Response of Rain-Fed Upland Rice (Oryza Sativa L.) to Different Rates of Nitrogen and Phosphorus Nutrients on Vertisols of North Western Amhara, Ethiopia

Keywords

Nitrogen; Phosphorus; Upland Rice; Yield.

Abstract

A field experiment was carried out at Metema and Tach Armachiho districts of North Western Amhara to investigate the effect of nitrogen and phosphorous fertilizer rates on yield and yield components of upland rice during the main cropping season of 2020/2021. At both experimental sites, a factorial combination of four levels of nitrogen (0, 46, 92 and 138kg ha-1) and three level of P2 O5 (0, 23, 46 kg ha-1) were tested in randomized complete block design with three replications. A combined analysis of variance revealed highly significant (p<0.01) difference among the traits panicle length, number of effective tillers and grain yield for the interaction effect of Nitrogen and Phosphorus nutrients rates while thousand seed weight was significant (p<0.05). For other traits recorded, non-significant interaction effect was observed while significant for one or two of the nutrient rates applied. The combined application of 92 and 46 kg N - P2 O5 ha-1 gave yield of 6170 kg ha-1 which is higher than other fertilizer rate interactions. The partial budget analysis also indicated that the application of 92 and 46 kg N - P2O5 ha-1 had the highest net benefit (Birr 119,245.3 ha-1), with acceptable marginal rate of return (1151.48%) as compared to other treatments. Therefore, application of 92 kg N ha-1 and 46 kg P2 O5 ha-1 is recommended for upland rice growers in both Tach Armachiho and Metema areas and other similar agro-ecologies

Abstract

A field experiment was carried out at Metema and Tach Armachiho districts of North Western Amhara to investigate the effect of nitrogen and phosphorous fertilizer rates on yield and yield components of upland rice during the main cropping season of 2020/2021. At both experimental sites, a factorial combination of four levels of nitrogen (0, 46, 92 and 138kg ha-1) and three level of P2 O5 (0, 23, 46 kg ha-1) were tested in randomized complete block design with three replications. A combined analysis of variance revealed highly significant (p<0.01) difference among the traits panicle length, number of effective tillers and grain yield for the interaction effect of Nitrogen and Phosphorus nutrients rates while thousand seed weight was significant (p<0.05). For other traits recorded, non-significant interaction effect was observed while significant for one or two of the nutrient rates applied. The combined application of 92 and 46 kg N - P2 O5 ha-1 gave yield of 6170 kg ha-1 which is higher than other fertilizer rate interactions. The partial budget analysis also indicated that the application of 92 and 46 kg N - P2O5 ha-1 had the highest net benefit (Birr 119,245.3 ha-1), with acceptable marginal rate of return (1151.48%) as compared to other treatments. Therefore, application of 92 kg N ha-1 and 46 kg P2 O5 ha-1 is recommended for upland rice growers in both Tach Armachiho and Metema areas and other similar agro-ecologies.

INTRODUCTION

Rice (Oryza sativa L.) belongs to the family Poaceae; it is an essential food crop and a major food grain for more than half of the world’s population [1]. It is a cereal crop that has been gathered, consumed and cultivated by many people worldwide for more than 10,000 years, longer than any other crop [2]. To meet the food demand of an ever-increasing human population, the world’s rice grain production should be increased, while rice straw, after being chopped into fine parts, is used as animal feed. The global rice cultivation was estimated at total area 163 million ha with annual production averaging 730.2 million tons [3]. Rice production in Ethiopia has begun in recent years and is expected to grow. Although rice has been introduced to the country very recently, it is a productive crop next to maize in the country and is among the target commodities that have received due emphasis in the promotion of agricultural production by the government of Ethiopia to ensure household as well as national food security in the country [4].food crops, normally without any fertilizer used [5]. The major rice producing regions in the country are the Amhara, Oromia and South and Ethiopia regions with a share of 76%, 14.9%, and 5.2%, respectively [6]. Rice cultivation, however, continues on potential land in the country [7]. Currently, rice is showing an increasing trend in Ethiopia in terms of the area of production as it increased from 24,434 ha in 2000 to 57,575.72 ha in 2019 [8]. Despite the fact that rice was introduced to Ethiopia 50 years ago, its production and productivity remain low. The average national yield of rice is about 2.96 t ha-1 [8] which is lower compared to the world average productivity of 5.1 t ha-1. This low rice productivity in the country is associated with a lack of various N and P sources of fertilizer and improved rice varieties [9]. Poor soil fertility is among the major factors limiting rice production in Ethiopia. Nitrogen, phosphorus, and potassium are applied as fertilizers in large quantities to rice fields and a deficiency of either of the nutrients leads to yield losses [10]. Nitrogen and phosphorus is often cited as the most limiting nutrients in the agricultural soil of Ethiopia. Relatively, those nutrients are deficient in valleys where nitrogen is subjected to leaching, while the limited availability of phosphorus is observed due to several factors [11]. Even though determination of an appropriate dosage of application would be both economical and appropriate to enhance the productivity and consequent profit of the grower, there are no scientific findings for the determination of the optimum N and P fertilizer level in the study area. Therefore, the objective of the study was to develop optimum rates of nitrogen and phosphorous nutrients for upland rice (NERICA-4) which could be used to enhance rice production increment in Metema and Tach Armachiho districts.

