International Journal of Plant Production
Volume:8 Issue: 3, Jul 2014

Global consciousness of food safety, health and environmental issues has stimulated interest in alternative agricultural systems like organic farming. Since information on organic farming of tuber crops is meagre, a field experiment was conducted in split plot design over a five-year period at Central Tuber Crops Research Institute, India. The aims were to evaluate the impact of organic, conventional and traditional production systems on yield, proximate composition and mineral content of tubers and soil physico-chemical and biological properties in three species of Dioscorea (white yam: D. rotundata, greater yam: D. alata and lesser yam: D. esculenta). The production systems were assigned to main plots and species to subplots. Organic farming (20.34 t ha-1) produced significantly higher yield over conventional practice (18.64 t ha-1) by 9%. All the species responded well to organic management, which lowered the bulk density and particle density slightly and improved the water holding capacity (by 15%) of soil. Tuber quality was improved with significantly higher Ca (72.67 mg 100g-1), slightly higher dry matter, crude protein, K and Mg contents. Organic plots showed significantly higher available K, by 34% and pH, by 0.46 unit and higher soil organic matter by 14%. The dehydrogenase enzyme activity (1.174 μg TPF formed g-1 soil h-1), population of bacteria, fungi and P solubilizers were promoted by 14%, 23%, 17% and 22% respectively. Thus organic farming was found to be an eco-friendly management strategy in yams for sustainable yield of quality tubers besides maintaining soil health. Technology involving farmyard manure, green manuring, neem cake, biofertilizers and ash was standardized.

The use of leaf mulch as a soil cover is effective in improving yield and soil fertility. The field experiment was conducted during 2010 and 2011 to study the effect of plant spacing (30 cm × 30 cm and 45 cm × 30 cm) and four mulches {pine needles (Pinus roxburghii), poplar leaf (Populus deltoides), silver oak (Grevillea robusta) tree leaf mulch and unmulched control} on growth, yield, quality of stevia and soil fertility. Weed count and dry weed weight was not affected by spacing levels during August and at the time of harvest, whereas, in unmulched plots it was significantly higher than mulched plots. Dry leaf yield, total dry biomass and leaf area index (LAI) were significantly higher in 30 cm × 30 cm spacing level and poplar leaf mulch. All the mulched plots significantly increased organic carbon (OC), available nitrogen (N), phosphorus (P) and potassium (K), bacterial and fungal population compared to unmulched plots. Rebaudioside-A content was higher in plots mulched with poplar leaves. Steviol glycosides were not significantly affected by different treatments. Soil biological activities were also enhanced by tree leaf mulches. Leaf mulch enhanced microbial biomass, relative to non-mulched soils, likely via improving C and water availability for soil microbes.

The root is an important plant part contributing to peanut productivity under water- limited conditions. Root volume, root surface area and root diameter may be characters responding to pre-flowering drought (PFD) in peanut. The objectives of this study were to investigate the responses to PFD for root surface area, root volume and root diameter and to determine the inter-relationships among the response of rooting traits and the response of yield. The experiment was conducted under field conditions in the dry season 2007 and 2009. A split-plot experiment in a randomized complete block design was used. The main plots were field capacity (FC) and PFD and six peanut genotypes as the sub-plots. Root volume, root diameter and root surface were measured by auger method at 25 days after emergence (DAE), first seed (R5) and physiological maturity (R7). Total dry weight and pod yield were measured at harvest. Root surface area of ICGV 98305 with increase in pod yield was greater in deeper soil layers under PFD compared toFC treatment at both stress and recovery periods. Under PFD conditions, the correlations between drought tolerance index (DTI) for root surface area at deeper soil layer and DTI for pod yield in both seasons were positive and significant at stress and recovery periods, but the correlations were not significant for root diameter and root volume. The response of peanut for root surface area at deeper soil layer contributed to pod yield. This finding could be useful for peanut production in these drought conditions.

The environmental, social and economical reasons indicate that the conventional agriculture constitute a continuous pressure contributing to the progressive worsening of environmental conditions, especially by an increasing apply high level of inputs. In this matter, the increasing use of saline irrigation water is one of the main factors resulting in salt accumulation in the plant rhizosphere influencing both physical, chemical and biological soil properties and agroecosystem productivity. In this situation, soil degradation emphasized the need to develop strategies of salt effected soil reclamation. One of the possible solutions is to use humic substances (HS), since there is an increasing need to their utilization in agriculture. They are the major components of soil organic matter, have multiple roles in plant growth and are the subject of study in various areas of agriculture, such as soil chemistry, soil fertility and plant physiology. Thus, our hypothesis account for a beneficial effect of HS in salt affected rhizosphere likely due to a ''direct'' action on the plant together with an ''indirect action'' on the metabolism of soil microorganisms, the dynamics of uptake of soil nutrients and soil physical conditions. In this paper we review the HS formation and components and their influences on improving saline soil properties as both direct and indirect effects.

