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The poor quality of cow dung in Ghana resulting from the opportunistic feeding mode of cattle impedes its adoption due to high quantities needed for application. This calls for nutrient optimization of cattle manure with inexpensive locally available sources of organic inputs that could enhance its quality. Though large volumes of crop residues and other agro-wastes are produced on-farm, they are underutilized and mostly a nuisance. Major food crops take approximately, 44 %, 42 % and 56 % of the total nitrogen (N), phosphorus (P) and potassium (K), respectively and are found in crop residues. There is therefore the need to develop appropriate technologies for utilizing agro-wastes by transforming them into useful “resources” with potentially available plant macro and micronutrients. Common agro-wastes in Ghana include cocoa pod husk (CPH), palm kernel cake (PKC), cattle manure (CM) and poultry manure. Hence, this review sought to explore the use of crop residues and agro-minerals to improve the quality of manure and consequently its fertilizer value for soil fertility improvement and increased crop yield. The review presented an assessment of resource potentials of some crop residues and local agro-mineral as a means of enhancing the quality of CM. Using published data, the review has identified that PKC, rock phosphate (RP) and CPH have high potential for improving the N, P and K contents of CM, respectively. In conclusion, it recommends the need to extensively explore the potential of other commonly available organic resource materials for their efficacy to improve the fertilizer value of cattle manure.

Low inherent nitrogen (N), phosphorus (P), and potassium (K) contents of smallholder farms limit maize grain yield. Maize grain yield response to N, P, and K mineral fertilizer application and economically optimal rates for nitrogen (EORN), phosphorus (EORP), and potassium (EORK) were evaluated on a Ferric Acrisol within the semi-deciduous forest zone of Ghana. The nutrient rates evaluated were N (0, 30, 60, 90, and 120 kg N ha−1), P (0, 30, 60, and 90 kg ha−1 P2O5), and K (0, 30, 60 and 90 kg ha−1 K2O). The treatments were arranged in a randomized complete block with three replications using an incomplete factorial design. Nutrient responses were determined using asymptotic quadratic-plus plateau functions. The best nitrogen rate for all P and K levels was 60 kg ha−1, which gave grain yield of 5 t ha−1. Nitrogen uptake, N agronomic and N recovery efficiencies peaked at 60 kg N ha−1 while N partial factor productivity declined with increasing N application rate. Cost to grain price ratios (CP) were 1.29, 1.65, and 1.65 for N, P, and K, respectively. The EORN was 61 kg ha−1, 32% less than the recommended 90 kg N ha−1 for maize production in the semi-deciduous forest zone of Ghana. Nitrogen application had the lowest CP ratio, making its application economically profitable than P and K. The findings suggest that the application of N at 61 kg N ha−1 to maize is economically profitable than at higher application rates. However, further studies should be conducted on farmers’ fields to validate the results obtained.

A better understanding of soil fertility factors that constraint positive crop response to fertilizer inputs will facilitate the improvement of soil nutrient management. In this study, a nutrient omission trial was carried out in a greenhouse condition to identify soil chemical properties limiting in non-responsive soils and to ascertain their effect on soybean (Glycine max) production. The treatments evaluated were control (distilled water), complete nutrient solution (all nutrients), and complete solution with the omission of each of N, P, K, Ca, Mg, and S and micronutrients (Fe, Zn, Cu, Mn, B, and Mo) arranged in a completely randomized design with three replications. After the greenhouse study, the identified limiting nutrients were tested with or without FertiSoil (commercial compost) in a 3 year field experiment. Results of the soil analyses showed low fertility status of the non-responsive soils. The sufficiency quotient index revealed non-responsive soils in all the sites to be predominantly limiting in P and K. The occurrence of other limiting nutrients was also identified: Pishegu (Zn, B), Serekpere (Mg, S), Daffiama Saapare (Ca, Mg, S), and Naaga (Mg, S, Zn, B). The nutrient inputs positively influenced soybean yield response in all the locations. The application of PKZnB with FertiSoil and FertiSoil alone significantly increased soybean grain yields by 585 and 477 kg ha−1, respectively, at Pishegu. Soybean grain yields also increased by 585, 573, and 364 kg ha−1 under the FertiSoil, PKMgS + FertiSoil, and PKMgS applications at Serekpere, respectively. At Daffiama Saapare, the highest (103%) percent increase in soybean grain yield was recorded from the combined application of PKMgSCa and FertiSoil. However, the application of FertiSoil and PKMgSCa singly equally increased soybean grain yield by 77%. Percent soybean grain yield increases of 86, 84, and 74% were observed when PKMgSZnB + FertiSoil, PKMgSZnB, and FertiSoil were applied, respectively, at Naaga. In absolute terms, 83% of the fields had a positive response to mineral fertilizer and 93% to FertiSoil and mineral fertilizer + FertiSoil applications. Organic amendment and/or site-specific fertilizer applications are the best options for alleviating poor or no crop responses to inputs and improve productivity on non-responsive soils.

