Continuous cultivation of rice–wheat cropping system in the Indo-Gangetic plains is under threat with decline in soil organic carbon (SOC), total factor productivity and overall sustainability. Pulses, an important component of crop diversification, are known to improve soil quality through their unique ability of biological N2 fixation, leaf litter fall and deep root system. Therefore, the effect of inclusion of pulses in the puddled rice system under organic and inorganic amendments on SOC pool and its management indices were evaluated in a long-term experiment after seven cropping cycles. The results indicated that inclusion of pulses in the rice-based system improved the SOC content, being greater in surface soil (0–20 cm) and declining with soil depth. Among the four carbon fractions determined, less labile carbon fraction (Cfrac3) was the dominant fraction in the puddled rice system, particularly under organic treatments, indicating that it is possible to maintain organic carbon for longer time in this system. The rice–wheat–mung bean system resulted in 6% increase in SOC and 85% increase in soil microbial biomass carbon as compared with the conventional rice–wheat system. Application of crop residues, farm yard manure (5 t ha−1) and biofertilisers had greater amount of carbon fractions and carbon management index (CMI) over control and the recommended inorganic (NPKSZnB) treatment in the soil surface, particularly in the system where pulses are included. Interestingly, in the puddled rice system, passive carbon pool is more in surface soil than deeper layers. The relative proportion of active carbon pool in surface layer (0–20 cm) to subsurface layer (20–40 cm) was highest in rice–wheat–rice–chickpea (1.14:1) followed by rice–wheat–mung bean (1.07:1) and lowest in the rice–wheat system (0.69:1). Replacing wheat with chickpea either completely or during alternate year in the conventional rice–wheat system also had positive impact on SOC restoration and CMI. Therefore, inclusion of pulses in the rice-based cropping system and organic nutrient management practices had significant impact on maintaining SOC in an Inceptisol of the Indo-Gangetic plains of India.

The results of research on the water relations and irrigation need of pineapple are collated and summarised in an attempt to link fundamental studies on crop physiology to irrigation practices. Background information on the centres of origin (northern South America) and of production (Brazil, Thailand and the Philippines) of pineapple is followed by reviews of crop development, including roots, plant water relations, crop water requirements and water productivity and irrigation systems. The majority of the recent research published in the international literature on these topics has been conducted in the United States (Hawaii) and Brazil. Pineapple differs from most other commercial crops in that it has a photosynthetic adaptation (crassulacean acid metabolism (CAM)) that facilitates the uptake of carbon dioxide at night, and improves its water-use efficiency under dry conditions. The crop is propagated vegetatively. The succulent leaves collect (and store) water in the leaf axils, where it is absorbed by surrounding tissue or by aerial roots. There is little published information on the effects of water deficits on vegetative growth, flowering or fruiting. Water stress can reduce the number of fruitlets and the fruit weight. After harvest, one or two ratoon crops can follow. Roots originate from just behind the stem-growing point, some remaining above ground (aerial roots), others entering the soil, reaching depths of 0.85–1.5 m. Root growth ceases at flowering. The ratoon crop depends on the original (plant crop) root system, including the axillary roots. Stomata are present on the abaxial leaf surfaces at relatively low densities (70–85 mm−2). They are open throughout the night, and close during the day before reopening in mid-afternoon. The degree to which CAM attributes are expressed depends in part on the location (e.g. tropics or subtropics), and possibly the cultivar, with the total amount of carbon fixed during the night varying from <3% to >80%. There are surprisingly few published reports of field measurements of crop water use and water productivity of pineapple. Two reports show evapotranspiration only occurring during the daytime. There is more uncertainty about the actual water use of pineapple, the value of crop coefficient (Kc) and relative rates of water loss (transpiration) and carbon gain (net photosynthesis), during the daytime and at night, under different water regimes. This is surprising given the amount of fundamental research reported on photosynthesis of CAM plants in general. Although pineapple is mainly a rainfed crop, it is widely irrigated. Drip irrigation is successfully used where the water supply is restricted, the cost of labour is high and cultivation techniques are advanced. Micro-jets can also be used, as can any of the overhead sprinkler systems, provided wind distortion is not a problem. There is a lack of reliable published data quantifying where irrigation of pineapple is likely to be worthwhile, how it is best practised and the benefits that can be obtained. This is remarkable considering the importance of pineapple as an internationally traded commodity.

The present study is to characterise the non-structural carbohydrate (NSC) status and its catabolism along with elongation growth in rice cultivars either possessing or not possessing the Sub 1 quantitative trait locus (QTL), i.e. Swarna and Swarna Sub1 exposed to seven days of complete submergence. During submergence, Swarna accelerated the rate of stem and leaf elongation and rapidly consumed NSC. In contrast, Swarna Sub1 consumed energy resources more slowly and maintained similar growth rate to that of non-submerged plants. Swarna Sub1 showed better utilisation of carbohydrate than that of Swarna by progressive induction of alcohol dehydrogenase, starch phosphorylase and total and α-amylase enzyme activity during submergence. Overall, submergence tolerance conferred by the Swarna Sub1 QTL is correlated with better maintenance and utilisation of NSC than that of Swarna.

