Effect of drought stress, integrated application of chemical and organic fertilizers and seed sowing method on forage yield of silage maize (Zea mays L. cv. SC704)

As one of the most important crops in Khuzestan, Iran, forage maize production faces limitations such as deficincy of water resources in summer, low soil organic matter content, heavy soil texture and soil salinity, which can be resolved by appropriated nutrition management and planting method to reduce some of these problems. To improve soil fertility, integrated application of chemical and organic fertilizers is eco-friendly and economically sustainable. The integarated application of organic and biological fertilizers in combiation with chemical fertilizers is an important integrated plant nutrition management strategy for sustainable productivity and production in cropping systems.

To evaluate the physiological traits and yield of silage maize with with integrated application of nitrogen fertilizer and sugarcane residue compost and seed sowing method under drought stress conditions, a field experiment was carried out in split split plot layout in randomized complete block design with three replications in 2021 summer in Ramhormoz, Khuzestan province, Iran. Treatments included irrigation after 30% (non-stress), 50% (moderate stress) and 70% (severe stress) deplation of available soil water (main plots), fertilizer treatments included 100% of nitrogen fertilizer requirement; 75% nitrogen + 25% compost, 50% nitrogen + 50% compost, 25% nitrogen + 75% compost and 100% compost (sub plots) and sowing methods, top of beds and in furrows (sub-sub plots). Samples of fresh forage were used to determine the relative water content (RWC), dry matter content and the dry forage yield. The leaf greenness index (SPAD) was measured using a portable chlorophyll meter at the 50% flowering stage on the fully developed leaf. Forage quality traits were measured using near infrared spectroscopy (NIR).

The results showed that the highest values of SPAD, chlorophyll a, chlorophyll b, RWC and cell membrane stability were obtained in 100% chemical fertilizer treatment under well irrigated condition. However, under modeate and severe drought stress conditions, combination of chemical and organic treatments with the 50% nitrogen and 50% compost of sugarcane residues had higher values. The maximum dry forage yield was obtained under well irrigated treatment, 100% chemical fertilizer and in furrow seed sowing. However, under moderate and severe stress conditions, the highest dry matter yield were obtained in integrated fertilizer application treatments and in furrow sowing. The lowest dry forage yiled was obtained in 100% organic fertilizer treatment and sowing on top of the bed. Under mild and even severe stress conditions, in furrow sowing method in comparison with the top of the bed, the effect of drought stress was mitigated, mainly due to better and longer condition for uptake of moisture and nutrients available for maize plants.

According to the results, it can be concluded that in furrow sowing method, better moisture could be preserved for longer time and optimal application of sugarcane compost as an organic input can improve the physical, chemical and biological properties of the soil, thus providing nutrients, especially nitrogen, and their slow release during the plant growth period which in turn may reduce the negative effect of drought stress and improve growth and yield of forage maize under the conditions of Khuzestan province.