(1) Application of inorganic fertilizers alone did not significantly increase wheat yields on acidic soils in southern Ethiopia, but combining fertilizers with organic amendments like farmyard manure or the biomass of Erythrina bruci led to major yield gains. (2) Integrated application of NP fertilizer with 10 tons/ha of farmyard manure or potassium increased wheat yields by over 300% at some sites. (3) On-farm trials confirmed that potassium is a limiting nutrient for wheat in acidic soils of the region.

1. THE ROLE OF SOIL ACIDITY AND SOIL FERTILITY MANAGEMENT FOR ENHANCED AND
SUSTAINED PRODUTION OF WHEAT IN SOUTHERN ETHIOPIA
Wassie Haile
College of Agriculture, Hawasa University, P.O.Box 05, Hawasa, Ethiopia. Email wassiehaile@yahoo.co.uk
Abstract
Wheat production in south Ethiopia is constrained by declining soil fertility and soil acidity. To address these constraints, experiments on effect of integrated application of organic-inorganic fertilizers and lime
application, effect of transferred biomass of Erythrina bruci and of-farm K verification trail were conducted on acidic soils of Chencha and Hagreselam in the last five years. The results revealed that application of N
and P at 23:20:0 and 46:40:0 kg/ha in the form of urea and TSP did not significantly increase the yield of wheat compared with the control at Chencha. But combined application of NP with 5 and 10 t/ha of
farmyard manure (FYM) significantly increased the grain yield. NP applied at 46:40kg/ha + 10 tha FYM increased the grain yield by 454% and 297% over the control and NP treatment applied at 46:40:0 kg/ha
alone respectively att Chencha. Application of NP with potassium (K) have also significantly increased the grain yield wheat compared with NP, control and FYM treatments. Similarly, integrated application NP +
FYM and NP + K treatments significantly increased the grain yield of wheat at Hagreselam in 2007, compared with control and either source applied alone. This implies that K is a limiting nutrient in both Chencha
and Hagereselam areas. On-farm verification study results proved that K is a limiting nutrient for wheat production in acidic soils of south. Application of lime with NP fertilizers significantly increased the yield of
wheat in these areas but the magnitude of yield improvement was not so high relative to that obtained with integrated application of inorganic-organic fertilizers and NPK treatments. E. bruci biomass applied 10
t/ha increased the grain yield by 127% over the control and produced the same yield as that obtained with recommended dose of NP (46:40 kg/ha) fertilizer at Kokate location. If NP fertilizers are continued to be
applied, It must be applied along with either with organic fertilizer such as FYM or K. The importance of K as a limiting nutrient at Chencha and Hagereselam areas has now been proved against the longstanding
conclusion that Ethiopian soils were rich in K. Thus, importation of K fertilizers might be necessary. E. bruci as an organic fertilizer should be promoted in areas where it exists abundantly.
Key word: Inorganic fertilizers, Organic fertilizer, integrated soil fertility management, wheat, Ethiopia
INTRODUCTION II. The effect of lime and NPK fertilizers on the yield of wheat
The effect of lime (0, 1.75 t/ha and 3.5 t/ha) was studied in a factorial combination of NP, NK PK and
 Declining soil fertility and soil acidity is one of the major challenges to wheat production in the southern Ethiopia.
NPK fertilizers on wheat at adic soils Hgreselam and chencha, southern Ethiopia in 2007-09.
 Application of inorganic fertilizer can adress the problem.
 But its cost is increasingly.
 more repeated use of ferilizers aggravate the depeletion of other macro and micro nutrients nutrients, acidify
soil,, promotes depletion of OM etc..
 Recently K is found to be limiting in some soils of Ethiooipia ( Abiye et al., 2004; Wassie, 2009).
 There are also soils which do not respond to NP application in the south.
 Thus, there is a need for the development and use of sound integrated soil fertility and acidity management
technology to improve and sustain crop production in Ethiopia.
 To these effects the effect of combined application of NP/NPK fertilizers with farm yard manue (FYM )and effect
of lime on wheat have been studied at acidic soils of Chencha and Hagreselam areas, south Ethiopia.
 The role of Erythrina bruci, nutrient rich, N-fixing endemic tree to Ethiopia in increasing the yield of wheat have
also been investigated
Figure 1. Effect of lime and NPK fertilizers on the grain yield of wheat at HagreSelam in 2007
I. Effect of integrated application of NP/NPK fertlizers and farm yard manure (FYM)
on the grain yield of wheat at acidic soils of Chencha and Hagreselam, South Ethiopia *N0P0 = 0:0 kg/ha N & P, N23P20 = 23:20 kg/ha N & P, N46P40 : 46:40 kg/ha N& P, N23P20K0 = 23:20:25
kg/ha N, P & K and N46P40K50 = 46:40:50 kg/ha N & P
 The experiment was conducted at Chencha & HagereSelam located at 37º.60’ E and 6º.13’ N . 6014‘ N & 38042‘ E
respectivelly.The soils of both areas are strongly acidic and P and K limited. The results revealed lime at full dose has only slightly improved the grain yield (Fig. 1). But with NP and NK
has and significantly increased compared with control and lime treatments. However, with NPK, application
 A factorial experiment consisting 3 levels (0, 5 and 10 tha-1) of farm yard manure (FYM) and 5 levels of NPK fertilizers (0:0:0, of lime did not produce significant yield difference compared with NPK treatmen alone. PK treatmnent
23:20:0, 46:40:0, 23:20:25 and 46:40:50 kgha-1) , laid out in RCB design with three replications. Wheat variety Simba was produced significantly higher yield than that NP and NK indicating that the soil is P & K limited than N.
planted as a test crop..
