Water stress induces some physiological changes in plants and has cumulative effects on crop growth and yield. Field experiments were conducted to study the effect of deficit irrigation (DI) on yield and some physiological parameters in cotton and maize in a sequential cropping system. Creation of soil moisture gradient is indispensable to explore the beneficial effects of partial root zone drying (PRD) irrigation and it could be possible only through alternate deficit irrigation (ADI) practice in paired row system of drip layout that is commonly practiced in India. In the present study, PRD and DI concepts (creation of soil moisture gradient) were implemented through ADI at two levels of irrigation using drip system. Maize was sown after cotton under no till condition without disturbing the raised bed and drip layout. Relative leaf water content (RLWC) and chlorophyll stability index (CSI) of cotton and maize were reduced under water stress. A higher level of leaf proline content was observed under severe water-stressed treatments in cotton and maize. RLWC and CSI were highest and leaf proline content was lowest in mild water deficit (ADI at 100% crop evapotranspiration once in three days) irrigation in cotton and maize. The same treatments registered higher values for crop yields, net income and benefit cost ratio for both the crops.

Most previous studies focused on intercropping systems involving two-crop associations. However, there is much scope to improve existing cropping systems by devising and evaluating modifications that allow more effective use of the season. To this effect, experiments were conducted to quantify efficiency of sequential intercropping consisting of maize (Zea mays L.), common bean (Phaseolus vulgaris L.) and mung bean (Vigna radiata (L.) Wilczek) during 2007 and 2009 cropping seasons, in southern Ethiopia. Treatments included three- and two-crop associations and equivalent sole crops of components. Land equivalent ratio (LER) and area time equivalency ratio (ATER) were used to estimate intercropping advantage. Maize had the highest partial LER, 0.95, whenever mung bean comes first in the sequence. Comparable partial LERs were observed in common bean irrespective of planting times while mung bean had greater partial LERs from simultaneous rather than sequential planting. Maize had the highest competitive ratio (1.56) followed by common bean (0.67) and mung bean (0.53). The three-crop association involving simultaneous planting of maize with mung bean followed by common bean (MZ + MB − CB) gave the highest mean total LER of 1.66. This combination also had the highest combined productivity and maximum monetary gain, which is above the minimum acceptable marginal rate of return. It exceeded advantages from intercrops of maize–common bean by 41% and maize–mung bean by 23%. Thus, farmers would get greater advantage from practicing sequential intercropping in areas where the season is sufficient to grow long-duration maize.

The choice of an appropriate cropping system is critical to maintaining or enhancing agricultural sustainability. Yield, profitability and water use efficiency are important factors for determining suitability of cropping systems in hot arid region. In a two-year field experiment (2009/10–2010/11) on loam sandy soils of Bikaner, India, the production potential, profitability and water use efficiency (WUE) of five cropping systems (groundnut–wheat, groundnut–isabgol, groundnut–chickpea, cluster bean–wheat and mung bean–wheat) each at six nutrient application rate (NAR) i.e. 0, 25, 50, 75, 100% recommended dose of N and P (NP) and 100% NP + S were evaluated. The cropping systems varied significantly in terms of productivity, profitability and WUEs. Averaged across nutrient application regimes, groundnut–wheat rotation gave 300–1620 kg ha−1 and 957–3365 kg ha−1 higher grain and biomass yields, respectively, than other cropping systems. The mean annual net returns were highest for the mung bean–wheat system, which returned 32–57% higher net return than other cropping systems. The mung bean–wheat and cluster bean–wheat systems had higher WUE in terms of yields than other cropping systems. The mung bean–wheat system recorded 35–63% higher WUE in monetary terms compared with other systems. Nutrients application improved yields, profit and WUEs of cropping systems. Averaged across years and cropping systems, the application of 100% NP improved grain yields, returns and WUE by 1.7, 3.9 and 1.6 times than no application of nutrients. The results suggest that the profitability and WUEs of crop production in this hot arid environment can be improved, compared with groundnut–wheat cropping, by substituting groundnut by mung bean and nutrients application.

