Intensification of maize production is imperative to improve food security for the rising population in the central rift valley (CRV) of Ethiopia, whose livelihood is principally based on rainfed maize that operates under shrinking landholding and high seasonal rainfall variability. This study examined different levels of intensification options in maize production by sequentially introducing minimum tillage and seed priming, phosphorus (P) fertilizer microdosing, surface mulching and nitrogen (N) fertilizer microdosing. Field experiments were conducted with five treatments, steps or levels consisting of conventional tillage (farmers practice as a control); minimum tillage + seed priming, unfertilized (step 1); step 1 + microdosing 53 kg ha−1 P (step 2); step 2 + 4 ton ha−1 maize stover as surface mulch (step 3) and step 3 + 53 kg ha−1 N (step 4). These steps represented increasing levels of intensification. Except at the lowest level (step 1), agronomic and economic responses improved with increasing levels of inputs. Relative to the very high and increasing gross margin, production costs were low but slowly increased with increasing levels of inputs. Except at the lowest level, the value cost ratio was above 4 even at the highest levels of inputs, demonstrating that such kind of intensification can be achieved with low risk. Likewise, the fertilizer use efficiency was quite high even at the highest of levels of inputs signifying the efficiency of the pocket application of fertilizer through the microdosing method. The improvement in maize establishment and yield and the reduction in the days to maturity could contribute to make maize production more adaptive to the existing seasonal rainfall variability. Depending on the affordability to the external inputs and their feasibilities, the different technology packages in the intensification ladder may give different choices for the farmers to improve maize production in the CRV of Ethiopia.

Eucalyptus spp. is the main tree used in cellulose production worldwide, cultivated mostly in extensive monocrop plantations. However, due to concerns on environmental impacts, fear on decrease of food production related to the size of cultivated area, its location near human settlements with few jobs generation, eucalypt cultivation is no longer encouraged in many places. At the same time, large plantations hold the opportunity to integrate eucalypt into agroforestry systems (AFS) in a variety of production systems with many social, economical and environmental advantages. In this study we studied canopy modifications of E. camaldulensis sprouts under different degrees of shade. The plants were located on a gradient of available solar irradiation ranging from 51 to 94%. E. camaldulensis showed canopy plasticity with modified radiation interception patterns under diverse irradiations. Most of these variations were of small amplitude with some important variables remaining almost unchanged (leaf density, canopy percentage, tree, trunk and canopy height) or increasing only slightly (leaf area index and canopy opening). The main changes presented by E. camaldulensis, with a steep increase towards full sun, were: foliage area, canopy surface, canopy volume and area of canopy projection. In order to design appropriate agroforestry systems with young eucalypt growing under the shade of other crops, it is necessary to determine at which point the observed variable changes can support reasonable production.

Hand-planted plots of across-row-oriented corn seeds (Zeamays L.) produce highly structured leaf canopies and have shown significant yield advantage over randomly planted plots in prior studies. For further investigation of the phenomenon by simulation, the objective of this study was to develop a probabilistic model for the correlation between seed orientation and initial plant orientation. In greenhouse trials, the azimuthal orientation of kernels of four different hybrids was recorded at planting. At collar setting of the seed leaf, the orientation of the seed leaf was determined and the angular data subjected to the analytical methods of circular statistics. The results indicate that the correlation between seed azimuth and seed leaf azimuth can be described by a von Mises distribution. The probabilistic seed to seed leaf azimuth model described herein may be implemented in simulation models to investigate the effect of canopy architecture, canopy closure and light interception efficiency of corn under conditions of seed oriented planting.

The systematic rather than random entry arrangement of honeycomb designs (HDs) has been deployed to sample the spatial heterogeneity. This hypothesis was studied in fairly homogeneous populations, assuming that their phenotypic variability stemmed absolutely from spatial rather than genetic heterogeneity. It was based on single plant performance in two separate trials of a maize hybrid and a wheat cultivar reflecting different level of spatial heterogeneity. In general, the HDs counteracted spatial heterogeneity well, particularly when the number of evaluated entries was limited. There was a suggestion that they do well even in a high number of entries with many replicates per entry. Distribution and layout of spatial heterogeneity across the experimental area did not affect the precision of the HDs. Standardized configuration, which ensures implementation of essential principles met in other experimental models such as blocking, replication and nearest-neighbour (NN) adjustment on the same baseline, renders the honeycomb experimental pattern advantageous over the classical experimental designs like the randomized complete block (RCB), the NN method and the lattice model.