Soil erosion is a major constraint to crop production on smallholder arable lands in Sub‐Saharan Africa (SSA). Although different agronomic and mechanical measures have been proposed to minimize soil loss in the region and elsewhere, soil management practices involving biochar‐inorganic inputs interactions under common cropping systems within the framework of climate‐smart agriculture, have been little studied. This study aimed to assess the effect of different soil and crop management practices on soil loss characteristics under selected cropping systems, typical of the sub‐region. A two‐factor field experiment was conducted on run‐off plots under different soil amendments over three consecutive cropping seasons in the semi‐deciduous forest zone of Ghana. The treatments, consisting of three soil amendments (inorganic fertilizer, biochar, inorganic fertilizer + biochar and control) and four cropping systems (maize, soyabean, cowpea, maize intercropped with soyabean) constituted the sub‐plot and main plot factors, respectively. A bare plot was included as a soil erosion check. Seasonal soil loss was greater on the bare plots, which ranged from 9.75–14.5 Mg ha⁻¹. For individual crops grown alone, soil loss was 31%–40% less under cowpea than under maize. The soil management options, in addition to their direct role in plant nutrition, contributed to significant (p 2 under soyabean cropping system but had VCR

Keeping livestock overnight on fallow arable lands (Corralling) is a traditional method of soil fertility amendment in West Africa. However, there is limited quantitative data on the interaction effects of stocking density of sheep and goats corralling (SDSG), maize plant density (MPD) and nitrogen fertilizer rate (NFR) on soil quality and yield of maize. A 2-yr study was conducted to determine the interaction effects of three SDSG (0, 70, and 140 head ha–¹), three MPD (66,667, 100,000, and 133,333 plants ha–¹) and three NFR (0, 60, and 90 kg ha–¹ N) on soil quality index (SQI) and maize yield in northern Ghana. The study was conducted using a split-split plot experiment replicated on eight farms. An adult sheep or goat was corralled in an area of 4 m² and 1 m² for the 70 and 140 head ha–¹ SDSG respectively for five nights during the dry seasons of 2014 and 2015 cropping seasons. Principal component and correlation matrix analysis were used to select minimum data set for SQI. The SQI for sheep and goats corralling increased by 51% compared with the control. The SDSG×MPD, SDSG×NFR and MPD×NFR interactions were significant on maize grain and biomass yields. The results suggest that, small-scale maize-livestock farmers could use either SDSG of 70 head ha–¹ with 90 kg ha–¹ NFR or SDSG of 140 head ha–¹ with 60 kg ha–¹ NFR and MPD at 133,333 plants ha–¹ to increase grain yield on Ferric lixisols in northern Ghana and similar ecologies in West Africa.

This is the accepted manuscript version of the work published in its final form as Benedicta Essel; Robert Clement Abaidoo; Andrews Opoku; Nana Ewusi-Mensah.Communications in Soil Science and Plant Analysis, 52 (5), 511-521.https://doi.org/10.1080/00103624.2020.1862151 Deposited byshareyourpaper.organdopenaccessbutton.org. We've taken reasonable steps to ensure this content doesn't violate copyright. However, if you think it does you can request a takedown by emailinghelp@openaccessbutton.org.