Declining land productivity is a major problem facing smallholder farmers today in Sub-Saharan Africa, and as a result increase in maize grain yield has historically staggered behind yield gains that have been achieved elsewhere in the world. This decline primarily results from reduction in soil fertility caused by continuous cultivation without adequate addition of external nutrient inputs. Improved soil fertility management practices, which combine organic and mineral fertilizer inputs, can enable efficient use of inputs applied, and can increase overall system's productivity. The trials were established at two sites with different soil fertility status to determine the effects of various organic sources (Tithonia diversifolia, Mucuna pruriens, Calliandra calothyrsus and cattle manure) and their combinations with mineral fertilizer on maize grain yield, economic return and soil chemical properties. Drought spells were common during the peak water requirement periods, and during all the seasons most (90%) of the rainfall was received before 50% flowering. In good and poor sites, there was a significant (p < 0.001) effect of season on maize grain yield. Tithonia diversifolia recorded the highest (4.2 t ha−1) average maize grain yield in the poor site, while Calliandra calothyrsus gave the highest (4.8 t ha−1) average maize grain yield in the good site. Maize grain yields were lower in treatments with sole fertilizer compared with treatments that included organic fertilizers. The maize grain yields were higher with sole organics compared with treatments integrating organic and inorganic fertilizers. Soil pH increment was statistically significant in the sole manure treatment in good and poor sites (t-test, p = 0.036 and 0.013), respectively. In the poor site, magnesium increased significantly in the sole manure and manure + 30 kg N ha−1 treatments with t-test p = 0.006 and 0.027, respectively. Soil potassium was significant in the sole manure treatment (t-test, p = 0.03). Generally the economic returns were low, with negative net benefits and benefit cost ratio of less than 1. Inorganic fertilizer recorded the highest net benefit and return to labour (p < 0.001 and <0.01, respectively) in the good site. The treatments that had very high maize grain yields did not lead to improved soil fertility, thus there is need for tradeoffs between yield gains and soil fertility management when selecting agricultural production technologies.

Field experiments were carried out over a period of three years to evaluate the effect of cover cropping faba bean with fibre sorghum, compared to mono-crop cultivation, on yield (dry matter), nitrogen utilization efficiency (NUE) and N fertilizer recovery fraction of sorghum. Experimental sites were located in central Greece on a fertile, clayey to loamy textured soil, and on a sandy soil of moderate fertility. A factorial combination of four nitrogen application rates (0, 50, 100, 150 kg ha−1) and three legume treatments (incorporated into the topsoil or harvested before the sowing of sorghum and mono-cropping) were tested in a split plot design in three blocks. The results showed importance of legume cover crops for both soil types as sorghum total dry biomass yield for clayey soil fluctuated from 23 to 27 t ha−1 for control plots, from 25.2 to 30.9 t ha−1 when faba bean was harvested and from 26.3 to 32.5 t ha−1 when incorporated, and for sandy soil the yield fluctuated from 18.1 to 22.1 t ha−1 for control plots, from 22 to 27 t ha−1 when faba bean was harvested and from 23.1 to 28.1 t ha−1 when incorporated. The NUE was estimated at 62 kg kg−1 and 60 kg kg−1 for clayey and sandy soils respectively. The N recovery fraction was doubled after incorporating faba bean as green manure, reaching large amounts for both soil types.

In arid and semiarid winter crop growing regions of southern Australia, low rainfall, high evaporation, and low soil moisture storage are the limiting factors for crop production. In this region canola (Brassica napus L.) is principally grown in rotation with wheat and pasture species. Some field studies have indicated Indian mustard (Brassica juncea L.) to be more drought tolerant than canola and therefore considered to be better adapted than canola to short season environments. A field experiment was conducted at Wagga Wagga in NSW to determine the effect of two soil moisture regimes on water use efficiency, harvest index, seed and oil quality of cv. Oasis of Indian mustard and cv. Skipton of canola. Significant year × stress and species × stress interaction effects were observed for grain yield, harvest index, seed weight, biomass water productivity, and grain water productivity. Irrigation during the post flowering period resulted in 50% and 200% increases in canola grain yield in the first year (year with higher in-crop water) and the second year (year with low in-crop water), respectively. For mustard, these values were 7% and 45%, respectively. Stressed mustard resulted in higher grain yield than stressed canola while irrigated canola performed better than irrigated mustard. High mustard biomass production resulted in lowering its harvest index. Generally, the biomass water productivity of mustard was higher than that of canola. Grain yield-based water productivity of stressed mustard was higher than that of stressed canola while irrigated canola had higher water productivity than irrigated mustard. When rainfall and actual evapotranspiration drop below some thresholds, mustard becomes a favourable crop. Generally, effects due to the water treatments (stressed v irrigated) were much larger than the differences due to species.

