Pyrolyzed and unpyrolyzed residues enhance maize yield under varying rates of application and fertilization regimes

Site description

The research took place at the Wadura site of the Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, situated in Sopore, Kashmir, at 34°17′N latitude and 74°33′E longitude (Fig. 1). Wadura is located at an elevation of 1,524 m above sea level and features a flat surface with good drainage. Based on meteorological data collected during the study, peak temperatures during the Kharif seasons of 2020 and 2021 ranged from 22.80 to 38.00 °C, while weekly minimum temperatures were between 8.70 and 19.30 °C. The average annual precipitation is 812 mm, with more than 80% of it attributed to western disturbances. The soil in the study area is classified as inceptisols, with a neutral pH and low availability of N and P, and medium availability of K.

Biochar production

The biochars were produced using patented technology IOT-based multipurpose pyrolyzer cum heater cum cooker. It works on the principle of a system approach patented under patent number 202011056587. The feedstock underwent pyrolysis at two distinct temperatures: 400 °C and 600 °C, individually, for 3 h, with a gradual increase of 8 °C per minute. The treatment consisted of three levels of rate of fertilizers viz., low (L- 1 t ha⁻¹); medium (M- 2 t ha⁻¹); high (H- 3 t ha⁻¹).

FTIR spectroscopy offers valuable insights into the molecular composition and structural properties of biochar derived from varying pyrolysis temperatures. By subjecting biomass to different thermal conditions, biochar is formed with distinct chemical functionalities and bonding arrangements. In this study through FTIR analysis of biochar, we elucidated the spectral signatures corresponding to functional groups such as hydroxyl, carbonyl, and aromatic structures, which undergo transformations during pyrolysis. Understanding these spectral variations can illuminate the influence of pyrolysis temperature on biochar properties, aiding in the optimization of production processes for desired biochar applications (Figs. 2A, 2B).

Experimental design, treatment details and field operation

An experiment was set up with three replications, thirty-eight treatments in a factorial randomized complete block design (F-RCBD). The treatment consisted of three factors, having 1st factor with seven levels of amendments viz., no material (A1); apple biochar (400 °C) (A2); apple biochar (600 °C) (A3); apple residue biomass (A4); dal weed biochar (400 °C) (A5); dal weed biochar (600 °C) (A6); dal weed residue biomass (A7), 2nd factor with three levels of rate of fertilizers viz., low (L- 1 t ha⁻¹); medium (M- 2 t ha⁻¹); high (H- 3 t ha⁻¹) and the 3rd factor with two levels of inorganic fertilizers viz., no fertilizer (N) and recommended dose of fertilizer (RDF) (F) (Table 1). The experiment consisted of forty-two treatment combinations with three replicates amounting to a total of 126 experimental units.

Plant height (cm)

The plant height measurement process involved tracking five specifically tagged plants situated in the penultimate rows of each plot. These measurements were conducted at 15-day intervals. The recorded heights of these plants were then averaged to derive the overall plant height in centimetres. The measurement encompassed the distance from the base of the soil surface to the fully opened top leaf, offering a comprehensive assessment of the plants’ vertical growth progress over time using a meter ruler.

Dry matter accumulation (t ha⁻¹)

Fifteen days after Sowing, three plants were randomly chosen from the penultimate row of every plot. These plants were harvested, meticulously chopped into small pieces, and then thoroughly mixed to ensure homogeneity. Subsequently, they underwent oven drying at a temperature range of 60–65 °C until reaching a constant weight. Following this, the dry weight was recorded using an electronic balance, and the values were averaged and expressed as grams per plant (g plant⁻¹). Finally, these values were converted into t ha⁻¹ to provide a standardized measure of biomass yield across the experimental plots.

Number of cobs plant⁻¹

Before the picking process, the total number of green cobs within five randomly marked plots was carefully counted.

Number of kernels cob⁻¹

In each plot, the number of kernels on five randomly selected cobs was manually counted. This meticulous counting process allowed for the determination of the average number of grains per cob. The resulting data provided valuable insights into the grain yield potential and variability across the experimental plots.

SPAD value

The relative chlorophyll content in maize plant leaves based on light absorption involved the use of a handheld SPAD-502 chlorophyll meter.

Cob length (cm)

The measurement of maize cob length was conducted following the harvesting of mature maize cobs. After removing any extraneous leaves or husks from five randomly selected cobs per plot, each cob was individually measured using a centimetre ruler. The measurement starts from the base where the cob attaches to the stalk and extends to the tip of the cob. Care was taken to ensure the measuring tool was aligned straight along the length of the cob for accurate results. To determine the average cob length, the number of cobs measured per plot is divided by the total of individual measurements.