Inherently low concentrations of soil nutrients and erratic rainfall pattern in sub-Sahara Africa limit soybean response to rhizobia inoculant and P-fertilizer. The study was conducted to: (i) improve soybean response to rhizobia inoculation and P-fertilizer through the addition of organic manure; (ii) enhance rain water use efficiency and (iii) determine the economic viability of combined application of the three factors in soybean cropping systems in the Northern region of Ghana. A factorial experiment with two levels of rhizobia inoculant, two levels of Phosphorus, two different kinds organic manure [fertisoil (a commercially prepared compost from urban waste, rice husks, of poultry manure and shea butter waste) and cattle manure] and a control arranged in randomized complete block design with three replications was established on farmers' fields. The combined application of rhizobia inoculant, P-fertilizer, and organic manure markedly increased nodulation, shoot biomass, haulms, harvest index (HI), P agronomic efficiency (P-AE), and rain water use efficiency (RUE) compared to the control. The combined application of rhizobia inoculant, P-fertilizer, and fertisoil increased grain yield by four-folds whereas the combined application of rhizobia inoculant, P-fertilizer, and cattle manure increased grain yield by three- folds. Harvest index, P-AE, and RUE were relatively higher with the fertisoil treatment combinations than with the cattle manure combinations and the control treatment. The application of rhizobia inoculant, P-fertilizer in combination with fertisoil was profitable with VCR of 2 as compared to the combination of cattle manure which had a VCR of 0.40. The results showed that fertisoil offers a better option of improving soybean response to rhizobia inoculant and P-fertilizer; and has the potential to enhance rain water use efficiency. However, the long term benefit must be quantified.

The interaction effect of stocking density of sheep and goat corralling (SDSG), maize planting density (MPD), and N fertilizer rate (NFR) on soil properties, weed diversity, and maize yield were ev...

The hypothesis that livestock corralling improves soil properties and weed species richness was investigated in a 2-year on-farm trial conducted in Sudan savanna agro-ecology of Ghana. The effect of three stocking densities of sheep and goats corralling (0, 70 and 140 head ha−1) on soil properties and weed species diversity was evaluated in a randomized complete block design with eight replicates. Sheep and goats weighing 27 ± 2.0 and 24 ± 1.5 kg, respectively, were corralled on fallow arable lands from 19: 00 to 06: 00 GMT hours daily for 178 nights during 2014 and 2015 cropping seasons. Soil parameters measured include pH, organic carbon (OC), total nitrogen, available phosphorus, exchangeable potassium, microbial biomass carbon, microbial biomass nitrogen, soil microbial quotient, earthworm cast, bulk density, porosity, and moisture. Soil properties and weed species diversity increased (P

Over the years, a scarcity of information on nutrient gains or losses has led to overemphasis being placed on crop yields and economic income as the direct benefits from fertilizer micro-dosing technology. There is increasing concern about the sustainability of this technology in smallholder Sahelian cropping systems. This study was designed in the 2013 and 2014 cropping seasons to establish nutrient balances under fertilizer micro-dosing technology and their implications on soil nutrient stocks. Two fertilizer micro-dosing treatments [2 g hill−1 of diammonium phosphate (DAP) and 6 g hill−1 of compound fertilizer Nitrogen-Phosphorus-Potassium (NPK) (15-15-15)] and three rates of manure (100 g hill−1, 200 g hill−1 and 300 g hill−1) and the relevant control treatments were arranged in a factorial experiment organized in a randomized complete block design with three replications. On average, millet (Pennisetum glaucum (L.) R.Br.) grain yield increased by 39 and 72% for the plots that received the fer...

An article published by American Journal of Experimental Agriculture 10(2): 1-11, 2016, Article no.AJEA.20072

SUMMARYRecent studies have reported the benefits of fertilizer microdosing in increasing crop yields in low input cropping systems. Little information is however available on the mechanisms underlying this effect. The objective of this study was therefore to explore the root-based mechanisms governing the growth enhancing phenomena of the fertilizer microdosing technology. A two-year experiment was conducted at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Research Station in Niger. Four treatments comprising (i) 2 g hill−1of diammonuim phosphate (DAP), (ii) 6 g hill−1of compound fertilizer NPK, (iii) broadcasting of 200 kg ha−1of compound fertilizer NPK (recommended rate) and (iv) unfertilized control was arranged in a randomized complete block design with four replications. On average, fertilizer microdosing treatments (2-g DAP hill−1and 6-g NPK hill−1) achieved 86% and 79% of the grain yields recorded from broadcasting of 200-kg NPK ha−1, respectively, in 2013 and 2014. The leaf area index and leaf chlorophyll content significantly increased with fertilizer microdosing at the early stage of millet growth. At the same stage, fertilizer microdosing enhanced the lateral root length density in the topsoil (0–20 cm) by 72% and 40% at respective lateral distances of 25 cm and 50 cm from the centre of the hill compared with broadcast of 200-kg NPK ha−1. Fertilizer microdosing did not significantly change soil pH in the root zone. It is concluded that the positive effect of fertilizer microdosing in increasing millet yield results from the better exploitation of soil nutrients due to early lateral roots proliferation within the topsoil.