To evaluate the effects of defoliation on green forage performance and grain yield (GY) variation in barley, five barley genotypes were imposed on three levels of defoliation treatments over two consecutive growing seasons in this study. The results indicated that green forage yields were significantly improved by repeated defoliation. The traits of green forage quality, including the ratio of dry weight to fresh weight, crude ash and calcium content were improved, while crude protein and crude fat were reduced, and crude fiber and phosphorus contents appeared not to be influenced by repeated defoliation. Plant height (PH), GY and other yield components, grain number per spike and thousand kernel weight, were significantly reduced by defoliation over the two growing seasons, while internode length below spike was less affected. Reduction in spike length and the number of spikes per plant were identified in only one year. Correlation analysis revealed that only PH exhibited a positive correlation with GY. Effects of genotype, interaction between genotype and defoliation, and environments on changes of forage yield and quality and GY were also discussed. Our current work provides a feasible approach to select elite barley cultivars with optimal defoliation treatments for both forage and grain uses in barley breeding programme.

Prolonged inability of yam tubers to sprout/germinate is associated with the expression of tuber dormancy, and the start of dormancy in tubers is linked to the onset of tuber formation. Although the plant hormone, abscisic acid (ABA) is known to regulate the onset and maintenance of dormancy in tubers, there are no known method(s) of inducing shoot growth (sprouting) on seed yam tubers that are harvested at 240 days after vine emergence or earlier. Therefore, this study was conducted to: (1) determine whether the absorption of fluridone, a reputed ABA inhibitor, prior to or during early seed yam tuber formation would induce sprouting, and (2) determine the effect of fluridone on early shoot growth. The study was a 2×4 factorial experiment arranged in a Completely Randomized Design (CRD) with eight treatment combinations replicated three times. Two species of yam with long dormancy durations were used: D. rotundata var TDr 131 and D. alata var TDa 98/01166; and three concentrations of fluridone were tested (30, 50, 100 µM). Young plants (69 days after vine emergence) of TDr 131 and TDa 98/01166 were grown in a coco coir medium hydroponics system using Hoagland's Nutrient Solution, with or without the test fluridone concentrations. In all fluridone treatments, most leaves of both species of yam had 30–90% of their surface bleached while the stems appeared purplish. In both Controls, all the newly formed seed tubers that were harvested at 90 and 104 days after vine emergence were dormant (devoid of any new shoots/sprouts). In contrast, over 70% of the seed tubers that developed in 30 and 100 µM fluridone had at least one new shoot, particularly in TDa 98/01166. The fluridone treatments did not significantly affect tuber weight or vegetative growth parameters like dimensions and number of leaves. This study has shown that the duration from vine emergence of the old tuber to sprouting of the new tuber can be reduced by more than half if young plants absorbed fluridone during early tuber development.

Water stress is one of the main environmental stress conditions that adversely affect growth and yield of crops. Sulphydryl (-SH) compounds have been reported to induce tolerance to abiotic stress conditions. A two-year (2010 and 2011) experiment was conducted at Bikaner, Rajasthan, India to test whether the exogenous applications of thiourea (500, 750 and 1000 mg L−1) and thioglycolic acid (200, 300 and 400 mg L−1) as a foliar spray would alleviate deleterious effects of water stress on clusterbean (Cyamopsis tetragonoloba L.). The -SH-treated plants showed higher membrane stability index, photosynthetic pigment content, photosynthetic capacity and antioxidant enzyme activities and lower lipid peroxidation compared with untreated plants. Compared with untreated plants, the -SH-treated plants had 11–18, 18–30, 17–57, 25–47, 14–22% higher membrane stability index, total chlorophyll content, antioxidant enzyme activities, net photosynthetic rate and seed yield, respectively; whereas the malondialdehyde content was 10–19% lower. These data suggest that under water deficit stress, exogenous -SH compound application improves photosynthesis by increasing photosynthetic pigment, protects plants against oxidative damage by scavenging reactive oxygen species and minimizing lipid peroxidation by elevated antioxidant enzyme activities. These results indicated the role of -SH compounds in diminishing the negative effects of water deficit on clusterbean and suggest that -SH compounds could be used as a potential bioregulator to improve plant growth and yield under water deficit conditions.