Cob girth (cm)

Measurement of maize cob girth was conducted following the harvest of mature maize cobs. After removing any extraneous leaves or husks from five randomly selected cobs per plot, each cob girth was individually measured using a flexible tape. The measurement was taken at the widest point around the circumference of the cob, ensuring the tape was snug but not overly tight.

Mean grain cob yield (t ha⁻¹)

Mean grain cob yield refers to the average amount of grain produced per cob of maize. The mean grain cob yield was calculated whereby the total number of cobs harvested per plot was divided by the total weight of grain harvested from five randomly selected cobs per plot. This provides an average measure of the productivity of individual maize cobs in terms of grain yield.

Cob yield (t ha⁻¹)

The cumulative weight of cobs harvested from each net plot across all pickings was initially measured in kilograms. Subsequently, this cumulative weight was converted to (t ha⁻¹) to provide a standardized measure of the overall yield of cobs across the experimental plots.

Test weight (100 kernel weight)

The test weight was estimated by specifically weighing the weight of 100 randomly selected grains from each plot. Using a precise weighing scale, we measured the total weight of these 100 grains, ensuring the scale was properly calibrated for accuracy. The recorded total weight of the 100 grains was then divided by 100 to calculate the average weight of a single grain. This average weight, expressed in grams, represented the test weight or 100 kernel weight of the maize samples.

Stover yield (t ha⁻¹)

After the completion of pickings, the green fodder harvested from each net plot was bundled and weighed, with the measurements recorded in kilograms per plot (kg plot⁻¹). To standardize the data and facilitate comparison, these weights were converted into t ha⁻¹. It’s important to note that the husk obtained during the harvesting process was also included in the total fodder yield calculation, providing a comprehensive assessment of the overall green fodder productivity across the experimental plots.

Statistical analysis

The results obtained from diverse parameters underwent statistical analysis employing established methodologies. Descriptive statistics, three-factor analysis, and analysis of variance (ANOVA) were conducted, followed by mean comparisons using Tukey’s HSD test at a significance level of p < 0.05 utilizing the R software. This thorough statistical evaluation facilitated a comprehensive examination of the data, enhancing insights into the relationships among various factors and their significance.

