• Authors:
    • Singh, A.
    • Kumar, R.
    • Pathak, H.
    • Jain, N.
    • Sasmal, S.
    • Bhatia, A.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 136
  • Issue: 3
  • Year: 2010
  • Summary: No-till farming in wheat is being practiced in the rice-wheat system of the Indo-Gangetic plains of south Asia for resource conservation. No-tillage leads to mitigation of carbon dioxide emission, but may emit more nitrous oxide (N2O) as compared to conventional tillage reducing mitigation benefit. The aim of this study was assessment of N2O emission in wheat grown under conventional and no-tillage and its mitigation using two new nitrification inhibitors, viz. S-benzylisothiouronium butanoate (SBT-butanoate) and S-benzylisothiouronium furoate (SBT-furoate). Cumulative emission of N2O-N was higher under no-tillage by 12.2% with urea fertilization and from 4.1 to 4.8% for the inhibitor treatments as compared to the conventional tillage. In no-tillage total emission of N2O-N reduced from 0.43% of applied N with urea to 0.29% of applied N with SBT-furoate treatment. The N2O-N emissions in SBT-butanoate treatment were at par with the standard dicyandiamide (DCD) inhibitor treatment. Water-filled pore space (WFPS) was higher on most days under no-tillage, with the largest emissions (>1000 mu g N2O-N m(-2) day(-1)) coming with nitrification of ammonium-N present in soil below 60% WFPS. Carbon efficiency ratio was highest (48.1) from SBT-furoate treatment under conventional tillage. The nitrification inhibitors used in the study increased yield of wheat, reduced global warming potential by 8.9-19.5% over urea treatment and may be used to mitigate N2O emission.
  • Authors:
    • Iyapo, O.
    • Solomon, M.
    • Bello, O.
  • Source: Proceedings of the 19th World Congress of Soil Science: Soil solutions for a changing world, Brisbane, Australia, 1-6 August 2010. Symposium 3.1.2 Farm system and environment impacts
  • Year: 2010
  • Summary: Most of the arable land in Nigeria is characterized by fragile soils, having undergone intensive weathering, leaching and they are dominated by low activity clay, are infertile, have low nutrient response and are either acid or posses tendencies to become acid due to continuous or over cultivation. Soils especially around the cities in Nigeria are used for growing vegetables, cereals like maize, legumes like melon, soybean and cowpea which have been cultivated continuously for a period upward of 20 years due to the lack of arable land and the good market for the crops. Studies were conducted on the soil properties, soil reaction (pH); total nitrogen, organic carbon, base saturation, microbial populations (fungi and bacteria) and the determination of crop response to nutrient applications. The results obtained showed that the pH is acidic ranging from 4.1 to 5.1 and values of total nitrogen, organic carbon, base saturation, microbial populations and the identified nitrogen fixers are low. There is about a 60% yield reduction for the cultivated crops. The uptake of the applied nutrients by the crops is low consequently the soil is generally of low productivity.
  • Authors:
    • Aune, J. B.
    • Benjaminsen, T. A.
    • Sidibe, D.
  • Source: Geoforum
  • Volume: 41
  • Issue: 4
  • Year: 2010
  • Summary: The aim of this article is to analyse the influence of commodified cotton production on soil fertility in southern Mali. From the late 1950s and until recently, production of both cash-crop cotton and food crops have increased rapidly in this region, giving it a reputation of being an African 'success story'. The flip side of this economic success is, however, said to be environmental degradation especially in terms of loss of soil fertility. We collected 273 soil samples in 19 villages located in various zones of land use intensity. In each village, the samples were collected on up to six different land use types varying with intensification. The analysis of the soil samples showed that soil fertility was highest in the sacred groves that have been protected and never cultivated. However, comparing soils under continuous cultivation and soils under fallow no clear trends in soil fertility were found. Cotton yields have declined since the early 1990s, while the total use of fertilisers has increased. This is often interpreted as proof of soil exhaustion, but there is no clear indication in this study that cotton-cereal rotation as practiced by smallholders in southern Mali reduces soil fertility. We argue that the decline in yields has been caused by an extensification process. Cotton fields expanded rapidly, due to attractive cotton prices in the 1990s, leading to falling investments per ha and cultivation of more marginal lands. These findings also have implications for a political ecology of commodity production and lead us to argue for an open-ended and empirically based 'critical political ecology'.