Limited availability of soil organic amendments and unpredictable rainfall, decrease crop yields drastically in the Sahel. There is, therefore, a need to develop an improved technology for conserving soil moisture and enhancing crop yields in the Sahelian semi-arid environment. A 2-year field experiment was conducted to investigate the mulching effects of Acacia tumida pruning relative to commonly applied organic materials in Niger on millet growth, yields and water use efficiency (WUE) under fertilizer micro-dosing technology. We hypothesized that (1) A. tumida pruning is a suitable mulching alternative for crop residues in the biomass-scarce areas of Niger and (2) combined application of A. tumida mulch and fertilizer micro-dosing increases millet yield and water use efficiency. Two fertilizer micro-dosing options (20 kg DAP ha−1, 60 kg NPK ha−1) and three types of organic mulches (millet straw, A. tumida mulch, and manure) and the relevant control treatments were arranged in factorial experiment organized in a randomized complete block design with four replications. Fertilizer micro-dosing increased millet grain yield on average by 28 %. This millet grain yield increased further by 37 % with combined application of fertilizer micro-dosing and organic mulch. Grain yield increases relative to the un-mulched control were 51 % for manure, 46 % for A. tumida mulch and 36 % for millet mulch. Leaf area index and root length density were also greater under mulched plots. Fertilizer micro-dosing increased WUE of millet on average by 24 %, while the addition of A. tumida pruning, manure and millet increased WUE on average 55, 49 and 25 %, respectively. We conclude that combined application of micro-dosing and organic mulch is an effective fertilization strategy to enhance millet yield and water use efficiency in low-input cropping systems and that A. tumida pruning could serve as an appropriate mulching alternative for further increasing crop yields and water use efficiency in the biomass-scarce and drought prone environment such as the Sahel. However, the economic and social implications and the long-term agronomic effects of this agroforestry tree in Sahelian millet based system have to be explored further.

Soil compaction is a major problem associated with conventional agriculture characterized by usage of heavy farm machinery. However, only few studies have quantified the dynamics of soil nutrients in compacted soils under restorative interventions, particularly in sub-Saharan Africa. Field and pot experiments were therefore conducted to evaluate the extent to which soil compaction modulates NH4+ and NO3− dynamics under organic amendment in Ghana. Soils were bulked to three (1.3, 1.5, and 1.7 Mgm−3) and four (1.3, 1.5, 1.7 and 1.9 Mgm−3) density levels in field and pot experiment respectively. The treatments were laid out in a factorial experiment, replicated three times with poultry manure applied at 4 and 6 t ha−1 with a control (0 t ha−1). Mineral N generally increased from 21 to 42 days after amendment (DAA) and declined at 63 DAA in both experiments. Soil compaction decreased NO3− more than NH4+ levels, the effects being more pronounced at 21 and 63 DAA in the field experiment. Application of poultry manure (PM) at 6 t ha−1 offsetted, to a large extent, the impact of soil compaction. The 4 and 6 t ha−1 PM produced similar (p > 0.05) grain yields of 3000.00±169.04 and 3004.44±277.99 kg ha−1 in the field experiment respectively. However, grain yield decreased by 135% in compacted soil at 1.7 Mgm−3, which received no amendment, compared to same compacted soil that received 4 t ha−1 poultry manure in the field experiment. Our finding suggests that addition of 4 t ha−1 PM is required for yield improvement in compacted soils less than 1.7 Mgm−3.