Pyrolyzed and unpyrolyzed residues affect maize growth and productivity

Plant height of maize crops treated with various amendments (A1 to A7) ranged from 168.22 to 293.87 cm (Table 2). The tallest plants were observed with amendment A3 (293.87 cm), followed by A6 (264.23 cm), while the shortest plants were associated with A1 (168.22 cm). Notably, amendments A3 and A5 showed significant differences compared to other treatments, while A2, A6, and A1, A4, and A7 were similar in their effects. Dry weights of maize under various amendments, both pyrolyzed and unpyrolyzed, are shown in Table 2. Among the treatments, the highest dry weight was recorded with amendment A4 (14.11 t ha⁻¹), followed by A3 (13.64 t ha⁻¹), while the lowest dry weight was observed with amendment A1 (7.37 t ha⁻¹). Dry weights for amendments A1 to A7 ranged from 7.37 to 14.11 t ha⁻¹. Significant differences were noted in dry weight among amendments A1, A2, A4, and A6, whereas amendments A3, A5, and A7 showed no significant differences in dry weight. The average number of cobs per plant ranged from 0.49 to 1.75. Amendment A6 exhibited the highest number of cobs per plant (1.77), followed closely by A3 (1.71), while A1 had the lowest (0.49). The order of mean cobs per plant was: A6 >A3 >A5 >A7 >A4 >A2 >A1. Notably, there were no significant differences in the number of cobs per plant between amendments A3, A5, and A6, or between A4 and A7. However, there were considerable variations in the number of cobs per plant between amendments A1 and A2. The number of kernels per cob ranged from 387.36 to 535.75. Amendment A3 had the most kernels per cob (535.75), followed by A6 (497.33), while A1 had the least (387.36). The order of kernels per cob from highest to lowest was A6 >A3 >A2 >A5 >A4 >A7 >A1. Notably, there were no significant differences in the number of kernels per cob between A2, A4, A5, and A7. However, there were notable differences between A1, A3, and A6. The SPAD values for maize with amendments A1 to A7 were 32.27, 55.55, 58.10, 31.94, 48.30, 52.08, and 35.61, respectively. These values ranged from 31.94 to 58.10, with A3 having the highest (58.10) and A4 the lowest (31.94). The order of SPAD values from highest to lowest was A3 >A2 >A6 >A5 >A7 >A1 >A4. Significant differences existed between A2, A3, A5, and A6, while A1, A4, and A7 were comparable. The cob length values for maize with amendments A1 to A7 were 16.48, 26.29, 27.36, 16.34, 23.23, 24.82, and 17.89 cm, respectively. These values ranged from 16.34 to 27.36 cm. Amendment A3 had the highest cob length (27.36 cm), followed by A2 (26.29 cm), and the lowest was A4 (16.34 cm). The order of cob length values was A3 >A2 >A6 >A5 >A7 >A1 >A4. Significant differences were found between A2, A3, A5, and A6, while A1, A4, and A7 were similar. Table 2 shows the cob girth of maize with various residues. Amendment A3 had the largest cob girth at 18.18 cm, followed by A2 at 17.65 cm, while the smallest was with A4 at 12.75 cm. The cob girth ranged from 12.82 to 18.18 cm across the different amendments. Significant differences were noted in cob girth for A2, A3, A5, and A6, while A1, A4, and A7 showed no significant variation. The cob girth mean values ranked as follows: A3 >A2 >A6 >A5 >A7 >A1 >A4. Table 2 outlines the mean grain cob yield values for maize crops, ranging from 0.69 to 1.40 t ha⁻¹. Amendment A3 had the highest yield at 1.40 t ha⁻¹, followed by A6 at 1.21 Mg ha-1, while A1 had the lowest yield at 0.69 t ha⁻¹. The order of yield was A3 >A6 >A2 >A5 >A4 >A7 >A1. Notably, there was no significant difference in yield between A2 and A6, but substantial differences existed among A1, A3, A4, A5, and A7 amendments. In Table 2, the grain yield of maize with amendments A1, A2, A3, A4, A5, A6, and A7 ranged from 3.27 to 4.78 t ha⁻¹. Amendment A3 had the highest mean yield at 4.78 Mg ha⁻¹, followed by A6 at 4.26 Mg ha⁻¹, while A1 had the lowest at 3.27 t ha⁻¹. The order of mean yield was A3 >A6 >A5 >A4 >A7 >A2 >A1. Significant differences were observed between the A1, A3, and A6 amendments, while A2 and A7, as well as A4 and A5 amendments, showed comparable yields. The test weight mean values for maize ranged from 117.54 to 305.42 gm across different amendments. Amendment A3 had the highest test weight at 305.42 gm, followed by A2 at 285.61 gm, while A1 had the lowest at 117.54 gm. The order of test weight values was A3 >A2 >A6 >A5 >A7 >A4 >A1. Significant differences were observed between A2, A3, A5, and A6 amendments, while A1, A4, and A7 showed similar weights. Table 2 displays the stover yield of maize crops with different amendments. Amendment A3 yielded the highest stover at 2.50 t ha⁻¹, followed by A2 at 2.27 t ha⁻¹, while A4 had the lowest yield at 0.86 t ha⁻¹. The stover yield ranged from 0.86 to 2.50 t ha⁻¹ across amendments. Significant differences were.

Comparative analysis for year of application of pyrolyzed and unpyrolyzed residues and its influences on maize growth and productivity

