Integrated breeding approaches for improving drought and heat adaptation in chickpea (Cicer arietinum L.)

Chickpea (Cicer arietinum L.) is a dry season food legume largely grown on residual soil moisture after the rainy season. The crop often experiences moisture stress towards end of the crop season (terminal drought). The crop may also face heat stress at the reproductive stage if sowing is delayed. The breeding approaches for improving adaptation to these stresses include the development of varieties with early maturity and enhanced abiotic stress tolerance. Several varieties with improved drought tolerance have been developed by selecting for grain yield under moisture stress conditions. Similarly, selection for pod set in the crop subjected to heat stress during reproductive stage has helped in the development of heat‐tolerant varieties. A genomic region, called QTL‐hotspot, controlling several drought tolerance‐related traits has been introgressed into several popular cultivars using marker‐assisted backcrossing (MABC), and introgression lines giving significantly higher yield than the popular cultivars have been identified. Multiparent advanced generation intercross (MAGIC) approach has been found promising in enhancing genetic recombination and developing lines with enhanced tolerance to terminal drought and heat stresses.     

Effect of cutting edge thickness and state of wear of ploughshare on draught force and heart rates of Sanga oxen in Ghana

In this study, draught forces and heart rates of oxen were measured during ploughing to assess ploughshare cutting edge performance. The main objective of the study was to examine the effect of cutting edge thickness and state of wear of animal-drawn mouldboard ploughshares on the draught force and the heart rates of oxen pulling the implement and to determine the optimum cutting edge that gives the least draught force and lowest heart rates when pulled by animals. To minimise soil variability, a field was ploughed, harrowed and left to consolidate for 4 weeks before field experiments started. A pair of Sanga oxen was used during the field test. Analyses of variance showed there were significant differences (p < 0.05) in the mean draught forces and the corresponding oxen heart rates for the cutting edges. The field test results indicated the draught forces and heart rates of the animals increased with increasing cutting edge thickness from 2 to 8 mm, but also increased slightly for the 1 mm edge. The draught forces of the other cutting edges relative to the 2 mm were 9%, 1%, 29%, 35% and 65% higher for the 1, 4, 8 mm, Reversed and double-sided, respectively. The heart rates induced by the other cutting edges relative to the 2 mm varied from under 1 to 12%. The draught of the cutting edges was between 6 and 10% of the body weight of the animals used for the experiment. The lowest draught force and heart rate were obtained for the 2 mm cutting edge. Since the 4 mm cutting edge generated draught forces and heart rates values as low as the 2 mm, it was considered potentially more durable under field conditions and could be the recommended cutting edge thickness for animal-drawn shares in similar soil conditions used for the experiment.     

Review and quantitative assessment of ex situ household rainwater harvesting systems in Ethiopia

Ex situ household rainwater harvesting (RWH) systems have been introduced at a large scale in Ethiopia to increase the water availability for smallholders through supplementary irrigation. The first objective of this paper is to review the performance of these systems in Ethiopia based on various assessment studies. The second objective is to provide quantitative biophysical and socio-economic analyses of ex situ household RWH systems contributing to the better understanding of their performance and the identification of options to improve their performance. Uptake of RWH systems by smallholders in Ethiopia is limited and the available information suggests that this is associated among others with poor planning and implementation, poorly functioning input and output markets and the lack of farmers’ skills to use these systems effectively. Our quantitative meta-analyses illustrate that water availability of three studied RWH systems is low in relation to crop water needs, particularly for maize. The variation in area that can be irrigated across years exposes users of RWH systems to considerable risks as the availability of irrigation water depends on prevailing rainfall conditions. The area that can be irrigated varies greatly depending on amount and distribution of rainfall, type of RWH system and crop type. The economics of onion (cash crop) are promising only for plastic lined RWH systems, but those for maize are unfavourable independent of the studied RWH systems. Associated labour requirements especially for water lifting and application are high and possibly constraining the sustainable use of RWH systems. The potential of ex situ household RWH systems to increase agricultural production and income is site-specific depending on biophysical, institutional and socio-economic conditions, and depends on household-specific conditions.     