Inadequate nutrient supply and insufficient rainfall are the most important limiting factors for crop production in the Sahelian agro-ecological zones. Targeted technology application may help to improve the efficient use of limited nutrient and water resources. The objective of this study was to determine the optimal combination of fertilizer micro-dosing and manure application rates for improved millet yield and enhanced water use efficiency in low input millet-based cropping system. A two-year field experiment was conducted at a research station in Niger using a randomized complete block design with three replications. The treatments consisted of the factorial combination of: (i) two fertilizer micro-dosing options (20 kg ha−1 of diammonium phosphate (DAP) and 60 kg ha−1 of NPK corresponding to 2 g hill−1 of DAP and 6 g hill−1 of NPK, respectively), (ii) cattle manure at four application rates (0 kg ha−1, 1000 kg ha−1, 2000 kg ha−1, 3000 kg ha−1) and (iii) two methods of manure application (broadcasting and hill placement). Millet grain yields under fertilizer micro-dosing combined with manure was increased on average by 59%, 83% and 113% for 1000 kg ha−1, 2000 kg ha−1 and 3000 kg ha−1, respectively compared with fertilizer micro-dosing alone. Combined applications of manure and fertilizer micro-dosing increased water use efficiency significantly. Hill placement of manure increased total dry matter on average by 23% and water use efficiency by 35% relative to manure broadcasting. The total root length density was increased by 66% and 42% in hill placement of manure at 25 cm and 50 cm, respectively, from the hill centre compared with manure broadcast. These results indicate that millet production with the fertilizer micro-dosing technology can be improved further by hill-placement of manure. The combination of 2000 kg ha−1 of manure and 20 kg DAP ha−1 hill-placed were most promising for increasing millet yield and the efficient use of limited nutrients and water in Sahelian millet based systems. There is need for testing this technology further together with farmers to valuate its effectiveness.

Soil erosion is a multifactor threat to crop production and the environment. Most studies on soil erosion characterization have not focused on soil nutrient loss associated with erosion. The aim of this study was therefore to quantify the magnitude of nutrient loss through soil erosion under different cropping systems and amendments to inform agronomic practices in sub-Saharan Africa (SSA). A field experiment was carried out on runoff plots with different cropping systems (sole maize, sole cowpea, sole maize and maize intercropped with soybean) as main plots and soil amendments (biochar, NPK (Nitrogen +Phosphorus +Potassium) fertilizer, NPK + biochar and a control (no amendment)) constituting the subplots in a randomized complete block design. For each block, a bare plot was included to assess the efficiency of the different crop and soil management practices on soil erosion. The study was carried out in three consecutive cropping seasons in the semi-deciduous forest zone of Ghana. The bare plots had the highest amounts of nitrogen (N), phosphorus (P), and potassium (K) eroded: 33.88, 12.35 and 12.75 kg ha-1 respectively followed by the control plots with magnitude of 20.43, 8.42 and 7.87 kg ha-1 respectively for N, P and K. Sole maize had the highest amounts of nutrient loss: 19.71, 8.12 and 7.27 for N, P and K respectively compared to all the other cropping systems where the losses varied respectively from 12.38 to 17.12, 6.67 to 7.49 and 5.81 to 6.75 kg ha-1 The legume-based cropping systems under inorganic fertilizer and biochar management effectively reduced nutrient loss more than all other treatment combinations. The off-site effect of soil erosion expressed as enrichment ratio (ER) was higher for all plots, which received inorganic fertilizer inputs varying from 1.93 to 3.06 while the other treatments had ERs of 1.51 to 2.03. The ERs of fine soil particles were greater than 1 (ranging from 1.14 to 3.6) being relatively higher than that of coarse particles (sand) with values below 1 (ranging from 0.62 to 0.88). The least cumulative monetary value of nutrient loss (30.82 US$ ha-1) was observed under cowpea cropping system which received NPK + BC treatment. Soil erosion affected directly soil nutrient depletion through nutrient loss; however, integrated soil fertility management associated with legume-based cropping systems can be alternative options to reducing its effects on croplands in SSA.

