Growth responses of C3 and C4 crops to soil physico-chemical properties in Rivers State, Nigeria

This study evaluated the growth responses of C3 and C4 crops to soil physico-chemical properties in Rivers State. The C3 crop refers to Pumpkin and Cucumber while C4 crop refers to Amaranthus in this study. The research work made use of three crops (Pumpkin, Cucumber and Amaranthus in some selected sites in Rivers State and the study was carried out both in the dry and wet seasons. Soil samples were collected from both topsoil (0-15cm) and subsoil (15-30cm). The crops and soil samples were taken to the laboratory for further analysis. Mean values and standard deviations were used to describe the analysis while analysis of variance (ANOVA), Duncan, and Kruskal Wallis were used to test the hypotheses. All analyses were carried out using Statistical Package for Social Sciences (SPSS) 21.1 Version. Findings showed that sand content in Oyigbo had the highest in the topsoil at 95.37% while Etche had highest in silt content at 1.87%. For the subsoil, Oyigbo also had the highest sand content at 93.30% while Ikwerre had the highest clay content at 6.63% in subsoil. For chemical properties of soil, total organic carbon and magnesium were highest in Oyigbo at 1.91% and 24.00% respectively for topsoil while for subsoil potassium was highest in Ikwerre at 8.30%. It was also discovered C3 and C4 crops planted in Oyigbo, Etche and Ikwerre varied from the nutrients standards recommended by USDA (2014). The following nutrients and minerals were considered: energy, carbohydrates, protein, total fat, cholesterol, dietary fiber, vitamins, folates, niacin, pantogenic acid, pyridoxine, riboflavin, thiamin, Electrolytes, sodium, potassium, calcium, iron, magnesium, manganese phosphorus, and zinc. For standards recommended by (USDA 2014), only energy, iron, zinc, manganese, vitamin E, riboflavin, pyridoxine, niacin and pantothenic acid at Oyigbo met the standards, also Riboflavin and iron at Ikwerre met the (USDA 2014) standards while only folates at Etche met the (USDA 2014) standards. The study recommended that the soil nutrients and pH should be improved across the three locations and the acidic nature of both topsoil and subsoil should be improved by neutralizing the soil with lime.


Introduction
Soil physico-chemical properties in our environment contribute to the growth of major crops in terms of physiological appearances and nutrients content [1]. Globally, this has become a major concern because when the soil in the environment does not meet up the standards required for such crop the effort of many farmers becomes unfruitful because such crop becomes unsafe for human consumption. Most crops generates their nutrients from the soil and the soil contains both the physical and chemical properties such as: the clay, sand, and the silt while the chemical properties such as the total organic carbon, available potassium, total nitrogen, exchangeable magnesium, exchangeable calcium, TEA are also found in the soil. There is a recommended standard for both C3 and C4 crops as indicated by [2]. [3] posited that there could be an alteration in crops when there is a change in soil's environment. Such alteration can effects the following: reduction in sugar and nutrient contents of plants, susceptibility for less development in the leaf, changes in stomata conductance, vegetative growth effect, and plant's variations in several locations. Consumption of crops should be based on recommended standards as seen in several countries where food production is controlled by a Federal Agency like in the case of Nigeria, we have National Agency for Food, Drug, Administration and Control (NAFDAC) the same is also applicable to crops produced in our environment. Because of changes in the climate variation such as evapotranspiration variation, temperature variation, carbon dioxide variation and other greenhouse gases there is need to measure the standards of farm produce before human consumption. This is what this study intends to achieve with USDA 2014 standards on crops produced in three locations in Rivers State. [4] maintained that many crops have lost their nutritional value and mineralogical standard in our environment.

Material and methods
The study area is Etche, Ikwerre and Oyigbo Local Government aresa of Rivers State in the Niger Delta Region of Nigeria. It is located in the southern region, and has been reported to be one of the major biodiversity hotspots in the world [5]' [6]. The ecosystem is home to several Crops such as Cucumber, Pumpkin and Amaranthus potentials. The three Local governments contains coal plain terrace soil that are recommended by the [7] for C3 and C4 crops. The prominent season for these locations is dry and wet seasons. The wet seasons starts from March to November while the dry seasons starts from November ending to February.The temperature (28 ±8 ºC) and relative humidity (50 -95%) is within the estimated range of the area [8]. Primary data were generated during the field data gathering using Atmometer for land level, GPS for location, and soil analyzer for soil, fertometer and crops collected where subjected to lab analysis. Soil samples were taken in various periods like the 43 rd period, 49 th periods, 56 th period, 63 rd period and 70 th periods in both dry and wet seasons [ [9], [10]. Topsoil sample was from 0-15cm while subsoil sample was from 15cm-30cm. The research design adopted in this work has a treatment combinations in Randomized Complete Block Design (RCBD) in factorial Experiment [11].