Determinants of sheep prices in the highlands of northeastern Ethiopia: implication for sheep value chain development

In order to assess and identify the determinants of sheep price and price variation across time, a time series data were collected from four selected markets in North Shewa, Northeastern Ethiopia on weekly market day basis for a period of 2 years. Data on animal characteristics and purpose of buying were collected on a weekly basis from randomly selected 15–25 animals, and a total of 7,976 transactions were recorded. A general linear model technique was used to identify factors influencing sheep price, and the results showed that sheep price (liveweight sheep price per kilogram taken as a dependent variable) is affected by animal characteristics such as weight, sex, age, condition, season, and color. Most of the markets’ purpose for which the animal was purchased did not affect significantly the price per kilogram. This may be due to the similarity of the markets in terms of buyer’s purpose. The results suggest that there will be benefit from coordinated fattening, breeding, and marketing programs to take the highest advantage from the preferred animals’ characteristics and selected festival markets. Finally, the study recommends for a coordinated action to enhance the benefit generated for all participant actors in the sheep value chain through raising sheep productivity, improving the capacity of sheep producers and agribusiness entrepreneurs to access and use latest knowledge and technologies; and strengthening linkages among actors in the sheep value chain.     

NITROGEN ACCUMULATION IN SHOOTS AS A FUNCTION OF GROWTH STAGE OF CORN AND WINTER WHEAT

Midseason fertilizer nitrogen (N) rates based on predicted yields can be projected if the quantity of N accumulated in winter wheat (Triticum aestivum L.) and corn (Zea mays L.) is known especially early in the growing season. This study was conducted in 2006 and 2007 to establish the amount of N accumulated in corn and winter wheat over the entire growing season. Plots representing three N fertilization rates 0, 45, and 90 kg ha^?1 at Stillwater and 0, 67, and 112 kg ha^?1 at Lahoma were selected from two long-term wheat experiments located at research stations in Stillwater and Lahoma, Oklahoma. For corn, three N fertilization rates 0, 112 and 224 kg ha^?1 at Lake Carl Blackwell and 0, 56 and 112 kg ha^?1 at Perkins were selected from N studies, located at research stations near Lake Carl Blackwell and Perkins, Oklahoma. Sequential aboveground biomass samples were collected from 1 m² area of wheat and 1.5 m long row (0.76 cm spacing) for corn throughout their respective growing seasons. In general, this work showed that more than 45% of the maximum total N accumulated could be found in corn plants by growth stage V8 (8th leaf collar fully unfolded). For winter wheat, more than 61% of the maximum total N accumulated at later stages of growth could be accounted for by Feekes growth stage 5 (F5, leaf strongly erected). Our findings are consistent with those of others showing that yield potential can be predicted at mid-season since such a large percentage of the total N accumulated was accounted for early on in the growing cycle of either wheat or corn.     

Effect of organic residue amendments and soil moisture on N mineralization,maize (Zea maysL.) dry biomass and nutrient concentration

Greenhouse pot experiments using four tropical soils were conducted to measure the effect of crop residues on nitrogen mineralization/immobilization and the growth of maize plants under two soil moisture regimes (pF2.5 and pF3.5). Nitrogen-rich residues of pigeon pea [PP, Cajanus cajan (L.) Millps, C/N, 18.8] enhanced plant growth and increased the assimilation of mineral elements (N, P and K) at both moisture regimes. Less nitrogen-rich residues of haricot beans [HB, Phaseolus vulgaris (L.), C/N, 28.9] had a slightly negative effect on plant growth and the assimilation of mineral elements, and a stronger negative effect was recorded for the most N-poor plant residue, maize [M, Zea mays (L.), C/N, 33.6]. For PP, we estimated the recovery of residue-nutrients in maize plants (net increase in N, P and K assimilation due to PP incorporation) as 19% for N, 88% for P and 86% for K in the high-moisture regime (pF2.5). The equivalent values for the drought-stress regime (pF3.5) were 10, 34 and 38%, respectively. The results demonstrate the immediate enhancement of plant growth by plant residues with a low C/N ratio, even under drought-stress conditions.     