MATERIALS AND METHODS

Description of the Study Area

Field experiment was conducted in Metema and Tach Armachiho districts during the main cropping season of 2020. These districts are located in the West Gondar Zone and Central Gondar of the Amhara national regional state, Ethiopia respectively. Metema district is 912 km from the capital city Addis Abeba and 200 km from Gondar and geographically located at 120 47’ Latitude to 38 027’ [12]. It is bounded by Sudan. The altitude of the Metema district ranges from 550 to 1608 meters above sea level (m.a.s.l). The mean maximum and minimum temperatures in the area are about 40.0 °C and 15.0°C, respectively. The mean annual rainfall in the area is about 650.5 mm and it is erratic and uneven in distribution. Tach Armachiho is located at latitude 130 19’ 60’’ and longitude 360 44’60’’. The district’s elevations range from 550 to 1600 meters. The mean maximum and minimum temperatures in the area are about 34.0°C and 13.0°C, respectively. The average annual rainfall in the area ranges between 600 and 605mm. In both districts, the rainy months extend from June until the end of September. However, most of the rainfall is received during July and August. The study area had a mono-modal rainfall characteristic. The location represents the major rice-producing agro ecology of the region. Some of the major crops grown in both districts include sorghum, sesame, cotton, soybeans and finger millet. Rice variety NERICA-4 was used for the experiment as it is high yielder variety and popular among the farmers in the study area.

Experimental Treatments, Design, Procedures and Trial Management

The treatments comprised factorial combinations of four levels of nitrogen (0, 46, 92, 138 kg N ha-1) and three levels of phosphorus (0, 23, 46 kg P2 O5 ha-1). Urea (46% N) and Triple Super Phosphate (46% P2 O5 ) were used as fertilizer sources for N and P2 O5 , respectively. A total of 12 treatment combinations was being studied in a randomized complete block design with three replications. The gross and net plot sizes were 3 m width and 3m length (9 m2) with 12 rows and 2.5 m width and 2.0 m length (5.0 m2) with 10 rows, respectively. The space between blocks, plots and row spacing was maintained at 1.5 m, 1m and 0.25 m, respectively. The date of planting was on July 2 and 3, 2020 for Tach Armachiho and Metema respectively, with a seed rate of 60 kg ha-1 at a depth of 3-5 cm. Except for the control plots, all phosphorus nutrient was applied at planting, while nitrogen was applied in splits. All other management practices were applied as per the general recommendations for rice. Initial soil samples were taken following the procedures of surface soil sampling at 0-30 cm soil depth from 5 random spots on the experimental site in a zigzag pattern by vertical insertion of the auger before planting. The samples were then air-dried, ground with a pestle and mortar, and passed through a 2 mm sieve to create a 1 kg composite sample that was labeled in plastic bags. The composite samples were taken to Gondar soil testing laboratories and Adet Research Center for selected physical and chemical properties, mainly soil texture (percent sand, silt and clay), soil pH, EC, CEC, total N, available P, Ca, K, Na, Mg, SOC and SOM. Data were collected on major agronomic and phenological characters. The collected data was subjected to analysis of variance (ANOVA) using SAS (9.0) and interpretations were drawn following the procedure described by Gomez AA [13]. Homogeneity of variances was tested using F test as described by Gomez AA [13]. According to the homogeneity test, all parameters were homogenous except days to maturity. Least significant differences (LSD) test at 1 and 5% level of probability was used. Correlation analysis was also done to examine the association between the yield and the yield-related components. The partial budget analysis as described by CIMMYT [14], was done to determine the economic feasibility.

