Biomass, Grain and Nitrogen Harvest Index of Rainfed Corn with Organic and Inorganic Fertilization in a Rhodic Luvisol of Yucatan, Mexico ()
1. Introduction
Soil is the medium in which plants grow to feed and clothe the world. Soil fertility is a basic need of crop production and is vital for soil to be productive. However, fertile soil is not necessarily productive soil, as other factors can limit production. Soil fertility, in modern agriculture, is part of a dynamic system, in which nutrients are extracted from the soil to be accumulated in harvested products [1].
Good soil fertility does not guarantee production, since nutrients may be in non-assimilable form. The inadequate supply of nutrients is a limiting factor for good yields, due to the fact that crops require certain quantities of nutrients according to their stage of development. The current practice of deciding on the fertilization dose is often based on general opinions with no local and specific experiences being neither effective nor economical.
The soil fertility depends on the relative rates of addition and removal of nutrients [2]. Therefore, to achieve a good fertilization program, it is necessary to know the kind and the optimal quantities of nutrients required to produce a profitable and sustainable crop in different types of soils.
In that way, fertilization should be done, based on the nutritional demand of the plant, to favor good yield expressions and to guarantee that most of the fertilizer applied is used by the crop [3].
In the state of Yucatan Mexico, corn is the main staple crop and although it is mainly cultivated on stony soils like the Leptosols, with low productive potential, there are important arable areas of rhodic Luvisols with better productive potential.
In an imminent, continuous demand for technology, basic nutrimental studies are needed to improve corn production. However, fertilization, associated with plant nutrition, is the main technological component that deserves more attention since it is the most expensive input.
To support fertilization programs it is pertinent to incorporate indicators or indexes able to measure the efficiency of fertilization as related to the uptake of nutrients by the plant and their allocation into different components of the Biomass including the Grain.
If the fertilizer applied is efficiently absorbed, the profitability of the crop can increase, and environmental pollution will be reduced.
This work aims: 1) to evaluate the effect of organic, inorganic and biofertilizers on corn Biomass production in a rhodic Luvisol of Yucatan, Mexico 2) To assess the Grain Harvest Index (GHI) and the Nitrogen Harvest Index (NHI) of corn crop under different fertilization formulas. 3) To assess the amount of Nitrogen (N) needed to produce one t·ha-1 of Grain.
2. Materials
The experiment was conducted in a favorable rainy season using a rhodic Luvisol located in the “Uxmal” Experimental Station of the National Institute of Forestry, Agricultural and Livestock Research of Mexico in the South of the state of Yucatán. The soil has a neutral pH (7.0), low Electrical Conductivity (EC = 0.43 mS/cm) and Medium Cation Exchange Capacity (CEC = 25 meq/100 gr, optimal concentration of both available Nitrogen as Nitric Nitrogen (NO3-N) and Phosphorus (P) but Potassium (K) in excess.
As a phytometer, the commercial white Grain Hybrid H-565 was established in experimental units of 5 m × 4 m (20 m2) in a projected population of 60,000 plants∙ha−1.
3. Methods
3.1. Treatments and Statistical Analysis
Twelve treatments were studied (Table 1) resulting from the combination of inorganic (N-P2O5-K2O) fertilization (80-40-00, 120-80-00 and 00-00-00) with two doses (0 and 5 t∙ha−1) of Chicken manure (0 and 5 t∙ha−1) and two doses (0% and 100%) of combined Biofertilizers (Azospirillum bacteria + Mycorrhizal fungus-Genus Glomus). The treatments were distributed in a Completely Randomized Block Design with two replications.
The Grain production (t∙ha−1, at 13% humidity) was subjected to an analysis of variance (ANOVA) comparing means with the Tukey test at 5% in order to select the best treatments.
Table 1. Treatments related to Chemical fertilizers in combination with Chicken manure and Biofertilizers applied in a rhodic Luvisol of Yucatan Mexico.