In the 1st year, maize plant heights ranged from 163.43 to 289.56 cm with amendments A1 to A7, while in the 2nd year, heights ranged from 173.01 to 298.18 cm. Amendment A3 consistently produced the tallest plants in both years, reaching 289.56 cm and 298.18 cm, followed by A6 with heights of 258.47 cm and 269.99 cm, respectively. The shortest plants were associated with A1, measuring 163.43 cm and 173.01 cm. Plant heights increased overall from the 1st to the 2nd year for all amendments. Significant differences in plant height were noted between amendments A3 and A5 in both years, while A2 and A6, and A1, A4, and A7 showed no significance. Table 3 displays the dry weight of maize crops in the 1st and 2nd years under different residues, both pyrolyzed and unpyrolyzed. In the 1st year, A4 had the highest dry weight (13.89 Mg ha⁻¹), followed by A3 (13.16 Mg ha⁻¹), while A1 had the lowest (6.96 Mg ha⁻¹). In the 2nd year, A4 still topped with the highest dry weight (14.33 Mg ha-1), followed by A3 (14.12 Mg ha⁻¹), and A1 remained the lowest (7.78 Mg ha⁻¹). Throughout both years, A1 consistently showed the lowest dry weight and A4 the highest. Dry weight mean values ranged from 6.96 to 13.89 Mg ha⁻¹ in the 1st year and from 7.78 to 14.33 Mg ha⁻¹ in the 2nd year. Dry weight mean values increased for all amendments in the 2nd year compared to the 1st year. Significant differences in dry weight were observed between A1 and A2 amendments in both years, while A1 = A2, and A3 = A4 = A5 = A6 = A7 showed no significant differences in dry weight. In maize, the number of cobs per plant ranged from 0.45 to 1.71 in the 1st year and from 0.54 to 1.78 in the 2nd year. For both years, each amendment fared as A1: 0.45 and 0.54 cobs per plant, A2: 0.73 and 0.78, A3: 1.67 and 1.75, A4: 1.12 and 1.21, A5: 1.62 and 1.69, A6: 1.71 and 1.78, and A7: 1.23 and 1.31 (Table 3). The 2nd year consistently saw more cobs per plant across all amendments. In both years, A6 topped with the most cobs per plant (1.71 and 1.78), followed by A3 (1.67 and 1.75), while A1 had the fewest (0.45 and 0.54). Across both years, there were no significant differences in the number of cobs per plant between A3, A5, and A6 (i.e., A3 = A5 = A6) or between A4 and A7 (i.e., A4 = A7). However, there were significant differences between A1 and A2 in both years. In the 1st and 2nd years, the average number of kernels per cob ranged from 382.35 to 528.42 and 392.37 to 543.08, respectively. Specifically, for the 1st and 2nd years, amendment A1 had 382.35 and 392.37 kernels per cob, A2 had 464.46 and 473.75, A3 had 528.42 and 543.08, A4 had 442.44 and 451.67, A5 had 451.49 and 460.92, A6 had 492.64 and 502.01, and A7 had 438.78 and 448.75, respectively (Table 3). In both years, A3 had the most kernels per cob (528.42 and 543.08), followed by A6 (492.64 and 502.01), with A1 having the fewest (382.35 and 392.37). Across both years, the number of kernels per cob was higher in the 2nd year. In both years, there were no significant differences in the number of kernels per cob between A2 and A5 (i.e., A2 = A5) or between A4 and A7 (i.e., A4 = A7). However, there were significant differences in the number of kernels per cob between A1, A3, and A6. In the 1st year, the SPAD values in maize crops with amendments A1, A2, A3, A4, A5, A6, and A7 were 31.58, 54.40, 56.93, 29.66, 46.86, 50.64, and 33.47, respectively, while for the 2nd year, they were 32.96, 56.70, 59.27, 34.22, 49.74, 53.51, and 37.75 (Table 3). For the 1st year, SPAD values ranged from 29.66 to 56.93, and for the 2nd year, they ranged from 32.96 to 59.27. In both years, the highest SPAD value was with amendment A3 (56.93 and 59.27), followed by A2 (54.40 and 56.70). Conversely, the lowest SPAD value for the 1st year was with A4 (29.66), and for the 2nd year was with A1 (32.96). SPAD values increased in the 2nd year for all amendments compared to the 1st year. Significant SPAD differences were observed between A5 and A6 for both years, while A1, A4, and A7 were comparable (A1 = A4 = A7), as were A2 and A3 (A2 = A3). The maize cob length varied from 15.38 to 26.87 cm and 16.77 to 27.86 cm, respectively for both years, with amendments A1 to A7 (Table 3). Amendment A3 had the longest cob length in both years (26.87 and 27.86 cm), followed by A2 (25.80 and 26.77 cm). The shortest cob length was with A4 in the 1st year (15.38 cm) and A1 in the 2nd year (16.77 cm). Cob length increased in the 2nd year for all amendments compared to the 1st year. Significant differences in cob length existed between A5 and A6 for both years, while A1, A4, and A7 were comparable (A1 = A4 = A7), as were A2 and A3 (A2 = A3). Table 3 shows maize cob girth for the 1st and 2nd year. In both years, A3 had the largest cob girth (17.94 and 18.42 cm), followed by A2 (17.41 and 17.89 cm). The smallest cob girth in the 1st year was with A4 (12.28 cm), and in the 2nd year, it was with A1 (12.96 cm). Cob girth for A1 to A7 in the 1st year ranged from 12.68 to 17.94 cm, and in the 2nd year, it ranged from 12.96 to 18.42 cm. Cob girth increased in the 2nd year. Significant differences in cob girth were found between A5 and A6 in both years. However, A1, A4, and A7 were similar (A1 = A4 = A7), as were A2 and A3 (A2 = A3). The grain cob yield in maize varied from 0.63 to 1.26 Mg ha⁻¹ in the 1st year and from 0.75 to 1.45 Mg ha_-1 in the 2nd year (Table 3). For amendments A1 to A7, grain cob yield in the 1st year ranged from 0.63 to 1.36 Mg ha⁻¹, and in the 2nd year, it ranged from 0.75 to 1.45 Mg ha⁻¹. Grain cob yield increased in the 2nd year. A3 had the highest yield (1.36 and 1.45 Mg ha⁻¹), followed by A6 (1.16 and 1.25 Mg ha⁻¹), while A1 had the lowest (0.63 and 0.75 Mg ha⁻¹) in both years. Grain cob yield was similar between A4 and A5 (A4 = A5) but differed significantly among A1, A2, A3, A6, and A7. In the maize crop, grain yield with amendments A1 to A7 ranged from 3.15 to 4.64 Mg ha⁻¹ in the 1st year and from 3.40 to 4.92 Mg ha⁻¹ in the 2nd year (Table 3). Amendment A3 had the highest yield (4.64 and 4.92 Mg ha⁻¹), followed by A6 (4.13 and 4.40 Mg ha⁻¹), with A1 having the lowest (3.15 and 3.40 Mg ha⁻¹) in both years. Yield differed significantly between A1, A3, A5, and A6, but A2, A4, and A7 (A1 = A4 = A7) were comparable. Test weight mean values ranged from 116.02 to 296.32 gm in the 1st year and from 119.06 to 312.52 gm in the 2nd year for amendments A1 to A7 (Table 3). In both years, test weight values ranged from 116.02 to 296.32 gm and 119.06 to 314.52 gm, respectively. A3 had the highest values (296.32 and 314.52 gm), followed by A2 (276.67 and 294.56 gm), while A1 had the lowest (116.02 and 119.06 gm) in both years. Test weight increased in the 2nd year. Significant differences were observed with A5 and A6, but A1, A4, and A7 (A1 = A4 = A5) and A2 and A3 (A2 = A3) were statistically similar. Table 3 outlines the stover yield of maize under various amendments over two years. The highest stover yield in both years was with A3 (24.20 and 25.93 Mg ha⁻¹), followed by A2 (20.77 and 24.55 Mg ha⁻¹). However, the lowest yield in the 1st year was with A4 (7.04 Mg ha⁻¹), and in the 2nd year was with A1 (9.18 Mg ha⁻¹). Stover yield ranged from 7.04 to 24.20 Mg ha⁻¹ in the 1st year and 9.18 to 25.93 Mg ha⁻¹ in the 2nd year. The 2nd-year yield increased compared to the 1st year. In the 1st year, significant differences were observed with A3 and A5, while A1, A4, and A7 (A1 = A4 = A7) and A2, A6 (A2 = A6) showed no significant difference. In the 2nd year, A5 and A6 had significant differences, while A1, A4, and A7 (A1 = A4 = A7) and A2, A3 (A2 = A3) did not.