Field experiment was conducted for 2 seasons to study the influence of drip fertigation in combination with or without bio fertilizers on yield, plant uptake and soil fertility of Bt cotton. The treatments comprised of four levels of drip fertigation viz., 75, 100, 125 and 150 per cent of recommended dose of fertilizers (RDF, NPK) combined with and without bio fertilizers, drip irrigation with soil surface application of 100 per cent RDF and surface irrigation with soil surface application of 100 per cent RDF as control. Biofertilizers used for fertigation is azophosmet containing Azospirillum, phosphobacterium and pink pigmented facultative methylotroph. Most of the yield attributes viz., number of sympodial branches per plant, number of fruiting points, bolls per plant, plant uptake and available soil N, P and K of Bt cotton were significantly increased by the drip fertigation treatments. Application of 150 per cent RDF as drip fertigation combined with biofertigation of liquid formulation of azophosmet @ 250 ml (1012 cells ml-1) ha-1 registered the highest seed cotton yield of 3395 kg ha-1 and was significantly superior over control. Biofertigation significantly increased seed cotton yield and a progressive increase in seed yield was noticed with increasing levels of NPK fertilizer application. Application of nutrients through drip fertigation improved seed cotton yield by 43.0 per cent compared with conventional surface irrigation with soil surface application of fertilizers. The nutrient uptake pattern and post harvest soil fertility status also followed similar trend and confirmed the significance of drip fertigation with biofertilizers.

Biomass of legumes grown as catch crops improves soil properties and thus soil conditions for following crops. The aim of this study was to evaluate the effect of field pea (Pisum sativum L.) grown as a catch crop and used for green manure on soil properties and yielding of spring barley (Hordeum vulgare L.). Field experiments were conducted in 2008-2011 in the randomized block design with four replications, in typical black earth. The experimental factor was the time and way of catch crop incorporation: in autumn–with plowing (1); in the spring–with disking (2); control–without a catch crop (3). The soil with the catch crop contained significantly higher mineral nitrogen in the topsoil during tillering of barley than the control. Catch crop caused significant decrease in soil moisture and increase in penetration resistance in the topsoil in autumn. No significant effect of the catch crop on soil moisture during spring barley growing season in the following spring was obtained. Catch crop plowing in autumn caused significant decrease in soil penetration resistance in the 20-30 cm layer in early spring. Catch crop biomass plowed positively affected the number of spikes in sequential spring barley. Leaving pea as mulch for winter caused significant increase in 1000 grain weight compared to the control. Field pea grown as a catch crop for green manure can be recommended for increasing mineral nitrogen concentration and the soil biological activity in the topsoil. However, its influence on spring barley yield in fertile soils is low.

Potato grown for early or off-season production plays a crucial role in the economy of several areas in the Mediterranean countries. Irrigation is important for determining yield and earliness, thus a better investigation of plant response under various pedo-climatic conditions can help to improve resource use efficiency and farmer income. A two-year field research (2009-2010) was carried out in Apulia region, southern Italy, on cv Spunta grown under three irrigation regimes: full irrigation (I100), 50% of full irrigation (I50) and rainfed (I0). Treatments were arranged in a randomized complete block design with three replicates. Plant water status, plant growth and, at harvesting, water use efficiency, yield and quality parameters were quantified. Water stress significantly affected yield response: as an average of the two years, a marketable yield decrement of 25.9 and 63.6% was observed in I50 and rainfed compared with I100 treatment, respectively. On the contrary, tuber dry matter and specific gravity increased moving from irrigated treatments to the rainfed one and varied also as a function of experimental year. The results confirmed that irrigation is required for early potato cultivation because rainfall is not sufficient to meet crop water needs. In addition, the study indicated that the irrigation regime reduced by 50% of crop water requirements was able to furnish satisfactory yield, with tuber quality characteristics similar or even better than those obtained under full irrigation.

A microplot experiment was conducted in soybean–wheat cropping system at New Delhi during 2010-11 and 2011-12 to study the effect of continuous or cyclic tillage, viz., conventional tillage (CT) and zero-tillage (ZT) and residue management of either soybean (SR) and/or wheat (WR) on yield performance and soil physico-chemical properties. The experiment was laid out in randomized block design with two replications in microplots of size 4×1.4 m. Plant height of soybean was influenced due to tillage and residue management at different growth stages. All yield attributes of soybean were showed variation due to treatments. The harmful effects of ZT on yield attributes could be overcome with residue application on soil surface. The results indicated that tillage and residue management to the immediate crop of soybean was more important for increasing grain yield (26%) and stover production (32%) of soybean and the residual effect of residue to previous soybean was relatively small. The change in organic C was relatively small even with regular addition of crop residues. There was no change in available nutrients (N, P and K) due to tillage and residue management treatments. The variation in soil physical properties was also small and a significant improvement may be expected over several years of continuous application of crop residue and ZT.