Treatment |
Chemical fertilizer N-P2O5-K2O (kg∙ha−1) |
Chicken manure (t∙ha-1) |
Biofertilizer (azospirillum + mycorrhiza) |
1 |
120-80-00 |
5 |
100 |
2 |
80-40-00 |
5 |
100 |
3 |
120-80-00 |
5 |
0 |
4 |
80-40-00 |
5 |
0 |
5 |
00-00-00 |
5 |
0 |
6 |
120-160-00 |
0 |
0 |
7 |
120-120-00 |
0 |
0 |
8 |
120-80-00 |
0 |
0 |
9 |
80-40-00 |
0 |
0 |
10 |
120-80-00 |
0 |
100 |
11 |
00-00-00 |
0 |
100 |
12 |
00-00-00 (Control) |
0 |
0 |
With information on Aboveground Biomass (dry basis), the Grain Harvest Index (GHI) and the Nitrogen Harvest Index (NHI) were calculated for three extreme treatments: T12 as the Control (00-00-00), T6 (120-160-00) representing the Chemical Treatment and T3 (120-80-00+Chicken manure) representing a Chemical plus an Organic Manure Treatment taking into account the information of the first replication only.
3.2. Grain Harvest Index (GHI)
In order to calculate the Grain Harvest Index (GHI), the aerial Total Biomass (TB) was partitioned in Partial Biomass (PB) as: Stalk, Leaves, Cob and Seed measured in kg∙ha−1 dry basis. The formula for GHI was the next:
SHI = [Weight of Grain/Weight of Total Biomass (Stalk + Leaves + Cob + Seed)]*100
This index measures the percentage of Grain produced as compared to the TB.
3.3. Nitrogen Harvest Index (NHI)
At physiological maturity, the NHI, as an indicator of the magnitude of N remobilized from vegetative structures to the Grain was measured. The Nitrogen Harvest Index (NHI), considered, as well, as the percentage (%) of Nitrogen (N) extracted by the Grain, from the Total N accumulated in the Biomass, was calculated by taking into account.
1) The percentage (%) of N in each of the Biomass components (Stalk, Leaves, Cob and Seed).
2) The production (kg∙ha−1) of each Biomass component.
3) The content of N in kg ha−1 in each Biomass component.
So the NHI was calculated as follows:
NHI (%) = [(N Content (kg∙ha−1) in Seed)/(N Content in Total Biomass (kg∙ha−1)]
The NHI is considered an important index positively associated with Grain yield.
3.4. Nitrogen Needed to Produce 1 t∙ha−1 of Grain
It is important to know the amount of nutrients needed to produce corn because deficiencies or excess of any mineral nutrient can affect the development of the plant. In that sense, the amount of N (kg∙ha−1) to produce one ton of Grain was calculated using the next parameters.
1) N extracted for the Total Biomass (kg∙ha−1)
2) Grain produced in t ha-1 out of the Total Biomass
The formula used was the next:
N for 1 t∙ha−1 = N extracted for the Total Biomass (kg∙ha−1)/Grain produced (t∙ha−1)
4. Results
4.1. Grain Yield and Statistical Analysis
The ANOVA (Table 2) showed highly significant differences between yield of treatments when the calculated p was of 0.009 and the maximum limit of p expected was of 0.05. Table 3 shows the Grain yields (t∙ha−1) at commercial humidity of 13% of all treatments, their corresponding relative yields (%), as compared to the Control, and the Comparison of Means (Tukey test at 5%).
Table 2. Analysis of variance (ANOVA) of treatments related to Chemical fertilizers in combination with Chicken manure and Biofertilizers applied in a rhodic Luvisol of Yucatan Mexico.
Source of varrietion |
Square sum |
Degree of freedom |
Mean square |
F |
P (0.05) |
Treatments |
28.98604583 |
11 |
2.635095076 |
4.585858473 |
0.0090 |
Replications |
0.030104167 |
1 |
0.030104167 |
0.05239031 |
0.8231 |
Error |
6.320745833 |
11 |
0.574613258 |
|
|
Total |
35.33689583 |
23 |
|
|
|
The T1: (120-80-00) + Chicken manure + Biofertilizer was statistically outstanding (A). However, T1 together with other nine treatments (T2, T6, T3, T7, T9, T5, T4, T8, and T10) are statistically equals sharing the same letter A.
There are two other groups formed by sharing letters B and C with ten treatments each one. However, the Control (00-00-00) showed the lowest value with the letter C.