Papaya has never been found in the wild, but is believed to have originated in tropical America from where it has spread throughout the tropics and subtropics. This fruit crop is particularly important in India and Brazil. Most research on the water relations of papaya has been undertaken in Brazil and on the island of Guam (United States of America). Papaya is a short-lived large herb, growing to a height of up to 10 m. Leaves emerge from the upper part of the unbranched stem. After a juvenile period, lasting for about two months, flowers begin to develop in leaf axils. Flowering continues throughout the year as new leaves emerge. The plants, which are dioecious, begin to bear fruit within a year after planting, sustaining high yields for two years before yields decline. The ‘effective’ root depth varies with the method of irrigation, but can reach 0.55 m. The seedlings and the trees are susceptible to wind damage, a topic that has been well researched. Stomata are only found on the abaxial leaf surface. They are sensitive to changes in the saturation deficit of the air. Stomata also respond quickly to changing light conditions. On clear days, midday suppression of photosynthesis occurs as a result of partial closure of the stomata. In the morning, there is a time lag between water loss by transpiration and sap flow, as water is taken from storage in the hollow stem. Few attempts have been made to measure the actual water use of papaya, and there are no reliable published values for the crop coefficient. Limitations to the design of the papaya irrigation experiments reported so far make it difficult to reconcile the results in practical ways. Water productivities equivalent to 1.8 to 2.8 kg (fresh fruit) m−3 (irrigation water) have been obtained. Although papaya is generally considered to be drought sensitive and responsive to irrigation, there is a shortage of good experimental evidence to support this view. There is a need to establish practical irrigation schedules for this remarkable crop. A uniformity of approach to irrigation experimentation and a common, universally agreed nomenclature would facilitate this process.

The establishment of leys for biomass production during the winter months could be an alternative feed resource of low cost for small ruminants in Mediterranean basin. For this purpose, an experiment was carried out with six plant species mixtures (PSM) that were cut up to seven times from seeding. The results showed that all the PSM had their highest growth at the 2nd cut with Festuca arundinacea, Lolium perenne, Dactylis glomerata, Trifolium repens (FLDT) being superior as the dry matter production concerns compared with the PSM that gave seven cuts. The crude protein and the ether extracts contents in all the PSM decreased from the 1st to the last cut, while that of NDF and ADF increased. The concentrations of myristic, palmitic, stearic, oleic and linoleic acid increased in all the PSMs from the 2nd to the 5th cut, while the opposite was observed for the α-linolenic acid content. The concentration of α-linolenic acid was higher in the FLDT PSM when compared to others during all cuts. Taking into account all the examined parameters together, the FLDT seems to be superior to the other PSMs as animal feed for small ruminants, particularly during the period where there is no available grass from natural grasslands.

Sorghum (Sorghum bicolor (L.) Moench) is a major staple crop of Burkina Faso where farmers continue to cultivate photoperiod-sensitive guinea landraces as part of the strategy to minimize risk and ensure yield stability. In the Boucle du Mouhoun region, however, sorghum farmers appear to have insufficient varietal choice due to cropping systems having shifted towards more intensive cultivation of cotton and maize, and rainfall patterns having decreased over the past decade. In search for new varietal options that can respond to this changing context, researchers decided to give farmers access to ex-situ national collections along with the opportunity to evaluate recent improved varieties. From 2002 to 2007, researchers and farmers worked closely together to implement on-farm testing, including varietal selection trials, crop management and multi-locational trials. Farmers’ choices tend to differ among groups, villages and years, with the exception of four particular landraces: two originating from a collection carried out in the Mouhoun region more than 30 years previous to this research, and two other landraces that came from the dissimilar agro-ecological zones of Burkina Faso. These four were the most commonly selected landraces out of 36 cultivars that covered both improved and landrace varieties. Farmers’ selection criteria were focused on adaptation to agro-climatic conditions as well as specific grain qualities for processing and consumption. The potential usefulness of each variety was verified via multi-locational trials. The paper also shows that wide dissemination of experimental seed, not just across the Mouhoun region but also at a national scale, was largely achieved through collaboration with a strong farmer organisation in conjunction with farmer training programs focused on the on-farm seed production and the commercialisation of this seed.

