The results of soil analysis for pedochemical and fertility indices of the soils influencing maize crop production in the Cross River agro-ecology of Nigeria is presented in Table 3 and Fig 2 to 5. The results reveal that organic carbon (Fig 2) ranged from 1.40 g/kg3
in Obanliku soil to 2.84 g/kg3
in Ikom LGA soil. Available Phosphorus (Fig 3) varied 3.31 mg/kg in Obanliku soil to 29.24 mg/kg in Odukpani LGA soil. The amount of Calcium in the agroecology ranged from 0.67 Cmol/kg3
in Akpabuyo soil to 5.00 cmol/kg3
in Obudu soil. Similarly, the volume of Magnesium was found to vary from 1.01 Cmol/kg3 in Obudu soil to 2.48 Cmol/kg3 in Akamkpa soil while Potassium varied between 0.31 Cmol/kg3
in Etung soil to 0.60 Cmol/kg3
in Calabar South soil. The value of total nitrogen (Fig 4) in the Cross River agroecology varied from 0.11 g/kg3
in Bekwarra soil to 0.24 g/kg3
in Akamkpa LGA soil. Cation exchange capacity (CEC) in the agroecology also varied from 7.01 Cmol/kg3
in Abi soil to 12.01 Cmol/kg3
in Calabar South soil. Soils in the agroecology were more acidic 5.00 in Calabar Municipality soil to less acidic 0.61 in Ogoja LGA soil. Micro nutrients status was reported for Boron and Zinc contents in the agroecology among other micro nutrients analysed. Boron varied from 0.52 mg/kg3
in Akamkpa soil to 2.01 mg/kg3
in Etung soil while Zinc also ranged from 1.93 mg/kg3
in Odukpani soil to 5.0 mg/kg3
in Boki soil of the Cross River agroecology of Nigeria. The result of fertility indices of the soils in the cross river agroecology is presented in Table 4. Based on the fertility ratings indices used as shown in (Table 2), Potassium nutrient was rated high throughout the cross river agroecology. The results also show that 33.33% of the soils in the agroecology was rated high, medium and low for available phosphorus fertility nutrient while the remaining soils has medium and low ratings of 33.33% each for available phosphorus nutrient (Table 4). Total nitrogen nutrient fertility ratings for the agroecology soils showed 77.78% high fertility ratings and 22.22% medium fertility ratings. Results of organic carbon nutrient fertility rating of the soils (Table 4) shows that organic carbon content of the soils in the agroecology had a high fertility rating of 72.23% while 27.67% of the soils in the agroecology had medium rating for organic carbon content.
Table 3: Identification of pedochemical characteristics of soils influencing local maize production in the cross river agro-ecology of Nigeria.
Table 4: Identification of fertility indices of soils influencing local maize production in the Cross River agro-ecology of Nigeria.
Fig 2: Organic carbon for cross river agroecology ranged from high to very high >2.0.
Fig 3: Phosphorus for cross river agroecology is moderate and range from 7-20.
Fig 4: Potassium for cross river agroecology is moderate and range from >0.31-0.60.
In summary the fertility status of the soils of cross river agroecology can be rated as High in potassium, organic carbon, total nitrogen and available phosphorus. Medium in organic carbon, total nitrogen and available phosphorus and only low in available phosphorus in some areas (Table 4). With good management options such as good conservation practices, adequate control of pests and diseases and proper use of organic and inorganic fertilizer, it can increase and positively influence the sustainable production of maize in the cross river agroecology.
Principal component analysis of pedochemical and fertility indices supporting local maize production in cross river agro-ecology of Nigeria
Ten (10) principal components (PC) contributed the total 100% to support maize crop production in the agroecology and were used to explain the variations in the Eigen values and percentage contributions from pedochemical and fertility indices enhancing maize crop production in the Cross river agroecology. The major contribution to support maize productivity in the agroecology was from PC1
with a high Eigen value of 70.876 and the highest percentage contribution of 94.992% out of 100% (Table 5). The principal contributing pedochemical and fertility indices to the PC1 is phosphorus with a major loading value of 0.979 (Table 6) while Zinc (-0.005) was the least loading or releasing nutrient in PC1
towards the maize crop productivity.