Influence of different amendments and rate of application on maize growth and productivity

Figure 3A revealed plant height as affected by different amendments and application rates. Among the amendments, there were significant variations in plant height, as well as among the application rates. Across L, M, and H rates, A3 resulted in the tallest plants, with significant differences noted. Conversely, A1, A4, and A7 led to the shortest plants, showing no variation among them. Generally, the highest plant heights were achieved with the H application rate, followed by the M and L rates. Figure 3B illustrates how different residues and application rates affect dry weight. Dry weight varied significantly across different residues and application rates. For M and H application rates, A3 resulted in higher dry weight compared to other amendments. However, for L application rates, A4 showed greater dry weight compared to other residues. Conversely, the lowest dry weight across all application rates was observed with A1 and A2, which were statistically similar. Dry weight decreased in the following order: H >M >L application rates. The influence of different amendments and application rates on grain yield is shown in Fig. 3C. Grain yield varied significantly depending on the type of amendment and application rates. A3 application consistently led to the highest grain yield across L, M, and H application rates, while A1 resulted in the lowest grain yield. Grain yield was highest with the H application rate, followed by the M and L application rates. Figure 3D revealed stover yield as affected by various amendments and rates of application. Stover yield varied notably among the amendments and application rates. The A3 amendment consistently led to the highest stover yield across L, M, and H application rates, showing significant variation. Conversely, the lowest stover yield was associated with the A1 amendment at the L rate and the A4 amendment at the M and H rates. Stover yield was highest with the H application rate, followed by the M and L rates.