The response to sulphur (S) and irrigation of mustard although site-specific, is less studied across sites. Economics and greenhouse gases (GHGs) emissions are other important considerations for developing resource-efficient technologies, but hardly studied in mustard. The objectives of this study were to appraise productivity, economics and GHGs emissions under three irrigation regimes combined with four levels of S, laid out in a split plot design with three replications. Results showed that two irrigations at 30 and 60 DAS combined with 60 kg S ha−1 resulted in highest gross and net returns, which were 30.9 and 37.2% higher than that in single irrigation at 30 DAS, and 47.2 and 68.0% higher than that in single irrigation at 60 DAS without S application, respectively. Estimated GHGs emissions from common inputs (machinery, diesel, fertilizer and insecticides) of mustard were 1486.2 kg CO2 eq ha−1 with greater share (95%) of fertilizer. Econometric analysis predicts that 1% increase in irrigation and S use will lead to 10.29 and 9.98% increase in mustard yield, respectively.

Phosphorus deficiency in tropical acid soils is a problem because soluble inorganic phosphorus is fixed by aluminium and iron. Organic amendments could be used to overcome phosphorus fixation in acid soils. Thus, the objectives of this study were to (i) improve soil phosphorus availability using biochar and compost produced from poultry manure and pineapple leaves respectively, and (ii) determine whether the use of biochar and compost could improve phosphorus, nitrogen, potassium, calcium and magnesium uptake and dry matter production of Zea mays L. cultivation on a tropical acid soil. Organic amendments significantly increased soil pH compared with non-organic amendments. Organic amendments also significantly reduced exchangeable acidity and exchangeable forms of aluminium and iron, and effectively fixed aluminium and iron instead of phosphorus. As a result, phosphorus availability in soil increased. Besides increasing the availability of nitrogen, potassium, calcium and magnesium in soil, organic amendments improved nutrients uptake and dry matter production of Zea mays L. Biochar and compost can be used to improve the productivity of Zea mays L. on acid soils by reducing phosphorus fixation.

Tillage and use of organic manure are important agronomic practices that sustain high crop and soil productivity. Hence, a three-year (2007 to 2009) study was conducted to evaluate the effect of site, tillage and poultry manure (PM) treatments on soil and plant nutrients composition, growth and yield of cocoyam (Xanthosoma sagittifolium). The study was a 2 × 5 × 5 factorial experiment with two sites (Owo – site 1 and Obasooto – site 2), five tillage methods; manual clearing (MC), manual ridging (MR), manual mounding (MM), ploughing plus harrowing (P+H) and ploughing plus harrowing twice (P+2H) and five levels of PM (0, 2.5, 5.0, 7.5, 10.0 t ha−1). Treatments were replicated thrice. Soil OM, N, P, K, Ca, Mg and leaf nutrients reduced with increase in tillage intensity, thus MC conserved soil nutrients the most, and increased nutrient uptake. Soil and plant nutrient concentration was lowest under the P+2H treatment. The MC, MR and MM treatments led to faster growth and higher tuber yield. As PM increased from 0 to 10.0 t ha−1 soil pH, OM, soil and plant N, P, K, Ca and Mg increased. The 7.5 t ha−1 PM gave the highest leaf K, Ca and Mg values. Owo site had significantly higher yield and growth parameters of cocoyam compared with Obasooto site. Yield and growth parameters of cocoyam increased with increase in PM level up to 7.5 t ha−1. Out of all tillage cum manure treatments, MC+7.5 t ha−1 PM gave the highest values of yield and growth parameters.

This study was conducted to improve wheat production under vegetative (early season) drought stress. Hydroprimed and osmoprimed (with CaCl2) seeds of wheat cultivars Lasani-2008 (LS-2008) and Triple Dwarf-1 (TD-1), were sown in 20 (narrow), 25 (medium), and 30 cm (wider) spaced rows. Crop was grown under well-watered conditions till physiological maturity or was subjected to drought stress (50% field capacity) during vegetative phase and then grown under well-watered conditions. Drought stress caused substantial reduction in grain and biological yields, related traits, harvest index (HI) and water use efficiency (WUE). Nonetheless, planting osmoprimed seeds in narrowly spaced rows significantly improved the grain yield, HI and WUE. However, wheat planted in wider rows had bold grains. Furthermore, wheat cultivar LS-2008 produced better yield, even under drought stress, than cultivar TD-1. Economic analysis indicated that planting osmoprimed seeds of wheat cultivar LS-2008 in narrowly spaced rows under early season drought yielded maximum economic benefits. In conclusion, planting osmoprimed seeds of cultivar LS-2008 in narrowly spaced rows is a good agronomic option to improve the wheat performance under early season drought stress.

In the published article Hussain et al., (2016) the name of the last co-author was spelt incorrectly. The author's name should have read as: M. Farooq.