Table 5: Eigen values and percentage contribution of principal component to soil fertility in the study area.
Table 6: Loading values showing percentage contribution of pedochemical indices to soil fertility enhancing maize production in the cross river agroecology.
Table 5 and 6 revealed that PC2
had an Eigen value of 2.0315 and contributed only 2.7227% to the total 100% enhancement of maize production in the agroecology. Calcium was the major contributing element with a loading value of 0.560 to PC2 and CEC was the least released nutrients (-0.773) in this component. Total nitrogen was the most released nutrient that contributed 0.995 loading value (Table 6) towards growth and yield of maize in PC10 which showed an Eigen value of 0.00008 with the least percentage contribution of 0.00001% to the total 100% (Table 5). Also in PC10, soil acidity index had the least loading value of -0.006 to the component towards the enhancement of maize production in the agroecology.
Table 7 presents result of the percentage contribution of the bulked soil from the different LGAs used for the cultivation of the test (maize) crop revealed the contribution of the different Cross River agroecology towards maize productivity in the area. For PC1, soils in Bakassi agroecology of Cross River contributed the highest pedochemical and fertility inputs to maize productivity with a loading value of 13.222 while soils in Obanliku showed the least loading value of -12.84 in PC1 towards maize productivity in the Cross River agroecology. For PC2, soils in Boki agroecology had the major contributing or loading value with 2.281 to maize productivity in PC2 while soil in Bekwarra with small loading value of -2.270 was the least contributor to maize production in PC2. The soils in Akamkpa contributed the most of pedochemical and fertility inputs to the production of maize with loading value of 0.014 in PC10 while soils in Bakassi and Calabar Municipality had the least inputs of pedochemical and fertility towards maize productivity in PC10 with a loading value of -0.009.
Table 7: Loading values showing percentage contribution of agro-ecology to soil fertility for maize production in the study area.
The dendrogram in Fig 6 delineated and categorized the 18 LGAs in the Cross River agroecology in terms of relationship in pedochemical and fertility indices into 2 major clusters. This shows that all soils in the Cross River agroecology have the same parent material. Cluster 1 has 2 major sub cluster groups C1 and C2. Each of the three subgroups contains six LGAs as depicted in the dendrogram. Group 1 (C1) consist of Biase, Boki, Etung, Ogoja, Ikom and Abi LGAs. Group 2 (C2) consist of Odukpani, Akamkpa, Bakassi, Akpabuyo, Calabar Municipality and Calabar South LGAs and group 3 (C3) consist of Bekwarra, Obanliku, Obudu, Obubra, Ogoja and Yala LGAs.
Fig 5: Total nitrogen for cross river agroecology is ranged from moderately low (0.11 -0.15) to medium (0.16-0.20) to moderately high (0.21-0.24).
Yield performance of local maize (Zea mays L) grown in the different soils of the cross river agroecology
Fig 6: Dendrogram showing pedochemical and nutrient status cluster relationship among LGAs agroecology in the study area.
Table 8 present results on the yield performance of local maize genotypes collected from across all eighteen local government areas of Cross River State and grown on same soil here in Calabar. The results indicates that significant (p<0.05) differences were observed from yield components like size of cobs, kernels per row, days to maturity and 100 seed weight per plant among the evaluated maize. Maize cob sizes ranged from 10.00±1.15 cm in Yala soil to 14.77±0.39 cm of maize planted in Akpabuyo soil (Table 8). Days to maturity ranged from 84.67±3.84 days in maize planted in Akamkpa soil to 94±1.53 days in maize planted in Odukpani soil. The weight of a 100 seed per treatment varied (p<0.05) significantly among the local maize and range from 14.59±1.56 g in maize planted in Calabar municipality soil to 28.54±0.52 g obtained from maize planted in Obudu soil. The number of kernels per row also differed (P<0.05) significantly among the local maize. Maize planted in Akamkpa soil had the least kernels number per row of cob of 10.67±1.20 while maize planted in Obanliku soil had the highest number of kernels per row of cob measuring 15.00±0.58 (Table 8).