  • Authors:
    • Wruck, F.
    • Feigl, B.
    • Bernoux, M.
    • Cerri, C.
    • Raucci, G.
    • Carvalho, J.
    • Cerri, C.
  • Source: Soil & Tillage Research
  • Volume: 110
  • Issue: 1
  • Year: 2010
  • Summary: Changes in land use can result in either sources or sinks of atmospheric carbon (C), depending on management practices. In Brazil, significant changes in land use result from the conversion of native vegetation to pasture and agriculture, conversion of pasture to agriculture and, more recently, the conversion of pasture and agriculture to integrated crop-livestock systems (ICL). The ICL system proposes a diversity of activities that include the strategic incorporation of pastures to agriculture so as to benefit both. In agricultural areas, for example, the implementation of ICL requires the production of quality forage for animals between crops as well as the production of straw to facilitate the sustainability of the no-tillage (NT) management system. The objective of this study was to evaluate the modifications in soil C stocks resulting from the main processes involved in the changes of land use in Amazonia and Cerrado biomes. For comparison purposes, areas under native vegetation, pastures, crop succession and ICL under different edapho-climatic conditions in Amazonia and Cerrado biomes were evaluated. This study demonstrated that the conversion of native vegetation to pasture can cause the soil to function either as a source or a sink of atmospheric CO 2, depending on the land management applied. Non-degraded pasture under fertile soil showed a mean accumulation rate of 0.46 g ha -1 year -1. Carbon losses from pastures implemented in naturally low fertile soil ranged from 0.15 to 1.53 Mg ha -1 year -1, respectively, for non-degraded and degraded pasture. The conversion of native vegetation to agriculture in areas under the ICL system, even when cultivated under NT, resulted in C losses of 1.31 in six years and of 0.69 Mg ha -1 in 21 years. The conversion of a non-degraded pasture to cropland (soybean/sorghum) released, in average, 1.44 Mg of C ha -1 year -1to the atmosphere. The ICL system in agricultural areas has shown evidences that it always functions as a sink of C with accumulation rates ranging from 0.82 to 2.58 Mg ha -1 year -1. The ICL produces soil C accumulation and, as a consequence, reduces atmospheric CO 2 in areas formerly cultivated under crop succession. However, the magnitude of C accumulation in soil depends on factors such as the types of crops, the edapho-climatic conditions and the amount of time the area is under ICL.
  • Authors:
    • Ekeleme, F.
    • Kamara, A.
    • Dugje, I.
  • Source: Nigerian Journal of Weed Science
  • Volume: 23
  • Year: 2010
  • Summary: Striga gesnerioides is considered a major constraint to improving cowpea productivity in the semi arid region of Africa. A field survey was conducted in a farmer participatory process in 100 cowpea fields to determine farmers' crop production practices that influence infestation by the parasitic weed. Fields with emerged Striga plants were sampled in the Northern Guinea Savanna (NGS), and Sudan Savanna (SS). The results showed that prolonged duration of land use for more than 6 years and, the continuous cropping of cowpea increased Striga infestation and reduced grain yield, while increased phosphorus levels between 30-45 kg P 2O 5 ha -1 reduced Striga infestations in NGS. The improved and Striga resistant cowpea variety (IT97K 499-35) and rotation of cowpea with cereals reduced Striga infestations which increased grain yield of cowpea. Increased phosphorus levels of between 30-45 kg P 2O 5 ha -1 reduced Striga infestation and increased grain yield of cowpea in SS, but late planting of sole cowpea fields promoted infestation. Striga counts were generally greater for all the practices in NGS than SS, while grain yield was greater for all the practices in SS than NGS. Increase in period of land use and relay intercropping contributed less to reducing infestation, while Phosphorus fertilizer application, use of resistant variety and rotation contributed more to decrease in infestation and increase in yield in both ecological zones. Therefore, the major factors that promote Striga infestation are: prolonged land use, growing varieties that are not resistant to Striga, continuous cropping of cowpea, inadequate phosphorus fertilization and late planting of cowpea. Consequently, Striga infestations could be reduced through integrated control by combining resistant cowpea varieties, adequate phosphorus fertilizer application, and rotation of cowpea with cereals.
