.362ab
T6 = S. aculeata + N60 76.41a 83.86a 86.82a 84.70a 0.382a 0.398a 0.364a
T7= C. juncea + N0 56.40f 66.19e 76.07f 72.66f 0.360d 0.382c 0.350b
T8= C. juncea + N15 64.12de 72.67cd 79.2e 74.69ef 0.362cd 0.384bc 0.353ab
T9= C. juncea + N30 67.77cd 78.05abc 81.57d 78.79cd 0.369bcd 0.387abc 0.355ab
T10= C. juncea + N45 71.55abc 80.52a 84.12bc 82.96ab 0.377abc 0.393abc 0.361ab
T11= C. juncea + N60 75.49a 82.74a 86.55a 84.28a 0.380ab 0.396ab 0.362ab
T12 = N60 72.97ab 80.55a 84.15bc 80.68bc 0.368bcd 0.385bc 0.353ab
CV (%) 4.38 4.65 1.49 2.01 2.08 1.44 1.62
LSD (0.05) 4.95 5.93 2.03 2.63 0.017 0.012 0.12
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Averages from three independent experiments are shown

*Values followed by different letters in the same column are significantly different from each other at 5% level of significance

Table 4.

Correlation between grain yield and leaf area index (LAI) of rice as influenced by green manures and different levels of nitrogen

Parameters LAI 60 LAI 70 LAI 80 LAI 90 GY
LAI 60 1.000
LAI 70 0.985** 1.000
LAI 80 0.983** 0.997** 1.000
LAI 90 0.969** 0.994** 0.995** 1.000
GY 0.949** 0.949** 0.950** 0.942** 1.000
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LAI 60, LAI 70, LAI 80 and LAI 90 are the leaf area index (LAI) at 60, 70, 80 and 90 DAT respectively and GY = rice grain yield (t ha−1)

**Indicate correlation is significant at 1% level

Table 5.

Correlation between grain yield and percent light intercepted (%LI) of rice as influenced by green manures and different levels of nitrogen

Parameters % LI 60 % LI 70 % LI 80 % LI 90 GY
% LI 60 1.000
% LI 70 0.984** 1.000
% LI 80 0.977** 0.980** 1.000
% LI 90 0.966** 0.949** 0.976** 1.000
GY 0.959** 0.931** 0.968** 0.983** 1.000
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% LI 60, %LI 70, %LI 80 and %LI 90 are the percent light intercepted (%LI) at 60, 70, 80 and 90 DAT respectively and GY = rice grain yield (t ha−1)

**Indicate correlation is significant at 1% level

The mean photosynthetic efficiency of plant is best indicated by net assimilation rate (NAR) under a particular environment. The NAR was also significantly influenced by the integration of Sesbania aculeata and Crotalaria juncea with N (Table 3). However, the highest NAR was found from the T6 treatment at 80 DAT which was statistically similar to the T11 treatment at the same DAT and the lowest was recorded from the T1 (control) treatment at 100 DAT (Table 3). As increased nitrogen produces more leaf area and leaf area harvest that may accumulate more dry matter assimilation. The NAR was gradually increased from 60 DAT to 80 DAT and then decreased regardless of different treatment (Table 3). The mutual leaf shading by older leaves which have lost photosynthetic ability lead to decreased NAR with increasing age of the plants.

Incorporation of Sesbania aculeata and Crotalaria juncea with N significantly influenced the dry matter (DM) production of rice (Table 6). During the entire growing periods, the maximum DM production was found from the T6 treatment. This might be due to balanced supply of nutrients in soil through addition of GM which improve plant growth and increase DM production. The results of the Table 6 showed that DM production increased rapidly before flowering stage and then increased slowly up to maturity. It might be due to decrease in chlorophyll content, photosynthetic capacity and shedding of leaves at the latter stage of the crops. Data regarding yield contributing characters and yield as influenced by integration of Sesbania aculeata and Crotalaria juncea with N is shown in Table 7. Analysis of the data revealed that the treatments had significant effect on plant height, tillers hill−1, panicle length, number of filled grain panicle−1 and grain yield of rice. However, among the treatments, the highest plant height, tillers hill−1, panicle length, number of filled grain panicle−1 and grain yield was recorded from the T6 treatment and the lowest was recorded from T1 (control) treatment (Table 7). The results of this research indicate that application of N60 was inefficient for optimizing rice yield compared to the combined application of GM and N fertilizers. Lee et al. (2010) and Shah et al. (2017) found that incorporation of GM in soil dramatically increased the number of effective tiller per hill, panicle length, filled grain per panicle, and yield of rice. It has been reported that the balanced supply of nutrients is important for improving plant growth and also for increasing rice yield (Caballero et al.1996). In addition to the macro-nutrients (N, P, and K), green manuring plants also contains micro-nutrients (e.g. Ca, Mg, Si, and Zn, etc.) (Chen and Zhao 2009; Lu et al. 2011), which may promote and maintain the sustainable nutrients supply to the soil. Efthimiadou et al. (2010) found that combining GM with N enhanced the photosynthetic rate and stomatal conductance of rice, and led to increase in the dry matter accumulation as well as rice yield versus N fertilizers alone. These positive effects of GM may be the result of the aboveground and/or belowground plant biomass, with high amount of N and a relatively low carbon-to-nitrogen ratio (C/N), leading to release of plant-available N (Gilmour et al. 1998; Blanco-Canqui et al. 2012). Due to deep root system, GM crops also increase P and K availability in plough layer of paddy soil which is favorable to promote the N absorption of rice (Bullock 1992; Fageria et al. 2005) and may increase the plumpness of rice grains. Xie et al. (2017) showed that combining GM (chinese milk vetch) with N promoted plant growth due to its positive role in mitigation of oxidative damages by increasing antioxidant activity in rice roots.