Table 8: Yield performance of local maize (Zea mays) grown in different soils of the cross river agroecology.
The number of tassels per plant, days to tasseling, +number of cobs per plant and days to silking did not show any significant (p>0.05) differences among the local maize evaluated. However, average number of tassels numbering 9.00±1.15 was counted from the maize planted in Odukpani soil while the highest numbers of tassels per plant of 14.33±2.18 were counted from the maize planted in Boki and Akpabuyo soils respectively (Table 8). Average days to tasseling among the maize ranges from 55.67±1.33 days in maize planted in Calabar Municipality soil to 62.69±2.60 days in maize planted in Calabar South soil. Similarly, average number of cobs per plant varied from 1.00±0.00 across 94% of all evaluated to 1.33±0.33 obtained from Yakurr soil. Average number of days to silking evaluated among the maize ecotype did not show any significant (p>0.05) differences among the ecotypes. The least number of days to silk development in maize was recorded from Akamkpa soil (63.67±1.20 days) while the highest number of days to silk development was counted from maize planted in Yakurr soil (68±0.58 days.
The high acidity values for the study area could be attributed to the present of high sulphate derivable from domestic waste and the acidity is suggested to be proportional to the amount of sulphate present in the water. Maize plants do not tolerate acidity below pH 3.0 critical level (Ubi, et al., 2016; Adu, 1992)
. In general, it may be suggested that irrigation water below a pH of 3.5 may be unsuitable for rice growth in the state as yields of maize could be reduced due to sulphur accumulation (Gweshengwe et al., 2020; Binswanger and Pringal, 1988)
Calcium and Magnesium (Ca, Mg) are cations (positively charged ions) which are present in soil. In most cases the sum of Ca and Mg are reported in milliequivalents/liter. Together Ca + Mg may be used to establish the relationship to total salinity and to estimate the sodium hazard. Cation exchange capacity is low in some places with attendant implication on nutrition and holding capacity. Acidity indicator showed high degree of acidic soils within the state which is inimical to maize crop production. Liming option can be used to properly address this (Bonhemme et al., 1994).
Fertility ranking of nutrients in terms of their values in the bulk soils on the average showed that potassium was all high, organic carbon was high to medium, total nitrogen was high to medium while available phosphorus was high, medium and low (Fig 7). Ranking the nutrients in terms of the percentages in the soil samples gave a similar trend with maize, indicating that the uptake of nitrogen was significantly higher than values of either P, K, Ca, Mg, B or Zn under similar experimental condition (Beltrab et al., 1996).
Fig 7: Ratings for soil fertility classes in Nigeria (FAO, 1996).
These findings in the present study may be attributed to the fact that no treatment was applied in the cause of the research on the local maize. Hence, the contrast with the reports of (Agbachom et al., 2022, Christo and Onuh, 2005)
, all of whom have reported that yield attributes of maize varied (p<0.05) significantly among maize varieties placed on different fertilizer trials. This present result is contrary to the reports because of the non- application of fertilizer treatments to the test crops as reported by (Eze and Obi, 2008; Eshiet, 1985)
. It was also gathered from the present study that days to tasseling, number of tassels per plant, number of cobs per plant and days to silking did not differ (p<0.05) significantly among the evaluated maize ecotypes. This also agrees with the reports and findings by (Ubi et al., 2016),
who in their various works reported that the days to tasseling, number of tassels per plant, number of cobs per plant and days to silking did not differ (p<0.05) significantly among the evaluated maize ecotypes treated with different organic fertilizers (Kalu et al., 2022).
The evaluation provides the baseline fertility data through which subsequent and future soils can be evaluated for decision on best management practices to improve soil productivity on a sustainable basis and intensification of agriculture through an integrated approach that involves land and nutrient management to enhance food security and farm income.