The paper describes value chain actors and institutional arrangements along value chains, and identifies major determinants of farmers’ decision making to work with middlemen/traders ‘jabbans’ (or cheese makers), and based on those identify short implications for research, development and policy processes. We hypothesize that small-scale sheep producers are more dependent on middlemen for market and loans than larger holders, leading to welfare losses. Our empirical findings based on a Heckman model applied for 120 farming households conducted in Khanasser region (Syria) show that despite unequal benefits, local arrangements are more blessing than curse for the poor. Small-scale sheep producers and middlemen developed intricate institutional arrangements that are mutually beneficial. Producers act collectively to pool sufficient quantity of milk to be attractive to traders (jabban) while gaining access to market and cash loans mainly for feed. This provides the middlemen needed supplies with reduced transaction costs. This suggests that development organizations should support local capacity of producing organizations to work together, small-scale producers to organize, develop small scale dairy processing workshops for pooling and possibly processing milk, support training for direct market access and facilitate access to loans. Finally, supporting organizations such as rural financial services and micro-finance need to ensure up-to-date market information is available to ensure fair prices are paid. They should also be able to negotiate favourable conditions for loans and reach out to these resource-poor rural populations where formal credit systems are absent.

An on-farm study was conducted from 2009 to 2012 with communities in the Manjawira, Mpingu and Zidyana Extension Planning Areas in the Ntcheu, Lilongwe and Nkhotakota districts of central Malawi. The aim of the study was to evaluate the effects of the principles (no-tillage and mulching) and components (fertilization and weeding) of conservation agriculture (CA) on crop productivity and weeds, and the interactions between principles and components, and to suggest strategies for introducing CA to smallholder farmers. The treatments consisted of tillage, fertilizer application, residues management and weed control strategies. While combined analysis showed that mulching is as effective as tillage in controlling weeds, the interaction between site and treatment revealed that in the more humid environment of Zidyana, weed dry matter obtained under no-tillage and residues plus fertilizer (NT+F+R) was 0.6 mg ha−1 lower than under CP+F. Results suggest that about 6.0 mg ha−1 of mulch is required to have a similar effect as tillage in controlling weeds. Fertilizer had an overriding effect on maize yield, regardless of tillage and crop residue management. Mulching was beneficial over tillage in the drier environment of Manjawira, where maize yield obtained under NT+F+R was 1.2 mg ha−1 greater than under CP+F. Our results show that the introduction of no tillage has benefits only if it is accompanied by fertilizer application, retention of crop residues as surface mulch, and improved weed control. Increasing availability and accessibility of inputs (fertilizers and herbicides) to farmers is critical for adoption of CA at scale in Malawi.

Soil acidity and phosphorus (P) deficiency are some of the major causes of low maize yields in Kenya. This study determined the immediate and residual effects of lime and P fertilizer on soil pH, exchangeable aluminium (Al), available P, maize grain yield, agronomic P use and P fertilizer recovery efficiencies on a western Kenya acid soil. The treatments were: P fertilizer (0, 26 and 52 kg P ha−1 as triple super phosphate) and lime (0, 2, 4 and 6 tons lime ha−1) applied once at the beginning of the study. A burnt liming material with 92.5% calcium carbonate equivalent was used. Soil samples were analysed prior to and after treatment application. The site had low soil pH–H2O (4.9), available P (2.3 mg kg−1), total N (0.17%), high Al (2.0 cmol kg−1 exchangeable Al and 29% Al saturation). Lime reduced soil pH and exchangeable Al, leading to increased soil available P. Lime at 2, 4 and 6 tons ha−1 maintained soil pH ≥ 5.5 for 2, 3 and 4 years, respectively. The study observed that the recommended P fertilizer rate (26 kg P ha−1) for maize production in Kenya was inadequate to raise soil available P to the critical level (≥10 mg P kg−1 soil bicarbonate extractable P) required for healthy maize growth. To maintain soil available P at the critical level where 52 kg P ha−1 and combined 52 kg P ha−1 + 4 tons lime ha−1 were applied, it would be necessary to reapply the same P fertilizer rate after every one and two cropping seasons, respectively. The 4-year mean grain yield increments were 0.17, 0.34, 0.50, 0.58 and 1.17 tons ha−1 due to 2, 4, 6 tons lime ha−1, 26 kg P and 52 kg P ha−1, respectively. Both agronomic P use and P fertilizer recovery efficiencies increased with increasing rates of lime and decreased with increasing rates of P fertilizer. Therefore, combined applications of both lime and P fertilizer are important for enhancing maize production on P-deficient acid soils in western Kenya.