Table 6.

Effect of green manuring crops and nitrogen levels on dry matter production at different growth stages of rice

Treatments Dry matter production (g m2)
60 DAT 70 DAT 80 DAT 90 DAT 100 DAT 110 DAT
T1 = Control 195i 231j 327l 431j 507k 589k
T2= S. aculeata + N0 435g 484h 552j 687h 781i 853i
T3 = S. aculeata + N15 471f 514g 589h 734f 823h 915g
T4 = S. aculeata + N30 621d 658e 719f 846e 933f 1062f
T5= S. aculeata + N45 711b 755b 833c 985c 1057c 1134c
T6 = S. aculeata + N60 755a 815a 929a 1095a 1184a 1277a
T7= C. juncea + N0 414h 462i 535k 637i 755j 819j
T8= C. juncea + N15 473f 509g 581i 721g 819h 896h
T9= C. juncea + N30 597e 643f 712g 841e 917g 1055f
T10= C. juncea + N45 716b 743c 817d 979c 1038d 1121d
T11= C. juncea + N60 751a 817a 903b 1068b 1173b 1261b
T12 = N60 681c 721d 803e 941d 1008e 1083e
CV (%) 2.43 2.74 1.37 1.56 1.44 1.46
LSD (0.05) 9.1 10.03 5.59 10.29 8.80 10.07
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Averages from three independent experiments are shown

*Values followed by different letters in the same column are significantly different from each other at 5% level of significance

Table 7.

Effect of green manuring crops and nitrogen levels on yield contributing characters and yield of rice

Treatments Plant height (cm) Number of effective tillers hill−1 Panicle length (cm) Filled grain panicle−1 1000 seeds wt. (g) Grain yield (t ha−1)
T1 = Control 92.7d 7.3f 18.17d 83.56d 21.12 2.31g
T2= S. aculeata + N0 98.9bcd 9.8de 21.83bc 96.24c 22.13 3.87e
T3 = S. aculeata + N15 100.7bcd 10.4bcde 22.01bc 97.55bc 22.17 4.09cd
T4 = S. aculeata + N30 104.6abc 11.1abcde 22.66ab 103.11ab 22.25 4.23c
T5= S. aculeata + N45 106.8abc 11.7ab 23.11a 105.46a 22.41 4.88a
T6 = S. aculeata + N60 109.2a 12.4a 23.77a 106.74a 22.46 5.01a
T7= C. juncea + N0 98.4cd 9.6e 21.71bc 95.05c 22.09 3.65f
T8= C. juncea + N15 99.8bcd 10.1cde 21.89bc 96.22c 22.13 3.97de
T9= C. juncea + N30 104.1abc 10.9bcde 22.47b 102.45ab 22.20 4.12c
T10= C. juncea + N45 105.4abc 11.4abc 22.98ab 104.86a 22.37 4.65b
T11= C. juncea + N60 108.4ab 11.8ab 23.46a 106.13a 22.42 4.90a
T12 = N60 105.2abc 11.2abcd 22.79ab 104.16a 22.32 4.51b
CV (%) 4.33 6.57 5.01 2.62 3.51 2.71
LSD(0.05) 9.01 1.54 1.41 5.77 1.63 0.15
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Averages from three independent experiments are shown

*Values followed by different letters in the same column are significantly different from each other at 5% level of significance