Amendment variability and fertilizer regimes affect maize growth and productivity

Figure S1A revealed plant height affected by various amendments and fertilizer regimes. Plant height varied significantly among different fertilizer regimes and amendments. The tallest plants were observed with the A3 amendment when paired with the RDF. Conversely, the shortest plants were associated with the A1 and A7 amendments, regardless of fertilizer application. Overall, plants treated with the RDF were taller than those without fertilizer across all amendments. Statistically significant differences in plant height were noted between the two fertilizer regimes, with the RDF resulting in taller plants compared to N. Figure S1B depicts the effect of various amendments and fertilizer regimes on dry weight. Dry weight varied significantly depending on the fertilizer regime and the type of amendments applied. The highest dry weight was observed when using the A3 amendment with the RDF. Conversely, the lowest dry weight occurred when applying the A1 amendment with the RDF or N. Across different amendment types, maize crop dry weight was consistently higher when the RDF was applied compared to when N was used. The order of dry weight concerning the fertilizer regime was: RDF >N. Statistically significant differences in dry weight were observed between the two fertilizer regimes across different amendments. However, the application of the A5 amendment showed no significant difference in dry weight whether paired with the RDF or N. The influence of different amendments and fertilizer regimes on grain yield is shown in Fig. S1C. Grain yield varied significantly only with the application of the A3 amendment, depending on the fertilizer regime. The A1, A2, A4, A5, A6, and A7 amendments did not show significant differences in grain yield between the two fertilizer regimes (N and RDF). Grain yield was higher when the RDF was applied compared to N, regardless of the amendment type. The order of grain yield concerning the fertilizer regime was: RDF >N. The A3 amendment resulted in the highest grain yield when applied with the RDF, while the A1 amendment produced the lowest grain yield with both fertilizer regimes. Figure S1D revealed stover yield affected by various amendments and fertilizer regimes. The stover yield varied significantly depending on the fertilizer regimes and the type of amendments. Applying the A3 amendment with the RDF resulted in the highest stover yield, while the lowest yield was observed with the A1 amendment, regardless of the fertilizer regime. Stover yield was generally higher when the RDF was applied compared to N. The order of stover yield concerning the fertilizer regime was: RDF >N. Significant differences in stover yield between the two fertilizer regimes were observed only with the A2 and A3 amendments, while the A1, A4, A5, A6, and A7 amendments showed no significant differences in stover yield between the two fertilizer regimes.

Interactive effect of the amendment, year, rate of application and fertilizer regimes on maize growth and productivity

Figure S2A illustrates an interactive means of the maize plant height affected by amendment type, year, rate of application and fertilizer regimes. The A3 amendment showed the highest average interaction with maize plant height, followed by A2, while A1 and A7 had the lowest values. Specifically, in the 2nd year, using A3 at a H rate with the RDF led to taller plants compared to other amendments, regardless of the application year, rate, or fertilizer use. Figure S2B represents the dry weight influenced by four factors: amendment type, year, rate of application, and fertilizer regimes. Among the amendments, A3 had the highest average interaction with dry maize weight, followed by A4, while A1 had the lowest. Specifically, in the 2nd year, using A3 at an H rate with the RDF led to greater dry weight compared to other amendments applied in the 1st year at M or L rates without fertilizer. Figure S2C depicts grain yield as affected by amendment type, year, rate of application, and fertilizer regimes. The highest mean grain yield was associated with the A3 amendment, followed by A4, and lowest with A1. Specifically, applying A3 in the 2nd year at a H rate with RDF led to the highest grain yield compared to other amendments applied at L rates or N in either the 1st or 2nd year. Figure S2D revealed stover yield as affected by amendment type, year, rate of application, and fertilizer regimes. A3 amendment application recorded the highest interactive mean with maize stover yield, followed by the A2, while the lowest was observed in the A1 and A7 amendment applications, respectively. The A3 amendment type, 2nd year of application, H rate of application and the inclusion of the RDF resulted in higher stover yield than the other amendment types in the 1st or 2nd year at a L or M rate with no fertilizer addition. Figure 4 represents scatterplot between yields and soil carbon.