Evaluation and comparison of different economic and environmental scenarios for Bean (Phaseolous vulgaris L.) production via optimization of water superabsorbent, humic acid and cattle manure application rate

IntroductionMaintenance of soil fertility as a permanent bed for continuous production of agricultural products is one of the most important issues affecting the sustainability of food production. In order to achieve healthy food production, application of ecological inputs such as cattle manure and organic acids are inevitable. Cattle manure is an excellent fertilizer containing nitrogen, phosphorus, potassium and other nutrients. It also adds organic matter to the soil which may improve soil structure, aeration, soil moisture-holding capacity, and water infiltration. Humic substances are a mixture of different organic compounds that extract from various sources such as soil, humus, peat, oxidized lignite and coal. They are different in molecular size and chemical structure. A little amounts of humic acid increase soil fertility by improving the physical, chemical and biological characteristics of soil. Water super absorbents are water absorbing polymers (they may contain over 99% water). They have been defined as polymeric materials which exhibit the ability of swelling in water and retaining a significant fraction (> 20%) of water within their structure, without dissolving in water content. The applications of hydrogels are grown extensively. These materials have 100% natural structures and do not have any harm for the environment. Development of using super absorbent hydrogels to reduce crises such as soil erosion, frequent droughts or providing food security requires knowledge of their behaviors and performances in the soil. To determine the optimal irrigation water and fertilizer, the use of mathematical models is inevitable. One of the most common methods used to optimize these factors is the central composite design. A central composite design is an experimental design, useful in response surface methodology, for building a second order (quadratic) model for the response variable without needing to use a complete three-level factorial experiment. Considering the importance of bean as the main crop in Fabaceae family and also the lack of comprehensive information in the field of simultaneous optimization of water super absorbent, humic acid and cattle manure, in this study, different economic and environmental scenarios for bean (Phaseolous vulgaris L.) production via optimization of water super absorbent, humic acid and cattle manure application was evaluated.
Materials & MethodsIn order to estimate optimized application rates of water superabsorbent, humic acid and cattle manure in cultivation of bean, an experiment as Box Benken design using Response Surface Methodology, was conducted at Research Farm of Ferdowsi University of Mashhad, during 2013-14 growing season. The experimental treatments were designed considering of the high and the low levels of water superabsorbent (80 and 160 kg.ha-1), humic acid (4 and 8 kg.ha-1) and cattle manure (0 and 30 t.ha-1) using MINITAB Ver. 17 statistical software, as the central point in every treatment replicated 3 times, so 15 treatment combinations were provided totally.
Results & DiscussionThe result showed that the highest seed yield obtained in the middle level of humic acid (6 kg.ha-1), so that application of 6 kg.ha-1 humic acid increased seed yield 15 and 11% compared to the levels of 4 and 8 kg.ha-1, respectively. The moderate increasing of cattle manure amounts led to an increase in dry matter yield, so that by increasing the amounts of cattle manure from 0 to 15 t.ha-1, dry matter yield increased by 36%, but more increasing the amounts of cattle manure from 15 to 30 t.ha-1 led to a decrease in dry matter yield by 4%. By increasing the amounts of superabsorbent, nitrogen losses decreased, so that the application of 120 kg.ha-1 superabsorbent decreased nitrogen losses 17% compared to the level of 80 kg.ha-1. Nitrogen use efficiency in the 6 kg.ha-1 level of humic acid was 16 and 13% more than the levels of 4 and 8 kg.ha-1, respectively. It seems that application of humic acid increased seed yield by improving soil physical properties. Amiri (2015) reported that humic acid and folic acid increased seed yield of Echium amoenum by 32 and 22% compared to control, respectively. The highest and the lowest seed yield of bean (Phaseolus vulgaris L.) obtained in treatments of 80 kg.ha-1 water super absorbent humic acid and Non-applicaion of water super absorbent and humic acid, respectively. El-Baz et al., (2012) evaluated effect of humic acid on yield and yield components of soybean (Glycine max L.) and reported that the highest seed yield obtained in level of 1000 ppm humic acid.
ConclusionsIn economic scenario, using 143.83 kg.ha-1 superabsorbent, 6.14 kg.ha-1 humic acid and 22.12 t.ha-1 cattle manure, resulted in 1613 kg.ha-1 seed yield. The nitrogen losses in environmental scenario decreased by 95% compared to economic scenario. Eco-environmental scenario attended to different aspects of resource optimization, therefore it seems using the optimized amounts of resources in this scenario (131.71 and 6.02 kg.ha-1 superabsorbent and humic acid and 0.30 t.ha-1 cattle manure, respectively) are the best levels of ecological inputs in this research.