Seasonal drought stresses as a result of changes in global climate and local weather conditions are among the major factors adversely affecting growth and productivity of Robusta coffee (Coffea canephora pierre ex froehner) in many areas producing the crop. It is believed that there exists a wide range of genetic variability among Robusta coffee clones for traits associated with drought tolerance. Therefore, in an attempt to determine differences among Robusta coffee clones for some growth, physiological and biochemical parameters and identify drought-tolerant materials, 12 months old seedlings of six clones (IC-2, IC-3, IC-4, IC-6, IC-8 and R-4) were subjected to two treatments: well-watered control and drought-stressed (soil drying) by withholding irrigation for three weeks in a rain shelter at University Putra Malaysia, Malaysia. The rate of stress development, expressed as extent of wilting and damage to leaves, was considerably higher for clones IC-8, IC-4, R-4 and IC-2 than for IC-3 and IC-6 during the stress period. Leaf water potential (LWP), stomatal conductance (gs) and rate of net photosynthesis (PN) progressively decreased but leaf proline (LP) concentration substantially increased with time of exposure of the plants to soil drying. There was a considerable difference between coffee clones for the rate of change in these parameters. All the clones except IC-6 and IC-8 showed a negative carbon balance with the most negative value for R-4 at the end of the stress period. Six days after rewatering, LWP, gs and PN increased rapidly while LP concentration decreased and reached a level equivalent to those of well-watered plants, especially for clones IC-3 and IC-6. Among the drought-stressed plants, IC-6 and IC-3 had still significantly higher shoot growth, total dry matter yield and root to shoot ratio than did IC-2, IC-4, IC-8 and R-4. In general, clones IC-6 and IC-3 exhibited quite a better performance in almost all the parameters considered in this study and seemed to be less sensitive to drought stress. Hence, drought tolerance attributes in these clones could be linked to a more effective osmotic adjustment due to more rapid accumulation of LP and probably some morphological parameters, such as increased root-to-shoot ratio. However, further analyses at molecular level, detail biochemical studies and observations under diverse field conditions are required to come up with more conclusive recommendations.

The aim of this work was to test the performance of a shrimp-tomato culture system (STCS) in an arid-semiarid region (Sonora, Mexico) and to evaluate the water quality variables and phytoplankton variation of shrimp effluent and that water returning from the tomato module culture. The field study was conducted using groundwater and consisted of three circular tanks that were used for shrimp (Litopenaeus vannamei) farming and were coupled to one culture module of tomato plants (Lycopersicon esculentum). The shrimp effluent was used to irrigate the tomato plants. The yield was 11.1±0.2 kg shrimp per tank (3.9±2.0 ton ha−1) and 33.3 kg tomatoes per 45 plants (36.1±2.3 ton ha−1). During the culture, the concentrations of nutrients were (mg L−1): total N-ammonia, <0.001–0.848; N-nitrite, <0.001–1.45; N-nitrate, 5.2–172.2; dissolved reactive-P, <0.005–0.343. A total of 35 taxa belonging to three different algal classes were observed: Chlorophyta (87 to 98%), Bacilliariophyta (2 to 9%) and Cyanophyta (0–3%). This STCS allowed us to harvest the equivalent of 3.9 ton ha−1 of shrimp and 36.3 ton ha−1 of tomatoes, with a water consumption of 2.1 m3 per kg harvested of both products.