This study deals with the ecophysiological response of Criollo cacao cultivars to water deficit during initial establishment phase in an agroforestry system under shade of four timber species using a randomised block design. CO2 assimilation rate (A), transpiration (E) and stomatal conductance (gs), water potentials, pressure–volume curves and fluorescence measurements were studied during two dry and wet seasons. Survival rates, basal diameter and leaf concentrations of K, P and N were also determined. All cultivars exhibited 60% reduction in gs with drought, resulting in 73% decrease in A and E. Despite lower A, electron-transport rates were not significantly affected, suggesting the existence of electron sinks. Photochemical quenching is negatively affected by drought in some cultivars, whereas relative quantum yield of photosystem II and non-photochemical quenching remained the same during both the periods. Cultivars with the highest osmotic adjustment coincided with the highest survival rates, whereas growth and leaf nutrient concentrations were similar in all cultivars.

A comparative study of two lettuce varieties (Lactuca sativa: ‘Romaine’ and ‘Vista’) was conducted to understand the effect of iron deficiency on growth, biomass allocation, chlorophyll fluorescence and root and leaf enzymatic activity. After 15 days of growth in hydroponic solution under Fe-deficient and Fe-sufficient conditions, leaf chlorophyll concentration, activities of ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco) in leaves extract, ferric chelate reductase (FCR) and phosphoenolpyruvate carboxylase (PEPC) in root extracts were measured. We found that there were significant differences in fresh matter accumulation and pigment concentration between the varieties. Fresh weight and total leaf area and leaf number were significantly reduced under iron deficiency. There was also a significant decrease in photosynthetic pigment concentration in both varieties. In response to Fe deficiency, ‘Vista’ variety showed higher FCR and PEPC activities compared to ‘Romaine’ variety. Moreover, this increase was accompanied by an enhanced accumulation of phenolic compound in roots of ‘Vista’ variety. These findings show that ‘Romaine’ was more affected by iron deficiency than ‘Vista’.

The uptake of urea fertilizer (NDFF), applied with 150 kg nitrogen (N) ha−1, topdressed in five splits of 30 kg N ha−1 (30 N) each at 7, 26, 45, 70 and 83 days after transplanting (DAT) of rice (Oryza sativa L.), was investigated in an improved (Khangma Maap, KM) and a traditional (Janam, JN) cultivar in Bhutan highlands, using enriched 15N stable isotope. The treatments were arranged in a split–split plot design, with N fertilizer levels as main plots, cultivars as subplots and topdressing treatments as sub-subplots, with all the sub-subplots receiving the same dose except different timing of one split of enriched 15N to determine partial N fertilize use efficiency at each split dose. Although cultivar differences were not recorded in soil N accumulation and in total dry matter N, KM produced 21% higher grain yields compared to JN due to higher grain harvest index and partial factor productivity of N. Irrespective of the cultivars, topdressing timing had significant effects on NDFF, with highest mean N recovery (REN) of 29% of applied 30 N at 45 DAT during active tillering stage, resulting in mean NDFF total (grain + straw) uptake of 8.71 kg N ha−1 compared to least effective topdressing timing at 7 DAT with mean REN of 12% and NDFF total of 3.51 kg N ha−1. In similarity to topdressing at 45 DAT, topdressing at 70 DAT (panicle initiation stage) was equally effective with mean REN of 27% across the cultivars. Hence, fertilizer N topdressing recommendations that combine use of improved cultivars with N applications timed to coincide with maximum crop demand at 45 and 70 DAT, could enhance N fertilizer use efficiency for increased rice yields as well as reduce N losses downstream, which can cause adverse off-site environmental effects.

Although triple cropping in inland valleys of Nigeria is technically feasible, the third crop between the main crop and dry season non-rice crop has been considered not to be economically viable because of poor crop establishment due to soil inundation. The identification of an appropriate technology with low input, such as ratooning, would allow this niche to be utilized. Field experiments were conducted at the University of Agriculture, Abeokuta, Nigeria in 2007–2008 and 2008–2009 cropping seasons to evaluate the performance of the main and ratooned crops of lowland NERICA (New Rice for Africa) rice (Oryza sativa L.) varieties in a lowland rice–ratooned rice–fluted pumpkin (Telfairia occidentalis Hook F.) sequence. The experiment was laid out in a randomized complete block design with three replicates. The lowland rice varieties used were NERICA-L 19, NERICA-L 20, NERICA-L 22, NERICA-L 24, OFADA, NERICA-L 26, NERICA-L 41, NERICA-L 42, NERICA-L 44 and NERICA-L 47. The grain yield of the main rice crop ranged from 5.0 to 7.3 t ha−1 in 2007–2008 cropping season and from 4.1 to 9.1 t ha−1 in 2008–2009. The ratooned rice had a grain yield of 1.0–4.7 t ha−1 in 2007–2008 and 1.2–3.4 t ha−1 in 2008–2009. The total grain yield obtained in 2007–2008 from the main and ratooned rice crops in seven months was 6.7–11.6 t ha−1, while in 2008–2009 it was 5.3–2.6 t ha−1. The fresh leaf yield of fluted pumpkin ranged from 14.6 to 16.9 t ha−1 in 2007–2008 and from 18.3 to 19.8 t ha−1 in 2008–2009, similar to previously reported rainy season unfertilized yields. Thus, a ratooned rice crop appears to be a feasible technology capable of boosting rice production and consequently increasing the overall productivity of the inland valley in a rice–rice–vegetable cropping sequence.