  • Authors:
    • Chianu, J.
    • Kimetu, J.
    • Waswa, B.
    • Vanlauwe, B.
    • Kihara, J.
    • Bationo, A.
  • Source: Experimental Agriculture
  • Volume: 46
  • Issue: 1
  • Year: 2010
  • Summary: Many food production systems in sub-Saharan Africa are constrained by phosphorus (P).We hypothesized that within legume-cereal rotation systems: targeting P to the legume phase leads to higher system productivity, and that use of grain legumes leads to better economic returns than use of herbaceous legumes. Four P application regimes: (i) no P, (ii) P applied every season, (iii) P applied in season 1 only and (iv) P applied in season 2 only were tested for four seasons in three cropping systems (continuous maize, mucuna-maize rotation and soybean-maize rotation) in a split plot experiment set up in Nyabeda, western Kenya. Treatments where P was applied were better than no P treatments.While continuous cereal systems showed the need for application of P every second season, rotation systems involvingmucuna and soyabean indicated that application in one out of three seasons could be sufficient. Nitrogen fertilizer equivalence was 52 to >90 kg N ha -1 for soyabean and 37 to >90 kg N ha -1 for mucuna, depending on P fertilization and season. Analysis of marginal rates of return (MRR) showed that soybean-maize rotation with one application of P was the most economically viable option, with an MRR of at least 147% compared to other non-dominated options.
  • Authors:
    • Tittonell, P.
    • Leveque, J.
    • Sogbedji, J.
    • Guibert, H.
    • Kintche, K.
  • Source: Plant and Soil
  • Volume: 336
  • Issue: 1/2
  • Year: 2010
  • Summary: Soil degradation in the savannah-derived agroecosystems of West Africa is often associated with rapid depletion of organic carbon stocks in soils of coarse texture. Field experiments were conducted over a period of more than 30 years at two sites in semiarid Togo to test the impact of agricultural management practices on soil C stocks and crop productivity. The resulting datasets were analysed using dynamic simulation models of varying complexity, to study the impact of crop rotation, fertiliser use and crop residue management on soil C dynamics. The models were then used to calculate the size of the annual C inputs necessary to restore C stocks to thresholds that would allow positive crop responses to fertilisers under continuous cultivation. Yields of all crops declined over the 30 years irrespective of crop rotation, fertiliser use or crop residue management. Both seed-cotton and cereal grain yields with fertiliser fluctuated around 1 t ha -1 after 20 years. Rotations that included early maturing sorghum varieties provided larger C inputs to the soil through residue biomass; around 2.5 t C ha -1year -1. Soil C stocks, originally of 15 t ha -1 after woodland clearance, decreased by around 3 t ha -1 at both sites and for virtually all treatments, reaching lower equilibrium levels after 5-10 years of cultivation. Soil C dynamics were well described with a two-pool SOM model running on an annual time step, with parameter values of 0.25 for the fraction of resistant plant material (K 1), 0.15-0.20 for the decomposition rate of labile soil C (K 2) and 8-10 t C ha -1 for the fraction of stable C in the soil. Simulated addition of organic matter to the soil 30 years after woodland clearance indicated that additions of 3 t C ha -1year -1 for 15-20 years would be necessary to build 'threshold' soil C stocks of around 13 t ha -1, compatible with positive crop response to fertiliser. The simulated soil C increases of 0.5 to 1.6% per year are comparable with results from long-term experiments in the region. However, the amounts of organic matter necessary to build these soil C stocks are not readily available to resource-poor farmers. These experimental results question the assumption that crop residue removal and lack of fertiliser input are responsible for soil C decline in these soils. Even when residues were incorporated and fertilisers used at high rates, crop C inputs were insufficient to compensate for C losses from these sandy soils under continuous cultivation.
  • Authors:
    • Zombre, P.
    • Dakuo, D.
    • Traore, O.
    • Koulibaly, B.
    • Bonde, D.
