اثر کاربرد اسید هومیک و کود فسفر بر تولید ماده خشک و کارایی مصرف آب گیاه نیشکر

بالا بودن نیاز گیاه به آب و فسفر از یک سو و محدود بودن منابع آبی کشور و نامساعد بودن شرایط جذب فسفر در خاک (از جمله ph بالا و میزان ماده آلی بسیار کم) از سوی دیگر، به مصرف بهینه آب و کود فسفر در این منطقه اهمیت ویژه‌ای می‌بخشد. این تحقیق با هدف بررسی اثر اسید هیومیک و کود فسفر بر سیستم ریشه‌ای، ماده خشک گیاهی و در نهایت کارایی مصرف آب اجرا گردید. این آزمایش گلخانه‌ای به صورت طرح فاکتوریل بر پایه طرح کامل تصادفی با تیمارهای اصلی سطوح مختلف فسفر (صفر، 125 و 250 کیلوگرم در هکتار) و اسید هومیک (غوطه‌ورسازی قلمه در محلول‌های 0، 0.3 و 0.5 درصد) در دو زمان برداشت (45 و 90 روز پس از کشت) با سه تکرار، در جنوب استان خوزستان اجرا گردید. در این تحقیق طول و وزن خشک ریشه، ارتفاع و وزن خشک بوته اندازه‌گیری و در نهایت کارایی مصرف آب برای هر تیمار تعیین شد. نتایج نشان داد که مصرف اسید هومیک و کود فسفر، طول و وزن ریشه را بهبود داده و با تاثیر بر سیستم ریشه‌ای، ارتفاع بوته و ماده خشک گیاهی را به‌طور معنی‌داری (از 3.4 گرم و 26.5 گرم در تیمار شاهد به‌ترتیب به 10.1 گرم و 1/ 39 گرم در برداشت اول و دوم) افزایش داد. در نتیجه افزایش ماده خشک گیاهی کارایی مصرف آب نسبت به تیمار شاهد بین 2 تا 3 برابر در برداشت اول و حدود 50 درصد در برداشت دوم، افزایش یافت.

The Effect of Humic Acid and Phosphorus Fertilizer on Dry Matter and Water Use Efficiency of Sugarcane (Saccharum officinarum)

Sugarcane cultivation has been revived in Khuzestan province of Iran since the 1960s and  due to good results, gradually began to grow from north to south of this region. Currently, sugarcane is cultivated in more than 100,000 hectares of the province’s land and almost 25% of the country’s demand for sugar is produced in this region. Regarding the very low rainfall and water resources reduction of the country in recent years, the optimal use of irrigation water is very important. Sugarcane fields in Iran due to irrigation problems such as distribution and consumption management, and the lack of continuous and uniform water supply, have high water use per hectare. In other words, the irrigation water use of farms is twice to three times of the real water need of sugarcane. Irrigation water use efficiency or WUE, which can be calculated from the ratio of plant dry matter to water consumption per hectare (Anyia and Herzog, 2004), is a very important criterion that can be of use in evaluating and improving irrigation operations and optimal water consumption. The water use efficiency of sugarcane depends on various factors such as climate, soil characteristics, irrigation management, cane cultivar and plant growth stage.      Irrigation water quality, climate change, weeds and soil characteristics (high pH and low organic matter, for example) are the main factors that affect production of sugarcane in Iran. Therefore, the yield of the sugarcane is also far from the potential yield. Sugarcane fields of Khuzestan province are mainly rich in lime percentage and poor in organic matter and phosphorus. Soil pH in this region of the country is also about 88.5 and uptake of some elements such as phosphorus, by plants and phosphorus fertilizer efficiency in these soils (alkaline and calcareous soils) are expected to be low (Wang and Wang, 1995). The optimum use of phosphorus fertilizer and water irrigation are essential for the quantitative and qualitative function of sugarcane plants. Due to the very low mobility of phosphorus in soil, its uptake by plants such as sugarcane is affected by the number of soil and plant factors (especially plant root characteristics). Changes in these factors can lead to reduction or increase of P uptake by the crop. Because of the role of organic compounds in improvement of mobility and phosphorus uptake, the use of organic maters has been considered in several researches. Organic compounds can play a direct and indirect role in plant factors and in phosphorous uptake improvement, yield increase and finally water use efficiency improvement.