There is a clear trend of the influence that organic treatments have when mixed with biofertilizers (Chicken manure + Biofertilizer) and combined with inorganic fertilization. The T1 (120-80-00 + Chicken manure + Biofertilizer) obtained the highest yield with 10.58 T∙ha−1 followed by T2 (80-40-00 + Chicken manure + Biofertilizer) with 10.28 T∙ha−1. The inorganic T6 with the highest doses studied (120-160-00) obtained an average yield of 10.02 t∙ha−1. These three treatments achieved yields of more than 40% as compared to the control.
The Chicken manure by itself does not contribute to any significant increase in yield; but the combination of Chicken manure + Biofertilizers creates important synergies for an important increase in production. Any way, the yields remain satisfactory with 8.68 t∙ha−1 in T3 (120-80-00 + Chicken manure), 8.06 t∙ha−1 with T5 (00-00-00 + Chicken manure), 8.06 t∙ha−1 with T4 (80-40-00 + Chicken manure), 7.67 t∙ha−1 with T10 (120-80-00 + Biofertilizer) and 7.32 t∙ha−1, with biofertilizer alone T11 (00-00-00 + Biofertilizer).
The Biofertilizer alone is only 3% higher than the Control T12 (00-00-00), indicating little response to the application of Biofertilizers (Azospirillum + Mycorrhizae).
Looking at the three treatments (T1, T2 and T6), with the highest and similar yields, it seems that the Chemical treatment (T6) is the best option for corn production. From an economic point of view, the addition of Chicken manure, to the Chemical fertilizer is a non-profitable and extra expensive technological component.
Table 3. Grain yields (t∙ha−1) at commercial humidity of 13% and their corresponding relative yields (%) as compared to the control and the comparison of means by Tukey test (p = 0.05).
Treatment |
T∙ha−1 |
Relative yields (%) |
Comparison of means (Tukey 5%) |
I |
II |
Avarage |
T1. (120-80-00) + Chicken manure + Biofertilizer |
10.58 |
10.58 |
10.58 |
149.64 |
A |
T2. (80-40-00) + Chicken manure + Biofertilizer |
10.29 |
10.27 |
10.28 |
145.40 |
AB |
T6. (120-160-00) |
10.21 |
9.82 |
10.02 |
141.72 |
ABC |
T3. (120-80-00) + Chicken manure |
8.26 |
9.09 |
8.68 |
122.77 |
ABC |
T7. (120-120-00) |
9.24 |
7.99 |
8.62 |
121.92 |
ABC |
T9. (80-40-00) |
8.48 |
8.32 |
8.40 |
118.81 |
ABC |
T5. (00-00-00) + Chicken manure |
8.05 |
8.07 |
8.06 |
114.00 |
ABC |
T4. (80-40-00) + Chicken manure |
9.14 |
6.98 |
8.06 |
114.00 |
ABC |
T8. (120-80-00) |
7.46 |
8.65 |
8.06 |
114.00 |
ABC |
T10. (120-80-00) + Biofertilizer |
7.49 |
7.86 |
7.67 |
108.48 |
ABC |
T11. (00-00-00) + Biofertilizer. |
7.09 |
7.55 |
7.32 |
103.53 |
BC |
T12. (00-00-00) Control |
6.09 |
8.05 |
7.07 |
100.00 |
C |
4.2. The Chemical and the Chicken Manure vs. Biomass Production
Figure 1 shows the TB production (kg∙ha−1), dry basis, of three specific treatments. The Control T12 (00-00-00) obtained the lowest TB production with 10,800 kg∙ha−1 followed by T6 (120-160-00) with 12,190 kg∙ha−1 and T3 (120-80-00 + Chicken manure) with 14,798 kg∙ha−1. There was a TB reduction of 27% in T12 as compared to T3.
On the other hand, the production of Partial Biomass (PB) (Husk, Leave and Stalk) in the Control T12 (00-00-00) was 5500 kg∙ha−1 whilst for the Inorganic fertilizer T6 (120-160-00) it was 5140 kg∙ha−1 and for the T3 (120-80-00 + Chicken manure) the PB was the higher with 7608 kg∙ha−1. The Grain production (dry basis) were 5300, 7050 and 7190 kg∙ha−1 for T12, T6 and T3 respectively.
Although the PB was higher in the most complete T3 (Chemical fertilizer and Chicken manure) the Grain yield (7190 kg∙ha−1) was similar to that of the Chemical treatment T6 (7160 kg∙ha−1). It seems that in T3 there was a Luxury Consumption when plants were over-fertilized and the Biomass concentrated more in the Stalk than in the Grain as shown in Figure 1.