III. The effect of K and sulpher applied singly or in combination on the yield of
 NP treatments did not affect the grain yield at Chencha significantly increased the yield when combined with 5 and 10 t/ha wheat at on farmers, field HagreSelam conducted in 2011
FYM (Table 1).
 The highest grain yield was obtained from N46P40K50 + 10 t/ha FYM, N23P20K25 + 10 FYM and N46P40 + 10 t/ha FYM in that order The effect of K and sulphur on the yield of wheat was studied at Hagreselam area in 2011 on farmers’ field.
at Chencha. This implies that FYM has served as K source inaddition to other nutrients and none nutritional benefits.
The grain and biomass yields of wheat were found to be significantly affected by different treatments. The
Table 1. The Effect of integrated application of NP/NPK fertilizers and FYM on the grain highest grain yield of wheat was obtained from 50 kg/ha urea + 100 kg/ha DAP +43.33 KCl+50 CaSO4 than all
other treatments (Table 2). The next highest yield was obtained from 50 urea + 100 DAP+ 50 kg/ha CaSO4 .
yield of wheat at acidic soils of Chencha and HagreSelam areas of Southern Ethiopia
Table 2. The effect of potassium and sulphur applied singly or in combination on the yield of wheat
Grain Yield (q/ha)
No Treatments grown on different soil types in SNNPR in 2011.
Chencha Hagreselam
1 N0P0 + 0 FYM 6.1h 13.5d
2 N0P0 + 5 FYM 13.0gh 23.7bc
3 N0P0 + 10 FYM 17.8g 26.8abc
4 N23P20 + 0 FYM 11.3gh 26.8abcd
5 N23P20 + 5 FYM 22.1cde 27.6acd
6 N23P20 + 10 FYM 23.7bcde 29.4abc
7 N46P40 + 0 FYM 11.0gh 20cd
8 N46P40 +5 FYM 21.3def 34.6a
9 N46P40 + 10 FYM 31.0ab 29.4abc
10 N23P20K25 + 0 FYM 22.8bcde 27.6abcd
11 N23P20K25 + 5 FYM 28.0abcd 29.4abc
12 N23P20K25 + 10 FYM 33.3a 34.4a
13 N46P40K50 + 0 FYM 23.8bcd 32.8a
14 N46P40K50 + 5 FYM 30.7abc 34.1a
15 N46P40K50 +1 0 FYM 35.7a 34.9a
LSD 8.7 9.5
CV 22 19
Conclusions
IV.Effect of Erythrina bruci green biomass on th grain yield of wheat at Kokate, SNNPR
 Application of NP fertilizer did not significantly increase the yield of wheat at chencha location
The effce of green biomass of Erythrina bruci which is N-fixing and nutrient rich tree on the yield of wheat  But when it is applied with K or fram yard manure, the yield was significntly increased mplying that K is a limiting factor in the
have been studied at Kokate, south Ethiopia for two years (2010-2011). study areas.
 At Hagreselam area, NP has ignificantly increased the grain yield of wheat but it was further increased with FYM or K
Sole application of E. bruci biomass at 10 t/ha increased the grain yield by 127% over the control and  Application of limealone has only slightly increased yield of wheat in both locations
produced the same yield as that produced by recommended fertilizer for wheat production in Kokate area But the grain yield was significantly and appreciably increased when lime was applied with
(Fig. 2). The highest yield however was obtained from 50:50 combined application of inorganic and E.bruci NP
biomass.  With NPK, lime did not change the yield produced
 Onfarm verfification resultat hagreselam indicate that K is am limiting nutient at farmers field sugesting that K fertilizer should be
applied
 Erythina bruci green biomass produced significantly higher yield of wheat at Kokate, Wolaita Soddo comapred with control and
produced same yield of wheat as that yield that can be obtained with 46/40 kg/ha NP fertilizers
Recommendations
 If only inorganic fertilizers are to be applied, balanced applications of NPK at 23:20:25 kgha-
1 and 46:40:50 kgha-1 for Chencha and hagreSelam location is recommended for wheat
production respectivelly.
 Highigher yield If integrated application is to be the option 23:20:25 kg/ha NPK + 10
t/ha FYM is
Manure has to be applied at 10 t/ha or for best results
 Potassium is found to be limiting nutrient to wheat thus is recomded that , K fertilizer applied
Fig. 2. The effect of E. Bruci green biomass on the grain yield of wheat at Kokate over two years (2010-2011)
at Chencha and Selam areas.
 Application of lime as a means to mitigate soil acidity in the sudy ares have limited benfit
** a =control, b= 92 kg/ha N, c= 69 kg N/ha + 2.5 t/ha E. Bruci fresh biomass, d = 46 kg/ha N + 5 t/ha E.
Bruci fresh biomass, e = 23 kg/ha N + 7.5 t/ha E. Bruci fresh biomass and f = 10 t/ha E bruci fresh biomass
thus other options for combting soil acidity should be sought
 Application of fresh biomass of E bruci at 10 t/ha is recommended for wheat production in
Kokate area