  • Source: Tropicultura
  • Volume: 28
  • Issue: 3
  • Year: 2010
  • Summary: The effect of crop residues management on crops yields and nutrients balances in a cotton-cereals cropping system was studied in a long-term experiment carried out from 1982 to 2006. The experimental design was a simple nonrandomized blocks comparing extensive management of crops residues (T1), semiintensive management of crops residues (T2) and intensive management of crops residues (T3). Crops yields, soil chemical properties and mineral balances were measured. Results showed that after 25 years, soil carbon contents decrease was respectively 44%, 15% and 13%, with an extensive, semi-intensive and intensive management of crops residues. Total phosphorus decrease was 25% in all the treatments. Exchangeable Ca and Mg declined from 2.43 to 1.37 cmol+ kg -1 and 0.9 to 0.29 cmol+ kg -1 respectively while the Sum of Exchangeable Bases declined from 3.79 to 1.79 cmol+ kg -1. Recycling crops residues to compost and manure increased cotton yields from 13 to 22%, maize yields from 45 to 60%, and sorghum yields from 19 to 44%. Mineral balance in N, P, K and S was improved after 25 years of continuous cultivation while using compost or manure. At the same time, the decline of soil properties was due to nutrients losses which need to be evaluated. This study recommends integrated crops residues management and the use of rock phosphate to improve sustainability in cottoncereals cropping systems.
  • Authors:
    • Akinpelu, A.
    • Amangbo, L.
    • Ano, A.
    • Njoku, S.
    • Ebeniro, C.
  • Source: Journal of Agriculture and Social Research (JASR)
  • Volume: 10
  • Issue: 2
  • Year: 2010
  • Summary: A field trial was conducted for 2 years to determine cropping system effect on yield of some sweetpotato and okra cultivars in an intercropping system. Sweetpotato variety TIS 87/0087 produced significantly (P
  • Authors:
    • Obi, M.
    • Obalum, S.
  • Source: Soil & Tillage Research
  • Volume: 108
  • Issue: 1/2
  • Year: 2010
  • Summary: Evaluation of the impact of tillage-mulch practices under different cropping systems on soil physical properties is needed in southeastern Nigeria to identify those combinations with the potential of alleviating the physical constraints of the Ultisols predominant in the area. An investigation was carried out on a sandy loam soil at Nsukka to determine the effects of no-till (NT) and conventional tillage (CT) each with bare fallow (B) and mulch cover (M) on soil physical properties under three cropping systems [sole sorghum ( Sorghum bicolor L. Moench), sole soybean ( Glycine max L. Merrill), and sorghum-soybean intercrop]. The layout was a split-plot in randomized complete block design, with the tillage systems as the main plots and the mulch practices as the sub-plots. The treatments [no-till and bare (NTB), no-till with mulch (NTM), conventional tillage and bare (CTB) and conventional tillage with mulch (CTM)] were replicated four times. The selected key parameters evaluated after two years were density of earthworm casts, soil organic matter (SOM), bulk density (BD), total porosity (TP), pore size distribution (PSD), mean weight diameter (MWD), and saturated hydraulic conductivity (K sat). Earthworm activity was significantly ( P≤0.001) higher with NT under the intercrop system. Values were generally very low for SOM (1.06-1.48%), moderate for BD (1.34-1.51 Mg m -3) and TP (46-52%), and low to moderate for MWD (1.1-2.9 mm). The K sat was within the slow to rapid range (8.1-57.0 cm h -1). Neither the tillage nor the mulch factors influenced SOM, BD, PSD, and MWD in the cropping systems. The TP was significantly ( P≤0.05) higher in the CT compared to the NT under the sole sorghum, where interaction showed higher value in the CTM compared to the rest. There was significant ( P≤0.05) enhancement of K sat in the CT under the sole sorghum and the intercrop systems; whereas the value was significantly ( P≤0.01) higher in the bare fallow under the sole soybean. The cropping systems had more pronounced effect on the physical properties than the tillage-mulch management practices. All the measured parameters indicated significant ( P≤0.05) improvements under the sole soybean, except BD and MWD which were significantly ( P≤0.05) improved under the intercrop. Intercropping cereals and legumes on NT may be ideal for alleviating the soil's structural constraints.