Figure 1. Production of dry base Biomass (Kg∙ha
−1) partitioned in Husk, Leaf, Stalk and Grain with different fertilization treatments in a
rhodic Luvisol of Yucatan Mexico. Uxmal-INIFAP Experimental Station.
4.3. Harvest Indexes (GHI-NHI) and Kilograms of N to Produce
1 t∙Grain∙ha−1
The values of Grain Harvest Index (GHI), Nitrogen Harvest Index (NHI) and kilograms of N needed to produce 1 t∙ha−1 of Grain are shown in Tables 4-6 for T12, T6 and T3 respectively.
The GHI referred to as 0.49 (49%), 0.57 (57%) and 0.48 (48%) for T12, T6 and T3 respectively are in the range (0.50 - 0.52) reported by Cimpiatti, et al. (2010) [4]. This means that, regardless of the treatments, between 48 and 57% of the TB is concentrated in the Grain.
To calculate the NHI, both the N content in each component of the TB and the kilograms per hectare produced were used. By instance, the N contents in Grain were similar in all three treatments: 1.34%, 1.27% and 1.30% for T12, T6 and T3 respectively. That was not the case for N in Leaves where N was lower in the Control T12 (0.43%) vs. 0.68 and 0.80% for T6 (Chemical fertilizer) and T3 (Chemical fertilizer and Chicken manure) respectively.
It was found that the Grain in T12, T6 and T3 accumulates 71.02, 89.53 and 93.47 Kg of N∙ha−1 respectively; representing 74% of the total N extracted by the TB (95.02 Kg of N∙ha−1) for T12, 77% for T6 (115.18 Kg of N∙ha−1) and 70% for T3 (132.04 Kg of N∙ha−1).
In that way, the NHI of 0.74, 0.77 and 0.70 for T12, T6 and T3 are in accordance with the findings of Hutsh and Shuber, (2023) [5] who reported an average NHI of 0.75.
On the other hand, in order to produce 1 t∙ha−1 of Grain, it is needed 18.00, 16.33 and 18.35 Kg∙N∙ha−1 extracted by the TB for T12, T6 and T3 respectively (Tables 4-6). This is in accordance with different authors who suggested values of 23.1 [6] and 15.0 kg∙N [7] for each ton of Grain to be produced.
Table 4. Biomass Production (kg∙ha−1 dry basis), Grain Harvet Index (GHI), Nitrogen Harvest Index (NHI) and Kilograms of N to produce 1 t∙Grain∙ha−1 in the Control (00-00-00) T12. Uxmal-INIFAP Experimental Station at Yucatan Mexico.
Treatment |
Parameters |
Stalk |
Leaf |
Husk |
Grain |
Partial Biomass |
Total Biomass |
T12 (00-00-00) |
Kg∙ha−1 |
2340 |
1980 |
1180 |
5300 |
5500 |
10,800 |
Harvest Index (HI) per component |
0.22 |
0.18 |
0.11 |
0.49 |
|
|
N (%) in each Biomass component |
0.44 |
0.43 |
0.44 |
1.34 |
|
|
Kg∙N∙ha−1 exported to each component. |
10.29 |
8.51 |
5.19 |
71.02 |
|
95.022 |
Nitrogen Harvest Index (NHI) |
0.10 |
0.089 |
0.054 |
0.74 |
|
|
kg∙N∙ha−1 to produce 1 t∙Grain∙ha−1 |
|
|
|
18.00 |
|
|
Table 5. Biomass Production (kg∙ha−1 dry basis), Grain Harvet Index (GHI), Nitrogen Harvest Index (NHI) and Kilograms of N to produce 1 t∙Grain∙ha−1 in the Chemical fertilizer T6 (120-160-00). Uxmal-INIFAP Experimental Station at Yucatan Mexico.
