The results of research into the water relations and irrigation requirements of lychee are collated and reviewed. The stages of plant development are summarised, with an emphasis on factors influencing the flowering process. This is followed by reviews of plant water relations, water requirements, water productivity and, finally, irrigation systems. The lychee tree is native to the rainforests of southern China and northern Vietnam, and the main centres of production remain close to this area. In contrast, much of the research on the water relations of this crop has been conducted in South Africa, Australia and Israel where the tree is relatively new. Vegetative growth occurs in a series of flushes. Terminal inflorescences are borne on current shoot growth under cool (<15 °C), dry conditions. Trees generally do not produce fruit in the tropics at altitudes below 300 m. Poor and erratic flowering results in low and irregular fruit yields. Drought can enhance flowering in locations with dry winters. Roots can extract water from depths greater than 2 m. Diurnal trends in stomatal conductance closely match those of leaf water status. Both variables mirror changes in the saturation deficit of the air. Very little research on crop water requirements has been reported. Crop responses to irrigation are complex. In areas with low rainfall after harvest, a moderate water deficit before floral initiation can increase flowering and yield. In contrast, fruit set and yield can be reduced by a severe water deficit after flowering, and the risk of fruit splitting increased. Water productivity has not been quantified. Supplementary irrigation in South-east Asia is limited by topography and competition for water from the summer rice crop, but irrigation is practised in Israel, South Africa, Australia and some other places. Research is needed to determine the benefits of irrigation in different growing areas.

The objective of this study was to determine whether salicylic acid, nitric oxide (NO) and/or feeding by nymphs of the spittlebug Mahanarva spectabilis affect the concentration of total phenolic compounds and the dry matter content of different genotypes of elephant grass (Pennisetum purpureum). Four genotypes of elephant grass with varying levels of resistance to insect attack were treated with 4 mL of salicylic acid (1%) or 2 mL of NO per plant in the presence and the absence of nymphs. We determined the concentration of total phenolic compounds and the percentage dry matter of shoots and roots in the plants. We found that salicylic acid, NO and attack by M. spectabilis did not change significantly the total phenolic compounds concentration in any of the genotypes of elephant grass tested. However, we observed variations in the concentration of phenolic compounds produced between the resistant and susceptible genotypes, both in the shoot, when subjected to salicylic acid or nymphs, and in the roots in the presence of nymphs. Furthermore, the inducers resulted in variation in the dry matter content of the shoots and roots for most of the genotypes tested. Therefore, we conclude that chemical inducers and feeding by M. spectabilis nymphs cannot be used to elicit a resistance response in elephant grass by stimulating the production of phenolic compounds.

Cultivation of less productive soils such as closed landfills has become convenient because European subsidies covered part of the risk to obtain production. Aim of the research was to evaluate grain yields of maize hybrids belonging to different maturity classes (FAO 200, 300 and 400) (Gretzmacher, R. (1979). Die Bodenkultur 30:256--280) grown on closed landfills by the adoption of two minimum tillage methods (chisel plowing at 0.35 m plus disk harrowing at 0.20 m, or only disk harrowing at 0.20 m). Maize cultivation inserted in a winter cereal rotation had a grain production ranging from 4.6 t ha−1 (FAO 200, disk harrowing only) to 8.3 t ha−1 (FAO class 400, chisel plowing plus disk harrowing) in the two considered years (2011 and 2012). The adoption of chisel plowing coupled with disk harrowing reduced yield fluctuation between years, and furnished higher yield performance if compared with the single disk harrowing passage. The best growing hybrid cycles were those belonging to FAO class 300 with production similar to that of the longest maturity class, and with moisture content equal to the shortest maturity class.

The complex dynamics of the sulphur (S) cycle has prompted several questions concerning its bioavailability and evaluation by different extraction methods, and few studies under field conditions have been performed to elucidate available S on Brazilian soils under no-till (NT) cropping systems. A field experiment examined the effects of phosphogypsum (PG) applications on nutrient uptake and availability of S to maize and wheat crops under an NT system aiming to establish critic levels of S on an Oxisol (clay, kaolinitic, Rhodic Hapludox) in Parana state, Brazil. PG at the rates of 0, 3, 6 and 9 t ha−1 was applied on the surface of the plots in 1998 upon conversion from pasture to an NT cropping system, and in 2004 subplots received either 0 or 6 t ha−1 of PG on the surface. Effects of PG applications on nutrient uptake and available soil SO4-S to the maize and wheat crops were evaluated in 2004–2005. Increasing the surface-applied PG rate in 1998 increased Mg uptake by maize, and N, K, Ca and Mg uptake by wheat plants. Reapplication of PG in 2004 increased the uptake of N and P by maize, and the uptake of N, K, Ca and Mg by wheat plants. The PG rates surface-applied in 1998 have resulted in a long-term residual effect on soil by increasing SO4-S in surface and subsoil layers 6.5 and 7.5 years after application, affecting aboveground biomass, S uptake and S content in the leaves of the wheat crop. The reapplication of PG in 2004 increased maize S uptake, S content in leaves and grains and S exported by maize harvest, and increased wheat aboveground biomass, S uptake and S content in leaves. These effects were due to increasing available soil SO4-S from different depths extracted by 0.5 M ammonium acetate (NH4OAc) along with 0.25 M acetic acid (HOAc) and 0.01 M calcium phosphate (Ca(H2PO4)2). Both extractants were very similar in their ability to assess available soil S in these crops, and the 0–0.20-m layer is shown to be adequate for evaluating the concentration of available SO4-S in maize and wheat cultivated under NT.

Modern maize varieties have been bred for drought tolerance and early maturity, to assist farmers in avoiding or escaping the effects of moisture stress in drought-prone areas. This study evaluates the prospects for widespread adoption of these modern maize varieties as a climate change adaptation strategy for smallholder farmers. Data are from a detailed household survey completed in four rural villages in Southern Malawi between May and July 2010. The empirical analysis involves estimation of an ordered logit regression model because the dependent variable is categorical, with one category for nonadoption (has never grown modern maize varieties) and three categories for the duration of growing a modern maize variety among adopters (this year only, 2 to 5 years and 6 years or more). The empirical findings indicate a positive association between a farmer's perception of drought risk and the adoption and continued use of modern maize. Regression results also show that farmers that value the traits of early maturity and drought tolerance are more likely to adopt modern maize varieties. There is evidence of some disadoption among farmers dissatisfied with maize genotype performance, in terms of poor storability and yield under drought conditions. Finally, the study highlights the urgent need for maize breeders interested in sustained use of modern varieties to simultaneously address robust drought tolerance, early maturity and storability. This underscores the importance of cognizance of local farmer preferences in crop breeding efforts.

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.

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.

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.

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.