Potassium (K) is an essential nutrient and abundant cation in plant cells. The application of K+ could alleviate abiotic stress. However, it was reported that the alleviation of K+ on salt-stressed plants only happened when K+ concentration was low. Most studies were focused on effects of sodium salts on plants in salty soils, and little information was reported about potassium salts, especially a higher level of potassium in alkaline salts. To explore the effects of K+ in alkaline salts on plant growth, and whether it had a same destructive impact as Na+, we mixed two alkaline sodium salts (ASS) (NaHCO3:Na2CO3 = 9:1) and two alkaline potassium salts (APS) (KHCO3:K2CO3 = 9:1) to treat 10-day-old wheat seedlings. Effects of ASS and APS on growth, photosynthesis, ions absorption and solutes accumulation were compared. Results indicated that effects of potassium salts in soil on plants growth were related to K+ concentration. Both growth and photosynthesis of wheat seedlings decreased, and the reduction was higher in APS treatment than in ASS treatment at 40 mM alkalinity. ASS treatment absorbed Na+, competing with K+ and free Ca2+, and inhibited the absorption of inorganic anions. APS treatments accumulated K+ and reduced the absorption of anions, with no competition with other cations. Both APS and ASS treatments promoted free Mg2+ accumulation and inhibited H2PO4−uptake. The reduction of H2PO4− promoted organic acid synthesis indirectly. Soluble sugar and proline accumulation were also related to the alkaline condition and extra K+ addition. In conclusion, excess potassium ions in soil, especially in alkaline soils, were harmful to plants. APS was another severe salt stress, intensity of which was higher than ASS. The growth and physiological response mechanisms of wheat seedlings to APS were similar to ASS. Both inorganic ions and organic solutes took part in the osmotic adjustment. Differences for APS depended on K+, but ASS on Na+.

Seedling emergence and stand establishment of crops following the allelopathic crops are often affected. When the crops are grown in rotation, they are influenced by allelopathy of preceding crop. In this study, consisting of three independent experiments, allelopathic effect of tobacco, rich in several allelochemicals, on the subsequent maize and mungbean crops was investigated. In first experiment, maize and mungbean were sown in field previously occupied by tobacco or was fallow. In second experiment, maize and mungbean were planted in pots after the harvest of tobacco. Whereas in third experiment, maize and mungbean seeds were soaked in water or 2 and 4 mM nicotine and were then sown in soil-filled pots. Stand establishment, leaf emergence and growth of maize were significantly improved when grown after tobacco, whereas in mungbean these characters were suppressed when grown after tobacco. Likewise external application of nicotine improved the emergence uniformity, seedling dry weight and chlorophyll contents in maize and suppressed these parameters in mungbean. Tobacco allelopathy also increased the total soil nitrogen, zinc, iron, nicotine and total phenolics. Nicotine-induced change in chlorophyll contents and α-amylase activity seems the possible reason of differential response of maize and mungbean to tobacco allelopathy. When grown in rotation with tobacco, stand establishment and growth of maize were improved, whereas mungbean stand and growth were suppressed. In crux, allelopathic nature of the crops must be considered while making the crop rotations.

A field experiment was carried out at the farm of Indian Agricultural Research Institute, New Delhi to quantify the effect of elevated carbon dioxide (CO2) and different levels of N fertiliser application on nitrous oxide (N2O) and carbon dioxide (CO2) emissions from soil under maize. The experiment included five treatments: 60 kg N ha−1 under ambient CO2 (385 ppm) in open plots, 120 kg N ha−1 under ambient CO2 (385 ppm) in open plots, 160 kg N ha−1 under ambient CO2 (385 ppm) in open plots, 120 kg N ha−1 under ambient CO2 (385 ppm) in open top chambers (OTC) and 120 kg N ha−1 under elevated CO2 (500 ± 50 ppm) in the OTC. Peaks of N2O flux were observed after every dose of N application. Cumulative N2O emission was 13% lower under ambient CO2 as compared to the elevated CO2 concentrations. There was an increase in CO2 emissions with application of N from 60 kg ha−1 to 160 kg ha−1. Higher yield and root biomass was observed under higher N treatment (160 kg N ha−1). There was no significant increase in maize yield under elevated CO2 as compared to ambient CO2. The carbon emitted was more than the carbon fixed under elevated CO2 as compared to ambient CO2 levels. The carbon efficiency ratio (C fixed/C emitted) was highest in ambient CO2 treatment in the OTC.