AxB Amaranth (Ok) Pumpkin (Pu) Cucumber (Cc)
Carbon dioxide (Co) AmCo PuCo CcCo Table 2 ABxC The soil sample was taken from the surface down to 15cm that is from 0-15 cm and from 15cm to 30cm, it was also sent for laboratory test and the result is stated in chapter four. We took the soil temperature of the three plants starting from 0-2cm depth. This is because in planting amaranth and pumpkin, 2cm is recommended while that of cucumber 3 cm [7], [8], [9]  Land equivalent ratio to plant was also calculated, we have 5 by 5 for cucumber and pumpkin crops per bird and a total of 9 birds in a location. This gives each bird a 25 [11]  Geo-ecological data such as: evapotranspiration rates, carbon assimilates, temperature reading, physiochemical properties, relative humidity data and day length were also taken for the various locations studied etc [12], [13], [14], [15], [16].
All data were subjected to analysis in a RCBD in factorial experiment where interactions were tested for A x B; A x C, A x D, B x C, B x D, D x C, D x B others were on AB x C, AB x D, AC x D and ABC x D, they were subjected to ANOVA and Duncan analysis with error mean square.

Analysis of physico-chemical properties of soil and the comparison of the nutrients values with [3]
Standards.
The chemical analysis of soil properties shown in Table 4 reveals that pH in the three locations was weakly acidic ranging from 5.28 in Oyigbo to 6.10 in Etche. The  This also reflected on why there was poor growth in mostly Pumpkin across the three locations. This result conforms with the findings of [17], [18], [19]. Table 5 explains the chemical properties of soil in Etche, Oyigbo and Ikwerre and from the table, total organic carbon in the topsoil was highest at Oyigbo with 1.91%, available potassium recorded was most in Oyigbo at 13.05mg, the pH was also more in Etche at 6.10 while total exchangeable acidity was highest in Etche at 1.77mg. While at the subsoil, Total Exchangeable Acidity recorded 2.01mg in the same Etche and Total Organic carbon was more at Oyigbo with a value of 0.92. This implies that some chemical properties in the study area did not meet up to the requirement for C3 and C4 crops [19].   Table 8 shows the comparison between the nutrients and mineral values obtained in the study area with that of the [2]. From the table below, energy (kcal) recommended by USDA was 12kcal while none of the locations had up to that value, the same applied in carbon hydrates, protein, total fat, dietary fiber in Nutrients alone. In vitamin, the three locations met the standards for Folates (µg), vitamin E, while the rest did not, in minerals only manganese and zinc in Oyigbo met the standards while the rest did not. For electrolyte, sodium and potassium did not meet the required standards. This by implication means that cucumber, pumpkin and Amaranthus crops planted in these areas should be carefully consumed because of the less nutrients, minerals and electrolytes contents in them.

Conclusion
This study evaluated the growth responses of C3 and C4 crops to Soil Physio-Chemical Properties in Rivers State. A C3 crop in this study refers to Cucumber and Pumpkin while the C4 crop refers to Amaranthus. Methodologically, three locations were selected in Rivers State namely: Etche, Oyigbo and Ikwerre this is because the three locations have the coal plain terrace soil as recommended by [7] in planting Cucumber, Pumpkin and Amaranthus. Agronomic data such as: plant height, leaf number, 50% days flowering, maturity, total yields and geo-ecological data such as: evapotranspiration rates, carbon assimilates, temperature reading were collected. The study made use of Randomized Complete Block Design in factorial experiment. From the discussions of findings, it was revealed Pumpkin, Cucumber and Amaranthus responded to soil physico-chemical variations at the 43 rd , 49 th , 56 th , 63 rd and 70 th periods of observations in the field. This variation in soil physico-chemical properties also affected the crops Nutrients and mineral such as: Vitamin A, Vitamin K, Energy, Phosphorous, Protein, Height, Leaf, D/Fiber, and Cholesterol. Some of the nutrients and minerals obtained from the study did not meet up the standards recommended by [2]. Such minerals and nutrients are carbohydrates, protein, total fats, cholesterol, Vitamin A , Vitamin C, Vitamin K, Potassium, Calcium, Magnesium and Phosphorus.