Keywords

Weed; Wheat; Herbicide; Evaluation; Hadiya

Introduction

Teff (Eragrostis tef /Zucc. / Trotter) is a versatile cereal crop concerning adaptation for the diverse agro-climatic and soil conditions. For this reason, about 2.8 million hectares of land are cultivated annually, covering more than 28% of the total area annually under cereals in Ethiopia. However, its grain yield productivity level is generally low and equal to 1.15 Mg ha–1. Nitrogen and phosphorus nutrients are the major tef yield-limiting factors, the unbalanced and un-optimal fertilization of Ethiopian soils by applications of only DAP and urea (N and P containing fertilizers) for a long period has led to severe nutrient mining of the agricultural soils, particularly when the entire crop biomass (grain and stover) is removed from the land. Such low levels of tef yield are widely believed to be due to low soil fertility caused by low and unbalanced fertilizer application 1.

On the other hand, continuous application of DAP (Di-Ammonium Phosphate: 18%-46% N-P2O5) containing only Nitrogen (N) and Phosphorus (P) without due consideration of other nutrients is known to cause depletion of secondary and micronutrients. Recently, the agricultural extension program has promoted a blanket recommendation of 100 kg DAP and 100 kg urea/ha for all cereal crops and soil types but the actual application rate is 65 kg DAP and 45 kg urea/ha. The low and unbalanced fertilizers application together with poor soil fertility management is presented as the major cause for low agricultural productivity in Ethiopia 1. Under such conditions, the application of multinutrient blended fertilizers is acknowledged for being able to enhance the productivity and nutrient use efficiency of crops.

Recently, according to the soil fertility map Ethiopia soil analysis data revealed that the deficiencies of most of the nutrients such as nitrogen (86%), phosphorus (99%), sulfur (92%), born (65%), zinc (53%), potassium (7%), copper, manganese, and iron were widespread in Ethiopian soils. Similarly, Asgelil et al. found that the soil analyses and sitespecific studies also indicated that elements such as K, S, Ca, Mg and micronutrients (Cu, Mn, B, Mo and Zn) were becoming depleted and deficiency symptoms were observed in major crops in different parts of the country. Inorganic fertilizers have been an important tool to overcome soil fertility problems and are also responsible for a large part of the food production increases.

The drive for higher agricultural production without balanced use of fertilizers created problems of soil fertility exhaustion and plant nutrient imbalances not only of major but also of secondary macronutrient and micronutrients. Similarly 3,4 stated that the deficiencies of secondary macronutrients and micronutrients will arise if they are not replenished timely under intensive agriculture. Consequently, to overcome this problem, multi-nutrient balanced fertilizers containing N, P, K, S, B and Zn in blended form have been issued to ameliorate site-specific nutrient deficiencies and thereby increase crop production and productivity.

Having considered the problems outlined above, the Ethiopian government has been promoting the use of multinutrient blend fertilizers since 2015. The promotion of blend fertilizer follows from the results of the soil fertility survey and preparation of the regional nutrient deficiency atlas of the country under the Ethiopian Soil Information System project. To supply sulfur and Boron commercial fertilizer, DAP is replaced by NPSB. Since the composition of newly introduced fertilizer differs from that of familiar fertilizer (DAP), the appropriate rate is not determined, and insufficient information for Tef production in the study area. Therefore, this research aimed to determine the optimum level of NPS-B by supplementing N from urea for maximum yield of tef production and to determine the economically optimum level of NPS-B by supplementing N from urea fertilizer at Halaba district, Southern Ethiopia.

Methods

Description of the experimental area

The study was conducted during the 2019-2020 cropping season in the Halaba districts of Southern Ethiopia. The geographic locations of the experimental sites in Halaba (7°24’53.87” N and 38°6’55.54” E at an altitude of 1790 m.a.s.l.). The major crops are grown in the area where maize, wheat, sorghum, barley, tef, and pepper. The dominant soil type in the study area in Andisols.

Experimental set-up and procedure

The experimental sites were prepared for sowing using standard cultivation practices and were plowed using oxendrawn implements. The experiment was laid out in randomized complete block design with three replicates for each treatment and detail of the treatments (Table 1). The blended and phosphorus-containing fertilizers from NPSB and Triple Superphosphate (TSP) respectively were basally applied once at sowing to minimize losses and increase use efficiency. Tef (Quncho DZ-Cr-387 variety) was used. The nitrogen fertilizer from Urea was applied in the row two times; half at sowing and the other half during the maximum growth; between the third and fourth weeks of sowing, and at the full tillering stage. All other agronomic management practices were applied as per recommendation. The necessary data were collected at the right time and crop growth stage.

Crop, soil data sampling and analysis

The crop yield and yield components collected included several effective tillers, days to 50% flowering, days to panicle emergence, days to maturity, plant height, panicle length, grain yield, biomass yield and seed weight. Representative composite surface soil samples were collected from 0 cm-20 cm depth at each experimental unit just before sowing. After manual homogenization, the samples were ground to pass a 2 mm sieve. Soil particle size distribution was determined by the Boycouos hydrometric method 5; pH of the soils was measured in water suspension in a 1:2.5 (soil: water ratio); organic carbon was determined using the wet oxidation method 6; total nitrogen was determined using Kjeldahl digestion with concentrated H2SO4 and K2SO4-catalyst mixture 7 available P was determined using the Olsen method 8; total sulfur in soil extracts was done using Turbidimetric method. The cation exchange capacity was determined after extracting the soil samples by ammonium acetate method (1N NH4O Ac) at pH 7.0 Exchangeable Acidity (EA) Al+3 and H+ were determined from a neutral 1N KCl extracted solution through titration with a standard NaOH solution.

Table 1: Detail of treatment set up and nutrient levels. The nutrients level of in 100 kg of NPS-B were (18.1 N-36.1 P2O5 -0.0 K2O+6.7 S+0.0 Zn+0.71 B).