Forage and Grain Yield Response to Applied Sulfur in Winter Wheat as Influenced by Source and Rate

ABSTRACT

Recently, environmental quality issues related to sulfur (S) have made it necessary to reduce its release into the atmosphere in wet or dry forms, which in turn might influence the S requirement of crops. It is anticipated that by 2020, S deposition will decrease by up to 30% in eastern portions of Oklahoma and by 15% throughout the remainder of the state. This change calls for frequent monitoring and evaluation of S nutrition in wheat and other crops. Experiments were conducted at Hennessey and Perkins research stations for a period of seven years starting in the fall of 1996, with the objective of assessing the effect of different levels of elemental and sulfate-S fertilizers on the grain and forage yields of winter wheat in Oklahoma. The experimental design was a randomized complete block with three replications. Four S rates, 0, 56, 112, and 224 kg S ha^{? 1}, were applied to the plots from 1996 to 2002 as CaSO₄. Another two rates, 56 and 112 kg S ha^{? 1}, were included in the trials beginning in 1998 using 92% elemental S. Gypsum, as a source of S for winter wheat, resulted in a greater yield than did elemental S in cases where S fertilizer sources were deemed significant. In six of 14 trials from 1996 to 2002, applied S as CaSO4 significantly increased wheat-grain yields. Observing significant grain and forage yield increases due to applied S was important, but the response was sporadic and unpredictable from one year to the next.     

Carbon and nitrogen mineralization dynamics in different soils of the tropics amended with legume residues and contrasting soil moisture contents

Seasonal drought in tropical agroecosystems may affect C and N mineralization of organic residues. To understand this effect, C and N mineralization dynamics in three tropical soils (Af, An₁, and An₂) amended with haricot bean (HB; Phaseolus vulgaris L.) and pigeon pea (PP; Cajanus cajan L.) residues (each at 5 mg g⁻¹ dry soil) at two contrasting soil moisture contents (pF2.5 and pF3.9) were investigated under laboratory incubation for 100–135 days. The legume residues markedly enhanced the net cumulative CO₂–C flux and its rate throughout the incubation period. The cumulative CO₂–C fluxes and their rates were lower at pF3.9 than at pF2.5 with control soils and also relatively lower with HB-treated than PP-treated soil samples. After 100 days of incubation, 32–42% of the amended C of residues was recovered as CO₂–C. In one of the three soils (An₁), the results revealed that the decomposition of the recalcitrant fraction was more inhibited by drought stress than easily degradable fraction, suggesting further studies of moisture stress and litter quality interactions. Significantly (p < 0.05) greater NH₄⁺–N and NO₃⁻–N were produced with PP-treated (C/N ratio, 20.4) than HB-treated (C/N ratio, 40.6) soil samples. Greater net N mineralization or lower immobilization was displayed at pF2.5 than at pF3.9 with all soil samples. Strikingly, N was immobilized equivocally in both NH₄⁺–N and NO₃⁻–N forms, challenging the paradigm that ammonium is the preferred N source for microorganisms. The results strongly exhibited altered C/N stoichiometry due to drought stress substantially affecting the active microbial functional groups, fungi being dominant over bacteria. Interestingly, the results showed that legume residues can be potential fertilizer sources for nutrient-depleted tropical soils. In addition, application of plant residue can help to counter the N loss caused by leaching. It can also synchronize crop N uptake and N release from soil by utilizing microbes as an ephemeral nutrient pool during the early crop growth period.