RESULTS AND DISCUSSION

Soil Physical and Chemical Properties in the Study Areas

The soil analysis of the two sites indicated that the pH value of the soil was in the range of 6.7-7.2, which indicated that it was slightly acidic to neutral. It is suitable for rice production since rice grows well in heavy clay or clay loam soils. The texture of these soils is clay with low to moderate organic matter content and relatively easily weathering minerals (Table 1). The soil had low available phosphorus, which indicates that an additional P fertilizer is required for optimum crop growth and yield [15]. The result of the experimental area for total nitrogen was medium according to the rating of [16].

Days to 50% heading and days to 90% physiological maturity

The combined ANOVA indicated that the main effect of N and P rates and their interaction did not show significant difference on days to 50% heading and 90% days to maturity (Table 2).

Effect of Treatments on growth parameters of upland rice

Analysis of variance showed that the main effects of nitrogen (P<0.001) and phosphorous (P<0.01) fertilizer rates had significant on plant height and panicle length while their interaction had not been significant (P<0.05) on plant height but significant to panicle length (Table 2). Concerning the nitrogen rate, the tallest plant height (114.9 cm) was recorded at the highest nitrogen rate of 138 kg ha-1, while the shortest plant height (62.57 cm) was recorded at the control without N application (Table 6). In line with the present finding [17], reported that shorter plant height was noted at the control without N fertilizer application. With regard to phosphorous rate, the tallest rice plants (85.78 cm) were recorded at plots fertilized with 46 kg P2 O5 ha-1 while the shortest plants (79.9 cm) measured from the control without P application (Table 6). In line with the present results [18], and [19] reported significant effects of N application on plant height (Table 3&4). The longest panicle length (22.6cm) exhibited the interaction effects of 138kg ha-1 N and 46 kg of P2 O5 rates, while the shortest panicle length (14.5cm) was recorded from the control treatments (Table 7). In line with the findings of the present study [19]), reported that the application of nitrogen and phosphorus fertilizers significantly enhanced the growth of upland rice panicle length (Table 8).

Table 1: Selected soil physicochemical properties of the experimental site.

CEC=Cation Exchange Capacity, EC=electrical conductivity, ppm=Part per million.

Table 2: ANOVA for phenological and growth parameters of Upland rice as affected by rate of N and P₂O₅ applications at North Western Gondar, Ethiopia in 2020

DF= degree of freedom; DM=days to maturity; DH= days to heading; PL=panicle length; PH=plant height; CV= Coefficient of Variation, ns, *, ** and *** = non-significant, significantly different at 5 %, 1% and 0.1%, respectively

Table 3: ANOVA for phonological and growth parameters of Upland rice as affected by rate of N and P₂O₅ applications at North Western Gondar, Ethiopia in 2020.

DF= degree of freedom; SPP= Spikelet per panicle, ET= Effective tiller; NET=none effective tiller, TT=Total tiller; CV= Coefficient of Variation, ns, *, ** and

*** = non-significant, significantly different at 5 %, 1% and 0.1%, respectively

Table 4: ANOVA for phonological and growth parameters of Upland rice as affected by rate of N and P₂O₅ applications at North Western Gondar, Ethiopia in 2020

DF= degree of freedom; NFG= number of filled grain, TSW= Thousand seed weight; GY=Grain yield, BY=Biomass yield; CV= Coefficient of Variation, ns, *, ** and *** = non-significant, significantly different at 5 %, 1% and 0.1%, respectively

Table 5: ANOVA for phonological and growth parameters of Upland rice as affected by rate of N and P₂O₅ applications at North Western Gondar, Ethiopia in 2020

DF= degree of freedom; STY=Straw yield, HI=Harvest index CV= Coefficient of Variation, ns, *, ** and *** = non-significant, significantly different at 5 %, 1% and 0.1%, respectively

Table 6: The main effects of nitrogen and phosphorous rates on Plant height of rice in 2020.

Means followed by the same letters are not significantly different at 5% level of significant; LSD: Least Significant Difference at 1 and 5% level of significant, CV: coefficient of variation (%).

Table 7: The interaction effect of N and P fertilizer rates on panicle length (cm) of upland rice

ns, *, ** and = non-significant, significantly different at 5 %, and 1% respectively. Means followed by the same letter are not significantly different at 5% level of significance; LSD= least significant difference; CV= coefficient of variance.

Table 8: The interaction effect of N and P fertilizer rates on number effective tiller/m2 of upland rice

Table 9: Effect of nitrogen fertilizer rate on grain filled per panicle of upland rice.

Means followed by the same letters are not significantly different at 5% level of significant; LSD: Least Significant Difference at 1 and 5% level of significant, CV: coefficient of variation (%).

Number of