Citrus trees are often exposed to severe infectious diseases. Mal secco caused by Phoma tracheiphila (Petri) Kantschaveli and Gikashvili is one of the most destructive fungal diseases of lemons (Citrus limon Burm. F.). In the present study, antioxidant enzyme activity in different mal secco-resistant and susceptible citrus rootstocks including Cleopatra mandarin (C. reshni Tan.), sour orange (C. aurantium L.), rough lemon (C. jambhiri Lush.), Volkameriana (C. volkameriana Tan. and Pasq.), Carrizo citrange (Poncirus trifoliata L. Raf. X C. sinensis L. Osbeck) and trifoliate orange (P. trifoliata) was investigated. Possible differences in constitutive levels of these antioxidant enzymes and correlations between enzyme levels and mal secco caused by P. tracheiphila were examined. Among the rootstocks, Cleopatra mandarin was found to be resistant to mal secco, whereas rough lemon, sour orange and trifoliate orange were highly susceptible. Total peroxidase (TPX; EC: 1.11.1.7) activity increased in all infected rootstocks. Ascorbate peroxidase (APX; EC: 1.11.1.11) activity increased in most of the rootstocks and no correlation was found between catalase (CAT; EC: 1.11.1.6) activity and mal secco resistance. This study indicates that overall TPX activity is upregulated and APX activity is up- and down-regulated depending on the type of rootstock in response to P. tracheiphila infection.

Farmers around the world are concerned about the effects of human-induced salinity on crop yield and quality. Therefore, researchers are actively testing wild relatives of cultivated plants to identify candidates to improve crop performance under salt stress. A study was conducted to understand the effects of salt stress (Sodium chloride, NaCl) on cultivated tomato species (Solanum lycopersicum var. cerasiforme L.) and a wild tomato relative (Solanum chilense Dun.) from the Northern part of Chile. Plants were cultivated hydroponically under controlled environmental conditions for 112 days with nutrient solution containing 0 mM (3 dS m−1), 40 mM (6 dS m−1) and 80-mM (9 dS m−1) NaCl. Salt stress reduced the shoot biomass in S. lycopersicum but not in S. chilense. Both species were able to maintain the leaf water content; however, the cultivated S. lycopersicum showed osmotic adjustment, while S. chilense did not. Salt stress reduced the total fruit yield in S. lycopersicum based on a decrease in the mean fruit weight, but it had no impact on the number of fruits per plant. In contrast, salt stress had no significant impact on the fruit yield in S. chilense. Salt stress increased the total soluble solids content in S. lycopersicum and the titratable acidity in S. chilense. It was concluded that S. chilense displays a contrasting behaviour in response to prolonged exposure to moderate salinity compared with S. lycopersicum, and that this related species could be an interesting plant for breeding purposes.

The weedy variety of Oryza sativa occurs in several rice cultivation areas reducing both grain yield and quality. Prevention and crop rotation are considered the basic means to reduce its presence. Weed control in sorghum is generally attained with atrazine. In this study, the efficacy of both chemical and mechanical methods for control, under different soil tillage conditions, of weedy rice and barnyardgrass during sorghum cultivation was evaluated with the aim to reduce the application rate of atrazine. In the case of chemical control, the atrazine rate (1000, 1500, 2000, 2500 and 3000 ga.i. ha−1) and application timing (pre- and post-emergence) were assessed. With the mechanical control method, the number of interventions (inter-row hoeing with sorghum at 3, 4–5 and 6–8 leaves) to avoid weed competition was determined. The effect of the tillage system on weed population was investigated comparing conventional (ploughing), minimum-tillage (disc harrowing) and sod seeding (no-tillage) in combination with pre- and post-emergence herbicide treatments. The results showed that efficient control of weedy rice and barnyardgrass was achieved in lowlands with sorghum in rotation with rice. Both chemical and mechanical methods of weed control in sorghum gave a level of efficiency higher than 60%. The application of atrazine was more efficient in pre-emergence application, rather than in post-emergence treatments, in all soil tillage systems tested. On both weed species, the most suitable application rate was the pre-emergence treatment with 1500 ga.i. ha−1, and the adoption of higher rates did not significantly increase the herbicidal efficacy. The adoption of two or three mechanical interventions resulted in sorghum yield higher than the chemical post-emergence application, and similar to the application of atrazine in pre-emergence. Higher yield results were in accordance to greater weed control, being obtained in the conventional tillage system.