Treatment |
Parameters |
Stalk |
Leaf |
Husk |
Grain |
Partial Biomass |
Total Biomass |
T6 (120-160-00) |
Kg∙ha−1 |
2100 |
1990 |
1150 |
7050 |
5140 |
12,190 |
Harvest Index (HI) per component |
0.17 |
0.16 |
0.09 |
0.57 |
|
|
N (%) in each Biomass component |
0.38 |
0.68 |
0.36 |
1.27 |
|
|
Kg∙N∙ha−1 exported to each component. |
7.98 |
13.53 |
4.14 |
89.53 |
|
115.18 |
Nitrogen Harvest Index (NHI) |
0.069 |
0.11 |
0.036 |
0.77 |
|
|
kg∙N∙ha−1 to produce 1 t∙Grain∙ha−1 |
|
|
|
16.33 |
|
|
Table 6. Biomass Production (kg∙ha−1 dry basis), Grain Harvet Index (GHI), Nitrogen Harvest Index (NHI) and Kilograms of N to produce 1 t∙grain∙ha−1 in a Chemical and Organic Fertilizer T3 (120-160-00 + Chicken manure). Uxmal-INIFAP Experimental Station at Yucatan Mexico.
Treatment |
Parameters |
Stalk |
Leaf |
Husk |
Grain |
Partial Biomass |
Total Biomass |
T3 (120-80-00 + Chicken manure) |
Kg∙ha−1 |
3660 |
2460 |
1488 |
7190 |
7608 |
14,798 |
Harvest Index (HI) per component |
0.24 |
0.16 |
0.10 |
0.48 |
|
|
N (%) in each Biomass component |
0.37 |
0.80 |
0.36 |
1.30 |
|
|
Kg∙N∙ha−1 exported to each component. |
13.54 |
19.68 |
5.35 |
93.47 |
|
132.04 |
Nitrogen Harvest Index (NHI) |
0.10 |
0.15 |
0.04 |
0.70 |
|
|
kg∙N∙ha−1 to produce 1 t∙Grain∙ha−1 |
|
|
|
18.35 |
|
|
5. Discussion
In the first part of this work, related to Grain yields (Table 3) it was observed a synergic effect of Chicken manure and the Biofertilizer. However, Chicken manure alone was able to enhance yields (T5) but Biofertilizer was not (T11). Biofertilizers did not have any effect on yields even when applied with Chemical fertilizers (T10). Biofertilizers were activated only when Chemical fertilizers were added with the Chicken manure.
It seems that the Mycorrhizal fungi, in the biofertilizer, found enough nutrients, coming from both the Chicken manure and the Chemical fertilizer. N was transported into the roots and plant through their hyphae when in contact with a fertile soil.
Sorensen, et al., (2009) [8] suggests that the increase in the Mycorrhizal colonization are due to the presence of Organic Matter as a source of energy for soil organisms. According to Uriel-Figueroa, et al. (2015) [9] the N in Chicken manure is two times higher (2.6% - 4.65%) than that of the Bovine Manure (0.91% - 2.44%).
On the other hand, it is possible that the excesses of Nitrogen, coming mainly from Chicken manure, are inhibiting the activity of the Azospirillum bacteria. The biological N fixation process decreases when soils have high N content as mentioned by Steenhoudt and Vanderleyden, (2000) [10]. These authors mention that the Nitrogen Fixation Structural Genes (nif) are highly conserved among all nitrogen-fixing bacteria and the Transcriptional Activator NifA is required for N fixation. In Azospirillum brasilense and H. seropedicae, NifA is inactive when N is in excess.
On the othe hand, in the second part of the research, it was found a highest 0.8% of N in leaves when Chichen manure was combined with the Chemical fertilizer (T3 = 120-80-00 + Chicken manure), whilst in the Control (T12) and the Chemical treatment (T6) the N reduced to 0.43% and 0.68% respectively (Tables 4-6). The Partial Biomass (PB) of T3 (7608 kg∙ha−1), which is the sum of all components except Grain, was higher than both the Control (5500 kg∙ha−1) and the Chemical treatment (5140 kg∙ha−1).
However, eventhough T3 showed higher TB, PB and N content in leaves than those of the Chemical T6, both treatments had practically the same Grain Yields (7190 vs. 7050 kg∙Grain∙ha−1). This could be related to the N Luxury Consumption (LC) when a soil is overfertilized. In this sense, yield can be decreased by excesive N as suggested by Cope and Rose, (1973) [11].
The LC occurs when the crop absorbs nutrients without a corresponding increase in yield involving also an extra cost of fertilization. In our case, it seems that N in T3 was absorbed but no assimilated to enhance kernels production.