We have investigated the effect of two nitrification inhibitors, 3,4-dimethylpyrazole phosphate (DMPP) and dicyandiamide (DCD), on the accumulation of \({\text{NH}}^{{\text{ + }}}_{{\text{4}}} {\text{ - N}}\) and \({\text{NO}}^{ - }_{3} - {\text{N}}\) after incorporation of cauliflower residues in incubation experiments. Cauliflower leaves were incubated with soil and DCD or DMPP at two application rates [8.93 and 17.9 mg active component (ac) kg−1 for DCD; 0.89 and 1.79 mg ac kg−1 for DMPP]. Both doses of DCD and DMPP increased \({\text{NH}}^{ + }_{4} - {\text{N}}\) on average by 18.9 and 26.0 mg N kg−1 for DCD1 (during 30 days) and DCD2 (during 45 days), respectively, and on average by 14.4 mg N kg−1 for DMPP1 and DMPP2 during a period of at least 95 days. In DCD-treated soils, \({\text{NO}}^{{\text{ - }}}_{{\text{3}}} {\text{ - N}}\) data followed an S-shaped curve, indicating that nitrification restarted during the experiment: inhibition was on average 24% during 35 days for DCD1 and on average 45% during 49 days for DCD2. Thereafter, \({\text{NO}}^{ - }_{3} - {\text{N}}\) amount in DCD-treated soils exceeded that of the cauliflower-only treatment by 31% for DCD1 and 78% for DCD2, probably due to a nitrogen release from DCD itself and a priming effect induced by DCD. In DMPP-treated soils, \({\text{NO}}^{ - }_{3} - {\text{N}}\) data followed a linear pattern since nitrification was inhibited during the complete incubation (95 days): inhibition was on average 56 and 64% for DMPP1 and DMPP2, respectively. DMPP did not affect the N mineralization of the crop residues. Under favourable conditions, DCD is able to inhibit the nitrification from crop residues for 50 days and DMPP for at least 95 days. Hence, especially DMPP shows a potential to reduce \({\text{NO}}^{ - }_{3} \) leaching after incorporation of crop residues.

The effect of neem seed oil and neem leaf extract as organic nitrification inhibitors (NIs) on the accumulation of NH4+ and NO3-, and nitrification inhibition after incorporation of crop residue was investigated in an incubation experiment. Dicyandiamide (DCD) applications of 15 and 30 kg active ingredient ha(-1) were used as low and high doses of a synthetic NI. Soil samples were amended with 21 g kg(-1) cauliflower leaves and treated with NIs at a rate of 30 kg ha(-1) of neem seed oil, 60 kg ha(-1) of neem leaf extract, 15 kg ha(-1) of DCD, and 30 kg ha(-1) DCD. Samples were incubated at temperatures corresponding to field temperatures during fall and winter in Flanders, Belgium. Neem seed oil increased NH4+ accumulation by 8.9 mg kg(-1) and decreased NO3- by 13.5 mg kg(-1) within a month. High and low doses of DCD increased NH4+ accumulation by 48.2 and 1.6 mg kg(-1), respectively. Nitrification was inhibited by 29% for 30 days by the low dose of DCD, 58% in 30 days by neem seed oil, and 42% in 45 days by the high dose of DCD. Nitrification was not inhibited by the neem leaf extract.

Field experiments were conducted at Oil Palm Research Institute, Kusi from 2002 to 2004 to evaluate the effect of roundup – salt mixtures on the control of weeds and soil microbial biomass. The efficacy of roundup at 0.47 kg a.i./ha mixed with either 0.23 kg/ha of sodium chloride or 0.53 kg/ha of ammonium sulphate or 0.24 kg/ha of urea was compared with roundup at 1.44 kg a.i/ha and manual weeding. The treatments were arranged in randomized complete block design and replicated four times. The roundup and its salt mixtures effectively controlled weeds up to 3 months after treatment (MAT) in both 2002 and 2003 trials. In 2002, roundup with sodium chloride, roundup with ammonium sulphate and roundup with urea maintained a substantial weed control of 77%, 79% and 87% respectively at 3 MAT compared to the 80% and 41% weed control by roundup only and manually weeding. By 3 MAT in 2003, the % weed control for roundup with sodium chloride, roundup with ammonium sulphate, roundup with urea, roundup only and manual weeding were 63%, 60%, 63%, 65% and 43% respectively. These weed control measures were however ineffective in the 2004 trial. The addition of ammonium sulphate or urea to roundup increased soil microbial C accumulation significantly by 115% and 650% respectively while the application of roundup with sodium chloride, roundup only and manual weeding stimulated microbial C accumulation slightly by 57%, 33% and 30% respectively. Microbial P also increased by 267%, 137%, 81%, 75% and 45% following the application of roundup with urea, roundup with ammonium sulphate, roundup only, roundup with sodium chloride and manual weeding respectively. The use of roundup – salt mixtures reduced the annual cost of manual weeding per hectare by 76% (¢1,735,000) and annual cost of applying roundup at the labeled rate also by 47 % (¢480,000). The addition of salts to reduced rate of roundup is therefore a cost efficient strategy to control weeds in oil palm plantations. Journal of the Ghana Science Association Vol. 9 (2) 2007: pp. 61-75