The data of this research revealed that incorporation of Sesbania aculeata and Crotalaria juncea with N significantly reduced soil bulk density (Table 8). The lowest bulk density (1.11) was recorded from the T6 treatment, while the highest (1.32) was recorded from the T1 (control) treatment. This might be due to increase in soil organic matter (OM) resulting from the degraded GM by micro-organisms. Green manure may increase the soil microbial activities for OM decomposition which led to enhancement of soil porosity and reduction in soil bulk density. Soil pH was not significantly influenced by the different treatments (Table 8). Although, incorporation of GM had slightly lower soil pH compared with T1 (control) treatment. The decrease in soil pH may be due to production of CO2 and organic acids during decomposition of incorporated GM. Some other authors also reported that application of different types of GM also decreased soil pH (Dhar et al. 2014; Adekiya et al. 2017). At pH below 7.0, R-OH might have dissociated as R+ and OH− and the H− decreased soil pH eventually. The results of this study showed that incorporation of Sesbania aculeata and Crotalaria juncea with N significantly increased soil organic carbon, N, P, K, Ca, and S (Table 8). In most of the cases, the highest nutrients content of the post-harvest soil were found from the T6 treatment and the lowest from the T1 (control) treatment (Table 8). Noordwijk et al. (2015) observed that GM not only adds N in soil profile but also uptake residual N from deep soil profile to top soil by their downward root growth. Green manuring significantly increased the NH4 content and decreased the NO3− content in paddy field. Incorporation of GM in paddy soil also increased total N contents, and the quantity and quality of soil organic C (Zotarelli et al. 2012; Xie et al. 2017). Green manures are rich in different nutrients and affirmed that these nutrients are released into the soil by decomposed GM. Our results were supported by many other researchers (Dhar et al. 2014; Adekiya et al. 2017) who reported higher soil OM, organic carbon, N, P, K, Ca, Mg and S contents due to incorporation of GM. It has also been reported that in addition to the macro-nutrients (N, P, and K), GM also contains micro-nutrients (e.g. Ca, Mg, Si, and Zn, etc.) (Chen and Zhao 2009; Lu et al. 2011), which may promote and maintain the sustainable nutrients supply to the soil.

Table 8.

Effect of green manuring crops and nitrogen levels on physical and chemical properties of postharvest rice soil

Treatment Bulk density (g/cc) pH Organic C (%) Total N (%) Available P (mg/kg) Exchangeable K (meq/100 g soil) Available S (mg/kg)
Initial value 1.35 5.76 0.81 0.064 4.86 0.138 21.21
T1 = Control 1.32a 5.73 0.83e 0.055i 4.69f 0.129f 20.57h
T2= S. aculeata + N0 1.19bcd 5.60 0.90cd 0.073g 5.75de 0.205de 22.38fg
T3 = S. aculeata + N15 1.17cde 5.60 0.92bcd 0.081f 6.11cd 0.219c 22.61def
T4 = S. aculeata + N30 1.15def 5.60 0.93bc 0.093d 6.23bcd 0.223c 22.83cd
T5= S. aculeata + N45 1.13ef 5.61 0.93bc 0.098c 6.43abc 0.248b 23.01bc
T6 = S. aculeata + N60 1.11f 5.62 0.97a 0.106a 6.71ab 0.269a 23.19ab
T7= C. juncea + N0 1.19bc 5.61 0.89d 0.069h 5.86de 0.194e 22.53ef
T8= C. juncea + N15 1.19bcd 5.61 0.89d 0.075g 6.16cd 0.216cd 22.76cde
T9= C. juncea + N30 1.17cde 5.62 0.90cd 0.088e 6.38abc 0.219c 22.91bc
T10= C. juncea + N45 1.15cdef 5.63 0.91bcd 0.095d 6.55abc 0.242b 23.13ab
T11= C. juncea + N60 1.12f 5.62 0.94ab 0.103b 6.83a 0.261a 23.36a
T12 = N60 1.22b 5.67 0.84e 0.083f 5.58e 0.248b 22.15g
CV (%) 2.25 2.01 2.55 2.05 4.95 3.060 2.23
LSD (0.05) 0.04 0.19 0.039 0.003 0.51 0.011 0.28
Open in a new tab

*Values followed by different letters in the same column are significantly different from each other at 5% level of significance

Averages from three independent experiments are shown

Conclusion

Green manuring is an important practice for sustainable agriculture. This study was conducted to understand the role of green manure in the morpho-physiology characters and yield of rice as well as how the application of these GM can help to manage soil fertility issues. Incorporation of Sesbania aculeata and Crotalaria juncea as GM with N significantly influenced the SPAD reading, LAI, %LI, net assimilation rate, dry matter production, plant height, tillers hill−1, panicle length and number of filled grain panicle−1, which ultimately enhanced the grain yield of rice. Combining Sesbania aculeata and Crotalaria juncea with N also had a significant role on macro and micro-nutrients status of post-harvest soil.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

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