It is suggested that in maize, and other crops, N can be remobilized (before silking), to ears to supply kernels formation [12] [13]. Yields are well related to an increase in the dry matter and the consequent accumulation of nutrients [14]. The N remobilization can be disrupted under stress conditions [15].
On the other hand, the N extracted for the TB to produce 1 t∙ha−1 of Grain was 18.0, 16.3 and 18.3 kg∙N∙ha−1 for T12, T6 and T3 respectively. This findings were not far away from those reported by different authors [6] [7].
On Table 7 below, there is a summary of the GHI, NHI and the kilograms of N needed to produce 1 ton of corn, product of this work, as compared to the literatue.
Table 7. Summary of principal finding on Grain Harvet Index (GHI), Nitrogen Harvest Index (NHI) and Kilograms of N to produce 1 ton∙Grain∙ha−1 of three extreme different treatmens as compared to the literature. Uxmal-INIFAP Experimental Station at Yucatan Mexico.
Treatments |
GHI (Index) |
NHI (Index) |
N for 1 t∙ha−1 (kg∙ha−1) |
T12 (Control) |
0.49 |
0.74 |
18.00 |
T6 (120-160-0) |
0.57 |
0.77 |
16.33 |
T3 (120-80-00 + Chicken manure) |
0.48 |
0.70 |
18.35 |
References |
0.50 - 0.52 [4] |
0.75 [5] |
23.10 [6] 15.00 [7] |
6. Conclusions
Nowadays, fertilization related to plant nutrition is one of the main issues to be investigated, from an agronomic point of view, since it is the most expensive input for corn and other crops. Fertilization research programs should pay attention to select indicators or indexes related to the uptake of nutrients and their allocation into different components of the Biomass, including the Grain.
In that way, farmers can be more efficient when applying fertilizers in the appropriate doses and at the correct time, reducing economic losses. And avoid environmental pollution.
This work aimed to discover new agronomic parameters, for corn Hybrid H-565, such as: the Grain Harvest Index (GHI), the Nitrogen Harvest Index (NHI) and the amount of Nitrogen (N) needed to produce one t∙t∙ha−1 of Grain. To do so, Total and Partial Biomass (TB and PB), as well as N (%) in each Biomass component was assessed.
After studying twelve treatments combined with Chemical fertilizer, Chicken manure and Biofertilizers (Azospirillum brasilense bacteria + Mycorrhiza fungus), the Grain production was subjected to an Analysis of Variance (ANOVA) comparing means with a 5% Tukey test.
Thie main conclusions were the next.
1) Significant statistical differences were found between treatments.
2) Corn production, is enhanced by applying Inorganic fertilizers, alone or combined with Chicken manure and/or Biofertilizers, but just three treatments (T1, T2 and T6) resulted with better relative yields (%) as compared to the Control (T12).
3) The T1 (120-80-00 + Chicken manure + Biofertilizer was the most outstanding with 10.58 t∙ha−1 followed by T2 (80-40-00 + Chicken manure + Biofertilizer) and T6 (120-160-00) with 10.28 and 10.02 t.ha-1 respectively.
4) In order to reduce costs, T6 is a better option than T1 and T2 since no additional Chicken manure nor Biofertilizers, as an extra cost, are needed, maintaining practically the same yields.
5) The GHI varied from 0.49 to 0.63 indicating that between 49% and 63% of the TB belongs to Grain. The T6 had the highest GHI with 0.57.
6) The NHI ranged between 0.63 and 0.81, suggesting that between 63% and 81% of the total N in the the TB is extracted by the Grain. The T6, again showed the higher NHI with 0.77.
7) To produce one ton Grain per hectare, the TB extracted between 16.33 and 18.35 kg∙N∙ha−1. The T6 shows the lowest value with 16.33 vs. T12 (18.00) and T3 (18.35). This means that the N in T6 was used more efficiently to produce Grain.
8) Although the combination of Chemical fertilizer with Chicken manure induced higher Biomass production, there was not a substantial increase in Grain yield. It seems that a Luxury Consumption of N can explain it.
Acknowledgements
We thank the National Institute of Forestry, Agricultural and Livestock Research (INIFAP) of MEXICO for financing this work.
Conflicts of Interest
The authors declare no conflicts of interest regarding the publication of this paper.